Combined HVAC and water heating system utilizing transcritical co 2 working fluid

Abstract

A combined heating, cooling, and hot water system that utilizes transcritical CO2 as a refrigerant / working fluid. The system uses dual compression of the CO2 to reach transcritical temperature and directs the flow and expansion of the transcritical CO2 between a gas cooler and evaporator for heating and cooling. The system can divert the working fluid to a gas cooler between a first and second compressor to heat a second fluid, such as water. The system can also include a ventilation device to pass air across the gas cooler to heat or cool a predetermined location.

Description

COMBINED HVAC AND WATER HEATING SYSTEM UTILIZING TRANSCRITICAL CO2 WORKING FLUID CROSS-REFERENCE TO RELATED APPLICATION

[0001] This invention claims the benefit of US Provisional Patent Application No. 63 / 617,133, filed on January 3, 2023, the entirety of which is hereby incorporated herein by this reference. STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH

[0002] This invention was made with support under Government grant numbers EEC 2113874 awarded by the NSF and W911SR-14-2-0001 RPP-2008 awarded by the Department of Energy (DOE), the Building Technologies Office (BTO) and the MSI STEM Research and Development Consortium. The government has certain rights in the invention. BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention generally relates to heating, ventilation, and air conditioning (HVAC) systems. More particularly, the present invention relates to a combined HVAC and hot water system that utilizes transcritical CO2 as the refrigerant / working fluid.

[0005] 2. Description of the Related Art

[0006] In transcritical CO2 refrigeration systems, the CO2 operates sometimes or exclusively above its critical point. Unlike subcritical refrigeration systems, transcritical CO2systems typically include a gas cooler to dissipate heat and utilize a high-pressure expansion valve to control introduction into the evaporator. Transcritical CO2 refrigeration systems have their working fluids go through subcritical and supercritical states. In typical operation, the fluid CO2is first boiled and expanded into a superheated vapor by an evaporator. Then a compressor increases the heat and pressure of the superheated vapor. Once that pressure exceeds the critical point of CO2(1069 PSIG / 73 BAR), the CO2is transformed into an undefined gas, a transcritical state, that has properties of both a liquid and a gas but indistinguishable as in either of those states.

[0007] A transcritical cycle occurs where the compressor discharge pressure is greater than the critical pressure and the refrigerant cannot be condensed. ThisDocket No. 010-24-11WO011 / 21cycle consists of only using CO2 in the unit and cooling it above the critical point, with no phase change during this cooling process. The transcritical cycle is common for these systems to work with high compressor discharge temperatures due to the need to reach high pressure, greater than 95 bar, in the gas cooler to be able to exchange heat with the environment.

[0008] There has been interest in modifying electrical HVAC systems with heat pumps (HPs) to utilize transcritical CO2as the refrigerant. Traditionally, HPs use either hydrofluorocarbons (R410A and R134), chlorofluorocarbons or hydrochlorofluorocarbons as refrigerants which unfortunately have high global warming potential (GWP>1000) and varying ozone depletion potentials (ODP). Thus, partly or pure CO2, commonly known as R-744 when used as a refrigerant, is desirous in use.

[0009] R-744 has a GWP of one and an ODP of zero while being a good conductor of heat, making it a prime candidate for electrified HVAC processes. However, there have been challenges in adapting R744 HP technologies, especially high-pressure operations that places the refrigerant in the supercritical zone (>1069psia), i.e. into the transcritical state having no obvious distinction between gaseous and liquid states. As such, R744 will have to run in a transcritical cycle where the fluid will be continuously cooled due to being superheated.

[0010] The need for high efficiency systems becomes more apparent in an indoor heating mode as the outdoor environmental temperature decreases. A transcritical system that can allow for Coefficient of Performance (COP) values close to 3 as typical winter temperatures approach 17– 25°F would greatly encourage the switch from traditional boilers to heat pump systems. As it becomes more of a challenge for residential customers to completely switch their current heating systems, the compactness, multi-service functionality and comparable efficiency of traditional heating systems will greatly increase the ability of heat pump systems to replace less environmentally friendly setups.

[0011] There is a general lack of research conducted on transcritical CO2heat pump systems for cold climates, but there has been some limited research in this area. There has been research on fin and tube heat exchangers for more efficient heat transfer. It was found that, with respect to CO2 gas coolers, the performance of heat exchangers was significantly affected by neighboring tubes.Docket No. 010-24-11WO012 / 21

[0012] A simple yet accurate tube by tube method has been experimented with. In the method, the heat transfer characteristics were analyzed for each tube. It was found that by decreasing the frontal area, the minimum temperature difference increased, and the heat transfer rate decreased. Increasing the tube pitch in a longitudinal direction yielded an increase in the heat transfer rate but also an increase in the pressure-drop across the system. Transverse pitch increase yielded the opposite for the heat transfer rate and the pressure drop.

[0013] Others have examined increasing the COP by introducing another heat exchanger into the system, which yielded some improvements in operation. Others have looked at the effects of high gas cooler outlet temperatures and determined that this caused high throttling irreversibility. The proposed solution there was to utilize an internal heat exchanger which allowed COP to be increased up to 2.96 at the different heating terminals.

[0014] There has also been experimentation with vapor injection and single stage systems using similar conditions. Heating capacity was seen to compare 7% favorably for the vapor injection cycle, while also showing 8-12% decrease in refrigerant discharge temperatures. The COP increased by about 4.4%.

[0015] Extant research has otherwise provided a general baseline at delving into the transcritical CO2system mostly for refrigeration cycles. For example, one design included a suction line heat exchanger, intercooler, and 2-stage CO2compressor. The 2-stage compression makes it easier to work with the high temperatures and pressures while making smaller tubes viable. That system became 20% more efficient than that of a conventional R134a system.

[0016] In view of the limited research conducted in transcritical CO2 cycles for heating space, especially in very cold climates, it is evident that practical design approaches and guidelines are needed to bring air source, environmentally friendly heat pump systems are needed. Such system design is especially needed for mid- size building capacities in cold climates. It is thus to such improvements that the present invention is primarily directed. BRIEF SUMMARY OF THE INVENTION

[0017] Briefly described, the present system is a heating, cooling, and water heating system that can use transcritical CO2 as a working fluid. The system can beDocket No. 010-24-11WO013 / 21configured to provide any or all heating or cooling functions. Furthermore, the system can include a ventilation system to create an HVAC system in a building.

[0018] When embodied as a heating system, the system contains a working fluid passage system containing, at least, a CO2 working fluid, with the working fluid passage system including a first gas cooler that exchanges heat in a first predetermined location, a second gas cooler that exchanges heat in a second predetermined location, a dual stage compressor is between the first gas cooler and second gas cooler, the compressor selectively compressing the working fluid into a transcritical state, and an expansion valve between the second gas cooler and first gas cooler. The working fluid passage system selectively engages in a compression cycle that receives low temperature working fluid from the first predetermined location at the first gas cooler, compresses the working fluid to a transcritical state, sending the compressed working fluid to the second gas cooler at the second predetermined location, expanding the working fluid in the expansion valve, and passing the expanded working fluid to the first gas cooler, thereby completing the compression cycle.

[0019] When embodied as a combined heating and cooling system, the working fluid passage system containing, at least, a CO2 working fluid, has a first gas cooler that exchanges heat in a first predetermined location, a second gas cooler that exchanges heat in a second predetermined location, a reversible flow, dual stage compressor between the first gas cooler and second gas cooler. The compressor includes a reversing valve, and there is an expansion valve between the first gas cooler and second gas cooler. The working fluid passage system selectively engages in a compression cycle that receives low temperature working fluid from either the first predetermined location at the first gas cooler or the second predetermined location, compresses the working fluid in the first compressor and second compressor, the compressed working fluid delivering high temperature working fluid at the either the first gas cooler at the first predetermined location or second gas cooler at the second predetermined location, expanding the high temperature working fluid in the expansion valve, and passing the expanded working fluid to the first gas cooler or second gas cooler, thereby completing the compression cycle.Docket No. 010-24-11WO014 / 21

[0020] In the embodiment of a combined heating, cooling and water heating system, the working fluid passage system contains, at least, a CO2 working fluid and a first gas cooler that exchanges heat in a first predetermined location, a second gas cooler that exchanges heat in a second predetermined location, a first compressor between the first gas cooler and second gas cooler, a second compressor between the first gas cooler and second gas cooler. The first compressor and second compressor form a reversing valve in the working fluid passage system, and there is an expansion valve between the second gas cooler and first gas cooler.

[0021] This system includes a second fluid heating system, such as water, that includes a third gas cooler in thermal coupling with the working fluid passage system between the first gas cooler and second gas cooler, the third gas cooler containing a second fluid, and a second fluid reservoir holding heated second fluid sent from the third gas cooler.

[0022] The working fluid passage system selectively engages in a compression cycle that receives low temperature working fluid from either the first predetermined location at the first gas cooler or the second predetermined location, compresses the working fluid in the first compressor and second compressor, the compressed working fluid delivering high temperature working fluid at the either the first gas cooler at the first predetermined location or second gas coolerat the second predetermined location, expands the high temperature working fluid in the expansion valve, and passes the expanded working fluid to the first gas cooler or second gas cooler, thereby completing the compression cycle. The third gas cooler selectively heats the second fluid from the compressed working fluid and sends the heated second fluid to the second fluid reservoir.

[0023] The working fluid can be compressed in the compressor exceeding 1200 psia such that the temperature of the working fluid is above the critical point, exceeding 150°F. When so embodied to both heat and cool, the fluid passage system can further include a first working fluid passage line between the first gas coolerand second gas cooler, and the compressor is located on the first working fluid passage. There is a second working fluid passage line between the first gas cooler and second gas cooler, and the expansion valve is located on the second working fluid passage line.Docket No. 010-24-11WO015 / 21

[0024] Further, the working fluid can be R744. It is preferred that the compression cycle has a coefficient of performance of at least 3. Additionally, the first and / or second gas cooler can have a staggered fin air-cooled design.

[0025] The present invention is therefore advantageous in that it provides an environmentally friendly HVAC system that uses CO2 as the working fluid, and can also heat water with the same system. The present invention also has industrial applicability in the design of residential and commercial heating and cooling systems, as well as water heating systems. These and other advantages of the present invention will be apparent to one of skill in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Fig.1 is a graph comparing sub-critical and transcritical CO2 cycles.

[0027] Fig.2 is a diagram of one embodiment of the system configured for heating a predetermined location with a ventilation device.

[0028] Fig.3 is a diagram of a Blackbox model flowchart to predict the performance of the heating system of Fig.2.

[0029] Fig.4 is a graph of the coefficient of performance against the outdoor temperature for R410a as the working fluid.

[0030] Fig.5 is a graph of the coefficient of performance against the outdoor temperature for R744 as the working fluid.

[0031] Fig.6 is a graph of the condenser capacity and compressor work against temperate for R410a and R744.

[0032] Fig.7 is a table of the coefficient of performance between R410a and R744.

[0033] Fig.8 is a table of the design data for one embodiment of a staggered-fin design of a gas cooler in the present system.

[0034] Fig.9 is a perspective view of one embodiment of the staggered-fin gas cooler design.

[0035] Fig.10A is one embodiment of a gas cooler design for use in the present system.

[0036] Fig.10B is a further embodiment of a gas cooler design.

[0037] Fig.11 is a diagram of one embodiment of a transcritical CO2heat pump for both heating and cooling a predetermined location with a ventilation device.

[0038] Fig.12 is a diagram of one embodiment of a transcritical CO2 heat pump system for heating, cooling, ventilation and water heating.Docket No. 010-24-11WO016 / 21DETAILED DESCRIPTION OF THE INVENTION

[0039] With reference to the figures in which like numerals represent like elements throughout the several views, Fig.1 is a graph comparing sub-critical and transcritical CO2 cycles. Fig.1 illustrates the need for high efficiency systems in a heating mode as the outdoor temperature decreases. Most desirous is a system that can allow for Coefficient of Performance (COP) values close to 3 as typical winter temperatures approach 17–25°F, which would greatly encourage the switch from boilers to heat pump systems. As it becomes more of a challenge for residential customers to completely switch their current heating systems, the compactness, multi-service functionality and comparable efficiency of traditional heating systems will greatly increase the ability of heat pump systems to replace less environmentally friendly setups.

[0040] Fig.2 is a diagram of one embodiment of the system 12 configured for heating a predetermined location at second gas cooler 16. The space heating configuration consists of vapor compression cycle that receives low temperature heat from the outdoor environment via an evaporator (first gas cooler 15) that contains CO2. The CO2enters the dual stage compressor 18 in a vapor state at low pressure where it is compressed to pressures exceeding 1200 psi, with temperatures above the critical point, exceeding 150°F. The CO2delivers the heat to the building space via a second gas cooler 16 where air from the room is heated and the refrigerant is cooled. This gas cooling process occurs at transcritical thermodynamic state. Further from the gas-cooling process, the CO2 undergoes an expansion thermodynamic process in an expansion valve 22 returning to the evaporator (first gas cooler 15) to close the cycle.

[0041] It should be apparent that the system 12 could have the second gas cooler 16 and first gas cooler 15 reversed to provide cooling. The space cooling configuration consists of vapor compression cycle that receives high temperature heat from the outdoor environment via the outdoor unit that contains CO2. The CO2 delivers cooling to the environment via a second gas cooler 16 where air from the room is cooled and the refrigerant is heated.

[0042] In one embodiment, the transcritical CO2 gas cooler has inlet temperatures above 200°F and rapidly cools in a single phase process to about 120°F. AllowingDocket No. 010-24-11WO017 / 21the air to heat. The dual operation of heating to cooling occurs by deviating the flow from the original heating space configuration to the compressor as shown.

[0043] Thus, in this embodiment Fig.2 Illustrates the basic setup of the elements for space heating system 12 for transcritical CO2. There is a working fluid passage system 14 containing, at least, a CO2 working fluid, the working fluid passage system 14 including a first gas cooler (evaporator) 15 that exchanges heat in a first predetermined location, a second gas cooler 16 that exchanges heat in a second predetermined location, and a dual stage compressor 18 between the first gas cooler 15 and second gas cooler 16, the compressor 18 selectively compressing the working fluid into a transcritical state. An expansion valve 22 is between the second gas cooler 16 and first gas cooler 15. In this embodiment, a ventilation device, here an electric fan 24, blows across the second gas cooler 16 to heat the second predetermined location. Also, compressor 18 includes a reverse valve 20 to maintain the direction of working fluid flow.

[0044] The working fluid passage system 14 selectively engages in a compression cycle that receives low temperature working fluid from the first predetermined location at the first gas cooler 15, compresses the working fluid at the compressor 20 to a transcritical state, sends the compressed working fluid to the second gas cooler 16 at the second predetermined location, expands the working fluid in the expansion valve 22, and passes the expanded working fluid to the first gas cooler 15, thereby completing the compression cycle.

[0045] In one embodiment, the working fluid is compressed in the compressor exceeding 1200 psia with temperatures above the critical point, exceeding 150°F. Further, the fluid passage system 14 can further have a first working fluid passage line 17 between the first gas cooler 15 and second gas cooler 16, and the compressor 18 is located on the first working fluid passage line 17, and a second working fluid passage line 19 between the first gas cooler 15 and second gas cooler 16, and the expansion valve 22 located on the second working fluid passage line 19. Here, the working fluid is R744, and the compression cycle includes a coefficient of performance of at least 3.

[0046] Also shown in the embodiment Fig.2, the system 12 includes a ventilation device 24 to pass air across the second gas cooler 16. A ventilation device (not shown) can also be located at the first gas cooler 15 for thermal exchange.Docket No. 010-24-11WO018 / 21Alternately, no ventilation device need be present in the system depending on the desired heating or cooling interfaces with the environment desired.

[0047] Fig.3 is a diagram 30 of a Blackbox model flowchart to predict the performance of the heating system of Fig.2. Fig.3 shows the details of the backbox model that considers all the thermodynamic properties of the heat pump system 12, whether R410 or R744 working fluid is used. A significant assumption is that there are non-spatial changes in the component of the systems, relying on total values of heat transfer at the evaporator (second gas cooler 16) or condenser (first gas cooler 15), or work at the compressor 18. The thermodynamic analysis is carried out using energy and mass balances in each component and in the whole unit. In this model, certain constraints were kept constant such as the thermodynamic properties at state 3 and the mass air flow rates and compressor efficiencies for each set of calculations. Energy balance comparisons were also done to ensure the stability of the system.

[0048] The performance results for R410 and R744 for variable outdoor conditions model are shown in Figs.4-6. The results for the various temperatures were attained using data that was provided by the vendor specification sheet for an older model of the same heat pump machine. Inputs of temperature and pressure for the cycle were assumed based on the given criteria. The compressor 18 efficiency was then calculated by comparing the results for a range of efficiencies and then pinpointing the correct value by matching the results with the vendor data that was provided.

[0049] Both systems using different working fluids are performance rated for temperatures of 47⁰F. The highlighted values indicate that a value of 3.65 was calculated while the machine suggests that the expected COP is 3.66. This means that the calculations are within 0.5% of the expected results and used to determine the efficiency of the compressor used in the model to be 67%. This model was then extrapolated to attain corresponding values for the R744 system. This allows us to move to the next step knowing that the COP is in an acceptable range.

[0050] Fig.4 is a graph 40 of the coefficient of performance against the outdoor temperature for R410a as the working fluid. Fig.5 is a graph 50 of the coefficient of performance against the outdoor temperature for R744 as the working fluid.Docket No. 010-24-11WO019 / 21

[0051] Fig.6 is a graph 60 of the gas cooler for R744 (or condenser for R410)capacity and compressor 18 work against temperate for R410a and R744. The gas cooler (or condenser) capacities at freezing temperatures are about 60% of their rated conditions, which keeps with industry standards. This model predicts and matches the COP and capacity values of the present system. Fig.7 is a table of the coefficient of performance between R410a and R744.

[0052] Using this, a gas cooler 90 (Fig.9) can be designed (such as first gas cooler 15 and / or second gas cooler 16) that can replace the traditional condenser in the heat pump system. The values observed in Figs.4-6 demonstrate the feasibility of converting a traditional heat pump into one that uses R744 instead. While the values of COP may be lower than that of R410, they are still reasonable and above the threshold of 1. The design of this gas cooler 90 is an important component of this CO2system. Fig.7 illustrates the benefit of the air-cooled gas cooler which has a more simplistic design, offers about 10-22% increase in heating capacity, a reduction in approach temperature by about 2-16°F.

[0053] The air-cooled gas cooler 90 has been modeled using Engineering Equation Solver (EES) software. Some variables were held constant during the calculation process and this is where the BlackBox model 30 (Fig.3) is useful for prediction.

[0054] One embodiment of the air-cooled gas cooler 90 is a staggered fin design. With staggered tube that allow for greater cooling at the exit temperature. This leads to much better efficiency of the heating system 12. As more particularly seen in Fig. 9, the air crosses the air-cooled fins 92 and cools the refrigerant located inside of the pipes 92. The gas cooler exit 98 will be located in the position away from the extreme temperatures at the inlet 96 of the gas cooler.

[0055] In order to optimally size this air-cooled gas cooler 90, the number of tubes 92 and the frontal area we calculated. Based on other equipment sizing as well, it was determined to build towards a 3.5-ton capacity gas cooler along with a COP of about 2.5-3.0. This allows for proper scaling of the compressor 18 and the evaporator (such as gas cooler 90). Based on calculations done for 1 tube and then adapted to design constraints, for the internal flow section, a total Reynolds Number of 8,000 was assumed. It is more beneficial to have the flow operate at turbulent conditions as it allows for better energy transfer between the two fluids. The heatDocket No. 010-24-11WO0110 / 21transfer coefficient was calculated using the Dittus–Boelter Equation which satisfies the condition of the Reynolds Number being between 6x10^3 and 10^7.

[0056] While modeling in EES, the properties in Fig.109 were used and kept constant, along with the fluid mass flow rates. ^^^^^^^^ 0.8 ^^^^^^^^ = 0.023^^^^^^^^^^^^ ^^^^^^^^^^^^ = ^̇^^^^^^^ ^^^^^^^^^^^^^^^^ = ^^^^^^^^^^^^^^^^∆^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ = (^̇^^^^^^^^^^^)^^^^^^^^^^^^

[0057] Fig.8 is a table of the design data for one embodiment of a staggered-fin design of a gas cooler 90 in the present system utilizing the above parameters. The external flow was then analyzed as well using the Sha’s Methodology. A pipe 92 diameter of 3 / 8” was used and the relevant thermodynamic properties were inputted as seen in. The above equations cover the process of finding the external flow properties and the gas cooler 90 sizing. The heat capacity value of the cold side is infinite, the inlet 96 temperature is equal to the outlet 92 temperature.Docket No. 010-24-11WO0111 / 21

[0058] After solving for the internal and external flow properties, the sizing of the HX was then estimated, again following Sha’s Methodology. EES allows for the recalling of base HX designs in its software.

[0059] This was done for the staggered fin option shown in Fig.9. Calculations were done to find the required HX volume, the overall heat transfer coefficients and the required HX area. Subsequently, it was possible to adjust the frontal area of the HX to adjust for a suitable number of tubes. This was done by classifying an array as the layout seen in Fig.9. It was then possible to determine the required number of tubes 92 by adjusting the cross-sectional areas of the design in EES.

[0060] Thus, in one embodiment, an assumed total equivalent pipe length of 28ft is required, with a total of 12 tubes of about 2.5ft each. The gas cooler 90 would be preferrable to have a longitudinal length less than 5ft. This should make it similar to the sizing of a traditional condensing unit.

[0061] Fig.10A is one embodiment of a gas cooler design 100 for use in the present system. The frontal area 102 was affected by L2 and L3. For our calculations, L2 was held constant while L3 was varied. Each 0.5-ton increase increases the size uniformly in the L1 direction. This figure helps to compare how the sizing of different machines will compare as scaling in size for the needs of larger locations for temperature control. The outlet area 104 is shown after heat transfer occurs.

[0062] Fig.10B is a further embodiment of a gas cooler design 106, illustrating the operational parameters for the working fluid passage. Here, the specific R744 refrigerant is used as the working fluid.

[0063] Fig.11 is a diagram of one embodiment of a transcritical CO2 heat pump for both heating and cooling a predetermined location, embodied with a ventilation device 120. The combined heating and cooling system 110, includes a working fluid passage system 113 containing, at least, a CO2 working fluid, and a first gas cooler 112 that exchanges heat in a first predetermined location, a second gas cooler 114 that exchanges heat in a second predetermined location. There is a reversible flow, dual stage compressor 116 between the first gas cooler 112 and second gas cooler 114, the compressor 16 includes a reversing valve 122 and dual flow valves 124.

[0064] There is an expansion valve 118 between the first gas cooler 112 and second gas cooler 114, and the working fluid passage system 113 selectivelyDocket No. 010-24-11WO0112 / 21engages in a compression cycle that receives low temperature working fluid from either the first predetermined location at the first gas cooler 112 or the second predetermined location at the second gas cooler 114, then compresses the working fluid in the compressor 116, the compressed working fluid delivering high temperature working fluid at the either the first gas cooler 112 at the first predetermined location or second gas cooler 114 at the second predetermined location, and expands the high temperature working fluid in the expansion valve 118 and passes the expanded working fluid to the first gas cooler 112 or second gas cooler 114, thereby completing the compression cycle.

[0065] Thus, the heating and cooling system 110, along with ventilation device 120, provides three services heating of building space, cooling of building space, and hot water utilizing electricity and zero GWP. This incorporates reversing the flow to allow for both heating and cooling of the room during winter and summer conditions respectively.

[0066] Fig.12 is a diagram of one embodiment of a transcritical CO2 heat pump system 130 for heating, cooling, ventilation and water heating. The system 130 includes a working fluid passage system 131 containing, at least, a CO2 working fluid, and a first gas cooler 132 that exchanges heat in a first predetermined location, a second gas cooler 134 that exchanges heat in a second predetermined location, and a first compressor 144 between the first gas cooler 132 and second gas cooler 134, and a second compressor 146 is between the first gas cooler 132 and second gas cooler 134. The first compressor 144 and second compressor 146 form a reversing valve in the working fluid passage system 131. There is an expansion valve 136 between the second gas cooler 134 and first gas cooler 132.

[0067] There is a second fluid heating system 142 that has a third gas cooler 130 in thermal coupling with the working fluid passage system 142 between the first gas cooler 132 and second gas cooler 134, with the third gas cooler 138 containing a second fluid, such as water, and a second fluid reservoir 148 holding heated second fluid sent from the third gas cooler 138.

[0068] In similar fashion to the other embodiments, the working fluid passage system 142 selectively engages in a compression cycle that receives low temperature working fluid from either the first predetermined location at the first gas cooler 132 or second gas cooler 134 the second predetermined location,Docket No. 010-24-11WO0113 / 21compresses the working fluid in the first compressor 144 and second compressor 146, the compressed working fluid delivering high temperature working fluid at the either the first gas cooler 132 at the first predetermined location or second gas cooler 134 at the second predetermined location; expanding the high temperature working fluid in the expansion valve 136, and passes the expanded working fluid to the first gas cooler 132 or second gas cooler 134, thereby completing the compression cycle, wherein the third gas cooler 138 selectively heating second fluid from compressed working fluid and sending the heated second fluid to the second fluid reservoir 148. There is also a ventilation device 140 passing air across second gas cooler 34.

[0069] The fluid passage system 131 can further include a first working fluid passage line 154 between the first gas cooler 132 and second gas cooler 146, and the first compressor 144 and second compressor 146 are located on the first working fluid passage line 154. There is a second working fluid passage line 152 between the first gas cooler 132 and second gas cooler 134, and the expansion valve 136 is located on the second working fluid passage line 156.

[0070] This traditional flow, water heating system incorporates the thermodynamic cycle where the CO2working fluid enters the evaporator (such as gas cooler 132), absorbs heat and becomes superheated at temperatures above 200°F and pressures above 8 MPa. The working fluid then flows through the second gas cooler 134 where condensation does not occur but begins to rapidly cool during this stage, while staying above its critical temperature and pressure. The working fluid then cools in a multi-stage expansion valve 136 process where it reliquefies and re-enters the evaporator to repeat the process.

[0071] Here, the vapor compression cycle that receives low temperature heat from the room, as through second cooler 134 via the working fluid that contains CO2. The CO2enters the first compressor 144 in vapor state at low pressures where it is ultimately compressed to pressures exceeding 1200psi, with temperatures above the critical point exceeding 150°F. Here, after initial compression at first compressor 144 to a first heated state, the third gas cooler 138 then takes the heat and transfers it into the second fluid reservoir 148, such as a hot water heater.

[0072] The CO2 working fluid delivers then goes the second compressor 146 and is fully compressed to the extreme heat of the transcritical state and then is sent to the first gas cooler 132 for thermal discharge to the environment. This gas coolingDocket No. 010-24-11WO0114 / 21process occurs at transcritical thermodynamic state. Further from the gas-cooling process, the CO2 undergoes an expansion thermodynamic process in an expansion valve 136 returning to the second gas cooler 134 to close the cycle.

[0073] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below, if any, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of one or more aspects of the invention and the practical application, and to enable others of ordinary skill in the art to understand one or more aspects of the invention for various embodiments with various modifications as are suited to the particular use contemplated. * * * * *Docket No. 010-24-11WO0115 / 21

Claims

CLAIMS What is claimed is:

1. A heating system, comprising: a working fluid passage system containing, at least, a CO2 working fluid, the working fluid passage system including: a first gas cooler that exchanges heat in a first predetermined location; a second gas cooler that exchanges heat in a second predetermined location; a dual stage compressor between the first gas cooler and second gas cooler, the compressor selectively compressing the working fluid into a transcritical state; and an expansion valve between the second gas cooler and first gas cooler, wherein the working fluid passage system selectively engaging in a compression cycle that: receives low temperature working fluid from the first predetermined location at the first gas cooler; compresses the working fluid to a transcritical state; sends the compressed working fluid to the second gas cooler at the second predetermined location; expands the working fluid in the expansion valve; and passes the expanded working fluid to the first gas cooler, thereby completing the compression cycle.

2. The system of claim 1, wherein the working fluid is compressed in the compressor exceeding 1200psia such that the temperature of the working fluid is above the critical point, exceeding 150°F.

3. The system of claim 1, wherein the fluid passage system further including: a first working fluid passage line between the first gas cooler and second gas cooler, and the compressor located on the first working fluid passage line; andDocket No. 010-24-11WO0116 / 21a second working fluid passage line between the first gas cooler and second gas cooler, and the expansion valve located on the second working fluid passage line.

4. The system of claim 1, wherein the working fluid is R744.

5. The system of claim 1, wherein the compression cycle includes a coefficient of performance of at least 3.

6. The system of claim 1, wherein the system includes a ventilation device to pass air across the first gas cooler.

7. The system of claim 1, wherein the first gas cooler heats the first predetermined location.

8. A combined heating and cooling system, comprising: a working fluid passage system containing, at least, a CO2working fluid, the working fluid passage system including: a first gas cooler that exchanges heat in a first predetermined location; a second gas cooler that exchanges heat in a second predetermined location; a reversible flow, dual stage compressor between the first gas cooler and second gas cooler, the compressor includes a reversing valve; and an expansion valve between the first gas cooler and second gas cooler, wherein the working fluid passage system selectively engaging in a compression cycle that: receives low temperature working fluid from either the first predetermined location at the first gas cooler or the second gas cooler 114 at the second predetermined location; compresses the working fluid in the compressor, the compressed working fluid delivering high temperature working fluid at the either the firstDocket No. 010-24-11WO0117 / 21gas cooler at the first predetermined location or second gas cooler at the second predetermined location; expands the high temperature working fluid in the expansion valve; and passes the expanded working fluid to the first gas cooler or second gas cooler, thereby completing the compression cycle.

9. The system of claim 8, wherein the working fluid is compressed in the compressor exceeding 1200psia with temperatures above the critical point, exceeding 150°F.

10. The system of claim 8, wherein the fluid passage system further including: a first working fluid passage line between the first gas cooler and second gas cooler, and the compressor located on the first working fluid passage line; and a second working fluid passage line between the first gas cooler and second gas cooler, and the expansion valve located on the second working fluid passage line.

11. The system of claim 8, wherein the working fluid is R744.

12. The system of claim 8, wherein the compression cycle includes a coefficient of performance of at least 3.

13. The system of claim 8, wherein the system further includes a ventilation device that passes air across the first gas cooler.

14. The system of claim 13, wherein the first gas cooler heats the first predetermined location.

15. The system of claim 13, wherein the first gas cooler cools the first predetermined location.

16. A combined heating, cooling and water heating system, comprising:Docket No. 010-24-11WO0118 / 21a working fluid passage system containing, at least, a CO2 working fluid, the working fluid passage system including: a first gas cooler that exchanges heat in a first predetermined location; a second gas cooler that exchanges heat in a second predetermined location; a first compressor between the first gas cooler and second gas cooler; a second compressor between the first gas cooler and second gas cooler; wherein the first compressor and second compressor form a reversing valve in the working fluid passage system; and an expansion valve between the second gas cooler and first gas cooler; a second fluid heating system, including: a third gas cooler in thermal coupling with the working fluid passage system between the first gas cooler and second gas cooler, the third gas cooler containing a second fluid; and a second fluid reservoir holding heated second fluid sent from the third gas cooler, wherein working fluid passage system selectively engaging in a compression cycle that: receives low temperature working fluid from either the first predetermined location at the first gas cooler or the second gas cooler at the second predetermined location; compresses the working fluid in the first compressor and second compressor, the compressed working fluid delivering high temperature working fluid at the either the first gas cooler at the first predetermined location or second gas cooler at the second predetermined location; expands the high temperature working fluid in the expansion valve; and passes the expanded working fluid to the first gas cooler or second gas cooler, thereby completing the compression cycle, wherein the third gas cooler selectively heating second fluid from compressed working fluid and sending the heated second fluid to the second fluid reservoir.Docket No. 010-24-11WO0119 / 2117. The system of claim 16, wherein the working fluid is compressed in the second compressor exceeding 1200psia with temperatures above the critical point, exceeding 150°F.

18. The system of claim 16, wherein the fluid passage system further including: a first working fluid passage line between the first gas cooler and second gas cooler, and the first compressor and second compressor located on the first working fluid passage line; and a second working fluid passage line between the first gas cooler and second gas cooler, and the expansion valve located on the second working fluid passage line.

19. The system of claim 16, wherein the second fluid is water.

20. The system of claim 16, wherein the working fluid is R744.Docket No. 010-24-11WO0120 / 21

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