Patent Application
20110265499
HVAC systems involving water-to-water central heat pumps are becoming more common. In their most basic form, such systems include a heat pump that warms or cools HVAC fluid circulated through pipes within a building. A fan blows air from the conditioned space across warmed or cooled coils connected to the pipes. The temperature of the air blown from the fan across the coil (typically done by a fan coil unit) is thus affected by the temperature-controlled HVAC fluid flowing within the pipes. By controlling the temperature and flow rate of the HVAC fluid within the pipes, the location and configuration of the pipes and fan coil(s), the speed and capacity of the fan coil(s), and the parameters of various additional equipment that may be incorporated into the system, the conditioned space can be maintained at required conditions with relative ease.
Although heat pump HVAC systems are commonly more efficient than conventional HVAC systems, they still consume electrical energy to operate. Differently configured heat pump HVAC systems vary in energy consumption and efficiency. Most systems do not take advantage of various sources of “free” energy. Additionally, most early heat pump HVAC systems were slow to respond to building and space load changes and were more difficult for users to control than conventional HVAC systems. When they thus rely upon backup systems, such as electric duct heaters, they can have relatively high instantaneous electricity demand and overall higher electricity consumption. The distributed small compressors create noise and vibration problems and require continuous HVAC liquid flow rates to stay operational. The total system power consumption can become a significant related expense that devalues the energy and operation cost savings the technology can create.
In some embodiments, the present invention provides an energy efficient HVAC system that optionally includes a water-to-water heat pump, along with one or more components configured to take advantage of unused energy sources and/or energy sinks, thereby significantly reducing the amount of energy that is potentially required to be added to the system for efficient operation.
In some embodiments, the present invention provides a heat pump including two heat exchangers connected by two or more refrigeration circuits, with each circuit having an expansion valve and a compressor that are optionally in electronic communication with a main controller, thereby permitting relatively precise remote control of the heat pump.
In some embodiments, the present invention provides a group of multi-circuit water-to-water heat pumps connected together in parallel in a modular fashion, with each circuit of each heat pump having a remotely controllable expansion valve and/or compressor, thereby providing a highly flexible and responsive heat pump system.
In some embodiments, the present invention provides multiple individual heat pumps and/or groups of heat pumps connected in parallel (see previous paragraph) that are connected in series in order to achieve a relatively large temperature difference, with each heat pump or heat pump group being configured to operate within its optimal temperature range in incrementally achieving the relatively large temperature difference.
In some embodiments, the present invention provides a method of operating a multi-circuit heat pump, including (a) receiving instructions concerning what is needed of the heat pump from a main controller based on input from sensors located in various places in the HVAC system and (b) responding to those instructions by activating (or maintaining activation of) or deactivating (or maintaining deactivation of) one or more compressors in a selected sequence and at selected time intervals, provided that such response is not restricted based on the detection of heat pump or HVAC system irregularities.
In some embodiments, the present invention provides a method of monitoring for irregularities in heat pumps that are either activated or pending activation to prevent premature wear or failure of heat pump components and/or to improve energy efficiency in the heat pumps.
In some embodiments, the present invention provides an energy transfer component that includes an outer tube made of thermally conductive material and a concentric inner tube that can be made of thermally insulative material, with (a) HVAC fluid flowing turbulently through the channel between the inner and outer tubes, optionally guided by a spiraling barrier, such that heat transfer occurs between the turbulently flowing HVAC liquid and the surrounding earth, water, or combination thereof and (b) HVAC fluid flowing laminarly inside the inner tube, thereby minimizing heat transfer between the HVAC fluid flowing between the inner and outer tubes and the HVAC fluid flowing inside the inner tube.
In some embodiments, the present invention provides system components assembled as a modular box, which enables fast and easy installation and replacement of the modular box, thereby permitting assembly and repair of the distribution equipment in a more suitable setting, such as a machine shop.
In some embodiments, the present invention provides a distribution system that optionally accommodates potable water as the HVAC fluid by regularly circulating the potable water through a single coil in a fan box, that optionally includes a controller, that is in electronic communication with a main controller and/or one or more other components of the HVAC system.
Details of several aspects and embodiments of the present invention are provided herein.
Related technology is disclosed in commonly owned U.S. patent application Ser. No. 12/607,535 (filed on Oct. 28, 2009 and titled HIGH-EFFICIENCY HEAT PUMPS); Ser. No. 12/607,760 (filed on Oct. 28, 2009 and titled METHODS AND EQUIPMENT FOR GEOTHERMALLY EXCHANGING ENERGY); Ser. No. 12/607,679 (filed on Oct. 28, 2009 and titled METHODS AND EQUIPMENT FOR HEATING AND COOLING BUILDING ZONES). Each of the applications noted in this paragraph are hereby incorporated by reference herein in their entirety
The following drawings are illustrative of particular embodiments of the present invention and therefore do not limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements.
The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments of the present invention. Examples of constructions, materials, dimensions, and manufacturing processes are provided for selected elements, and all other elements employ that which is known to those of skill in the field of the invention. Those skilled in the art will recognize that many of the examples provided have suitable alternatives that can be utilized.
It should be emphasized that the HVAC system of
The illustrative HVAC system of
This energy transfer can simultaneously (a) absorb heat energy into the heat pump refrigerant changing from liquid to gas at the evaporator heat exchanger 38, thereby chilling the HVAC fluid at the evaporator heat exchanger 38, and (b) reject heat from the heat pump refrigerant by temperature difference at the condenser heat exchanger 34, thereby heating the HVAC fluid at the condenser heat exchanger 34. In this way, cooling some HVAC fluid can be the free by-product of heating other HVAC fluid, and vice versa, from the same compressor work.
In heating the conditioned space 6, HVAC fluid can exit the heat pump 8 through heating loop 40 after passing through the condenser heat exchanger 34 and can then enter the conditioned space 6. In cooling the conditioned space 6, HVAC fluid can exit the heat pump 8 through cooling loop 42 after passing through the evaporator heat exchanger 38.
In some embodiments, components of the heat pump 8 can be selected and/or configured according to particular applications. In many embodiments, the heat pump 8 can have two or more refrigerant circuits.
Inside the heat pump 140, two separate circuits (circuit A and circuit B in
In many embodiments, the evaporator heat exchanger 142 and/or the condenser heat exchanger 144 are plate-and-frame heat exchangers. Heat pump refrigerant and HVAC fluid can be channeled through alternating gaps between the plates. The plates can be made of thermally conductive material in order to facilitate heat transfer between the heat pump refrigerant and the HVAC fluid. Heat transfer can occur according to the design of the heat exchangers 142, 144 and the HVAC system when the heat pump refrigerant and the HVAC fluid are both flowing through the respective gaps between the plates. In many embodiments, such as that of
For dual-circuit heat pumps, the heat pump refrigerant from one circuit can alternate with the heat pump refrigerant from the other circuit when flowing through the heat exchanger (evaporator 142 or condenser 144). In many embodiments, the heat exchangers can be of the brazed plate type, in which case the heat transfer fluids would flow through gaps between sealed plates. The respective fluids in the heat exchanger gaps would alternate between (a) heat pump refrigerant from circuit A, (b) HVAC fluid, (c) heat pump refrigerant from circuit B, (d) HVAC fluid, (e) heat pump refrigerant from circuit A, and so on. If both of the compressors 146A, 146B were operational, both gaps neighboring the HVAC fluid would have flowing heat pump refrigerant, meaning that the designed heat transfer could occur across each plate. If only one of the compressors 146A, 146B were operational, only one of the gaps neighboring the HVAC fluid would have flowing heat pump refrigerant, meaning that the designed heat transfer could occur across only half of the plates. If neither of the compressors 146A, 146B were operational, neither of the gaps neighboring the HVAC fluid would have flowing heat pump refrigerant, meaning that the designed heat transfer could not occur across any of the plates. By making operational both, either, or neither of the compressors 146A, 146B, the heat pump can operate at 100%, 50%, or 0% capacity.
In some embodiments, the absorption of heat from the HVAC fluid in the evaporator heat exchanger 142 in one or both of the heat pump circuits can be controlled via the expansion valves 148A, 148B. In many embodiments, the expansion valves 148A, 148B can be electronic expansion valves, which can control the superheat from the evaporator heat exchanger 142 across a broad range of valve percentages (e.g., from 0% to 100%). Many electronic expansion valves can react faster and more precisely to changing conditions in the evaporator heat exchanger 142 than a conventional expansion valve. Some electronic expansion valves can be configured to communicate electronically with an operator and/or a controller through a network (e.g., the Internet). In this way, the electronic expansion valves can be monitored and adjusted remotely. Often, the precise control of electronic expansion valves' superheat setting provides significant savings on operational costs. The high range of valve control and internal programming can enable continuous operation over a wider range of conditions from ice making to hot water heating on the same common refrigerant charge.
The performance of the dual-circuit heat pump 140 can be impacted by a variety of factors. As noted above, in some embodiments, the number of compressors 146A, 146B that are operational (along with, in some embodiments, modulation of one or both of the compressors 146A, 146B) can impact the performance of the heat pump 140. As also noted above, the pressure of the heat pump refrigerant in one or both of the circuits, as controlled via the expansion valves 148A, 148B, can impact the performance of the heat pump 140. In some embodiments, the selection of the heat pump refrigerant can impact the performance of the heat pump 140. Different heat pump refrigerants change states at different temperatures and pressures. The overall efficiency of the heat pump 140 can be affected by the characteristics of the refrigerant, including the energy absorbed or given off during a change of state. Thus, the selection of a heat pump refrigerant can have a significant impact on, e.g., the temperature difference across the heat pump 140 and the work input to motivate the temperature difference. In some embodiments, the volume of heat pump refrigerant added to either or both of the circuits can impact the performance of the heat pump 140. In some embodiments, the volume of oil in the heat pump refrigerant can impact performance of the heat pump 140. One or more of these and similar factors can be controlled to provide optimal heat pump performance, depending on the circumstances of the particular application. In some embodiments, the dual-circuit heat pump can reduce the number of mechanical connections and fittings for the HVAC fluids, thereby reducing flow restrictions while at the same time increasing performance.
In many embodiments, the heat pump 140 is designed and/or configured to produce repeatable temperature differences across the respective heat exchangers 142, 144. In some instances, flow properties of the HVAC fluid in the chilled HVAC fluid loop 152 and/or the hot HVAC fluid loop 154 can be adjusted with control valves 156, 157, 158, 159 to achieve temperature differences across the heat exchangers 142, 144 that differ from those that would have been achieved in absence of the adjustment with the control valves 156, 157, 158, 159. In some embodiments, a percentage of the HVAC fluid can bypass a heat exchanger by means of one or more bypass valves.
In some embodiments, multiple heat pumps 140 are made in modular fashion, such that each heat pump 140 is a self-contained unit with clearly defined interfaces to other HVAC system components, including other heat pumps. Such a setup can provide a significant degree of flexibility in operating capacity percentage. The number of heat pumps (and specifically the number of compressors) is directly related to the number of operating capacity levels. The number of operating capacity levels is equal to the number of compressors plus one (accounting for 0% operating capacity). For example, with five dual-circuit heat pumps connected in parallel, there are eleven operating capacity levels. Assuming that all five heat pumps have similar configurations, the heat pumps collectively can operate at 0% (none of the compressors operational), 10% (one of the ten compressors operational), 20% (two of the ten compressors operational), and so on. The HVAC fluid flow can have equivalent capacity levels of reduced pumping energy with each refrigerant circuit still operating at optimum capacity and efficiency. In this way, the heat pumps collectively can provide what the HVAC system demands in a more precisely tailored fashion, thereby significantly improving energy efficiency.
Heat pumps according to the present invention can be controlled in a variety of ways.
Referring to
Referring again to
In many embodiments, the instructions call for the activation or deactivation of one or both of the heat pump's compressors. The heat pump controller can determine whether the instructions call for deactivation of both compressors (deactivate if activated or remain deactivated if already deactivated) (206). If the heat pump controller determines that the instructions indeed call for deactivation of both compressors, the heat pump controller can signal both compressors accordingly (208, 210), which can result in both compressors being stopped (212, 214). If the heat pump determines that the instructions call for activation of at least one compressor (activate if deactivated or remain activated if already activated), the heat pump can move to the next level of analysis.
If the heat pump controller determines that the instructions call for activation of at least one of the compressors, the heat pump controller can determine whether the instructions call for activation of only one of the compressors (216) or activation of both of the compressors (218). If the heat pump controller determines that the instructions call for activation of only one of the compressors, the heat pump controller can signal activation of either compressor A (220) or compressor B (222). This can result in a call of compressor A (224) or compressor B (226), pending inspection for irregularities (described in greater detail below). Whichever compressor is not called is/remains deactivated (212, 214).
When instructions call for activation of only one compressor, the heat pump controller can call either compressor A or compressor B based on an alternating or priority wear schedule. If either compressor A or compressor B were always called in this situation, that compressor would wear significantly faster than the other. Accordingly, a schedule can be established to encourage even wear of the two compressors or the preservation of one of the components. The digital control of the embodiment can enable many scheduling variations. In some embodiments, the heat pump controller determines which of the compressors to call. In some embodiments, the main controller determines which of the two controllers to call.
When the heat pump controller determines that the heat pump controller calls for activation of both compressors, the heat pump controller can signal activation of the compressors in a staggered fashion. In some instances, the heat pump controller can signal activation of compressor A first, followed by activation of compressor B after a time delay (228). This can result in (a) a call of compressor A (224), pending inspection for irregularities, (b) a period of delay as determined by reduced Amperage of the first stage and verification after the delay of a continued need, and (c) a call of compressor B (226), pending inspection for irregularities. In some instances, the heat pump controller can signal activation of compressor B first, followed by activation of compressor A after a delay (230). This can result in (a) a call of compressor B (226), pending inspection for irregularities, (b) a period of delay and confirmations, and (c) a call of compressor A (224), pending inspection for irregularities. Which compressor to activate first is often determined according to a schedule designed to reduce the likelihood of uneven wear between the compressors or overall long-term reliability of the system. The heat pump controller and/or the main controller can make this determination in a manner similar to the determination of which compressor to call when only one compressor is requested.
In some embodiments, the call for activation of a compressor can open the source valve SV for the cold HVAC fluid to the evaporator heat exchanger and open the load (moderate) valve MV for the hot HVAC fluid to the condenser heat exchanger. In many embodiments, the valves will close when both compressors are off. Operating the valves in this manner can reduce the pumping costs of the system, enable modules to operate at lower system flows, and prevent refrigerant migrations within the heat pump system from occurring when the heat pump is not active.
As alluded to above, before activating one or both of the compressors, the heat pump can be inspected for one or more irregularities (232, 234). Such an inspection can also be called a safety inspection in reference to making sure that activation of the compressor(s) will not damage the heat pump. If the heat pump controller determines that activation of either of the compressors (232, 234) would be unsafe, the heat pump controller can disable the activation of the compressor(s) (212, 214). If the heat pump controller determines that activation of one or both compressors would not be unsafe (232, 234), the heat pump controller can proceed with activation of the compressor(s) (236, 238).
The heat pump controller can first activate the method (250). When a compressor is called, but before the compressor is turned on, the method can be activated. If the method detects no irregularities, the compressor can be turned on. In many embodiments, while the compressor is turned on, the method can run on a continuous basis. In such embodiments, if the method detects an irregularity or safety concern while the compressor is operating, the heat pump controller can cause the compressor to be deactivated. In most embodiments, the method of
In many embodiments, the method of
With the method in active mode, the heat pump controller can run a variety of safety tests. One test can prevent compressors from being subjected to repeated short cycles (252). A compressor subjected to repeated short cycles can wear prematurely or be damaged. Embodiments of the present invention can prevent short cycles, thereby reducing the likelihood of premature wear of the compressor or heat pump failure. The heat pump controller can determine whether a compressor was just recently deactivated (e.g., within the past 10 or 15 minutes). In such a situation, the heat pump controller typically delays activation of the compressor to give it an appropriate amount of recovery (e.g., 10-15 minutes). Given the large size of most HVAC systems and given the fact that gradual changes in space conditions are typically desirable, the delay in activation of one compressor does not typically impede performance of the HVAC system.
If the heat pump controller determines that the compressor was recently deactivated, the heat pump controller can generate an alarm signal, signifying a condition in which operation of the compressor would be unsafe to the compressor (254). If the test identifies a potentially unsafe short cycle in compressor A, the unsafe condition is associated with compressor A (256). If the test identifies a potentially unsafe short cycle in compressor B, the unsafe condition is associated with compressor B (258). Referring to
Referring again to
The third test of the illustrative method of
The fourth test of the illustrative method of
The fifth test of the illustrative method of
The sixth test of the illustrative method of
The seventh test of the illustrative method of
The eighth test of the illustrative method of
Monitoring for heat pump irregularities, e.g., by the illustrative method shown in
Many heat pump embodiments described herein can be assembled according to a variety of methods.
Compressors can be added to the heat pump frame (101). In many embodiments, the compressor is a scroll compressor. The compressor can be smooth in operation, compact, with good motor protection. The compact size of such embodiments can permit the compressor to be built into relatively small heat pump frames and modules that can be introduced to retrofit spaces through normal doorways. In some embodiments, the compressor includes relatively few moving parts with better reliability. In some embodiments, the compressor is quieter and more energy efficient than other compressors. An example of a compressor that is suitable for some embodiments of the present invention is the Copeland Scroll ZR380. One advantage of using many such compressors according to embodiments of the present invention is the relatively quiet operation. Quiet operation of the compressor can enable a tolerable noise level in a mechanical room, even with open construction of some embodiments. This allows an operator to readily see piping (e.g. to observe frosting, etc.) without the removal of covers or other sound attenuation panels. One advantage of using many such compressors according to embodiments of the present invention is staging of capacity to achieve ideal compressor loading. Staging of compressors on individual refrigeration circuits enhances reliability and performance of the HVAC system.
Condenser and evaporator heat exchangers can be added to the heat pump frame (102). The evaporator and condenser heat exchangers can be piped with the relevant compressors (103) in common or separate refrigerant circuits for the common hot and cold HVAC fluids. In some embodiments, components of the dryer shell can be silver soldered or Sil-Fos welded to minimize leaks. In some embodiments, the core of the dryer can be removed and replaced simply (e.g., without welding).
A pressure test can be conducted on the heat pump (104). The pressure test can comprise adding nitrogen to the heat pump for a period of 12 hours at a pressure of 250 psi. If the heat pump passes the pressure test, it can be ready for the next step in the assembly process. If the heat pump fails, the failing joint can be fixed and the pressure test can be repeated until it passes (104).
A control panel can be added to the heat pump frame (105). The control panel can be prefabricated. In some embodiments, the compressor mounting can be accessed through a hinged electrical panel, thereby maintaining maintenance access if the heat pump modules are connected side by side.
The various electrical components of the heat pump can be wired (106). The heat pump can then be subjected to an electrical test and safety certification. If the heat pump passes the electrical test and safety certification, the heat pump assembly process can be complete. If the heat pump fails the electrical test, the faulty wiring can be repaired, and the heat pump wiring and electrical components can be retested until the heat pump passes the electrical test and achieves safety certification (106).
As discussed herein, a first aspect of the present invention provides a method of providing improved efficiency in heating/cooling. The method can include operating an HVAC system that includes first and second heat pump compressors working together with corresponding heat pump expansion valves and heat pump heat exchangers. The method can include collecting HVAC fluid information concerning actual conditions of an HVAC fluid flowing in the HVAC system via sensors positioned in various places throughout the HVAC system. The method can include transmitting an update that includes HVAC fluid information. The method can include receiving control instructions at a heat pump controller. The method can include implementing the control instructions with the heat pump controller. Steps of the method can be repeated periodically during operation of the HVAC system.
In the first aspect, the control instructions based on the update. The control instructions can provide how the first and second heat pump compressors can cause actual conditions of the HVAC fluid to move more into conformity with desired conditions of the HVAC fluid. The control instructions can call for deactivation (or maintenance of deactivation) of both the first and second heat pump compressors. The control instructions can call for activation (or maintenance of activation) of either the first heat pump compressor or the second heat pump compressor. The control instructions can call for activation (or maintenance of activation) of both the first and second heat pump compressors.
In the first aspect, the control instructions can call for a variety of actions. The control instructions can call for activation (or maintenance of activation) of either the first heat pump compressor or the second heat pump compressor. In some such embodiments, the control instructions can specify which of the first and second heat pump compressors to activate (or maintain activation of). In some such embodiments, implementing the control instructions with the heat pump controller can include determining which of the first and second heat pump compressors to activate (or maintain activation of). In some such embodiments, which of the first and second heat pump compressors to activate (or maintain activation of) can be determined according to a priority wear schedule. The control instructions can call for activation of both the first and second heat pump compressors. In some such embodiments, implementing the control instructions with the heat pump controller can include activation of the first and second heat pump compressors in a staggered fashion. In some such embodiments, which of the first and second heat pump compressors to activate first can be determined according to a priority wear schedule.
In the first aspect, the first and second heat pump compressors can be part of a single heat pump. The heat pump can also include first and second expansion valves, a condenser heat exchanger, and an evaporator heat exchanger. The heat pump can have a first circuit configured to circulate a first refrigerant through the first heat pump compressor, the condenser heat exchanger, the first expansion valve, and the evaporator heat exchanger. The first heat pump can have a second circuit configured to circulate a second refrigerant through the second heat pump compressor, the condenser heat exchanger, the second expansion valve, and the evaporator heat exchanger.
In the first aspect, transmitting the update can comprise transmitting the update to a main controller. The main controller can be configured to compare actual conditions of the HVAC fluid with desired conditions of the HVAC fluid. The main controller can be configured to formulate the control instructions. Receiving the control instructions can include receiving the control instructions from the main controller. The main controller may be located remotely from the heat pump controller. The heat pump controller can receive the control instructions from the main controller via a network. The main controller can be configured to record data from the update. The main controller can be configured to present the data in graphical form to illustrate trends in performance of the HVAC system.
In the first aspect, at least one of the heat pump expansion valves can include an electronic expansion valve. The method can include receiving expansion valve instructions based on the update at an expansion valve controller. The method can include implementing the expansion valve instructions with the expansion valve controller. Receiving the expansion valve instructions at the expansion valve controller can include receiving the expansion valve instructions from a main controller. The main controller can be located remotely from the expansion valve controller. The expansion valve controller can receive the expansion valve instructions from the main controller via a network.
In the first aspect, the method may include one or more of the following steps/features. The first and second heat pump compressors can each be part of separate heat pumps. Implementing the control instructions with the heat pump controller can include conducting one or more safety tests (e.g., heat pump safety tests, overall HVAC system safety tests, etc.) and deactivating the first and second heat pump compressors upon detection of a safety concern or irregularity. In some embodiments, the HVAC system can include three or more compressors. In some such embodiments, the control instructions can convey how the compressors can cause actual conditions of the HVAC fluid to move more into conformity with desired conditions of the HVAC fluid.
As discussed herein, a second aspect of the present invention provides a method of providing improved efficiency in heating/cooling. The method can include receiving an update (such as those discussed in connection with the first aspect or elsewhere herein) at a main controller regarding operation of an HVAC system (such as those discussed in connection with the first aspect or elsewhere herein). The method can include comparing actual conditions of the HVAC fluid with desired conditions of the HVAC fluid. The method can include formulating control instructions (such as those discussed in connection with the first aspect or elsewhere herein). The method can include transmitting the control instructions from the main controller. The method can include confirming that the control instructions have been implemented. Steps of the method can be repeated periodically during operation of the HVAC system.
In the second aspect, the method may include one or more of the following steps/features. Confirming that the control instructions have been implemented can include confirming that the first and second heat pump compressors have been activated in a staggered fashion. In embodiments in which at least one of the heat pump expansion valves comprises an electronic expansion valve, the method can include formulating expansion valve instructions based on the update. In some such embodiments, the method can include transmitting the expansion valve instructions from the main controller. Transmitting the expansion valve instructions can include transmitting the expansion valve instructions from the main controller to an expansion valve controller. In embodiments in which the main controller is located remotely from the expansion valve controller, the main controller can transmit the expansion valve instructions to the expansion valve controller via a network. Receiving the update can include receiving the update from sensors positioned in various places throughout the HVAC system. Transmitting the control instructions can include transmitting the control instructions to a heat pump controller that is configured to implement the control instructions. In embodiments in which the main controller is located remotely from the heat pump controller, the main controller can transmit the control instructions to the heat pump controller via a network. In embodiments in which the control instructions call for activation (or maintenance of activation) of either the first heat pump compressor or the second heat pump compressor, the heat pump controller can be configured to determine which of the first and second heat pump compressors to activate (or maintain activation of). The heat pump controller can be configured to conduct one or more safety tests (e.g., heat pump safety tests, overall HVAC system safety tests, etc.) in the course of implementing the control instructions. The heat pump controller can be configured to deactivate the first and second heat pump compressors upon detection of a safety concern or irregularity. The method can include recording data from the update. The method can include presenting the data in graphical form to illustrate trends in performance of the HVAC system.
Various aspects of the present invention involve computer-readable media programmed with instructions for performing one or more of the methods discussed in connection with the first or second aspects or elsewhere herein. The media can include instructions for causing a programmable processor to perform the various steps of the respective methods. In some such embodiments, the computer-readable medium can include instructions for causing a programmable processor to receive control instructions (such as those discussed in connection with the first or second aspects or elsewhere herein) at a heat pump controller. The control instructions can be based on a previously transmitted update (such as those discussed in connection with the first or second aspects or elsewhere herein). In some such embodiments, a computer-readable medium can include instructions for causing the programmable processor to receive data from the main controller. In some such embodiments, a computer-readable medium can include instructions for causing the programmable processor to provide the data in graphical form to illustrate trends in performance of the HVAC system.
Referring again to
In heating operations, HVAC fluid can pass through the energy transfer component(s) on its way to the conditioned space 6 or on its way from the conditioned space 6. In some embodiments, HVAC fluid travels from the output of the heat pump's condenser heat exchanger 34 into the conditioned space 6, as well as into and through the main loop 50 (or to one or more individual energy transfer components), as well as back to the input of the heat pump's condenser heat exchanger 34. In this way, the energy transfer component(s) can provide HVAC fluid to the heat pump that is warmer than it otherwise would be. In many such embodiments, the energy transfer components can provide a larger change in temperature. In some embodiments, HVAC fluid travels from the output of the heat pump's condenser heat exchanger 34 through the main loop 50 (or to one or more individual energy transfer components) to the conditioned space 6 back to the input of the heat pump's condenser heat exchanger 34. In this way, the energy transfer component(s) can further warm HVAC fluid received from the heat pump 8. In some embodiments, HVAC fluid can pass through one or more energy transfer components between exiting the conditioned space 6 and entering the heat pump 8 and also pass through one or more energy transfer components between exiting the heat pump 8 and entering the conditioned space 6. The control system of the heat pump 8 can be regulated to account for the presence of one or more energy transfer components.
The HVAC system of
As with heating operations, in cooling operations, HVAC fluid can pass through the energy transfer component(s) which can reject heat away from the conditioned space 6. In some embodiments, HVAC fluid travels from the output of the heat pump's evaporator heat exchanger 38 to the conditioned space 6 through cooling loop 42 and (by way of the valving configuration 52) the main loop 50 (or to one or more individual energy transfer components) back to the input of the heat pump's evaporator heat exchanger 38. Energy transfer components that absorb energy from the HVAC fluid when their environments are warmer than the HVAC fluid become energy rejection components. In this way, the energy transfer component(s) can provide HVAC fluid to the heat pump that is cooler than it otherwise would be. In some embodiments, HVAC fluid travels from the output of the heat pump's evaporator heat exchanger 38 through the cooling loop 42 and the main loop 50 (or to one or more individual energy transfer components) to the conditioned space 6 back to the input of the heat pump's evaporator heat exchanger 38. In this way, the energy transfer component(s) can further cool HVAC fluid received from the heat pump 8. In some embodiments, HVAC fluid can pass through one or more energy transfer components between exiting the conditioned space 6 and entering the heat pump 8 and also pass through one or more energy transfer components between exiting the heat pump 8 and entering the conditioned space 6. As noted above, the control system of the heat pump 8 can be adjusted to account for the presence of one or more energy transfer components. Thus, in many embodiments, HVAC fluid can recover energy from, and/or reject energy to, one or more energy transfer components. HVAC systems can include various individual valve configurations enabling some of the energy transfer components to serve as energy recovery components and others to serve as energy rejection components. Many functional permutations and combinations are possible. [83] As discussed elsewhere herein, many embodiments can perform heating operations and cooling operations simultaneously. One or more compressors can be activated, causing heat pump refrigerant to cycle through the heat pump components. The heat pump refrigerant can chill HVAC fluid at the evaporator heat exchanger 38 and simultaneously heat HVAC fluid at the condenser heat exchanger 34. In this way, heating and cooling different HVAC fluids can involve no more compressor work than heating or cooling alone. HVAC systems can include a variety of components, which can be configured and operated in a variety of ways. Thus, embodiments of the present invention can reliably and efficiently serve a wide variety of applications.
HVAC systems according to embodiments of the present invention can arrange two or three or any suitable number of heat pumps (and/or groups of heat pumps arranged in parallel) in a series relationship to progressively increase the temperature of HVAC fluid passing through them. For example, a first heat pump can increase the temperature of HVAC fluid from 15 degrees Fahrenheit to 60 degrees Fahrenheit. A second heat pump can take that 60-degree HVAC fluid and increase its temperature to 120 degrees Fahrenheit. A third heat pump can take that 120-degree HVAC fluid and increase its temperature to 160 degrees Fahrenheit. This sequence can continue until the temperature of the HVAC fluid reaches a desired (e.g., selected, predetermined) level. In this example, three heat pumps increase the temperature of HVAC fluid from 15 degrees Fahrenheit to 160 degrees Fahrenheit. Even if achieving this kind of temperature difference with a single heat pump were feasible (which it most likely is not), the required energy input would be significantly greater than it would be for the incremental approach discussed herein. In some embodiments, the temperature of domestic hot water can be raised to 140 degrees Fahrenheit and process water to 160 degrees Fahrenheit. Thus, in many instances, multiple heat pumps arranged in a series relationship can provide additional functionality, improved system reliability, reduced wear on components, and increased efficiency.
Arranging multiple heat pumps in a series relationship can provide certain advantages in some embodiments. In many embodiments, each heat pump that is arranged in a series relationship experiences less strain than a single heat pump designed to achieve the same total temperature difference. In many such embodiments, the multiple heat pumps arranged in series provide for increased durability and longevity. In some embodiments, heat pumps that are optimized for certain temperature ranges can be selected. For example, in the example provided above, the first heat pump can be configured for peak efficiency between 15 and 60 degrees Fahrenheit, the second heat pump can be configured for peak efficiency between 60 and 120 degrees Fahrenheit, and the third heat pump can be configured for peak efficiency between 120 and 160 degrees Fahrenheit. A heat pump can be optimized for a given temperature range by adjusting one or more of a variety of factors. For example, different heat pump refrigerants can be used in each of the ranges, with each heat pump refrigerant having characteristics making it suitable for optimal efficiency within a given temperature range. Different heat pumps can operate at different pressures and/or with different heat pump refrigerant volumes to provide optimum operation within different temperature ranges. Though arranging multiple heat pumps in a series relationship has been discussed in connection with progressively increasing the temperature of HVAC fluid in heating operations, the same kind of arrangement can progressively decrease the temperature of HVAC fluid in cooling operations.
Referring again to
The HVAC system of
In many embodiments, the laundry heat transfer component 12 and the waste water heat transfer component 14 can have substantially the same flow-through structure.
The flow-through heat transfer component 300 of
The wall of the inner tube 304 can be configured to permit maximum heat transfer between the laundry exhaust or waste water and the HVAC fluid (e.g., can be made of thermally conductive material, such as a metal). The thickness of the wall of the inner tube 304 can relate to the thermal capacitance and absorptivity from the inner heat source, which could flow in either direction. The wall of the outer tube 302 can be made of thermally insulating material (e.g., a type of plastic) or an insulated metal, thereby inhibiting heat transfer between the HVAC fluid and the environment surrounding the flow-through heat transfer component 300. Many factors can be controlled to facilitate maximum heat transfer, such as contact surface area, direction of source flow, HVAC fluid flow rate, source flow rate, HVAC fluid temperature, and so on. In this way, the heat from the laundry exhaust or the waste water can be recovered and used in the HVAC system, allowing the HVAC system to perform more efficiently and sustainably. In some embodiments, the flow-through heat transfer component 300 can be used in reverse to heat the fluid within channel 306. In some embodiments, one or both of the inner and outer flows may be reversed. The insulating and conducting materials can be interchanged or made of the same material.
Referring again to
The ground energy transfer component 400 of
In many embodiments, HVAC fluid can enter the ground energy transfer component 400 from the inlet pipe 409 through inlet connector 407 and can exit through the outlet connector 408 into the outlet pipe 410. In some embodiments, HVAC fluid can enter the ground energy transfer component 400 from the outlet pipe 410 through the outlet connector 408 and exit through the inlet connector into the inlet pipe 409. In many embodiments, the cross-sectional area of the connector by which the HVAC fluid enters the ground energy transfer component can be smaller than the cross-sectional area of the corresponding HVAC pipe, thereby resulting in an increased flow velocity of the HVAC fluid. In many embodiments, the flow volume of the HVAC fluid entering the ground energy transfer component is substantially equal to the flow volume of the HVAC fluid exiting the ground energy transfer component.
When HVAC fluid enters the ground energy transfer component 400 from the inlet pipe 409 via the inlet connector 407, the HVAC fluid can flow downwardly in the channel 412 between the outer surface of the inner tube 402 and the inner surface of the outer tube 404. As the HVAC fluid flows downwardly within the channel 412, a barrier 414 guides the HVAC fluid around and around the inner tube 402 in a coil-like configuration. In many embodiments, the barrier 414 serves to maintain the inner tube 402 in a generally concentric relationship with the outer tube 404. In many embodiments, the barrier 414 can be constructed of deformable tubing (e.g., plastic or metal). In some embodiments, the tubing can be wrapped around the inner tube 402 to create coils in a desired configuration. The tubing can be hot-air welded to the inner tube 402 to substantially prevent HVAC fluid from flowing straight down in the channel 412 as opposed to along the barrier 414.
The HVAC fluid completes its path through the channel 412 along the barrier 414 as it approaches the base 416 of the ground energy transfer component 400. As the HVAC fluid approaches and reaches the base 416, it enters the interior of the inner tube 402. In many embodiments, HVAC fluid enters the interior of the inner tube 402 through holes 420. In some embodiments, the lower end of the inner tube 402 can be open, which can permit HVAC fluid to enter the interior of the inner tube 402 through that opening. In some embodiments, the inner tube 402 can have both holes 420 and an open lower end. In embodiments having holes 420 and a closed lower end, the inner tube 402 can be connected to the base 416 in a substantially rigid manner, thereby reducing the tensile stress on the plastic-to-metal or metal-to-metal adapters of the inlet connector 407 and the outlet connector 408. In many embodiments, the collective cross-sectional area of the holes 420 is greater than the cross sectional area of the interior of the inner tube 402, thereby permitting ease of passage. In some embodiments, the holes 420 can be arranged approximately symmetrically about the inner tube 402. In this way, the flow momentum of the HVAC fluid can be balanced due to flow through the each hole 420 being countered by flow through one or more opposite holes 420.
The HVAC fluid then flows relatively laminarly upward in the interior of the inner tube 402. The cross-sectional area of the interior of the inner tube 402 can be significantly greater than the cross-sectional area within the channel 412. In this way, flow velocity within the inner tube 402 can be reduced, thereby producing a more laminar flow. In many embodiments, the HVAC fluid contacts significantly less surface of the ground energy transfer component on the upward path than on the downward path. Similarly, in most embodiments, the HVAC fluid can flow substantially unimpeded by other surfaces within the inner tube 402, thereby producing a more laminar flow. The upward path is also generally a significantly shorter distance, without spiraling around the ground energy transfer component 400. The HVAC fluid then exits the ground energy transfer component 400 through the outlet connector 408 and flows back into the outlet pipe 410. In such an embodiment, because the vertical temperature gradient of the surrounding ground 406 is opposite to that of the HVAC fluid in channel 412—during both heating and cooling—the ground energy transfer component 400 can serve as a cross-flow heat exchanger with the ground or ground fluid.
As referenced above, the HVAC fluid can thermally react with the ground 406 while in the ground energy transfer component 400. The HVAC fluid within channel 412, as guided by barrier 414, can thermally react with the ground. In many embodiments, this flow path increases the amount of time that the HVAC fluid is in thermal communication with the surrounding ground 406. In some embodiments, the momentum of the HVAC fluid as it flows along the barrier 414 causes it to crash against the interior of the outer tube 404. This turbulence can result in greater heat transfer between the HVAC fluid and the surrounding ground 406. Turbulence can be increased by providing increased flow velocity of the HVAC fluid; subjecting the HVAC fluid to more frictional forces due to contacting the barrier 414, the inner tube 402, and the outer tube 404; and/or by subjecting the HVAC fluid to a greater degree of centripetal force. As the HVAC fluid contacts the barrier 414, the inner tube 402, and the outer tube 404, it should be noted that the outer tube 404 provides a larger surface area for heat transfer to occur and that the HVAC fluid is contacting at the peak of its centripetal velocity profile.
In some instances, the HVAC fluid recovers heat from the ground 406, resulting in HVAC fluid that is warmer near the base 416 than the HVAC fluid near the inlet connector 407. In some instances, the HVAC fluid dissipates heat to the ground 406, resulting in HVAC fluid that is cooler near the base 416 than the HVAC fluid near the inlet connector 407. Generally, the HVAC fluid recovers heat from the ground 406 when the ground 406 is warmer than the HVAC fluid, and the HVAC fluid dissipates heat to the ground 406 when the ground 406 is cooler than the HVAC fluid. In many instances, the HVAC fluid recovers heat from the ground when the HVAC system is heating, and the HVAC fluid dissipates heat to the ground when the HVAC system is cooling. The wall of the outer tube 404 can be configured to permit maximum heat transfer between the HVAC fluid and the ground 406 (e.g., can be made of thermally conductive material, such as stainless steel).
The heat transfer properties can be enhanced by the surface properties of the barrier 414, the angle of slope (pitch) of the barrier 414, the size of the passageway between two sections of the barrier 414, the flow rate of the HVAC fluid, the centrifugal forces, other factors, or combinations thereof. In some embodiments, the spaces between coils of the barrier 414 can be non-uniform. For example, a single ground energy transfer component can have some coils that are spaced further apart (e.g., in ground with a higher recovery rate, such as an underground stream; in ground with a convective heat transfer component, such as flowing waste water) and other coils that are closer together (e.g., in ordinary ground with a lower heat recovery rate). In this way, the ground energy transfer component 400 can be tuned to the ground conditions by adjusting the pitch of the barrier 414.
In many embodiments, the HVAC fluid in the interior of the inner tube 402 can be generally thermally insulated, resulting in a relatively constant temperature within the interior of the inner tube 402. The wall of the inner tube 402 can be made of thermally insulating material, thereby inhibiting heat transfer between the HVAC fluid flowing through channel 412 and the HVAC fluid flowing in the interior of the inner tube 402. The spiraling flow path can create a velocity profile at the interface between the inner tube 402 and the HVAC fluid is relatively small, thereby resulting in less heat transfer between the HVAC fluid in channel 412 and the HVAC fluid in the interior of the inner tube 402.
Insulating the HVAC fluid within the interior of the inner tube 402 can generally preserve the effect of the heat transfer that occurred while HVAC fluid was flowing through channel 412. In some embodiments, a small amount of heat may transfer between HVAC fluid flowing within the inner tube 402 to HVAC fluid flowing within the outer tube 404. In such embodiments, the heat is transferred within the system, meaning that the heat is not lost to the surrounding environment. Providing both a heat transfer path and a return insulated path (or vice versa) can provide several advantages, such as improving the total heat transfer, reducing the volume of fluid, and improving the HVAC system response rate. In this way, embodiments of the ground energy transfer component 400 can be easily integrated into HVAC systems. The ground energy transfer component 400 can aid in recovering energy from the ground 406 (e.g., ground having the above-mentioned ground conditions) to be used in HVAC systems.
In some embodiments, the flow path through the ground energy transfer component 400 can be reversed. HVAC fluid can enter the ground energy transfer component 400 from the outlet pipe 410 via the outlet connector 408, flow downwardly within the interior of the inner tube 402 toward base 416, flow back upwardly through channel 412 (while recovering heat from the ground 406 or dissipating heat to the ground 406), and then exit the ground energy transfer component 400 to the inlet pipe 409 via the inlet connector 407.
Embodiments of the ground energy transfer component 400 can provide one or more of the following advantages. Some embodiments are closed systems, meaning that they can accommodate HVAC fluids such as antifreeze while remaining environmentally friendly. As closed systems, the HVAC fluid is not affected by ground or water minerals. In such embodiments, the welds in the outer tube and base can be air tight, as can the relevant connectors. Some embodiments provide more efficient heat transfer as compared with some closed geothermal wells. Some embodiments provide equal or better heat transfer as compared with open geothermal wells, but without environmental exposure to the ground or mineral exposure to the HVAC system. This increased efficiency can permit ground energy transfer components that are significantly shorter than geothermal wells. For example, many ground energy transfer component embodiments are less than 50 feet long. Many ground energy transfer component embodiments come in standard pipe lengths (e.g., 21 feet, etc.). Many ground energy transfer component embodiments are capable of fitting within a single (e.g., 6-inch diameter) bore hole. Some embodiments have a significantly smaller footprint than most conventional horizontal geothermal wells, some of which may be buried in relatively shallow ground. Some embodiments, such as those having outer tubes made of mill grade stainless steel, can provide significantly enhanced durability. Some embodiments can be used in connection with relatively small pumping heads and/or can operate at relatively low flow rates. Some embodiments are relatively inexpensive and/or simple to manufacture (e.g., due to the simple construction, the wide availability of base materials, etc.). Some embodiments provide the above-noted heat transfer benefits without diminishing the appearance of the building into which they are incorporated (e.g., they have no rejection towers, propane tanks, exhaust stacks, etc.).
Many ground energy transfer components can be installed with relative ease. For example, a 4-inch hollow-stem auger can be inserted into the ground at a desired depth. The ground energy transfer component can then be slid into the interior of the auger. The auger can then be removed from the hole, leaving the ground energy transfer component intact. This can permit installation in even wet ground conditions. It can also reduce or eliminate the need for holding the hole open during installation. In installing ground energy transfer components in rock, a 3.7-inch cored hole can be used, thereby reducing the required amount of rock drilling. In many instances, the ground energy transfer component can be pre-fabricated, thereby simplifying on-site installation. A variety of installation methods can be employed.
Some HVAC systems include multiple ground energy transfer components 400. Multiple ground energy transfer components are arranged in series in some systems. Multiple ground energy transfer components are arranged in parallel in some systems. Some parallel arrangements provide advantages, such as reduced resistance to flow in the HVAC system and thus lower pumping costs.
Some embodiments of the ground energy transfer component can be used in applications other than HVAC systems. Examples include heaters for intakes of hydroelectric power dams, industrial processes, and other suitable applications.
Referring again to
One of the energy transfer components of the illustrative HVAC system of
One energy transfer component of the illustrative HVAC system of
One energy transfer component of the illustrative HVAC system of
In the illustrative HVAC system of
In many instances, it is advantageous to build a complete distribution box in a setting more conducive to construction (e.g., a machine shop), as opposed to interconnecting the various components at the same time as installing the HVAC system. In many such instances, the setting more conducive to the construction may be located remotely from the HVAC system installation site. The setting may employ more specifically trained or alternately waged people to perform the task.
The connectors 514, 516, 518, 520, 522, 524 of the distribution box 500 can connect to HVAC pipes, thereby incorporating the distribution box 500 into an HVAC system. In many embodiments, the connectors 514, 516, 518, 520, 522, 524 of the distribution box 500 can be configured to permit the distribution box 500 to be connected to, and disconnected from, the remainder of the HVAC system relatively quickly.
As noted, HVAC fluid can flow through the distribution box 500. HVAC fluid can flow into the distribution box 500 via the hot HVAC fluid inlet pipe 502 and/or the cold HVAC fluid inlet pipe 504. A valve 526 can permit either hot HVAC fluid coming from the hot HVAC fluid inlet pipe 502 or cold HVAC fluid coming from the cold HVAC fluid inlet pipe 504 to pass through to pump 528. Pump 528 can pump the relevant HVAC fluid through the fan coil supply pipe 510 and into a fan coil. In some embodiments, the HVAC fluid can flow into the fan coil without the need of pump 528 (e.g., if the rest of the HVAC system is designed to provide the requisite pressure). After passing through the fan coil, the HVAC fluid can re-enter the distribution box via the fan coil return pipe 512. A valve 530 can channel the HVAC fluid out of the distribution box 500 via either the hot HVAC fluid outlet pipe 506 or the cold HVAC fluid outlet pipe 508. The valves 526 and 530 can be configured such that hot HVAC fluid and cold HVAC fluid do not mix. Hot HVAC fluid from HVAC fluid inlet pipe 502 can return to the hot HVAC fluid at hot HVAC fluid outlet pipe 506. Cold HVAC fluid from cold HVAC fluid pipe 504 can return to the cold HVAC fluid at cold HVAC fluid outlet pipe 508.
A controller 532 can control various aspects of the distribution box 500. The controller 532 can be in electrical communication with one or more inputs, such as thermostat 534. Thermostat 534 can be positioned within the appropriate zone. One or more individuals within the zone can manually adjust conditions of the zone via thermostat 534, or thermostat 534 can operate according to various pre-selected conditions. Other inputs that can be in electrical communication with the controller 532 include various sensors. For example, a temperature sensor can be positioned in the fan coil supply pipe 510 such that the temperature sensor can inform the controller 532 of the temperature of the HVAC fluid entering the fan coil. Several other inputs are used in various embodiments.
Based on information provided by one or more inputs, the controller 532 can control various aspects of the distribution box 500. For example, the controller 532 can instruct valve 526 to permit only hot HVAC fluid to pass through to the pump 528 (e.g., during a heating operation) or to permit only cold HVAC fluid to pass through to the pump 528 (e.g., during a cooling operation). In some instances, the controller 532 can control the flow rate and/or displacement of the pump 528. In some embodiments, the controller 532 can instruct valve 530 to channel returning HVAC fluid through the hot HVAC fluid outlet pipe 506 (e.g., during a heating operation) or through the cold HVAC fluid outlet pipe 508 (e.g., during a cooling operation). In some instances, the controller 532 can (digitally) instruct the blower of the fan coil to various pre-wired stages of speed or it can instruct the blower of the fan coil to any increment of speed on a variable (analogue) signal.
Like other controllers discussed herein, the controller 532 can be implemented in digital electronic circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, electric relays and switches and/or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device. These various implementations can include relays and switches from a remote controller device (e.g., a thermostat) wired or wirelessly connected to the assembled body of an embodiment of the invention.
In many instances, the controller can be connected via a network (e.g., a LAN, a WAN, the Internet, etc.) to other components of the HVAC system. Examples of components to which the controller 532 may be connected include controllers of other distribution boxes, controllers for one or more of the various energy transfer components, controllers for one or more heat pump, operator input devices/stations, zone input sensors (e.g., a sensor to indicate whether the zone has transitioned from a closed system to an open system, such as through the opening of a door or window), and other suitable components. In this way, an operator (e.g., a hotel employee at the front desk) can provide instructions to the controller 532, such as whether the zone is occupied, one or more set-point temperatures for the zone, changes to the set-point temperature or limit set points, changes to the actual temperature, whether to cease heating/cooling in the zone, and so on. In this way, the operator can remotely control various HVAC conditions within a given zone with relative ease.
In many HVAC system embodiments in which a controller and corresponding pump(s) and valve(s) regulate the HVAC fluid entering the fan coil, the HVAC fluid can enter only one coil within the fan box, as opposed to two separate coils (one for cold HVAC fluid and the other for hot HVAC fluid).
Referring again to
Distribution components similar to the distribution box 500 of
In the foregoing detailed description, the invention has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims. Thus, some of the features of preferred embodiments described herein are not necessarily included in preferred embodiments of the invention which are intended for alternative uses.
This application is a continuation of U.S. application Ser. No. 12/607,930, filed Oct. 28, 2009, which claims priority under 35 U.S.C. §119(e) to U.S. provisional application 61/108,961, filed Oct. 28, 2008, the entirety of which is hereby incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 61108961 | Oct 2008 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12607930 | Oct 2009 | US |
| Child | 13179296 | US |
