CO2 for efficient utilization of multi-terminal low-temperature thermal energy 2 Transcritical air source heat pump system

Abstract

A multi-terminal, low-temperature, high-efficiency CO2 transcritical air-source heat pump system is disclosed, comprising a heat pump circulation system, a water circulation system, and a domestic hot water circulation system. This invention ensures both indoor heating and convenient domestic hot water production, guaranteeing stable and efficient operation throughout the year. The multi-terminal indoor heating system connects low-temperature and high-temperature heating terminals in series at the water tank outlet, controlled by four shut-off valves. This satisfies residents' comfort requirements without excessive waste, achieving two goals at once. In winter, when frost forms on the evaporator surface, the system can defrost quickly without significantly impacting the system, ensuring normal operation within its reasonable operating range. This invention, as a multi-terminal, low-temperature, high-efficiency CO2 transcritical air-source heat pump system, solves the problems of low efficiency and high defrosting costs associated with existing heat pumps.

Description

Technical Field

[0001] The invention belongs to a heat pump and relates to a direct-heating heat pump. Background Art

[0002] Heat pumps can use a small amount of driving energy to transfer heat from a low-temperature heat source to an object with a temperature higher than the ambient temperature. Conventional working fluids of heat pumps, HCFC and HFC, have negative effects of destroying the ozone layer and aggravating the greenhouse effect, which is not conducive to sustainable development. Therefore, in recent years, CO2 transcritical air source heat pumps have become the focus of research and development in the field of heat pumps. This is because, on the one hand, CO2 working fluid is more environmentally friendly and easy to obtain; on the other hand, due to the supercritical nature of the working fluid in the air cooler, it is particularly suitable for producing hot water with higher temperature through countercurrent heat exchange, which is more energy-saving.

[0003] The temperature in northern my country is often very low in winter, and some rural areas often use coal-fired boilers for heating. In recent years, environmental and energy issues have attracted more and more attention, and the country has also attached more and more importance to environmental protection and energy conservation, so air energy heat pumps have been widely promoted. The commonly used heat pump hot air blower has low inlet and outlet temperatures and has a good energy-saving effect, but the dry hot air blown out during heating in winter often makes people feel uncomfortable, the indoor air is not good, and the human body comfort is reduced. Some high-temperature heating terminals, such as radiators and floor heating, use natural convection during heating, which can ensure the heating effect without blowing, but requires a lot of pipeline laying and modification. At the same time, the inlet and outlet temperatures of the high-temperature heating terminals are relatively high, and the high-temperature heat source of the heat pump is at a high temperature for a long time, which will lead to large throttling losses in the circulation system and a low performance coefficient.

[0004] In the prior art, in order to solve the above problems, the technical measures that can be adopted mainly include variable frequency compression, cascade compression, the use of binary or ternary mixed working fluids, and air replenishment and enthalpy increase under low temperature conditions. These technologies are helpful to improve the efficiency of heat pumps to a certain extent, but they cannot completely solve the problem, and some technologies have not been popularized in home use. In addition, these technologies will more or less make the system complicated and increase the cost. For small households, the cost is too high and the energy saving significance is not great. Summary of the invention

[0005] In order to overcome the shortcomings of low efficiency and high defrosting cost of existing heat pumps, the present invention provides a CO2 transcritical air source heat pump system with multi-terminal low-temperature thermal energy efficient utilization, which improves heat pump efficiency and reduces defrosting cost.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A CO2 transcritical air source heat pump system for efficient utilization of multi-terminal low-temperature thermal energy, comprising a compressor, a first air cooler, a second air cooler, a first throttling device, a second throttling device, a first filter, a second filter, an evaporator, a gas-liquid separator, a first stop valve, a second stop valve, a third stop valve, a first check valve and a second check valve, wherein the exhaust port of the compressor is connected to the inlet of the first stop valve and the inlet of the third stop valve respectively, the outlet of the first stop valve is connected to the first inlet of the first air cooler, the first outlet of the first air cooler is connected to the first inlet of the second air cooler, the first outlet of the second air cooler is connected to the inlet of the first filter, and .... The outlet of a filter is connected to the inlet of a first throttling device, the outlet of the first throttling device is connected to the inlet of a first one-way valve, the outlet of the first one-way valve is connected to the inlet of a second filter, the outlet of the second filter is connected to the inlet of an evaporator, the outlet of the evaporator is connected to the inlet of a gas-liquid separator, the first outlet of the gas-liquid separator is connected to the inlet of a compressor, the second outlet of the gas-liquid separator is connected to the inlet of a second stop valve, the outlet of the second stop valve is connected to the inlet of a second one-way valve, the outlet of the second one-way valve is connected to the inlet of the compressor, the outlet of the third stop valve is connected to the inlet of the second throttling device, and the outlet of the second throttling device is connected to the inlet of the second filter.

[0008] Furthermore, the heat pump also includes a low-temperature heating terminal, a high-temperature heating terminal, a constant temperature water tank, a water pump, a fourth stop valve, a fifth stop valve, a sixth stop valve, and a seventh stop valve. The second outlet of the first air cooler is connected to the inlet of the constant temperature water tank, the outlet of the constant temperature water tank is connected to the inlet of the fourth stop valve, the first interface of the fifth stop valve, and the inlet of the sixth stop valve, respectively, the outlet of the fourth stop valve is connected to the inlet of the high-temperature heating terminal, the outlet of the high-temperature heating terminal is connected to the inlet of the low-temperature heating terminal and the second interface of the fifth stop valve, respectively, the outlet of the low-temperature heating terminal is connected to the inlet of the seventh stop valve, the outlet of the seventh stop valve is connected to the inlet of the water pump and the outlet of the sixth stop valve, respectively, and the outlet of the water pump is connected to the second inlet of the first air cooler.

[0009] Furthermore, the heat pump also includes a sanitary hot water tank, the tap water interface is connected to the second inlet of the second air cooler, the second outlet of the second air cooler is connected to the sanitary hot water tank, and the outlet of the sanitary hot water tank is the sanitary hot water outlet.

[0010] Furthermore, the heat pump also includes an electric heating device, which is arranged in the middle and lower part of the gas-liquid separator.

[0011] Furthermore, the heat pump also includes a temperature sensor, a variable frequency fan and a control device. The temperature sensor is located at the air side inlet of the evaporator and is connected to the control device; the variable frequency fan is also connected to the control device.

[0012] The technical concept of the present invention is to connect the low-temperature heating terminal and the high-temperature heating terminal in series. Here, the commonly used hot air blower is used as the low-temperature heating terminal, and the radiator is used as the high-temperature heating terminal. For example, the hot air blower can be installed in the bathroom, kitchen, storage room and other places that are not used for a long time, and the radiator can be installed on the bedroom floor where comfort needs to be guaranteed, so as to ensure the best heating comfort. Based on the principle of energy cascade utilization, high-temperature hot water is first used for heating through the radiator, and then heats the hot air blower to blow out hot air, which reasonably utilizes the waste heat, reduces the temperature of the high-temperature heat source of the heat pump, optimizes the operating conditions of the heat pump, reduces the power consumption of the compressor, and improves the system performance coefficient. At the same time, the system improves the hot gas bypass defrost system and uses it for heat pump defrosting as an improvement point of this system.

[0013] The present invention is also provided with a second air cooler. The medium-temperature high-pressure gas passing through the first air cooler will be further cooled in the second air cooler and used to heat tap water to obtain sanitary hot water, thereby further reducing the exhaust temperature and pressure of the compressor and improving the energy efficiency of the system. Sanitary hot water does not require a very high temperature (30℃-45℃). Installing it on the second air cooler for heating can fully utilize the waste heat and produce sanitary hot water, which can be said to kill two birds with one stone.

[0014] The beneficial effects of the present invention are mainly manifested in:

[0015] 1. When the system is running, especially in low temperatures in winter, compared with ordinary heat pump cycles, this system has a higher energy efficiency coefficient (COP) and is more energy-efficient. It consumes less electricity and is more efficient when heating the room at the same temperature.

[0016] 2. When frost forms on the surface of the evaporator in winter, this system can quickly defrost without causing too much impact on the system, ensuring that the system operates normally within a reasonable working range.

[0017] 3. The system uses CO2 as refrigerant, which is more environmentally friendly. Its efficiency is higher than that of ordinary heat pumps and has a wide range of applications. It is especially suitable for winter heating in the north. It has significant energy-saving effects and economic benefits and has broad development prospects.

[0018] 4. Effectively utilize the waste heat released by the air cooler and adopt multi-stage cooling to meet both indoor heating needs and bathroom hot water needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a diagram of a CO2 transcritical air source heat pump system for efficient utilization of multi-terminal low-temperature thermal energy, wherein 1: compressor; 2: first stop valve; 3: first air cooler; 4: second air cooler; 5: first filter; 6: first throttling device; 7: first non-return valve; 8: second filter; 9: evaporator; 10: gas-liquid separator; 11: second stop valve; 12: second non-return valve; 13: third stop valve; 14: second throttling device; 15: electric heating device; 16: constant temperature water tank; 17: high-temperature heating terminal; 18: low-temperature heating terminal; 20: fourth stop valve; 21: fifth stop valve; 22: sixth stop valve; 23: seventh stop valve; 26: water pump; 27: sanitary hot water tank; 28: temperature sensor; 29: variable frequency fan; 30: control device.

[0020] Figure 2 This is a diagram of the system without sanitary hot water installed, in which 1: compressor; 2: first stop valve; 3: first air cooler; 4: second air cooler; 5: first filter; 6: first throttling device; 7: first non-return valve; 8: second filter; 9: evaporator; 10: gas-liquid separator; 11: second stop valve; 12: second non-return valve; 13: third stop valve; 14: second throttling device; 15: electric heating device; 16: constant temperature water tank; 17: high temperature heating terminal; 18: low temperature heating terminal; 20: fourth stop valve; 21: fifth stop valve; 22: sixth stop valve; 23: seventh stop valve; 26: water pump; 28: temperature sensor; 29: variable frequency fan; 30: control device.

[0021] Figure 3 This is a diagram of the system with a sub-low temperature heating terminal installed, in which 1: compressor; 2: first stop valve; 3: first air cooler; 4: second air cooler; 5: first filter; 6: first throttling device; 7: first non-return valve; 8: second filter; 9: evaporator; 10: gas-liquid separator; 11: second stop valve; 12: second non-return valve; 13: third stop valve; 14: second throttling device; 15: electric heating device; 16: constant temperature water tank; 17: high temperature heating terminal; 18: low temperature heating terminal; 19: sub-low temperature heating terminal; 20: fourth stop valve; 21: fifth stop valve; 22: sixth stop valve; 23: seventh stop valve; 24: eighth stop valve; 25: ninth stop valve; 26: water pump; 27: sanitary hot water tank; 28: temperature sensor; 29: variable frequency fan; 30: control device. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings.

[0023] Reference Figure 1 to Figure 3A CO2 transcritical air source heat pump system for efficient utilization of multi-terminal low-temperature thermal energy comprises a compressor, a first air cooler, a second air cooler, a first throttling device, a second throttling device, a first filter, a second filter, an evaporator, a gas-liquid separator, a first stop valve, a second stop valve, a third stop valve, a first check valve and a second check valve, the exhaust port of the compressor is connected to the inlet of the first stop valve and the inlet of the third stop valve respectively, the outlet of the first stop valve is connected to the first inlet of the first air cooler, the first outlet of the first air cooler is connected to the first inlet of the second air cooler, the first outlet of the second air cooler is connected to the inlet of the first filter ... and the The outlet of a filter is connected to the inlet of a first throttling device, the outlet of the first throttling device is connected to the inlet of a first one-way valve, the outlet of the first one-way valve is connected to the inlet of a second filter, the outlet of the second filter is connected to the inlet of an evaporator, the outlet of the evaporator is connected to the inlet of a gas-liquid separator, the first outlet of the gas-liquid separator is connected to the inlet of a compressor, the second outlet of the gas-liquid separator is connected to the inlet of a second stop valve, the outlet of the second stop valve is connected to the inlet of a second one-way valve, the outlet of the second one-way valve is connected to the inlet of the compressor, the outlet of the third stop valve is connected to the inlet of the second throttling device, and the outlet of the second throttling device is connected to the inlet of the second filter.

[0024] Furthermore, the heat pump also includes a low-temperature heating terminal, a high-temperature heating terminal, a constant temperature water tank, a water pump, a fourth stop valve, a fifth stop valve, a sixth stop valve, and a seventh stop valve. The second outlet of the first air cooler is connected to the inlet of the constant temperature water tank, the outlet of the constant temperature water tank is connected to the inlet of the fourth stop valve, the first interface of the fifth stop valve, and the inlet of the sixth stop valve, respectively, the outlet of the fourth stop valve is connected to the inlet of the high-temperature heating terminal, the outlet of the high-temperature heating terminal is connected to the inlet of the low-temperature heating terminal and the second interface of the fifth stop valve, respectively, the outlet of the low-temperature heating terminal is connected to the inlet of the seventh stop valve, the outlet of the seventh stop valve is connected to the inlet of the water pump and the outlet of the sixth stop valve, respectively, and the outlet of the water pump is connected to the second inlet of the first air cooler.

[0025] Furthermore, the heat pump also includes a sanitary hot water tank, the tap water interface is connected to the second inlet of the second air cooler, the second outlet of the second air cooler is connected to the sanitary hot water tank, and the outlet of the sanitary hot water tank is the sanitary hot water outlet.

[0026] Furthermore, the heat pump also includes an electric heating device, which is arranged in the middle and lower part of the gas-liquid separator.

[0027] Furthermore, the heat pump also includes a temperature sensor, a variable frequency fan and a control device. The temperature sensor is located at the air side inlet of the evaporator and is connected to the control device; the variable frequency fan is also connected to the control device.

[0028] Example 1: Normal working mode.

[0029] like Figure 1 As shown, the normal working mode of this system has two cycles, a heat pump cycle and a water cycle. In the water circulation system under the normal working mode, the fifth stop valve 21 and the sixth stop valve 22 are closed, the fourth stop valve 20 and the seventh stop valve 23 are opened, the high-temperature heating terminal 17 is connected to the low-temperature heating terminal 18 and is respectively located in different rooms. The two are connected in series to absorb the heat released by the air cooler 3 and then heat the room. The low-temperature heating terminal (such as the floor radiation heating terminal) can be installed in the bathroom, kitchen, storage room and other places that are not used for a long time, and the high-temperature heating terminal (such as the radiator) can be installed in the bedroom where comfort needs to be guaranteed to ensure the best heating comfort. The high-temperature hot water first passes through the high-temperature heating terminal and then passes through the low-temperature heating terminal, which reasonably utilizes the waste heat and reduces the temperature of the high-temperature heat source of the heat pump, thereby improving the energy efficiency coefficient of the system. At the same time, the second air cooler 4 is also working, continuously heating the tap water to produce sanitary hot water and storing it in the water tank 27, such as Figure 2 This part can also be removed. Compared with some cities that only use heat pump radiators as heating devices, a lot of energy is saved, not to mention the less efficient heating furnaces or electric heaters.

[0030] Embodiment 2: Low temperature heating terminal working mode or high temperature heating terminal working mode

[0031] like Figure 1 As shown, in some special cases, the residents may stay in one room, so it is not necessary to activate both heating devices. The present invention installs 4 stop valves in the water circulation system to control the two heating devices. For example, if only the low-temperature heating terminal is needed to work but not the high-temperature heating terminal, the fourth and sixth stop valves are closed, and the fifth and seventh stop valves are opened. When only the high-temperature heating terminal is needed to work but not the low-temperature heating terminal, the seventh stop valve is closed, and the fourth, fifth and sixth stop valves are opened. At the same time, the second air cooler is also working, continuously heating the tap water to produce sanitary hot water and storing it in the water tank. Figure 2 This part can also be removed. This design can ensure that the system runs in the most energy-saving mode.

[0032] Example 3: Hot gas bypass defrost mode

[0033] like Figure 1As shown, when the temperature on the surface of the evaporator 9 is lower than the dew point temperature in the air, the water vapor in the air will gradually condense on the surface of the evaporator to form a frost layer, which is a very common phenomenon in winter in the north. The present invention uses the hot gas bypass defrosting system for a CO2 transcritical air source heat pump system with multi-terminal low-temperature heat energy efficient utilization. When the frost layer on the evaporator is too thick and affects the operation, the fourth stop valve is closed and the fifth stop valve is opened. At this time, the high-temperature CO2 refrigerant discharged from the compressor 1 will flow through the fifth stop valve and directly enter the air-cooled evaporator for defrosting. After heat exchange, the CO2 refrigerant flows through the gas-liquid separator 10 and enters the compressor to complete the cycle.

[0034] During the normal operation of the system, the oil in the compressor will dissolve in the refrigerant and run out of the compressor, and finally precipitate in the gas-liquid separator. As the system works, the oil in the compressor will become less and less, which will make the system unable to operate normally and even cause the compressor to burn out. Therefore, the present invention installs the electric heating device 15 in the middle and lower part of the gas-liquid separator, sets a period of time for it to heat regularly, and connects an oil return pipe at the bottom. As the electric heater heats, the oil will dissolve in the refrigerant liquid and flow back into the compressor through the second stop valve 11, ensuring that the compressor works in a safe environment.

[0035] Example 4: Heating sanitary hot water mode

[0036] The system is provided with a second air cooler 4 for producing sanitary hot water. The medium-temperature high-pressure gas passing through the first air cooler will be further cooled in the second air cooler and used to heat tap water to obtain sanitary hot water. The sanitary hot water tank 24 is installed in the bathroom. During the day, as the indoor heating is provided, hot water will be continuously stored in the hot water tank and can be used by the residents at any time. If the residents do not need sanitary hot water, or the outdoor temperature is too low in winter and there is no way to get hot water of sufficient temperature, they can also use Figure 2 The structure in the embodiment of the present invention removes the sanitary hot water module to ensure that the room is adequately heated. If the resident is in urgent need of sanitary hot water, the water pump 26 can be turned off to quickly prepare sanitary hot water.

[0037] Example 5: Multi-stage heating mode

[0038] like Figure 3 As shown, on the basis of the original system, this system is equipped with a sub-low temperature heating terminal 19 and two stop valves, further subdividing the heat source temperature provided by the heat pump and lowering the lower temperature limit of the heat source utilization, so as to make refined utilization and improve the efficiency of the heat pump. By analogy, in principle, the heating terminal can be divided into more levels, and the energy efficiency coefficient COP can be further improved on the original basis. The specific number of levels can be changed according to the ambient temperature and economic conditions, which greatly improves the working conditions of the system.

[0039] Embodiment 6: Summer hot water production mode

[0040] In summer, residents do not need heating mode, they only need the system to provide a certain amount of domestic hot water every day. Figure 2 The structure in. Because the working conditions of each component of this system are designed based on the condition of -20℃ in winter, the high evaporation temperature in summer will cause the compressor to consume too much power and burn out. Therefore, this system installs a temperature sensor at the air side inlet of the evaporator and connects it to the control device, and the other end of the control device is connected to the variable frequency fan of the evaporator. When the air temperature exceeds the set value, the control device controls the variable frequency fan to reduce the speed, increase the evaporator temperature difference, reduce the refrigerant temperature in the evaporator, and thus reduce the power consumption of the compressor. Ensure that the system operates under reasonable and safe conditions.

Claims

1. A CO2 transcritical air source heat pump system for efficient utilization of multi-terminal low-temperature thermal energy, characterized in that: The system includes a compressor, a first air cooler, a second air cooler, a first throttling device, a second throttling device, a first filter, a second filter, an evaporator, a gas-liquid separator, a first stop valve, a second stop valve, a third stop valve, a first check valve, and a second check valve. The exhaust port of the compressor is connected to the inlet of the first stop valve and the inlet of the third stop valve, respectively. The outlet of the first stop valve is connected to the first inlet of the first air cooler, the first outlet of the first air cooler is connected to the first inlet of the second air cooler, the first outlet of the second air cooler is connected to the inlet of the first filter, and the outlet of the first filter is connected to the first throttling device. The inlet of the device is connected, the outlet of the first throttling device is connected to the inlet of the first one-way valve, the outlet of the first one-way valve is connected to the inlet of the second filter, the outlet of the second filter is connected to the inlet of the evaporator, the outlet of the evaporator is connected to the inlet of the gas-liquid separator, the first outlet of the gas-liquid separator is connected to the inlet of the compressor, the second outlet of the gas-liquid separator is connected to the inlet of the second stop valve, the outlet of the second stop valve is connected to the inlet of the second one-way valve, the outlet of the second one-way valve is connected to the inlet of the compressor, the outlet of the third stop valve is connected to the inlet of the second throttling device, and the outlet of the second throttling device is connected to the inlet of the second filter.

2. The CO2 transcritical air source heat pump system for efficient utilization of multi-terminal low-temperature thermal energy according to claim 1, characterized in that: The heat pump also includes a low-temperature heating terminal, a high-temperature heating terminal, a constant temperature water tank, a water pump, a fourth stop valve, a fifth stop valve, a sixth stop valve and a seventh stop valve. The second outlet of the first air cooler is connected to the inlet of the constant temperature water tank, the outlet of the constant temperature water tank is connected to the inlet of the fourth stop valve, the first interface of the fifth stop valve, and the inlet of the sixth stop valve, respectively, the outlet of the fourth stop valve is connected to the inlet of the high-temperature heating terminal, the outlet of the high-temperature heating terminal is connected to the inlet of the low-temperature heating terminal and the second interface of the fifth stop valve, respectively, the outlet of the low-temperature heating terminal is connected to the inlet of the seventh stop valve, the outlet of the seventh stop valve is connected to the inlet of the water pump and the outlet of the sixth stop valve, respectively, and the outlet of the water pump is connected to the second inlet of the first air cooler.

3. The CO2 transcritical air source heat pump system for efficient utilization of multi-terminal low-temperature thermal energy as claimed in claim 1 or 2, characterized in that: The heat pump also includes a sanitary hot water tank, the tap water interface is connected to the second inlet of the second air cooler, the second outlet of the second air cooler is connected to the sanitary hot water tank, and the outlet of the sanitary hot water tank is the sanitary hot water outlet.

4. The CO2 transcritical air source heat pump system for efficient utilization of multi-terminal low-temperature thermal energy as claimed in claim 1 or 2, characterized in that: The heat pump further comprises an electric heating device, which is arranged in the middle and lower part of the gas-liquid separator.

5. The CO2 transcritical air source heat pump system for efficient utilization of multi-terminal low-temperature thermal energy as claimed in claim 1 or 2, characterized in that: The heat pump also includes a temperature sensor, a variable frequency fan and a control device. The temperature sensor is located at the air side inlet of the evaporator and is connected to the control device; the variable frequency fan is also connected to the control device.

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