This invention relates to defrost cycles for heat pumps and methods of defrosting heat exchangers. Particular embodiments concern heat pumps, defrost cycles, and defrost methods for heat pumps with microchannel outdoor coils.
Heat pump HVAC units have been used for some time to heat and cool spaces that people occupy such as the interior of buildings. Heat pumps have also been used for other purposes such as heating water and providing heat for industrial processes. Heat pumps are typically more efficient than alternative heat sources, such as electrical resistance heating, because heat pumps extract heat from another source, such as the environment, in addition to providing heat produced from the consumption of electrical power. As a result, heat pumps often reduce energy consumption in comparison with alternatives.
More broadly speaking, a heat pump is a machine or device that transfers thermal energy from one location, at a lower temperature, to another location, which is at a higher temperature. Accordingly, heat pumps move thermal energy in a direction opposite to the direction that it normally flows. Thus, air conditioners and freezers are also types of heat pumps, as used herein. Some types of heat pumps are dedicated to refrigeration only, some types are dedicated to heat only, and some types perform both functions, for instance, depending on whether heating or cooling is needed at the time. Further, in some applications, the heating and the cooling are both put to beneficial use at the same time.
In many applications, heat pumps extract heat from air, such as outdoor air, when a heat pump is being used to provide heat. In other examples, heat pumps extract heat from air that is being cooled such as air in a freezer when the heat pump is being used to cool the freezer. When a heat pump is used to extract heat from outdoor air, if the outdoor air temperature is close to or below freezing, moisture in the air can be deposited onto the outdoor air heat exchanger of the heat pump forming frost on the heat exchanger. The same may occur on a heat exchanger used to cool a freezer or refrigerator, as other examples. Build up of frost on the heat exchanger can interfere with heat transfer from the air to the refrigerant in the heat pump. Specifically, frost can insulate the heat exchanger, or can even block air flow through the heat exchanger. To address this problem, heat pumps have been operated in a defrost mode during a brief defrost cycle, during which the heat exchanger is warmed to melt the frost.
For example, heat pumps that are used in an HVAC application to heat and cool a building, when being used in a heating mode, may interrupt the heating mode periodically to run a defrost cycle. In the defrost cycle, the heat pump may be operated in the cooling mode, except without the outdoor air fan running. In this mode, hot refrigerant gas is delivered to the outdoor air heat exchanger heating the heat exchanger and melting frost that has accumulated on the heat exchanger. After the defrost cycle has been completed, the heat pump returns to the heating mode until another defrost cycle is initiated.
In recent years, microchannel heat exchangers have replaced other types of heat exchangers in various applications including automobile air conditioning. Microchannel heat exchangers typically have a first header, a second header, and multiple cross tubes extending from the first header to the second header. See U.S. patent application Ser. No. 12/561,178, Publication 2010/0071868, for example. Usually, each of the multiple cross tubes directly connects at one end to the first header and each of the multiple cross tubes directly connects at the other end to the second header. Moreover, in microchannel heat exchangers, the first header is often parallel to the second header, the multiple cross tubes are often parallel to each other, the headers are often perpendicular to the cross tubes, and the multiple cross tubes typically each include multiple contiguous parallel refrigerant passageways therethrough (e.g., extending from the first header to the second header). These refrigerant passageways are typically smaller than refrigerant passageways in prior heat exchanger designs (e.g., tube and fin heat exchangers), which is the origin of the name “microchannel”. Furthermore, most microchannel heat exchangers include multiple fins between the cross tubes, and the fins are typically bonded to the cross tubes. Microchannel heat exchangers generally offer a relatively high effectiveness relative to their cost and the restriction that they provide, in comparison with prior heat exchangers used for similar purposes. Microchannel heat exchangers generally also require less refrigerant, in comparison with prior heat exchangers used for similar purposes, and are also generally smaller and lighter in weight than alternative heat exchangers providing equivalent performance.
Microchannel heat exchangers have also been used in place of other types of heat exchangers in residential air conditioning units. In heat pump HVAC units, however, it has been found that microchannel heat exchangers do not defrost as well as certain prior heat exchangers. For example, if during a defrost cycle, hot refrigerant gas is introduced into the first header and travels though the cross tubes to the second header, the second header and the ends of the cross tubes that are connected to the second header often have not gotten warm enough to melt all of the frost there within a desired amount of time. As a result, frost or ice may remain on this portion of the heat exchanger after the defrost cycle is ended, or it may be necessary to extend the defrost cycle and remain in the defrost mode for a longer time.
Microchannel heat exchangers have been know for years to offer performance advantages, particularly relative to cost, size, weight, and the amount of refrigerant that is needed, in comparison with other types of heat exchangers. A long-felt need has existed to use microchannel heat exchangers in HVAC applications, but attempts to use microchannel heat exchangers for outdoor air heat exchangers in heat pumps have failed due to problems defrosting this type of heat exchangers. Others have taken many different approaches to resolving these problems, but none of their efforts have been successful and no heat pumps have been marketed that use a microchannel heat exchanger for the outdoor air heat exchanger.
U.S. Pat. No. 4,407,137 (Hayes) concerns a method and apparatus for defrosting a heat exchanger (50) having multiple rows (52 and 54) of cross tubes (Abstract, FIGS. 1 and 2, col. 3, lines 7-31). In Hayes, a solenoid valve (92) is opened during the defrost cycle to allow the hot refrigerant gas to bypass the second row (54) of the heat exchanger to the first row (52) of the heat exchanger to better defrost the first row where most of the frost typically accumulates in the tube and fin type of heat exchanger shown (col. 4, lines 45-52). Hayes uses three vertical headers on one side of the heat exchanger (FIG. 1 and col. 3, lines 25-26), which include an intermediate header (70) connected with feeder tubes (64 and 66) to the two rows (52 and 54) of cross tubes of the heat exchanger (50). The intermediate header is connected to each of the other headers (60 and 80) by horizontal cross tubes (rows 52 and 54) that pass through vertical fins (58, FIG. 1) and by feeder tubes (62, 64, 66, and 68). In Hayes, the refrigerant delivered to the second header through solenoid valve 92 and refrigerant conduit (hot gas bypass line) 90, passes through the cross tubes of coil row 52 before reaching header 60 (analogous to the second header of various embodiments herein). Hayes does not teach or suggest passing refrigerant through a header (e.g., 60, 70, or 80) of heat exchanger 50 without also passing that refrigerant through the cross tubes of coil row 52.
In various applications, in the defrost mode, as hot refrigerant gas is delivered to the heat exchanger, a portion of this heat will be transferred to the environment surrounding the heat exchanger. In particular, heat may be transferred via convection to air around the heat exchanger. Heat that is transferred to the air is not available or is less available to defrost the heat exchanger, especially for portions of the heat exchanger that are physically below the location where the heat is transferred to the air. As mentioned, in prior heat pumps, the outdoor air fan was typically turned off during the defrost cycle, which avoids heat loss to the surrounding air through forced convection. Natural convection still occurs, however, under such circumstances, carrying the hot air and heat upward where the heat is lost to the environment. For example, air heated by the heat exchanger can travel upward through the fan, pushed up by buoyancy forces from denser colder air, and colder air tends to flow through the heat exchanger to replace the warm air that has risen. This colder air flowing through the heat exchanger continues to cool the heat exchanger, cooling the refrigerant and taking heat away from the intended purpose of melting the frost. As a result, frost has remained on the heat exchanger, particularly on the lower portion of the heat exchanger, after a defrost cycle is completed, and it has been necessary to extend the defrost cycle and remain in the defrost mode for a longer time in order to defrost a heat exchanger completely or adequately.
Extending the defrost cycle in HVAC applications, for example, is undesirable because the heat pump delivers cold air to the space during the defrost cycle, which may lower the temperature in the space significantly below the thermostat set point temperature, may cause a cold draft and discomfort to the occupants of the space during the defrost mode, may cause the occupants of the space to believe that the heat pump is not working properly, or a combination thereof, for instance. Extension of defrost cycles and less effective defrost cycles may be undesirable in other applications (besides HVAC) as well, among other things, because heating or cooling is unavailable during the defrost cycle and because energy used during the defrost cycle does not contribute to the heating or cooling that is intended to be produced by the heat pump.
As a result, needs or potential for benefit or improvement exist for defrost cycles for heat pumps and methods of defrosting heat exchangers of heat pumps that are more effective, that direct hot refrigerant gas to areas of the heat exchanger that otherwise would not get warm enough, that take less time to complete, that work effectively with microchannel heat exchangers, or a combination thereof, as examples. In addition, needs or potential for benefit or improvement exist for defrost cycles for heat pumps, and methods of defrosting heat exchangers, that reduce the amount of heat loss to the air from the heat exchanger during the defrost cycle, that reduce natural convection during the defrost cycle, or a combination thereof, as examples. Needs and potential for benefit or improvement also exist for heat pumps and methods of defrosting heat exchangers that that are inexpensive, that can be readily manufactured, that are easy to install, that are reliable, that have a long life, that are compact, that are efficient, that can withstand extreme environmental conditions, or a combination thereof, as examples.
Further, needs or potential for benefit or improvement exist for methods of controlling, manufacturing, and distributing such heat pumps, HVAC units, buildings, systems, devices, and apparatuses. Other needs or potential for benefit or improvement may also be described herein or known in the HVAC or heat pump industries. Room for improvement exists over the prior art in these and other areas that may be apparent to a person of ordinary skill in the art having studied this document.
This invention provides, among other things, heat pumps with improved defrost cycles, methods of defrosting heat exchangers, and methods of improving the effectiveness of defrost cycles of heat pumps. Various embodiments include a defrost valve located in a refrigerant conduit that opens during a defrost cycle to deliver hot refrigerant gas to a portion of the heat exchanger that otherwise defrosts more slowly or less completely than other portions of the heat exchanger. Particular embodiments pass hot refrigerant gas through a header of the heat exchanger without passing that same hot refrigerant gas through any of the cross tubes of the heat exchanger. In a number of embodiments, the defrost valve is open only during a portion of the defrost cycle. Further, in some embodiments, the fan that is used to blow air through the heat exchanger is operated in a reversed direction during the defrost cycle to counteract natural convection through the heat exchanger.
Various embodiments provide, for example, as an object or benefit, that they partially or fully address or satisfy one or more of the needs, potential areas for benefit, or opportunities for improvement described herein, or known in the art, as examples. Certain embodiments provide, for instance, heat pumps having improved defrost cycles, and methods of defrosting heat exchangers, that are more effective, that direct hot refrigerant gas to areas of the heat exchanger that otherwise would not get warm enough, that take less time to complete, that work satisfactorily with microchannel heat exchangers, or a combination thereof, as examples. In addition, a number of embodiments provide defrost cycles for heat pumps, and methods of defrosting heat exchangers, that reduce the amount of heat loss to the air from the heat exchanger during the defrost cycle, that reduce natural convection during the defrost cycle, or a combination thereof, as examples. Various embodiments are reasonably inexpensive, can be readily manufactured, are easy to install, are reliable, have a long life, are compact, are efficient, can withstand extreme environmental conditions, or a combination thereof, as examples.
Specific embodiments of the invention provide various heat pumps having improved defrost cycles. In a number of embodiments, for example, the heat pump can include, for example, a compressor, at least one expansion device, and a first heat exchanger. Further, in various embodiments, the first heat exchanger can include, for instance, a first header, a second header, and multiple cross tubes extending from the first header to the second header. Further still, in particular embodiments, each of the multiple cross tubes connects to the first header, each of the multiple cross tubes connects to the second header, the first header is parallel to the second header, and the multiple cross tubes are parallel to each other. Even further, in a number of embodiments, the multiple cross tubes each include multiple contiguous parallel refrigerant passageways therethrough. Even further still, various embodiments of such a first heat exchanger include multiple fins between the cross tubes that are bonded to the cross tubes.
Moreover, certain of these embodiments include at least one first connection point to the first heat exchanger where refrigerant is delivered to the first heat exchanger from the compressor during the defrost cycle, a second connection point to the first heat exchanger where refrigerant exits the first heat exchanger during the defrost cycle, and a third connection point to the first heat exchanger where refrigerant is also delivered from the compressor to the first heat exchanger during at least part of the defrost cycle. Further, a number of embodiments include a first refrigerant conduit connecting a discharge port on the compressor to the at least one first connection point of the first heat exchanger, a second refrigerant conduit connecting the second connection point of the first heat exchanger to the at least one expansion device, and a third refrigerant conduit connecting the first refrigerant conduit to the third connection point of the first heat exchanger. In various embodiments, a defrost valve is located in the third refrigerant conduit between the first refrigerant conduit and the third connection point of the first heat exchanger, and, when the defrost valve is closed, refrigerant flow through the third refrigerant conduit is blocked.
Furthermore, various such embodiments further include a control system that controls the defrost valve and opens the defrost valve during the defrost cycle allowing refrigerant to flow through the third refrigerant conduit to the third connection point to the first heat exchanger. Additionally, in a number of such embodiments, the first connection point to the first heat exchanger is at the first header, the second connection point to the first heat exchanger is at the second header, and the third connection point to the first heat exchanger is also at the second header. Even further, in various embodiments, refrigerant that, during at least part of the defrost cycle, passes through the third refrigerant conduit, through the defrost valve, and through the third connection point to the first heat exchanger, passes through the second header, heating the second header between the third connection point and the second connection point, without passing through any cross tubes of the first heat exchanger.
Further, in some such embodiments, the first heat exchanger includes a top and a bottom, the first header extends across the top of the first heat exchanger, and the second header extends across the bottom of the first heat exchanger. Further still, in certain embodiments, the first header is horizontal, the second header is horizontal, and each of the multiple cross tubes directly connects to the first header and directly connects to the second header. Even further, in particular embodiments, the first heat exchanger consists essentially of the first header, the second header, the multiple cross tubes, the multiple fins between the cross tubes (e.g., bonded to the cross tubes), the at least one first connection point to the first heat exchanger, the second connection point to the first heat exchanger, and the third connection point to the first heat exchanger. In particular embodiments, the first heat exchanger has only two headers, the first header and the second header.
Still further, certain embodiments can include, for example, an extension tube located within the second header, where the extension tube within the second header is substantially parallel to the second header, and the third connection point to the first heat exchanger is at the extension tube. Even further, in some embodiments, the second header has a first end and a second end, each of the multiple cross tubes connects to the second header between the first end and the second end, the second connection point to the first heat exchanger is at the second end of the second header, and the third connection point to the first heat exchanger is at the first end of the second header. Even further still, in particular embodiments, the first header has a third end and a fourth end, each of the multiple cross tubes connects to the first header between the third end and the fourth end, and the at least one first connection point to the first heat exchanger consists of a single first connection point at the third end of the first header. On the other hand, in other embodiments, the first header has a third end and a fourth end, and each of the multiple cross tubes connects to the first header between the third end and the fourth end, but the at least one first connection point to the first heat exchanger includes a primary first connection point to the heat exchanger at the third end of the first header and a secondary first connection point to the heat exchanger at the fourth end of the first header, and the first refrigerant conduit connects the discharge port on the compressor to the primary first connection point and to the secondary first connection point.
Additionally, in some embodiments, the control system includes a digital controller that can include, for example, programming instructions to open the defrost valve during the defrost cycle to defrost the first heat exchanger between the third connection point and the second connection point. In addition, in particular embodiments, the digital controller further includes programming instructions to keep the defrost valve closed when the heat pump is not in the defrost cycle. In certain embodiments, the digital controller further includes programming instructions to keep the defrost valve closed during part of the defrost cycle to defrost the first heat exchanger between the at least one first connection point and the second connection point.
What's more, in a number of embodiments, such a heat pump can include, for example, a first fan positioned and configured to move air through the first heat exchanger, and the control system can include a digital controller having, for instance, programming instructions to operate the first fan in a reversed direction during at least part of the defrost cycle to reduce natural convection through the first heat exchanger during the at least part of the defrost cycle. Further, in various embodiments, the heat pump can include a reversing valve located in the first refrigerant conduit between the discharge port on the compressor and the at least one first connection point of the first heat exchanger. In some embodiments, the third refrigerant conduit connects to the first refrigerant conduit between the reversing valve and the at least one first connection point of the first heat exchanger, for example. Further still, in some embodiments, the heat pump can include, as examples, a second heat exchanger, a fourth refrigerant conduit connecting the at least one expansion device to the second heat exchanger, a fifth refrigerant conduit connecting the second heat exchanger to the reversing valve, and a sixth refrigerant conduit connecting the reversing valve to an inlet port on the compressor.
Other specific embodiments of the invention provide various methods, for example, of defrosting a first heat exchanger of a heat pump. Such a heat pump can include, for example, the first heat exchanger, a compressor, at least one expansion device, and a second heat exchanger. Moreover, the first heat exchanger can include, for example, headers, multiple cross tubes, a first connection point to the first heat exchanger, a second connection point to the first heat exchanger, and a third connection point to the first heat exchanger. In a number of embodiments, such a method can include (e.g., in any order except where a particular order is explicitly indicated), at least certain acts. Such acts may include, for example, an act of operating the heat pump in a defrost mode during a defrost cycle, for instance, including delivering refrigerant from the compressor to the first connection point (i.e., of the first heat exchanger). Such a method can also include, in various embodiments, acts of, (e.g., during the defrost cycle), passing the refrigerant through the first heat exchanger from the first connection point (i.e., to the first heat exchanger), through the multiple cross tubes, to the second connection point (e.g., of the first heat exchanger), and (e.g., also during the defrost cycle) passing the refrigerant from the second connection point (i.e., of the first heat exchanger), through the at least one expansion device, and then to the second heat exchanger. Such a method can also include, in a number of embodiments, acts of, (e.g., during the defrost cycle), passing the refrigerant through the second heat exchanger, and then back to the compressor, and (e.g., during at least part of the defrost cycle) delivering at least part of the refrigerant from the compressor to the third connection point (i.e., of the first heat exchanger). Further, such a method can also include, in various embodiments, an act of, (e.g., during the defrost cycle), passing the at least part of the refrigerant from the third connection point (i.e., of the first heat exchanger), through one of the headers, to the second connection point (i.e., of the first heat exchanger), without passing the at least part of the refrigerant through any of the cross tubes of the first heat exchanger.
Further, in some such embodiments, the one of the headers of the first heat exchanger includes a first end and a second end, each of the cross tubes connect to the one of the headers between the first end and the second end, and the second connection point of the first heat exchanger is at the second end of the one of the headers. Further still, in various embodiments, the third connection point of the first heat exchanger is at the first end of the one of the headers, and the act of passing the refrigerant from the third connection point (i.e., of the first heat exchanger), through the one of the headers, to the second connection point (i.e., of the first heat exchanger) includes passing the refrigerant from the first end, through the one of the headers, to the second end. Even further, in some such embodiments, each cross tube includes multiple contiguous parallel refrigerant passageways therethrough, the first heat exchanger further includes multiple fins between the cross tubes that are bonded to the cross tubes, and the act of passing the refrigerant through the first heat exchanger from the first connection point (i.e., of the first heat exchanger), through the multiple cross tubes, to the second connection point (i.e., of the first heat exchanger) includes heating the multiple fins between the cross tubes.
In a number of embodiments, the act of delivering refrigerant from the compressor to the third connection point (i.e., of the first heat exchanger) includes opening a solenoid valve in a bypass refrigerant line extending from a supply refrigerant line connected to the first connection point (i.e., of the first heat exchanger), the bypass refrigerant line extending to the third connection point (i.e., of the first heat exchanger). Moreover, in some embodiments, such a method includes, during a first portion of the defrost cycle, not passing refrigerant through the third connection point (i.e., of the first heat exchanger), and during a second portion of the defrost cycle, passing refrigerant through the third connection point. Furthermore, in certain embodiments, the headers consist of a first header and a second header, the first connection point (i.e., to the first heat exchanger) is at the first header, the second connection point (i.e., to the first heat exchanger) is at the second header, and the third connection point (i.e., to the first heat exchanger) is also at the second header. Further, in a number of such embodiments, the act of passing the at least part of the refrigerant from the third connection point (i.e., of the first heat exchanger), through one of the headers, to the second connection point (i.e., of the first heat exchanger) includes passing the at least part of the refrigerant through the second header without passing the at least part of the refrigerant through any of the cross tubes of the first heat exchanger.
In various embodiments, the first heat exchanger is an outdoor air heat exchanger, the second heat exchanger is an indoor air heat exchanger, the first heat exchanger includes a top and a bottom, the first header extends across the top of the first heat exchanger, and the second header extends across the bottom of the first heat exchanger. Further, in some embodiments, each cross tube of the first heat exchanger includes multiple contiguous parallel refrigerant passageways therethrough, each of the multiple cross tubes directly connects to the first header, and each of the multiple cross tubes directly connects to the second header. Even further, in some embodiments, the first heat exchanger further includes multiple fins between the cross tubes that are bonded to the cross tubes, and the act of passing the refrigerant through the first heat exchanger from the first connection point (i.e., of the first heat exchanger), through the multiple cross tubes, to the second connection point (i.e., of the first heat exchanger) includes heating the multiple fins between the cross tubes. Even further still, in some embodiments, the act of delivering refrigerant from the compressor to the third connection point (i.e., of the first heat exchanger) includes opening a solenoid valve in a bypass refrigerant line extending from a supply refrigerant line connected to the first connection point (i.e., of the first heat exchanger), the bypass refrigerant line extending to the third connection point (i.e., of the first heat exchanger).
In still other specific embodiments, the invention provides various heat pumps that can include, for example, a compressor, at least one expansion device, and a first heat exchanger having a top and a bottom. Such a heat exchanger can consist essentially of, for example, a first header extending across the top of the first heat exchanger, a second header extending across the bottom of the first heat exchanger, multiple cross tubes extending from the first header to the second header, multiple fins between the cross tubes that are bonded to the cross tubes, and three types of connection points. In a number of such embodiments, each of the multiple cross tubes is directly connected to the first header, each of the multiple cross tubes is directly connected to the second header, and the multiple cross tubes each include multiple contiguous parallel refrigerant passageways therethrough. Further, in various embodiments, the three types of connection points consist of at least one first connection point where refrigerant is delivered to the first heat exchanger from the compressor during the defrost cycle, a second connection point where refrigerant exits the first heat exchanger during the defrost cycle, and a third connection point where refrigerant is also delivered from the compressor to the first heat exchanger during at least part of the defrost cycle.
In a number of such embodiments, the heat pump further includes a first fan positioned and configured to move air through the first heat exchanger, a second heat exchanger, and a first refrigerant conduit connecting a discharge port on the compressor to the at least one first connection point of the first heat exchanger, where the first refrigerant conduit does not include any part of the first heat exchanger. Further, in various embodiments, such a heat pump further includes a reversing valve located in the first refrigerant conduit between the discharge port on the compressor and the at least one first connection point of the first heat exchanger, a second refrigerant conduit connecting the second connection point of the first heat exchanger to the at least one expansion device, where the second refrigerant conduit does not include any part of the first heat exchanger, and a third refrigerant conduit connecting the first refrigerant conduit to the third connection point of the first heat exchanger. Still further, a number of such embodiments include a defrost valve, for example, located in the third refrigerant conduit between the first refrigerant conduit and the third connection point of the first heat exchanger, where, when the defrost valve is closed, refrigerant flow through the third refrigerant conduit is blocked, and a fourth refrigerant conduit connecting the at least one expansion device to the second heat exchanger. Even further, various embodiments include a fifth refrigerant conduit connecting the second heat exchanger to the reversing valve, a sixth refrigerant conduit connecting the reversing valve to an inlet port on the compressor, and a control system that controls the defrost valve, for example, that opens the defrost valve during the defrost cycle allowing refrigerant to flow through the third refrigerant conduit to the third connection point.
In a number of such embodiments, the control system includes a digital controller, for example, having programming instructions to open the defrost valve during the defrost cycle to defrost the first heat exchanger between the third connection point and the second connection point, and having programming instructions to keep the defrost valve closed when the heat pump is not in the defrost cycle. Further, in various embodiments, the third refrigerant conduit connects to the first refrigerant conduit between the reversing valve and the at least one first connection point of the first heat exchanger, the first connection point is at the first header, the second connection point is at the second header, and the third connection point is also at the second header. Further still, in a number of such embodiments, refrigerant that, during at least part of the defrost cycle passes through the third refrigerant conduit, through the defrost valve, and through the third connection point, passes through the second header, heating the second header between the third connection point and the second connection point, without passing through any cross tubes of the first heat exchanger.
Moreover, in some such embodiments, the second header has a first end and a second end, each of the multiple cross tubes connects to the second header between the first end and the second end, the second connection point to the first heat exchanger is at the second end of the second header, and the third connection point to the first heat exchanger is at the first end of the second header. Further, in a number of embodiments, during the defrost cycle, when the defrost valve is open, a first quantity of refrigerant passes from the compressor, and the defrost valve, the third refrigerant conduit, or both, are sized so that less than half of the first quantity of refrigerant from the compressor passes through the third connection point, and more than half of the first quantity of refrigerant from the compressor passes through the (e.g., at least one) first connection point. Further, in some embodiments, a centerline of the third connection point is within 20 degrees from a centerline of the second header. Further still, in some embodiments, a centerline of the third connection point is within 20 degrees from a centerline of the cross tubes. In addition, various other embodiments of the invention are also described herein, and other benefits of certain embodiments may be apparent to a person of ordinary skill in the art.
These drawings illustrate, among other things, examples of certain aspects of particular embodiments of the invention. Other embodiments may differ. Various embodiments may include aspects shown in the drawings, described in the specification, shown or described in other documents that are incorporated by reference, known in the art, or a combination thereof, as examples.
A number of embodiments of the subject matter described herein include heat pumps, for example, with improved defrost cycles, methods of defrosting heat exchangers, and methods of defrosting heat exchangers and of improving the effectiveness of defrost cycles of heat pumps, as examples. These systems and methods may be used, for instance, with heat pumps having a microchannel (e.g., outdoor) heat exchanger. Various embodiments include a defrost valve located in a refrigerant conduit that opens during a defrost cycle to deliver hot refrigerant gas to a portion of the heat exchanger that otherwise defrosts more slowly or less completely than other portions of the heat exchanger. Particular embodiments pass hot refrigerant gas through a header of the heat exchanger (e.g., without that refrigerant passing through any cross tubes of that heat exchanger). Certain embodiments have two different connection points to the heat exchanger that are on the same header of the heat exchanger, one such connection point acting as an inlet to the heat exchanger and the other such connection point acting as an outlet from the heat exchanger. Further, in some embodiments, the fan that is used to blow air (e.g., outdoor air) through the heat exchanger is operated in a reversed direction during at least part of the defrost cycle to counteract natural convection through the heat exchanger.
In various embodiments, in a defrost mode, during a defrost cycle, refrigerant is delivered from the compressor to a first connection point of a first heat exchanger. The refrigerant is passed through the first heat exchanger from the first connection point (e.g., through multiple cross tubes) to a second connection point of the first heat exchanger. Further, also during the defrost cycle, the refrigerant is passed from the second connection point of the first heat exchanger, through at least one expansion device, and then to a second heat exchanger. Even further, the refrigerant is passed, in a number of embodiments, through the second heat exchanger, and then back to the compressor. Moreover, in certain embodiments, during at least part of the defrost cycle, refrigerant is delivered from the compressor to a third connection point of the first heat exchanger and is passed from the third connection point, through the second header, to the second connection point. Further, in various embodiments, the second connection point and the third connection point are both at the second header. Even further, in some embodiments, refrigerant that, during at least part of the defrost cycle, passes through the third refrigerant conduit, through the defrost valve, and through the third connection point, passes through the second header, heating the second header between the third connection point and the second connection point without passing through any cross tubes of the first heat exchanger. Further still, in a number of embodiments, the defrost valve is open only during a portion of the defrost cycle.
As used herein, “connection points”, are locations where a refrigerant conduit, such as refrigerant tubing, connects to the heat exchanger to deliver refrigerant to or from the heat exchanger. Connection points are openings on the heat exchanger before the heat exchanger is connected to the refrigerant conduits. A “refrigerant conduit”, as used herein, is an enclosed passageway that refrigerant flows through during at least one mode of operation of the heat pump. As used herein, “refrigerant conduit” may include, as examples, tubing (e.g., copper), pipe, fittings, passageways through valve bodies, passageways through other components such as mufflers, dryers, accumulators, and compensators, as examples, or a combination thereof. As used herein, however, except where specifically stated otherwise, “refrigerant conduit” does not include any part of one or more headers or cross tubes of a heat exchanger (e.g., first heat exchanger 11 or second heat exchanger 12). In the HVAC context, as used herein, a “heat exchanger” (e.g., 11 or 12) is a component (e.g., of heat pump 10) that is used to heat or cool the refrigerant, and that, unless stated otherwise, is installed in the heat pump as a unit by connecting refrigerant conduits (e.g., 101, 102, and 103) at the connection points (e.g., 111, 112, and 113) of the heat exchanger. In a number of embodiments, the heat exchanger may also be (e.g., separately) structurally supported or attached when installed in the heat pump. In contrast, various refrigerant conduits (e.g., 101, 102, and 103) can be formed from separate components joined when the heat pump is assembled.
In the embodiment depicted, first refrigerant conduit 101 connects discharge port 131 on compressor 13 to first connection point 111 of first heat exchanger 11. As used herein, in this context, “connects” or “connecting” means provides, or providing an enclosed passageway therebetween for refrigerant to flow through, at least during one mode of operation of the heat pump. Further, as used herein, “directly connects” or “directly connecting” means provides, or providing an enclosed passageway therebetween for refrigerant to flow through, at least during one mode of operation of the heat pump, without another conduit or component therebetween. In the embodiment depicted, first refrigerant conduit 101 directly connects to discharge port 131 on compressor 13 and first refrigerant conduit 101 directly connects to first connection point 111 of first heat exchanger 11. Other embodiments, however, may differ.
Further still, in this embodiment, second refrigerant conduit 102 connects second connection point 112 of first heat exchanger 11 to expansion devices 14 and 17, and third refrigerant conduit 103 connects first refrigerant conduit 101 to third connection point 113 of first heat exchanger 11. Even further still, in this embodiment, second refrigerant conduit 102 directly connects to second connection point 112 of first heat exchanger 11 and second refrigerant conduit 102 directly connects to expansion devices 14 and 17. Similarly, third refrigerant conduit 103 directly connects to first refrigerant conduit 101 and third refrigerant conduit 103 directly connects to third connection point 113 of first heat exchanger 11. Other embodiments, however, may differ.
These “connection points” to the first heat exchanger, among other things, establish where the refrigerant is delivered to, and removed from, the heat exchanger, for example, during the defrost cycle. In particular embodiments, the refrigerant that is delivered from the compressor to the first heat exchanger through the third connection point exits the first heat exchanger through the second connection point. Further, in a number of embodiments, as described below with reference to other figures, both of these connection points are at the same header (e.g., the “second header”). As a result, in such embodiments, this portion of the refrigerant directly heats only the second header of the first heat exchanger.
Moreover, in this particular embodiment, defrost valve 15 is located in third refrigerant conduit 103, between first refrigerant conduit 101 and third connection point 113 of first heat exchanger 11. In this particular embodiment, when defrost valve 15 is closed, refrigerant flow through third refrigerant conduit 103 is blocked (i.e., completely blocked or substantially blocked to the extent that any leakage has a negligible impact on the performance of the heat pump) at defrost valve 15. Further, in the example of heat pump 10, control system 16 opens defrost valve 15 during the defrost cycle, for example, allowing refrigerant to flow through defrost valve 15 and third refrigerant conduit 103. In this operation, refrigerant flows to third connection point 113 to defrost first heat exchanger 11 between third connection point 113 and second connection point 112, for instance, during at least part of the defrost cycle.
Various embodiments have at least one expansion device, for instance, one or two expansion devices. In the embodiment shown, heat pump 10 has two expansion devices 14 and 17. In the embodiment illustrated, expansion device 14 is used when the refrigerant flows in one direction, and expansion device 17 is used when the refrigerant flows in the opposite direction. In this embodiment, expansion device 14 is used when heat pump 10 is operated in a cooling mode (i.e., cooling second heat exchanger 12) or in a defrost mode (i.e., defrosting first heat exchanger 11) and expansion device 17 is used when heat pump 10 is being operated in a heating mode (i.e., heating second heat exchanger 12). In this context, an expansion device being “used” means that the expansion device produces a substantial restriction to flow or pressure differential (i.e., across the expansion device). When an expansion device is not being used, in a number of embodiments, refrigerant passes through the expansion device or through a check valve arranged in parallel thereto, with little or no resistance to flow or pressure differential across the expansion device.
Although
Still referring to
Turning now to the internal components of the heat exchanger,
In a number of embodiments, the first heat exchanger (e.g., 11 or 20) can be a standard or common design microchannel heat exchanger, for instance, without requiring expensive modifications such as special fins (e.g., slanted or extending beyond the cross tubes and connected to shed condensation) or an added intermediate (e.g., third) header and additional connections to cross tubes associated therewith. Further, in the particular embodiment shown, and in a number of embodiments, there are no feeder tubes between either header 21 or header 22 and any of cross tubes 23 and each of multiple cross tubes 23 directly connects to first header 21 and each of multiple cross tubes 23 directly connects to second header 22. As used herein, in this context, “directly connects” means “connects” without another conduit or component therebetween (e.g., each of multiple cross tubes 23 connects to first header 21 without another conduit or component, such as one or more feeder tubes, between any of cross tubes 23 and first header 21, and each of multiple cross tubes 23 connects to second header 22 without another conduit or component, such as one or more feeder tubes, between any of cross tubes 23 and second header 22).
Even further, as used herein, a “cross tube” in a heat exchanger is one of multiple tubes connected in parallel that extend from one header of the heat exchanger to another header of the heat exchanger (i.e., each cross tube is connected to the one header and to the other header). Further still, in a number of embodiments, including the embodiment shown in
Moreover, as used herein, a “header” in a heat exchanger is an enclosed passageway that refrigerant flows through during at least one mode of operation of the heat pump that connects multiple cross tubes of the heat exchanger together. A header can distribute or deliver refrigerant to multiple cross tubes, can collect refrigerant from multiple cross tubes, or both, for example, in different modes of operation of the heat pump. For example, in heat exchanger 20 shown in
In a number of embodiments, headers can be made of tubing, for example, with multiple connections (e.g., direct connections or indirect connections with feeder tubes) to cross tubes spaced along the length of each header (e.g., as shown in
Moreover, in the embodiment shown in
Extension tube 44, in the embodiment shown in
In various embodiments, the third connection point (e.g., 113, 213, or 413) to the heat exchanger (e.g., first heat exchanger 11, 20, or 40) is parallel to, or concentric with, the second header (e.g., 22 or 42). Heat exchangers 20 and 40 are examples of such a configuration. In other embodiments, the third connection point can be at or within a specific angle from the header (e.g., second header 22 or 42) or cross tubes (e.g., 23), as other examples. In certain embodiments, a centerline of the third connection point can be at or within a specific angle from a centerline of the header (e.g., second header 22 or 42) or a centerline of the cross tubes (e.g., 23), as other examples. In different embodiments, such a specific angle can be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 degrees. In particular embodiments, the third connection point can be at or within 20 degrees from the header (e.g., second header 22 or 42, for instance, when viewed from the perspective of
Some embodiments include a distributor tube in the second header (e.g., second header 22 shown in
As mentioned, in the embodiment illustrated in
In a number of embodiments, the at least one first connection point (e.g., 111 shown in
Further, in various embodiments, the second connection point (e.g., 112 shown in
Moreover, in the embodiments illustrated in
In the embodiment shown in
Other embodiments can have connection points that are not at headers or that are at headers but are not at the ends of the headers. In some embodiments, for example, one or more connections may tee into the header at the midpoint (e.g., 425) or may be spaced along the header, as examples. In certain embodiments, one or more headers may extend all the way around the unit (e.g., at the top or at the bottom of the unit) and may lack an “end”, but may include a tee or other fitting forming a connection point to the header at one or more locations around the unit. Further, other embodiments of heat exchangers do not have a header or headers with cross tubes extending between the headers, but rather, have a continuous refrigerant pathway that may be larger in cross section than the passageways of the cross tubes described herein and longer, in order to provide the necessary or desired heat transfer performance.
Furthermore, in the embodiment shown in
Moreover, in the embodiment shown, if heat exchanger 20 is substituted for first heat exchanger 11 shown in
Further, in yet another embodiment, the first refrigerant conduit (e.g., 101 shown in
In various embodiments, the control system (e.g., 16 shown in
Furthermore, in some embodiments, the digital controller (e.g., 160) further includes programming instructions (e.g., 162) to keep the defrost valve (e.g., 15) closed when the heat pump (e.g., 10) is not in the defrost cycle. “Keep(ing) the defrost valve closed”, as used herein, means while the heat pump (e.g., compressor 13) is operating. When the heat pump is not operating (e.g., when compressor 13 is stopped or off), the defrost valve (e.g., 15) can be closed or open. In a number of embodiments, however, defrost valve 15 is normally closed, is closed when not powered, or is closed when the heat pump (e.g., compressor 13) is stopped or off, for instance. In addition, in some embodiments, the digital controller (e.g., 160) further includes programming instructions (e.g., 163) to keep the defrost valve (e.g., 15) closed during part of the defrost cycle, for example, to direct more (e.g., all when the defrost valve is closed) of the hot refrigerant through the at least one first connection point (e.g., 111, 2111 and 2112, or 411) to defrost, or to better defrost, the first heat exchanger (e.g., 11, 20, or 40) between the at least one first connection point (e.g., 111, 2111 and 2112, or 411) and the second connection point (e.g., 112, 212, or 4121 and 4122).
Furthermore, heat pump 10, in the embodiment shown in
In a number of embodiments, the first fan (e.g., 18) may be operated at a reduced or substantially reduced rate of speed (e.g., in the reversed direction) during the defrost cycle, in comparison with operation in the heating or cooling mode. As used herein, a “substantially reduced rate of speed” is less than or equal to 25 percent of the rated or maximum rate of speed. In particular embodiments, however, the “substantially reduced rate of speed” can be 25, 20, 15, 12, 10, 8, 7, 6, 5, 4, 3, 2, 1, or ½ percent of the rated or maximum rate of speed (e.g., of fan 18, fan motor 180, or a drive system therefor), as examples. Moreover, in certain embodiments, the “substantially reduced rate of speed” can be accomplished by intermittent operation (e.g., intermittent powering) or pulsing of the electrical power to the fan motor (e.g., 180). In particular embodiments, this intermittent operation or pulsing of the fan motor (e.g., 180) can be controlled by control system 16 or digital controller 160, for example, in the defrost board.
In a number of embodiments, motor 180 is a variable-speed motor and is capable of running in the reversed direction at a low speed. In various embodiments, a variable-speed drive unit may be included, such as a variable-frequency AC drive unit or a variable-voltage DC drive unit, as examples. In some embodiments, the minimum speed provided by the variable-speed drive unit may be sufficiently low with steady electrical power being provided to the motor (e.g., 180). In certain embodiments, however, the speed can be lowered further by providing power to the motor (e.g., 180) intermittently. In particular embodiments, this intermittent operation or pulsing of the fan motor (e.g., 180) can be controlled by control system 16 or digital controller 160, for example, by controlling the variable-speed drive unit.
Further, in some embodiments, the fan motor (e.g., 180) may be a single-speed motor or a two-speed motor, as examples, a variable-speed drive unit may not be provided, or a combination thereof, and the “substantially reduced rate of speed” may be accomplished by intermittent operation (e.g., intermittent powering) or pulsing of the electrical power to the fan motor (e.g., 180). In particular embodiments, this intermittent operation or pulsing of the fan motor (e.g., 180) can be controlled by control system 16 or digital controller 160, for example, by actuating a relay that turns electrical power to the fan motor (e.g., 180) on and off. Further, reversed operation of the first fan or outdoor fan can be used in combination with a defrost valve, or on units that do not have a defrost valve.
As further illustrated in
In the embodiment illustrated, defrost valve 15 is a separate valve. Defrost valve 15 can be a solenoid valve, for example, that is either fully open or fully closed. Defrost valve 15 can be electrically operated, pilot operated, or both, as examples. In some embodiments, a check valve can be provided in series with defrost valve 15 to allow flow only in one direction, while in other embodiments, defrost valve 15 can be kept closed when flow through defrost valve 15, in either direction, is undesirable. Further, in the embodiment illustrated, when defrost valve 15 is open, refrigerant from compressor 13 can flow through defrost valve 15 to third connection point 113, 213, or 413, and through first connection point 111, 2111 and 2112, or 411. In other embodiments, however, a three-way valve can be used, or two of the two-way valves can be used, so that when refrigerant from the compressor is directed to the third connection point, the refrigerant is prevented from also flowing to the first connection point.
Thus, in the embodiment illustrated, when defrost valve 15 is open, first header 21 or 41 and cross tubes 23 are not isolated from refrigerant flow (e.g., hot refrigerant gas from compressor 13) through first connection point 111, 2111, 2112, or 411). But in other embodiments (e.g., where a three-way defrost valve is used where third refrigerant conduit 103 tees into (or directly connects to) first refrigerant conduit 101 instead of defrost valve 15 shown), when the defrost valve is open (i.e., positioned to allow hot refrigerant gas to flow into third connection point 113, 213, or 413), first header 21 or 41 and cross tubes 23 are isolated from refrigerant flow (e.g., hot refrigerant gas from compressor 13) through first connection point 111, 2111, 2112, or 411). In such embodiments, however, when the defrost valve is open (i.e., allowing hot refrigerant gas to flow into third connection point 113, 213, or 413), as trapped refrigerant within first header 21 or 41 and cross tubes 23, cools and contracts (e.g., condenses), hot refrigerant gas can enter cross tubes 23 from second header 22 or 42, and can enter first header 21 or 41 from cross tubes 23.
In the embodiment shown, defrost valve 15, third refrigerant conduit 103, or both, can be sized to deliver an appropriate amount of hot refrigerant to third connection point 113, 213, or 413, for instance. Further, in some embodiments, defrost valve 15, third refrigerant conduit 103, or both, can be sized so that less than half of the refrigerant from compressor 13 passes through third connection point 113, 213, or 413, for instance, while more than half of the refrigerant from compressor 13 passes through first connection point 111, 411, or 2111 and 2112. Further still, in some embodiments, defrost valve 15, third refrigerant conduit 103, or both, can be sized so that about 10, 20, 30, 40, or 50 percent of the refrigerant from compressor 13 passes through third connection point 113, 213, or 413, for instance, while the remainder of the refrigerant from compressor 13 passes through first connection point 111, 411, or 2111 and 2112. In this context, “about” means within plus or minus five (5) percent of the quantity (i.e., mass flow rate) of the refrigerant that passes from the compressor (e.g., 13) during the defrost cycle when the defrost valve (e.g., 15) is open. On the other hand, in some embodiments, defrost valve 15, third refrigerant conduit 103, or both, can be sized so that about 60, 70, 80, or 90 percent of the refrigerant from compressor 13 passes through third connection point 113, 213, or 413, for instance, while the remainder of the refrigerant from compressor 13 passes through first connection point 111, 411, or 2111 and 2112. In other embodiments, defrost valve 15 can be of a type suitable to modulate and throttle refrigerant therethrough and can deliver a regulated or measured amount of refrigerant to third connection point 113, 213, or 413, as another example. In some embodiments, defrost valve 15 can be part of an integrated valve module that performs other functions as well, or can be part of another component. In particular embodiments, for example, the defrost valve can be part of the reversing valve (e.g., 150), for example.
In many of the embodiments described herein, during a defrost cycle, refrigerant is delivered to the (e.g., first) heat exchanger (e.g., 11) at two different connection points (e.g., 111 and 113 shown in
As shown in
Referring to
Moreover, certain of these embodiments include at least three connection points or types of connection points to the (e.g., first) heat exchanger where refrigerant is delivered to or removed from the heat exchanger. Examples of these connection points or types of connection points include (e.g., at least one) first connection point (e.g., 111, 2111 and 2112, or 411) to the first heat exchanger where refrigerant is delivered to the first heat exchanger from the compressor during the defrost cycle. Another example of these three (e.g., types of) connection points is a second connection point (e.g., 112, 212, 4121 and 4122) to the first heat exchanger where refrigerant exits the first heat exchanger during the defrost cycle. Still another example of these three (e.g., types of) connection points is a third connection point (e.g., 113, 213, or 413) to the first heat exchanger where refrigerant is delivered from the compressor to the first heat exchanger during at least part of the defrost cycle.
Further, a number of these embodiments include a first refrigerant conduit (e.g., 101) connecting a discharge port (e.g., 131) on the compressor (e.g., 13) to the at least one first connection point (e.g., 111, 2111 and 2112, or 411) of the first heat exchanger (e.g., 11, 20, or 40), a second refrigerant conduit (e.g., 102) connecting the second connection point (e.g., 112, 212, 4121 and 4122) of the first heat exchanger to the at least one expansion device (e.g., 14, 17, or both), and a third refrigerant conduit (e.g., 103) connecting the first refrigerant conduit to the third connection point (e.g., 113, 213, or 413) of the first heat exchanger. In various embodiments, a defrost valve (e.g., 15) is located in the third refrigerant conduit between the first refrigerant conduit and the third connection point of the first heat exchanger, and, when the defrost valve is closed, refrigerant flow through the third refrigerant conduit is blocked.
Furthermore, various such embodiments further include a control system (e.g., 16) that controls the defrost valve (e.g., 15) and opens the defrost valve during the defrost cycle allowing refrigerant to flow through the third refrigerant conduit to the third connection point to the first heat exchanger. Additionally, in a number of such embodiments, the first connection point to the first heat exchanger is at the first header (e.g., 21 or 41), the second connection point to the first heat exchanger is at the second header (e.g., 22 or 42), and the third connection point to the first heat exchanger is also at the second header. Thus, the second connection point and the third connection point are at the same header in such embodiments.
Various embodiments go against conventional wisdom by mixing hot refrigerant gas with cooler refrigerant liquid, for example, in the second header (e.g., 22 or 42), as well as by introducing the hot refrigerant gas (e.g., during the defrost cycle) at the same header where that refrigerant exits the heat exchanger (e.g., 11, 20, or 40). Although the different headers of heat exchangers are commonly used for different purposes depending on the cycle of the heat pump (e.g., heating mode v. defrost mode), in the prior art, the header of a heat exchanger is only used for one type of connection point (e.g., inlet or outlet) at a time, not both. As a result, it would not have been expected that locating an inlet connection point (e.g., the third connection point) and an outlet connection point (e.g., the second connection point) at the same header (e.g., the second header) would have produced an improved defrost cycle. In fact, such a modification would have been expected to decrease the effectiveness of the defrost cycle. Consequently, various embodiments of the present invention produce an unexpected result.
Even further, in various embodiments, refrigerant that, during at least part of the defrost cycle, passes through the third refrigerant conduit, through the defrost valve, and through the third connection point to the first heat exchanger (e.g., 11, 20, or 40), then passes through the second header (e.g., 22 or 42), heating the second header between the third connection point to the first heat exchanger and the second connection point to the first heat exchanger without passing through any cross tubes (e.g., 23) of the first heat exchanger. As used herein, refrigerant that passes through certain components of a heat exchanger “without passing through any cross tubes of the (e.g., first) heat exchanger” bypasses all of the cross tubes of the heat exchanger, whether such cross tubes are in the same row or different rows of the heat exchanger. As used herein, refrigerant passing through some of the cross tubes (e.g., whether or not cross tubes 23 shown) of a heat exchanger, but not through other cross tubes of that same heat exchanger (e.g., 23), is not sufficient to meet the condition of not passing through “any” cross tubes of the heat exchanger.
Further, in some such embodiments, the first heat exchanger includes a top (e.g., 28 or 48) and a bottom (e.g., 29 or 49), the first header (e.g., 21 or 41) extends across the top of the first heat exchanger, and the second header (e.g., 22 or 42) extends across the bottom of the first heat exchanger. Further still, in certain embodiments, the first header is horizontal and the second header is horizontal (e.g., as shown in
In a number of embodiments, the second header (e.g., 22 or 42), which is heated during the defrost cycle, extends (e.g., horizontally) across the bottom (e.g., 29 or 49) of the (e.g., first) heat exchanger (e.g., 11, 20, or 40). This configuration differs from that of typical prior art heat pumps, for example, where the headers are at the side and the cross tubes are horizontal, or from most prior art uses of microchannel heat exchangers. The fact that the second header extends across the bottom of the heat exchanger, in some embodiments, can help to defrost the heat exchanger because air surrounding the header is heated and rises to heat the fins above. In addition, in a number of embodiments, the less-dense hot refrigerant gas entering the second header at the third connection point (e.g., 113, 213, or 413) stays at the top of the second header heating the bottom ends of the cross tubes (e.g., 23, as shown in
Even further, in particular embodiments, the first heat exchanger (e.g., 20) consists essentially of the first header (e.g., 21), the second header (e.g., 22), the multiple cross tubes (e.g., 23), the multiple fins (e.g., 34) between the cross tubes (e.g., bonded to the cross tubes), the at least one first connection point (e.g., 111, 2111 and 2112, or 411) to the first heat exchanger, the second connection point (e.g., 112, 212, or 4121 and 4122) to the first heat exchanger, and the third connection point (e.g., 113, 213, or 413) to the first heat exchanger. As used herein, saying that a component “consists essentially of” a list of parts, means the component includes only those parts on the list plus additional parts that do not materially affect the basic characteristics of the component. Further, as used herein, saying that a heat exchanger “consists essentially of” a list of parts means that the heat exchanger cannot include any additional headers, cross tubes, or feeder tubes (i.e., connecting the headers to the cross tubes) not specifically included in the list of parts. In particular embodiments, the first heat exchanger has only two headers, the first header and the second header for example.
Still further, certain of these embodiments can include, for example, an extension tube (e.g., 44 shown in
Even further still, in particular embodiments (e.g., shown in
Additionally, in some such embodiments, the control system (e.g., 16) includes a digital controller (e.g., 160 shown in
What's more, in a number of embodiments, such a heat pump can include, for example, a first fan (e.g., 18 shown in
Still other embodiments include heat pumps (e.g., 10 or 50) that include, for example, a compressor (e.g., 13), at least one expansion device (e.g., 14, 17, or both), and a first heat exchanger (e.g., 11, 20, or 40) having a top (e.g., 28 or 48) and a bottom (e.g., 29 or 49). Such a heat exchanger can consist essentially of, for example, a first header (e.g., 21 or 41) extending across the top (e.g., 28 or 48) of the first heat exchanger, a second header (e.g., 22 or 42) extending across the bottom (e.g., 29 or 49) of the first heat exchanger, and multiple cross tubes (e.g., 23) extending from the first header to the second header, multiple fins (e.g., 34) between the cross tubes that are bonded to the cross tubes, and three types of connection points. In a number of such embodiments, each of the multiple cross tubes is directly connected to the first header, each of the multiple cross tubes is directly connected to the second header (e.g., as shown in
In a number of such embodiments, the heat pump further includes a first fan (e.g., 18) positioned and configured to move air through the first heat exchanger, a second heat exchanger (e.g., 12), and a first refrigerant conduit (e.g., 101) connecting a discharge port (e.g., 131) on the compressor to the at least one first connection point of the first heat exchanger (e.g., where the first refrigerant conduit does not include any part of the first heat exchanger). Further, in various embodiments, such a heat pump further includes a reversing valve (e.g., 150) located in the first refrigerant conduit between the discharge port on the compressor and the at least one first connection point of the first heat exchanger, a second refrigerant conduit (e.g., 102) connecting the second connection point of the first heat exchanger to the at least one expansion device, wherein the second refrigerant conduit does not include any part of the first heat exchanger, and a third refrigerant conduit (e.g., 103) connecting the first refrigerant conduit to the third connection point of the first heat exchanger.
Still further, a number of such embodiments include a defrost valve (e.g., 15), for example, located in the third refrigerant conduit (e.g., 103) between the first refrigerant conduit (e.g., 101) and the third connection point (e.g., 113, 213, or 413) of the first heat exchanger (e.g., wherein, when the defrost valve is closed, refrigerant flow through the third refrigerant conduit is blocked), and a fourth refrigerant conduit (e.g., 104) connecting the at least one expansion device to the second heat exchanger (e.g., 12). Even further, various embodiments include a fifth refrigerant conduit (e.g., 105) connecting the second heat exchanger to the reversing valve, a sixth refrigerant conduit (e.g., 106) connecting the reversing valve to an inlet port (e.g., 132) on the compressor, and a control system (e.g., 16) that controls the defrost valve, for example, that opens the defrost valve during the defrost cycle allowing refrigerant to flow through the third refrigerant conduit to the third connection point.
In a number of such embodiments, the control system (e.g., 16) includes a digital controller (e.g., 160), for example, having programming instructions (e.g., 161) to open the defrost valve during the defrost cycle to defrost the first heat exchanger between the third connection point and the second connection point, and having programming instructions (e.g., 162) to keep the defrost valve closed when the heat pump is not in the defrost cycle. Further, in various embodiments, the third refrigerant conduit connects to the first refrigerant conduit between the reversing valve and the at least one first connection point of the first heat exchanger, the first connection point is at the first header, the second connection point is at the second header, and the third connection point is at the second header. Further still, in a number of such embodiments, refrigerant that, during at least part of the defrost cycle passes through the third refrigerant conduit, through the defrost valve, and through the third connection point, passes through the second header (e.g., 22 or 42), heating the second header between the third connection point and the second connection point without passing through any cross tubes (e.g., 23) of the first heat exchanger. Moreover, in some such embodiments, the second header (e.g., 22 or 42) has a first end (e.g., 271 or 471) and a second end (e.g., 272 or 472), each of the multiple cross tubes connects to the second header between the first end and the second end, the second connection point to the first heat exchanger is at the second end (e.g., 272 or 472) of the second header, and the third connection point to the first heat exchanger is at the first end (e.g., 271 or 471) of the second header.
In a number of embodiments, during the defrost cycle, when the defrost valve (e.g., 15) is open, a first quantity of refrigerant passes from the compressor (e.g., 13, for instance, through discharge port 131 and first refrigerant conduit 101), and the defrost valve (e.g., 15), the third refrigerant conduit (e.g., 103), or both, are sized so that less than half of the first quantity of refrigerant from the compressor passes through the third connection point (e.g., 113, 213, or 413), and more than half of the first quantity of refrigerant from the compressor passes through the (e.g., at least one) first connection point (e.g., 111, 2111 and 2112, or 411). Further, in some embodiments, a centerline of the third connection point (e.g., 113, 213, or 413) is within 20 degrees from a centerline of the second header (e.g., 22 or 42). Further still, in some embodiments, a centerline of the third connection point (e.g., 113, 213, or 413) is within 20 degrees from a centerline of the cross tubes (e.g., 23).
In a number of embodiments, various methods include (e.g., in any order except where a particular order is explicitly indicated), at least certain acts. As used herein, “any order” includes acts being performed at the same time. The example of method 600, shown in
In the embodiment illustrated, method 600 also includes act 602 of delivering refrigerant from the compressor (e.g., 13) to the first connection point (e.g., 111 shown in
In this particular embodiment, method 600 also includes act 604 of (e.g., during the defrost cycle), passing the refrigerant from the second connection point (e.g., 112 shown in
In a number of embodiments, acts 602 to 605 may take place at the same time. Further, acts 602 to 605 may take place, in some embodiments, starting during act 601, for example, when act 601 begins. Moreover, where refrigerant is described as passing through one component and then another component, refrigerant may be passing through both components at the same time, but the word “then” indicates that the one component is located upstream from the other component. In the embodiment illustrated, method 600, shown in
Concerning acts 602 and 606, for example, as used herein, operating in a defrost mode or in a defrost cycle, to defrost the first heat exchanger, requires that the refrigerant be delivered from the compressor (e.g., 13) to the first heat exchanger (e.g., 11, 20, or 40) without the refrigerant passing through the second heat exchanger (e.g., 12) between the compressor and the first heat exchanger. Consequently, the refrigerant is hot when it reaches the first heat exchanger to defrost the first heat exchanger. The refrigerant can pass through other components, however, between the compressor and the first heat exchanger, such as reversing valve 150 shown in
In various embodiments, the heat pump can include a first fan (e.g., 18 shown in
In a number of embodiments, act 607 includes operating the first fan (e.g., 18) at a reduced or substantially reduced rate of speed (e.g., in the reversed direction) during the defrost cycle, in comparison with operation in the heating or cooling mode, for example. Moreover, in particular embodiments, the reduced or substantially reduced rate of speed can be accomplished in act 607 by intermittent operation (e.g., intermittent powering) or pulsing of power to the fan motor (e.g., 180), for instance, under the control of control system 16 or digital controller 160 (e.g., including programming instructions or software operating thereon). Reducing natural convection through the heat exchanger can result in the heat exchanger defrosting more effectively, more quickly, or both, for instance, at least under particular circumstances. Further, in certain embodiments, the fan (e.g., 18) may be operated, for instance, briefly, at a high speed in a forward or reversed direction (or both, alternately), for instance, at the end of the defrost cycle, to blow moisture, debris, or both from the heat exchanger or to dry the heat exchanger. Other embodiments, however, may omit this act of high-speed fan operation in the defrost cycle.
In different embodiments, acts 606, 607, or both, can be performed during all or part of the defrost cycle. For example, in certain embodiments, during a first portion of the defrost cycle, the refrigerant is not delivered to or passed through the third connection point (e.g., 113, 213, or 413). In other words, in this first portion of the defrost cycle, act 606 is not performed. The defrost valve (e.g., 15), for example, may remain closed during this first portion of the defrost cycle. Then during a second portion of the defrost cycle, this example of the method includes delivering and passing refrigerant through the third connection point (e.g., 113, 213, or 413), for instance, by opening the defrost valve (e.g., 15). Thus, act 606 is performed during the second portion of the defrost cycle, in this embodiment. During these different portions of the defrost cycle, different portions of the heat exchanger (e.g., 11, 20, or 40) are defrosted or defrosting is focused in those portions of the heat exchanger during these portions of the defrost cycle. In particular, in this example, in the case of heat exchanger 20 shown in
Furthermore, in different embodiments, the fan (e.g., 18) can be operated in the reversed direction (i.e., reversed in comparison with fan operation in the heating mode or the cooling mode) during all or part of the first portion of the defrost cycle, during all or part of the second portion of the defrost cycle, or both. In other words, in some embodiments, act 607 is performed during just part of the defrost cycle (e.g., started in act 601). In a number of embodiments, when the fan (e.g., 18) is not being operated in the reversed direction, the fan can be turned off. The speed of the fan (e.g., 18) in the reversed direction and the extent to which it is operated in the reversed direction, as opposed to being turned off, can be experimentally determined. In addition, the amount of time and sequence that the defrost valve is open or that hot refrigerant is delivered to the third connection point (e.g., 113, 213, or 413) can be experimentally determined. In other embodiments, however, feedback can be utilized to control one or more aspects of the defrost cycle. For example, in some embodiments, feedback from defrost sensor 25 shown in
Referring to
Referring to
In a number of embodiments, act 606, shown in
Some methods include just a portion of the acts illustrated in method 600 in
Further, various methods include act 608, shown in
In a number of embodiments, act 608, of returning to the heating mode, may include, for example, switching reversing valve 150 (i.e., to the heating mode), and operating fan 18 in the normal forward direction. There can be a delay, in some embodiments, before fan 18 is started in the forward direction, for instance, until heat exchanger 11 becomes cold. Compressor 13 and indoor air fan or second fan 19 can continue to operate (e.g., through act 608), in a number of embodiments. On the other hand, if the thermostat does not call for heating, act 608 of returning to the heating mode may include turning off the unit until heating is demanded by the thermostat. Act 608 may be initiated by control system 16 or digital controller 160, for example.
As mentioned, certain embodiments include methods (e.g., 600), for example, of defrosting a first heat exchanger (e.g., 11, 20, or 40) of a heat pump (e.g., 10 or 50). Such a heat pump can include, for example, as described, the first heat exchanger, a compressor (e.g., 13), at least one expansion device (e.g., 14, 17, or both), and a second heat exchanger (e.g., 12). Moreover, the first heat exchanger can include, for example, headers (e.g., 21 and 22, or 41 and 42), multiple cross tubes (e.g., 23), a first connection point (e.g., 111, 2111, 2112, or 411) to the first heat exchanger, a second connection point (e.g., 112, 212, 4121, or 4122) to the first heat exchanger, and a third connection point (e.g., 113, 213, or 413) to the first heat exchanger. In a number of embodiments, such a method can include (e.g., in any order except where a particular order is explicitly indicated), at least certain acts. Such acts may include, for example, an act (e.g., starting in act 601) of operating the heat pump in a defrost mode during a defrost cycle, for instance, including delivering refrigerant (e.g., in act 602) from the compressor to the first connection point (i.e., of the first heat exchanger).
Such a method can also include, in various embodiments, acts of, (e.g., during the defrost cycle), passing the refrigerant (e.g., in act 603) through the first heat exchanger from the first connection point (i.e., the first connection point of the first heat exchanger), through the multiple cross tubes, to the second connection point (e.g., of the first heat exchanger). Such a method can further include, in certain embodiments, (e.g., also during the defrost cycle) passing the refrigerant (e.g., in act 604) from the second connection point (i.e., of the first heat exchanger), through the at least one expansion device (e.g., 14), and then to the second heat exchanger (e.g., 12). Such a method can also include, in a number of embodiments, acts of, (e.g., during the defrost cycle), passing the refrigerant through the second heat exchanger, and then back to the compressor (e.g., in act 605), and (e.g., during at least part of the defrost cycle) delivering at least part of the refrigerant from the compressor to the third connection point of the first heat exchanger (e.g., in act 606). Further, such a method can also include, in various embodiments, an act of, (e.g., during the defrost cycle), passing the at least part of the refrigerant from the third connection point (i.e., of the first heat exchanger), through one of the headers (e.g., header 22 or 42), to the second connection point (i.e., of the first heat exchanger), without passing the at least part of the refrigerant through any of the cross tubes (e.g., 23) of the first heat exchanger.
Further, in some such embodiments, the one of the headers (e.g., 22 or 42) of the first heat exchanger (e.g., 11, 20, or 40) includes a first end (e.g., 271) and a second end (e.g., 272), each of the cross tubes connect to the one of the headers between the first end and the second end, and the second connection point (e.g., 212) of the first heat exchanger is at the second end (e.g., 272) of the one of the headers (e.g., 22). Further still, in various embodiments, the third connection point (e.g., 113 or 213) of the first heat exchanger (e.g., 11 or 20) is at the first end (e.g., 271) of the one of the headers (e.g., 22), and the act (e.g., 606) of passing the refrigerant from the third connection point (i.e., of the first heat exchanger), through the one of the headers (e.g., 22), to the second connection point (e.g., 112 or 212) of the first heat exchanger includes passing the refrigerant from the first end (e.g., 271), through the one of the headers (e.g., 22), to the second end (e.g., 272). Even further, in some such embodiments, each cross tube (e.g., 23) includes multiple contiguous parallel refrigerant passageways (e.g., 33 shown in
In a number of embodiments, the act of delivering refrigerant from the compressor to the third connection point of the first heat exchanger (e.g., in act 606) includes opening a solenoid valve (e.g., 15) in a bypass refrigerant line (e.g., 103) extending from a supply refrigerant line (e.g., 101) connected to the first connection point (e.g., 111, 2111, 2112, or 411) of the first heat exchanger, the bypass refrigerant line (e.g., 103) extending to the third connection point (e.g., 113, 213, or 413) of the first heat exchanger. Moreover, in some embodiments, such a method includes, during a first portion of the defrost cycle, not passing refrigerant through the third connection point (e.g., 113, 213, or 413) of the first heat exchanger, and during a second portion of the defrost cycle, passing refrigerant through the third connection point (e.g., 113, 213, or 413) of the first heat exchanger. Furthermore, in certain embodiments, the headers consist of a first header (e.g., 21 or 41) and a second header (e.g., 22 or 42), the first connection point (e.g., 111, 2111, 2112, or 411) to the first heat exchanger is at the first header, the second connection point to the first heat exchanger (e.g., 112, 212, 4121, or 4122) is at the second header, and the third connection point to the first heat exchanger (e.g., 113, 213, or 413) is at the second header (e.g., 22 or 42). Further, in a number of such embodiments, the act (e.g., 606) of passing the at least part of the refrigerant from the third connection point, through one of the headers, to the second connection point includes passing the at least part of the refrigerant through the second header (e.g., 22 or 42) without passing the at least part of the refrigerant through any of the cross tubes (e.g., 23) of the first heat exchanger.
In various embodiments, the first heat exchanger (e.g., 11, 20, or 40) is an outdoor air heat exchanger, the second heat exchanger (e.g., 12) is an indoor air heat exchanger, the first heat exchanger includes a top (e.g., 28 or 48) and a bottom (e.g., 29 or 49), the first header (e.g., 21 or 41) extends across the top of the first heat exchanger, and the second header (e.g., 22 or 42) extends across the bottom of the first heat exchanger. Further, in some embodiments, each cross tube (e.g., 23) of the first heat exchanger includes multiple contiguous parallel refrigerant passageways (e.g., 33) therethrough, each of the multiple cross tubes directly connects to the first header, and each of the multiple cross tubes directly connects to the second header. Even further, in some embodiments, the first heat exchanger further includes multiple fins (e.g., 34) between the cross tubes that are bonded to the cross tubes, and the act (e.g., 603) of passing the refrigerant through the first heat exchanger from the first connection point (i.e., of the first heat exchanger), through the multiple cross tubes, to the second connection point (i.e., of the first heat exchanger) includes heating the multiple fins between the cross tubes. Even further still, in some embodiments, the act (e.g., in act 606) of delivering refrigerant from the compressor to the third connection point (i.e., of the first heat exchanger) includes opening a solenoid valve (e.g., 15) in a bypass refrigerant line (e.g., 103) extending from a supply refrigerant line (e.g., 101) connected to the first connection point (e.g., 111, 2111, 2112, or 411), the bypass refrigerant line extending to the third connection point (e.g., 13, 213, or 413).
Various embodiments of the subject matter described herein include various combinations of the acts, structure, components, and features described herein, shown in the drawings, or known in the art. Moreover, certain procedures may include acts such as obtaining or providing various structural components described herein, obtaining or providing components that perform functions described herein. Furthermore, various embodiments include advertising and selling products that perform functions described herein, that contain structure described herein, or that include instructions to perform functions described herein, as examples. Such products may be obtained or provided through distributors, dealers, or over the Internet, for instance. The subject matter described herein also includes various means for accomplishing the various functions or acts described herein or apparent from the structure and acts described.
This patent application claims priority to international patent application serial number PCT/US2013/042266, filed under the Patent Cooperation Treaty (PCT) on May 22, 2013, titled: Defrosting A Heat Exchanger In A Heat Pump By Diverting Warm Refrigerant To An Exhaust Header, which claims priority to U.S. non-provisional patent application Ser. No. 13/477,973, filed on May 22, 2012, titled: Heat Pump With Improved Defrost Cycle and Method of Defrosting a Heat Exchanger. This patent application is also related to U.S. non-provisional patent application Ser. No. 13/572,116, filed on Aug. 10, 2012, titled: Method And Apparatus For Defrosting A Microchannel Heat Exchanger In A Heat Pump By Diverting Warm Refrigerant To An Exhaust Header, which also claims priority to U.S. non-provisional patent application Ser. No. 13/477,973. All of these related patent applications have the same inventors as the current patent application and the same assignee, and the contents of all of these related patent applications are incorporated herein by reference.
Number | Date | Country | |
---|---|---|---|
20140026601 A1 | Jan 2014 | US |
Number | Date | Country | |
---|---|---|---|
Parent | PCT/US2013/042266 | May 2013 | US |
Child | 14044786 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 13477973 | May 2012 | US |
Child | PCT/US2013/042266 | US |