Patent Application
20160238291
The application relates generally to vapor compression systems in refrigeration, air conditioning and chilled liquid systems.
Conventional chilled liquid systems used in heating, ventilation and air conditioning systems include an evaporator to effect a transfer of thermal energy between the refrigerant of the system and another liquid to be cooled. One type of evaporator includes a shell with a plurality of tubes forming a tube bundle, or a plurality of tube bundles, through which the liquid to be cooled is circulated. The refrigerant is brought into contact with the outer or exterior surfaces of the tube bundle inside the shell, resulting in a transfer of thermal energy between the liquid to be cooled and the refrigerant. For example, refrigerant can be deposited onto the exterior surfaces of the tube bundle by spraying or other similar techniques in what is commonly referred to as a “falling film” evaporator. In a further example, the exterior surfaces of the tube bundle can be fully or partially immersed in liquid refrigerant in what is commonly referred to as a “flooded” evaporator. In yet another example, a portion of the tube bundle can have refrigerant deposited on the exterior surfaces and another portion of the tube bundle can be immersed in liquid refrigerant in what is commonly referred to as a “hybrid falling film” evaporator.
As a result of the thermal energy transfer with the liquid, the refrigerant is heated and converted to a vapor state, which is then returned to a compressor where the vapor is compressed, to begin another refrigerant cycle. The cooled liquid can be circulated to a plurality of heat exchangers located throughout a building. Warmer air from the building is passed over the heat exchangers where the cooled liquid is warmed, while cooling the air for the building. The liquid warmed by the building air is returned to the evaporator to repeat the process.
The present invention relates to a vapor compression system including a compressor, a condenser, an expansion device and an evaporator connected by a refrigerant line. The evaporator includes a shell, a first tube bundle; a hood; a distributor; a first supply line; a second supply line; a valve positioned in the second supply line; and a sensor. The first tube bundle includes a plurality of tubes extending substantially horizontally in the shell. The distributor is positioned above the first tube bundle. The hood covers the first tube bundle. The first supply line is connected to the distributor and an end of the second supply line is positioned near the hood. The sensor is configured and positioned to sense a level of liquid refrigerant in the shell. The valve is configured and positioned to regulate flow in the second supply line in response to a sensed level of liquid refrigerant from the level sensor.
The present invention also relates to a vapor compression system includes a compressor, a condenser, an expansion device and an evaporator connected by a refrigerant line. The evaporator includes a shell; a first tube bundle; a hood; a distributor; a supply line; a pump; an expansion device; a sensor; and wherein the first tube bundle comprises a plurality of tubes extending substantially horizontally in the shell. The distributor is positioned above the first tube bundle. The hood covers the first tube bundle. The supply line is connected to the expansion device and the expansion device is connected to a discharge of the pump. The sensor is configured and positioned to sense a level of liquid refrigerant in the shell. The pump is operated in response to a sensed level of liquid refrigerant decreasing below a predetermined level when the expansion device is in an open position.
The present invention further relates to an evaporator including a shell; a tube bundle; an enclosure; and a supply line. The tube bundle includes a plurality of tubes extending substantially horizontally in the shell. The enclosure receives refrigerant from the supply line and provides liquid refrigerant for the tube bundle and vapor refrigerant for an outlet connection in the shell.
Motor 50 used with compressor 32 can be powered by a variable speed drive (VSD) 52 or can be powered directly from an alternating current (AC) or direct current (DC) power source. VSD 52, if used, receives AC power having a particular fixed line voltage and fixed line frequency from the AC power source and provides power having a variable voltage and frequency to motor 50. Motor 50 can include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source. For example, motor 50 can be a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor or any other suitable motor type. In an alternate exemplary embodiment, other drive mechanisms such as steam or gas turbines or engines and associated components can be used to drive compressor 32.
Compressor 32 compresses a refrigerant vapor and delivers the vapor to condenser 34 through a discharge line. Compressor 32 can be a centrifugal compressor, screw compressor, reciprocating compressor, rotary compressor, swing link compressor, scroll compressor, turbine compressor, or any other suitable compressor. The refrigerant vapor delivered by compressor 32 to condenser 34 transfers heat to a fluid, for example, water or air. The refrigerant vapor condenses to a refrigerant liquid in condenser 34 as a result of the heat transfer with the fluid. The liquid refrigerant from condenser 34 flows through expansion device 36 to evaporator 38. In the exemplary embodiment shown in
The liquid refrigerant delivered to evaporator 38 absorbs heat from another fluid, which may or may not be the same type of fluid used for condenser 34, and undergoes a phase change to a refrigerant vapor. In the exemplary embodiment shown in
In the “surface intercooler” arrangement, the implementation is slightly different, as known to those skilled in the art. Intermediate circuit 64 can operate in a similar matter to that described above, except that instead of receiving the entire amount of refrigerant from condenser 34, as shown in
Liquid refrigerant that flows around the tubes of tube bundle 78 without changing state collects in the lower portion of shell 76. The collected liquid refrigerant can form a pool or reservoir of liquid refrigerant 82. The deposition positions from distributor 80 can include any combination of longitudinal or lateral positions with respect to tube bundle 78. In another exemplary embodiment, deposition positions from distributor 80 are not limited to ones that deposit onto the upper tubes of tube bundle 78. Distributor 80 may include a plurality of nozzles supplied by a dispersion source of the refrigerant. In an exemplary embodiment, the dispersion source is a tube connecting a source of refrigerant, such as condenser 34. Nozzles include spraying nozzles, but also include machined openings that can guide or direct refrigerant onto the surfaces of the tubes. The nozzles may apply refrigerant in a predetermined pattern, such as a jet pattern, so that the upper row of tubes of tube bundle 78 are covered. The tubes of tube bundle 78 can be arranged to promote the flow of refrigerant in the form of a film around the tube surfaces, the liquid refrigerant coalescing to form droplets or in some instances, a curtain or sheet of liquid refrigerant at the bottom of the tube surfaces. The resulting sheeting promotes wetting of the tube surfaces which enhances the heat transfer efficiency between the fluid flowing inside the tubes of tube bundle 78 and the refrigerant flowing around the surfaces of the tubes of tube bundle 78.
In the pool of liquid refrigerant 82, a tube bundle 140 can be immersed or at least partially immersed, to provide additional thermal energy transfer between the refrigerant and the process fluid to evaporate the pool of liquid refrigerant 82. In an exemplary embodiment, tube bundle 78 can be positioned at least partially above (that is, at least partially overlying) tube bundle 140. In one exemplary embodiment, evaporator 138 incorporates a two pass system, in which the process fluid that is to be cooled first flows inside the tubes of tube bundle 140 and then is directed to flow inside the tubes of tube bundle 78 in the opposite direction to the flow in tube bundle 140. In the second pass of the two pass system, the temperature of the fluid flowing in tube bundle 78 is reduced, thus requiring a lesser amount of heat transfer with the refrigerant flowing over the surfaces of tube bundle 78 to obtain a desired temperature of the process fluid.
It is to be understood that although a two pass system is described in which the first pass is associated with tube bundle 140 and the second pass is associated with tube bundle 78, other arrangements are contemplated. For example, evaporator 138 can incorporate a one pass system where the process fluid flows through both tube bundle 140 and tube bundle 78 in the same direction. Alternatively, evaporator 138 can incorporate a three pass system in which two passes are associated with tube bundle 140 and the remaining pass associated with tube bundle 78, or in which one pass is associated with tube bundle 140 and the remaining two passes are associated with tube bundle 78. Further, evaporator 138 can incorporate an alternate two pass system in which one pass is associated with both tube bundle 78 and tube bundle 140, and the second pass is associated with both tube bundle 78 and tube bundle 140. In one exemplary embodiment, tube bundle 78 is positioned at least partially above tube bundle 140, with a gap separating tube bundle 78 from tube bundle 140. In a further exemplary embodiment, hood 86 overlies tube bundle 78, with hood 86 extending toward and terminating near the gap. In summary, any number of passes in which each pass can be associated with one or both of tube bundle 78 and tube bundle 140 is contemplated.
An enclosure or hood 86 is positioned over tube bundle 78 to substantially prevent cross flow, that is, a lateral flow of vapor refrigerant or liquid and vapor refrigerant 106 between the tubes of tube bundle 78. Hood 86 is positioned over and laterally borders tubes of tube bundle 78. Hood 86 includes an upper end 88 positioned near the upper portion of shell 76. Distributor 80 can be positioned between hood 86 and tube bundle 78. In yet a further exemplary embodiment, distributor 80 may be positioned near, but exterior of, hood 86, so that distributor 80 is not positioned between hood 86 and tube bundle 78. However, even though distributor 80 is not positioned between hood 86 and tube bundle 78, the nozzles of distributor 80 are still configured to direct or apply refrigerant onto surfaces of the tubes. Upper end 88 of hood 86 is configured to substantially prevent the flow of applied refrigerant 110 and partially evaporated refrigerant, that is, liquid and/or vapor refrigerant 106 from flowing directly to outlet 104. Instead, applied refrigerant 110 and refrigerant 106 are constrained by hood 86, and, more specifically, are forced to travel downward between walls 92 before the refrigerant can exit through an open end 94 in the hood 86. Flow of vapor refrigerant 96 around hood 86 also includes evaporated refrigerant flowing away from the pool of liquid refrigerant 82.
It is to be understood that at least the above-identified, relative terms are non-limiting as to other exemplary embodiments in the disclosure. For example, hood 86 may be rotated with respect to the other evaporator components previously discussed, that is, hood 86, including walls 92, is not limited to a vertical orientation. Upon sufficient rotation of hood 86 about an axis substantially parallel to the tubes of tube bundle 78, hood 86 may no longer be considered “positioned over” nor to “laterally border” tubes of tube bundle 78. Similarly, “upper” end 88 of hood 86 may no longer be near “an upper portion” of shell 76, and other exemplary embodiments are not limited to such an arrangement between the hood and the shell. In an exemplary embodiment, hood 86 terminates after covering tube bundle 78, although in another exemplary embodiment, hood 86 further extends after covering tube bundle 78.
After hood 86 forces refrigerant 106 downward between walls 92 and through open end 94, the vapor refrigerant undergoes an abrupt change in direction before traveling in the space between shell 76 and walls 92 from the lower portion of shell 76 to the upper portion of shell 76. Combined with the effect of gravity, the abrupt directional change in flow results in a proportion of any entrained droplets of refrigerant colliding with either liquid refrigerant 82 or shell 76, thereby removing those droplets from the flow of vapor refrigerant 96. Also, refrigerant mist traveling along the length of hood 86 between walls 92 is coalesced into larger drops that are more easily separated by gravity, or maintained sufficiently near or in contact with tube bundle 78, to permit evaporation of the refrigerant mist by heat transfer with the tube bundle. As a result of the increased drop size, the efficiency of liquid separation by gravity is improved, permitting an increased upward velocity of vapor refrigerant 96 flowing through the evaporator in the space between walls 92 and shell 76. Vapor refrigerant 96, whether flowing from open end 94 or from the pool of liquid refrigerant 82, flows over a pair of extensions 98 protruding from walls 92 near upper end 88 and into a channel 100. Vapor refrigerant 96 enters into channel 100 through slots 102, which is the space between the ends of extensions 98 and shell 76, before exiting evaporator 138 at an outlet 104. In another exemplary embodiment, vapor refrigerant 96 can enter into channel 100 through openings or apertures formed in extensions 98, instead of slots 102. In yet another exemplary embodiment, slots 102 can be formed by the space between hood 86 and shell 76, that is, hood 86 does not include extensions 98.
Stated another way, once refrigerant 106 exits from hood 86, vapor refrigerant 96 then flows from the lower portion of shell 76 to the upper portion of shell 76 along the prescribed passageway. In an exemplary embodiment, the passageways can be substantially symmetric between the surfaces of hood 86 and shell 76 prior to reaching outlet 104. In an exemplary embodiment, baffles, such as extensions 98 are provided near the evaporator outlet to prevent a direct path of vapor refrigerant 96 to the compressor inlet.
In one exemplary embodiment, hood 86 includes opposed substantially parallel walls 92. In another exemplary embodiment, walls 92 can extend substantially vertically and terminate at open end 94, that is located substantially opposite upper end 88. Upper end 88 and walls 92 are closely positioned near the tubes of tube bundle 78, with walls 92 extending toward the lower portion of shell 76 so as to substantially laterally border the tubes of tube bundle 78. In an exemplary embodiment, walls 92 may be spaced between about 0.02 inch (0.5 mm) and about 0.8 inch (20 mm) from the tubes in tube bundle 78. In a further exemplary embodiment, walls 92 may be spaced between about 0.1 inch (3 mm) and about 0.2 inch (5 mm) from the tubes in tube bundle 78. However, spacing between upper end 88 and the tubes of tube bundle 78 may be significantly greater than 0.2 inch (5 mm), in order to provide sufficient spacing to position distributor 80 between the tubes and the upper end of the hood. In an exemplary embodiment in which walls 92 of hood 86 are substantially parallel and shell 76 is cylindrical, walls 92 may also be symmetric about a central vertical plane of symmetry of the shell bisecting the space separating walls 92. In other exemplary embodiments, walls 92 need not extend vertically past the lower tubes of tube bundle 78, nor do walls 92 need to be planar, as walls 92 may be curved or have other non-planar shapes. Regardless of the specific construction, hood 86 is configured to channel refrigerant 106 within the confines of walls 92 through open end 94 of hood 86.
As shown in
In an exemplary embodiment, one arrangement of tubes or tube bundles may be defined by a plurality of uniformly spaced tubes that are aligned vertically and horizontally, forming an outline that can be substantially rectangular. However, a stacking arrangement of tube bundles can be used where the tubes are neither vertically or horizontally aligned, as well as arrangements that are not uniformly spaced.
In another exemplary embodiment, different tube bundle constructions are contemplated. For example, finned tubes (not shown) can be used in a tube bundle, such as along the uppermost horizontal row or uppermost portion of the tube bundle. Besides the possibility of using finned tubes, tubes developed for more efficient operation for pool boiling applications, such as in “flooded” evaporators, may also be employed. Additionally, or in combination with the finned tubes, porous coatings can also be applied to the outer surface of the tubes of the tube bundles.
In a further exemplary embodiment, the cross-sectional profile of the evaporator shell may be non-circular.
In an exemplary embodiment, a portion of the hood may partially extend into the shell outlet.
In addition, it is possible to incorporate the expansion functionality of the expansion devices of system 14 into distributor 80. In one exemplary embodiment, two expansion devices may be employed. One expansion device is exhibited in the spraying nozzles of distributor 80. The other expansion device, for example, expansion device 36, can provide a preliminary partial expansion of refrigerant, before that provided by the spraying nozzles positioned inside the evaporator. In an exemplary embodiment, the other expansion device, that is, the non-spraying nozzle expansion device, can be controlled by the level of liquid refrigerant 82 in the evaporator to account for variations in operating conditions, such as evaporating and condensing pressures, as well as partial cooling loads. In an alternative exemplary embodiment, expansion device can be controlled by the level of liquid refrigerant in the condenser, or in a further exemplary embodiment, a “flash economizer” vessel. In one exemplary embodiment, the majority of the expansion can occur in the nozzles, providing a greater pressure difference, while simultaneously permitting the nozzles to be of reduced size, therefore reducing the size and cost of the nozzles.
While only certain features and embodiments of the invention have been shown and described, many modifications and changes may occur to those skilled in the art (for example, variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (for example, temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (that is, those unrelated to the presently contemplated best mode of carrying out the invention, or those unrelated to enabling the claimed invention). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.
This application is a divisional of, claiming priority and benefit from U.S. application Ser. No. 12/747,286, entitled VAPOR COMPRESSION SYSTEM, having a filing date of Sep. 3, 2010, which is a PCT National Stage Entry of, claiming priority and benefit from PCT/US09/30592, entitled VAPOR COMPRESSION SYSTEM, having a filing date of Jan. 9, 2009, which claims priority and benefit from U.S. Provisional Application No. 61/020,533, entitled FALLING FILM EVAPORATOR SYSTEMS, filed Jan. 11, 2008, all of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61020533 | Jan 2008 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12747286 | Sep 2010 | US |
| Child | 15137759 | US |
