Air source CO2 heat pump unit adopting backwater cooling and heat recovery technology

Abstract

The application belongs to the technical field of refrigeration, air conditioning and heat pump, and particularly relates to an air source CO2 heat pump unit adopting backwater cooling and heat recovery technology, which comprises a CO2 compressor, an air cooler, a subcooler, a backwater cooler, an integrated evaporator / condenser, a throttling valve, a control valve and a user side. The application sets the subcooler and the backwater cooler after the air cooler, adopts the split type gravity circulation heat pipe technology, the air source integrated evaporator / cooling technology, and the integrated heat exchange technology composed of the integrated evaporator / condenser and the split type gravity circulation heat pipe heat end heat exchanger, and provides the cold source for reducing the working medium temperature before the throttling valve and the heat source for preheating the air before the evaporator on the basis of cooling and heat recovery of the system high-temperature backwater.

Description

Technical Field

[0001] This invention relates to the fields of refrigeration, air conditioning and heat pump technology, specifically to an air source CO2 heat pump unit that employs water return cooling and heat recovery technology. Background Technology

[0002] Carbon dioxide (CO2) has become a highly promising refrigerant for low-temperature heat pumps due to its advantages such as zero ozone depletion potential (ODP), extremely low global warming potential (GWP), wide availability, non-toxicity, non-flammability, and excellent flow and heat exchange properties.

[0003] However, due to the constraints of its thermodynamic properties, the heating performance of an air-source CO2 transcritical cycle heat pump system is severely limited by the outlet temperature of the gas cooler. The root cause lies in a significant technical contradiction within the air-source CO2 transcritical cycle heat pump system: the heat exchange advantage of the pseudo-critical temperature zone brought about by the high-temperature return water versus the collapse in overall system energy efficiency caused by the high-temperature return water.

[0004] In other words, while high-temperature return water close to its pseudocritical temperature can give full play to the efficient heat exchange characteristics of the air cooler, it also leads to excessive dryness after supercritical expansion, resulting in excessive loss of volumetric efficiency. At the same time, it causes the system's optimal exhaust pressure to be mismatched, causing the compressor to experience a sharp drop in efficiency under high pressure. On the other hand, directly reducing the outlet temperature of the gas cooler not only greatly weakens the heat exchange advantage of the pseudocritical temperature region, but also requires additional energy consumption, which also leads to a reduction in the overall efficiency of the system.

[0005] Therefore, how to reduce the temperature before the throttling valve while maintaining the heat exchange advantage of the pseudo-critical temperature zone in the air cooler without increasing energy consumption, so as to reduce its throttling loss, has become an important way to improve the overall efficiency of the air source CO2 transcritical cycle heat pump system.

[0006] Therefore, an air-source CO2 heat pump unit employing recirculating water cooling and heat recovery technology is proposed to address the aforementioned problems. Summary of the Invention

[0007] The purpose of this invention is to provide an air-source CO2 heat pump unit that employs water return cooling and heat recovery technology to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: an air source CO2 heat pump unit employing recirculation cooling and heat recovery technology, comprising a CO2 compressor, an air cooler, a recooler, a recirculation cooler, an integrated evaporator / condenser, a throttling valve, a control valve, and a user side; The discharge end of the CO2 compressor is connected to the first inlet of the air cooler, the first outlet of the air cooler is connected to the first inlet of the recooler, the first outlet of the recooler is connected to the inlet of the throttle valve, the outlet of the throttle valve is connected to the first inlet of the integrated evaporator / condenser, and the first outlet of the integrated evaporator / condenser is connected to the suction end of the CO2 compressor. The second outlet of the integrated evaporator / condenser is connected to the inlet of the control valve, the outlet of the control valve is connected to the first inlet of the return water cooler, and the first outlet of the return water cooler is connected to the second inlet of the integrated evaporator / condenser. The second inlet of the return water cooler is connected to the return water pipe on the user side, its second outlet is connected to the second inlet of the recooler, the second outlet of the recooler is connected to the second inlet of the air cooler, and the second outlet of the air cooler is connected to the water supply pipe on the user side.

[0009] Preferably, the return water cooler is a split-type gravity circulation heat pipe hot end heat exchanger, and the condenser of the integrated evaporator / condenser is the split-type gravity circulation heat pipe cold end heat exchanger. Together, they form a split-type gravity circulation heat pipe.

[0010] Preferably, the integrated evaporator / condenser is composed of a CO2 evaporator and a heat pipe cold end heat exchanger (i.e., a condenser) integrated together, and together with the return water cooler, forms an integrated heat exchanger.

[0011] Preferably, the CO2 working fluid circuit and water circuit of the gas cooler and the recooler are connected in series.

[0012] Preferably, the airflow direction of the integrated evaporator / condenser is from the condenser to the evaporator.

[0013] Preferably, a control valve is provided between the condenser of the integrated evaporator / condenser (i.e., the split gravity circulation heat pipe cold end heat exchanger) and the return water cooler (i.e., the split gravity circulation heat pipe hot end heat exchanger).

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention, by setting up a recooler and a return water cooler after the air cooler, and employing split gravity circulation heat pipe technology, integrated air-source evaporation / cooling technology, and an integrated heat exchange technology combining an integrated evaporator / condenser and a split gravity circulation heat pipe hot-end heat exchanger, uses the cooling and heat recovery of the system's high-temperature return water as a basis. It provides a cold source for reducing the working fluid temperature before the system's throttling valve and a heat source for preheating the air before the evaporator. This not only significantly reduces the throttling losses in the system's circulation process, but also maintains the heat exchange advantage of the pseudo-critical temperature zone in the air cooler and improves the evaporation pressure and temperature of the system's evaporator, as well as its anti-frost capability. In turn, it can reduce the compressor's compression ratio and improve its efficiency, providing a possibility for replacing existing technologies such as auxiliary working fluid cascade and composite systems that require significantly increased additional energy consumption.

[0015] Taking the standard low-temperature operating condition with supply and return water temperatures of 60℃ / 40℃ and outdoor ambient temperature of -12℃ as an example, theoretical calculations show that the air source CO2 transcritical cycle heat pump unit of the present invention, which adopts return water cooling and its heat recovery technology, improves the COPh by about 30% compared with the conventional single-stage compression transcritical CO2 heat pump cycle. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention.

[0017] In the diagram: 1 CO2 compressor, 2 air cooler, 3 recooler, 4 return water cooler, 5 integrated evaporator / condenser, 6 throttle valve, 7 control valve. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] Example: Please see Figure 1 The present invention provides a technical solution: An air-source CO2 heat pump unit employing recirculation cooling and heat recovery technology includes a CO2 compressor 1, an air cooler 2, a recooler 3, a recirculation cooler 4, an integrated evaporator / condenser 5, a throttling valve 6, a control valve 7, and a user side; The exhaust end of CO2 compressor 1 is connected to the first inlet of air cooler 2, the first outlet of air cooler 2 is connected to the first inlet of recooler 3, the first outlet of recooler 3 is connected to the inlet of throttle valve 6, the outlet of throttle valve 6 is connected to the first inlet of integrated evaporator / condenser 5, and the first outlet of integrated evaporator / condenser 5 is connected to the suction end of CO2 compressor 1, thus forming a CO2 circulation loop. In this circuit, the high-temperature and high-pressure CO2 gas discharged from the compressor 1 becomes a supercritical low-temperature fluid with a certain temperature difference from the outlet temperature of the air cooler 2 under the continuous cooling of the air cooler 2 and the recooler 3, thereby reducing its throttling loss; and such two-stage segmented cooling makes it possible to maintain the CO2 temperature at the outlet of the air cooler 2 near the pseudo-critical temperature, thereby ensuring the heat exchange performance and efficiency of the air cooler 2 as the main cooler. The second outlet of the integrated evaporator / condenser 5 is connected to the inlet of the control valve 7, the outlet of the control valve 7 is connected to the first inlet of the return water cooler 4, and the first outlet of the return water cooler 4 is connected to the second inlet of the integrated evaporator / condenser 5, thus forming a refrigerant circulation loop of the split gravity circulation heat pipe. In this loop, the return water cooler 4 acts as a split-type gravity-circulating heat pipe hot-end heat exchanger. The refrigerant liquid in it evaporates into gas under the heating of the system's return water and enters the condenser of the integrated evaporator / condenser 5 through a connecting pipe. This condenser, which also acts as a split-type gravity-circulating heat pipe cold-end heat exchanger, condenses into liquid under the cooling of ambient air and then returns to the return water cooler 4 by gravity through the connecting pipe. Thus, the heat released by the system's return water cooling is transferred to the integrated evaporator / condenser 5, providing a heat source for heating the inlet air and creating conditions for increasing the system's evaporation temperature. The second inlet of the return water cooler 4 is connected to the return water pipe on the user side, and its second outlet is connected to the second inlet of the recooler 3. The second outlet of the recooler 3 is connected to the second inlet of the air cooler 2, and the second outlet of the air cooler 2 is connected to the water supply pipe on the user side, thus forming a hot water circulation loop in the system. In this loop, the return water from the user side is first cooled in the return water cooler 4, thus providing a cold source for the deep cooling of CO2 at the outlet of the air cooler 2 by the recooler 3; and when the temperature difference between the return water outlet of the recooler 3 and the temperature of CO2 at the outlet of the air cooler 2, i.e. the pseudo-critical temperature of CO2, is maintained at a certain temperature difference, it ensures the efficient heat transfer of the air cooler 2. A control valve 7 is provided between the condenser of the integrated evaporator / condenser 5 (i.e., the split gravity circulation heat pipe cold end heat exchanger) and the return water cooler 4 (i.e., the split gravity circulation heat pipe hot end heat exchanger) to control and regulate the cooling degree of the system return water, so as to ensure that the return water outlet temperature of the recooler 3 and the CO2 outlet temperature of the air cooler 2 (i.e., the pseudo-critical temperature of CO2) maintain a certain temperature difference. The return water cooler 4 is a split gravity circulation heat pipe hot end heat exchanger, and the condenser of the integrated evaporator / condenser 5 is a split gravity circulation heat pipe cold end heat exchanger. Together, they form a split gravity circulation heat pipe.

[0021] The integrated evaporator / condenser 5 is composed of a CO2 evaporator and a heat pipe cold end heat exchanger, i.e., a condenser, which together with the return water cooler 4 form an integrated heat exchanger. This integrated heat exchanger has multiple functions including evaporation, condensation, and cooling.

[0022] The CO2 working fluid circuit and water circuit of air cooler 2 and recooler 3 are connected in series.

[0023] The airflow direction of the integrated evaporator / condenser 5 is from the condenser to the evaporator, thereby realizing the utilization of the system's return water cooling heat recovery, which can increase the evaporation temperature of CO2 and thus improve the overall efficiency of the system.

[0024] A control valve 7 is provided between the condenser of the integrated evaporator / condenser 5 (i.e., the split gravity circulation heat pipe cold end heat exchanger) and the return water cooler 4 (i.e., the split gravity circulation heat pipe hot end heat exchanger) to control and regulate the cooling degree of the system return water.

[0025] This unit, by installing a recooler 3 and a return water cooler 4 after the air cooler, and employing split gravity circulation heat pipe technology, integrated air-source evaporation / cooling technology, and integrated heat exchange technology combining an integrated evaporator / condenser 5 and a split gravity circulation heat pipe hot-end heat exchanger, can maintain the heat exchange advantage of the pseudo-critical temperature zone in the air cooler while reducing its temperature before the throttling valve to reduce its throttling losses. Furthermore, by using the recovered heat from the return water cooling to heat the inlet air temperature of the evaporator, the overall efficiency of the air-source CO2 transcritical cycle heat pump system is improved.

[0026] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description. Therefore, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An air-source CO2 heat pump unit employing recirculating water cooling and heat recovery technology, characterized in that, Includes a CO2 compressor (1), an air cooler (2), a recooler (3), a return water cooler (4), an integrated evaporator / condenser (5), a throttle valve (6), a control valve (7), and a user side; The exhaust end of the CO2 compressor (1) is connected to the first inlet of the air cooler (2), the first outlet of the air cooler (2) is connected to the first inlet of the recooler (3), the first outlet of the recooler (3) is connected to the inlet of the throttle valve (6), the outlet of the throttle valve (6) is connected to the first inlet of the integrated evaporator / condenser (5), and the first outlet of the integrated evaporator / condenser (5) is connected to the suction end of the CO2 compressor (1). The second outlet of the integrated evaporator / condenser (5) is connected to the inlet of the control valve (7), the outlet of the control valve (7) is connected to the first inlet of the return water cooler (4), and the first outlet of the return water cooler (4) is connected to the second inlet of the integrated evaporator / condenser (5). The second inlet of the return water cooler (4) is connected to the return water pipe on the user side, and its second outlet is connected to the second inlet of the recooler (3). The second outlet of the recooler (3) is connected to the second inlet of the air cooler (2), and the second outlet of the air cooler (2) is connected to the water supply pipe on the user side.

2. The air-source CO2 heat pump unit employing recirculating water cooling and heat recovery technology according to claim 1, characterized in that: The return water cooler (4) is a split gravity circulation heat pipe hot end heat exchanger, and the condenser of the integrated evaporator / condenser (5) is a split gravity circulation heat pipe cold end heat exchanger. Together, they form a split gravity circulation heat pipe.

3. An air-source CO2 heat pump unit employing recirculating water cooling and heat recovery technology according to claim 1, characterized in that: The integrated evaporator / condenser (5) is composed of a CO2 evaporator and a heat pipe cold end heat exchanger, i.e., a condenser, which together with the return water cooler (4) form an integrated heat exchanger.

4. An air-source CO2 heat pump unit employing recirculating water cooling and heat recovery technology according to claim 1, characterized in that: The CO2 working fluid circuit and water circuit of the gas cooler (2) and the recooler (3) are connected in series.

5. An air-source CO2 heat pump unit employing recirculating water cooling and heat recovery technology according to claim 1, characterized in that: The airflow direction of the integrated evaporator / condenser (5) is from the condenser to the evaporator.

6. An air-source CO2 heat pump unit employing recirculating water cooling and heat recovery technology according to claim 1, characterized in that: A control valve (7) is provided between the condenser of the integrated evaporator / condenser (5), i.e., the split gravity circulation heat pipe cold end heat exchanger, and the return water cooler (4), i.e., the split gravity circulation heat pipe hot end heat exchanger.

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