Carbon dioxide cascade heat pump system and implementation method thereof

Abstract

The invention belongs to the field of carbon dioxide heat pumps, and provides a carbon dioxide cascade heat pump system and an implementation method thereof.The system comprises a heat pump subsystem and a water side heat exchange subsystem; the heat pump subsystem comprises a carbon dioxide transcritical compressor, an air cooler, an air cooling valve, an intermediate heat exchanger, a carbon dioxide expansion valve, an evaporator, a high-temperature stage compressor, a condenser and a high-temperature stage expansion valve; the water side heat exchange subsystem comprises a heating circulating pump, a heating water return pipeline, a first heating water supply pipeline, a heating flow dividing pipeline and a second heating water supply pipeline. Through the air cooler and the air cooling valve, the effect that the carbon dioxide transcritical compressor outputs steam and operates in a transcritical mode and a subcritical mode at the same time is achieved, primary high-temperature water is secondarily heated through the temperature slippage characteristic of carbon dioxide, and the hot water preparation efficiency and the heat exchange efficiency of carbon dioxide are improved.

Description

Technical Field

[0001] The present invention relates to the field of carbon dioxide heat pumps, and in particular to a carbon dioxide cascade heat pump system and an implementation method thereof. Background Art

[0002] As a natural working fluid, carbon dioxide has an ozone depletion potential of 0 and a global warming potential of 1. It is low-cost, easily available, non-toxic and stable. Compared with traditional working fluid heat pump systems, carbon dioxide heat pumps have the advantages of a wide range of hot water temperatures and little restriction by ambient temperature. They can effectively reduce the consumption of fossil energy and improve energy efficiency. Due to the low critical temperature of carbon dioxide, the heat release process is not condensed in the two-phase region, but heat is released in the gas cooler in the area close to or exceeding the critical point. In the transcritical cycle, there is a large temperature glide, and hot water at a higher temperature can be obtained. It has great potential for use as a water heater.

[0003] The efficiency of the existing carbon dioxide heat pump transcritical cycle depends on the exhaust pressure and the air cooler outlet temperature. It is suitable for large temperature difference hot water heating. However, for the actual heating cycle, the return water temperature is relatively high, which affects the efficiency of the heat pump. Therefore, it is not suitable for small temperature difference heating cycle. In addition, the carbon dioxide system in the cascade unit acts as a low temperature stage and operates in the subcritical region. The temperature glide of carbon dioxide in the transcritical heat transfer process is not utilized to produce the thermodynamic properties of high-temperature hot water. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a carbon dioxide cascade heat pump system and its implementation method, through an air cooler and an air cooling valve, the carbon dioxide transcritical compressor outputs steam and operates in transcritical and subcritical mode at the same time, and utilizes the temperature glide characteristics of carbon dioxide to perform secondary heating of primary high-temperature water, thereby improving the efficiency of hot water production and the heat exchange efficiency of carbon dioxide.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A carbon dioxide cascade heat pump system, comprising: a heat pump subsystem and a water-side heat exchange subsystem; the heat pump subsystem comprises: a carbon dioxide transcritical compressor, an air cooler, an air cooling valve, an intermediate heat exchanger, a carbon dioxide expansion valve, an evaporator, a high-temperature compressor, a condenser and a high-temperature expansion valve; the water-side heat exchange subsystem comprises: a heating circulation pump, a heating return water pipeline, a first heating water supply pipeline, a heating diversion pipeline, and a second heating water supply pipeline;

[0007] The carbon dioxide transcritical compressor, the air cooler, the air cooling valve, the intermediate heat exchanger, the carbon dioxide expansion valve and the evaporator are connected in sequence; the high-temperature compressor, the condenser, the high-temperature expansion valve and the intermediate heat exchanger are connected in sequence; the output end of the carbon dioxide transcritical compressor is connected to the input end of the first refrigerant side of the air cooler; the output end of the first refrigerant side of the air cooler is connected to the input end of the air cooling valve; the output end of the air cooling valve is connected to the input end of the first refrigerant side of the intermediate heat exchanger; the output end of the first refrigerant side of the intermediate heat exchanger is connected to the input end of the carbon dioxide expansion valve; the output end of the carbon dioxide expansion valve is connected to the input end of the evaporator; the output end of the evaporator is connected to the input end of the carbon dioxide transcritical compressor; the second refrigerant side of the intermediate heat exchanger The output end of the refrigerant side is connected to the input end of the high-temperature compressor; the output end of the high-temperature compressor is connected to the input end of the second refrigerant side of the condenser; the output end of the second refrigerant side of the condenser is connected to the input end of the high-temperature expansion valve; the output end of the high-temperature expansion valve is connected to the input end of the second refrigerant side of the intermediate heat exchanger; the input end of the heating circulation pump is connected to the heating return water pipe; the input end of the condenser water side is connected to the output end of the heating circulation pump; the output end of the condenser water side is connected to the first heating water supply pipe; the first heating water supply pipe is connected to the heating shunt pipe and the second heating water supply pipe in sequence according to the water supply direction; the heating shunt pipe is connected to the input end of the water side of the air cooler; the output end of the water side of the air cooler is connected to the second heating water supply pipe;

[0008] The carbon dioxide transcritical compressor is used to compress the input low-temperature, low-pressure first refrigerant steam and output the high-temperature, high-pressure first refrigerant steam in the transcritical area; the air cooler is used to use the high-temperature, high-pressure first refrigerant steam to heat the primary high-temperature water input by the heating diversion pipeline; the air cooling valve is used to reduce the pressure of the high-temperature, high-pressure first refrigerant steam to the subcritical superheated steam zone to obtain the medium-temperature, medium-pressure first refrigerant steam; the intermediate heat exchanger is used to evaporate the low-temperature, low-pressure second refrigerant in a gas-liquid mixed state through the heat released by the condensation of the medium-temperature, medium-pressure first refrigerant steam to obtain the low-temperature, low-pressure second refrigerant steam and the medium-temperature, medium-pressure first refrigerant solution; the carbon dioxide expansion valve is used to reduce the pressure of the medium-temperature, medium-pressure first refrigerant solution to obtain the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state; the evaporator is used to evaporate the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state to obtain the low-temperature, low-pressure first refrigerant steam; the high-temperature compressor is used to compress the low-temperature and low-pressure second refrigerant steam to obtain high-temperature and high-pressure second refrigerant steam; the condenser is used to heat the low-temperature water input by the heating circulation pump through the heat released by condensation of the high-temperature and high-pressure second refrigerant steam to obtain primary high-temperature water and high-temperature second refrigerant solution; the high-temperature expansion valve is used to reduce the pressure of the high-temperature second refrigerant solution to obtain a low-temperature and low-pressure second refrigerant in a gas-liquid mixed state; the heating circulation pump is used to pump the low-temperature water in the heating return water pipe into the condenser; the first heating water supply pipe is used to transport the primary high-temperature water to the air cooler through the heating diversion pipe in a preset proportion for heating; the second heating water supply pipe is used to transport the primary high-temperature water heated by the air cooler to the first heating water supply pipe to obtain mixed high-temperature water, and transport the mixed high-temperature water to the target heating users.

[0009] Preferably, a method for implementing a carbon dioxide cascade heat pump comprises:

[0010] Compressing the low-temperature and low-pressure first refrigerant vapor by using the carbon dioxide transcritical compressor to obtain the high-temperature and high-pressure first refrigerant vapor;

[0011] The air-cooled valve is used to adjust the pressure of the high-temperature and high-pressure first refrigerant steam to a subcritical superheated steam region to obtain the medium-temperature and medium-pressure first refrigerant steam;

[0012] The heat released by condensation of the medium-temperature and medium-pressure first refrigerant vapor is used to evaporate the low-temperature and low-pressure second refrigerant in a gas-liquid mixed state through the intermediate heat exchanger to obtain the low-temperature and low-pressure second refrigerant vapor and the medium-temperature and medium-pressure first refrigerant solution;

[0013] Using the carbon dioxide expansion valve to reduce the pressure of the medium-temperature and medium-pressure first refrigerant solution to obtain the low-temperature and low-pressure first refrigerant in a gas-liquid mixed state;

[0014] Using the evaporator to evaporate the low-temperature and low-pressure first refrigerant in a gas-liquid mixed state to obtain the high-temperature and high-pressure first refrigerant vapor;

[0015] Compressing the low-temperature and low-pressure second refrigerant vapor by using the high-temperature stage compressor to obtain the high-temperature and high-pressure second refrigerant vapor;

[0016] The heat released by condensation of the high-temperature and high-pressure second refrigerant steam is used by the condenser to heat the low-temperature water input by the heating circulation pump to obtain the primary high-temperature water and the high-temperature second refrigerant solution;

[0017] Using the high-temperature expansion valve to reduce the pressure of the high-temperature second refrigerant solution to obtain the low-temperature and low-pressure second refrigerant in a gas-liquid mixed state;

[0018] Using the heating circulation pump to pump the low-temperature water in the heating return water pipe into the condenser;

[0019] Using the first heating water supply pipe and the heating diversion pipe to transport a fixed proportion of the primary high-temperature water to the air cooler;

[0020] The high-temperature and high-pressure first refrigerant steam in the transcritical region is used to heat the primary high-temperature water, and the primary high-temperature water heated by the air cooler is transported to the first heating water supply pipeline through the second heating water supply pipeline to obtain mixed high-temperature water;

[0021] The mixed high-temperature water is delivered to target heating users by using the first heating water supply pipeline.

[0022] Preferably, the high-temperature, low-pressure first refrigerant vapor is carbon dioxide refrigerant.

[0023] Preferably, a carbon dioxide cascade heat pump system for supplying water and heat at the same time comprises: a heat pump subsystem and a water-side heat exchange subsystem; the heat pump subsystem comprises: a carbon dioxide transcritical compressor, an air cooler, an air cooling valve, an intermediate heat exchanger, a carbon dioxide expansion valve, an evaporator, a high-temperature compressor, a condenser and a high-temperature expansion valve; the water-side heat exchange subsystem comprises: a heating circulation pump, a hot water circulation pump, a heating return water pipeline, a heating water supply first pipeline, a hot water return water pipeline, a hot water intermediate pipeline and a hot water heating pipeline;

[0024] The carbon dioxide transcritical compressor, the air cooler, the air cooling valve, the intermediate heat exchanger, the carbon dioxide expansion valve and the evaporator are connected in sequence; the high-temperature stage compressor, the condenser, the high-temperature stage expansion valve and the intermediate heat exchanger are connected in sequence; the output end of the carbon dioxide transcritical compressor is connected to the input end of the first refrigerant side of the air cooler; the output end of the first refrigerant side of the air cooler is connected to the input end of the air cooling valve; the output end of the air cooling valve is connected to the input end of the first refrigerant side of the intermediate heat exchanger; the output end of the first refrigerant side of the intermediate heat exchanger is connected to the input end of the carbon dioxide expansion valve; the output end of the carbon dioxide expansion valve is connected to the input end of the evaporator; the output end of the evaporator is connected to the input end of the carbon dioxide transcritical compressor; the output end of the second refrigerant side of the intermediate heat exchanger is connected to the input end of the high-temperature stage compressor The input end is connected; the output end of the high-temperature compressor is connected to the input end of the second refrigerant side of the condenser; the output end of the second refrigerant side of the condenser is connected to the input end of the high-temperature expansion valve; the output end of the high-temperature expansion valve is connected to the input end of the second refrigerant side of the intermediate heat exchanger; the input end of the heating circulation pump is connected to the heating return water pipeline; the input end of the hot water circulation pump is connected to the hot water return water pipeline; the output end of the heating circulation pump is connected to the first input end of the condenser water side; the output end of the hot water circulation pump is connected to the second input end of the condenser water side; the first output end of the condenser water side is connected to the first heating water supply pipeline; the second output end of the condenser water side is connected to the hot water intermediate pipeline; the input end of the air cooler water side is connected to the hot water intermediate pipeline; the output end of the air cooler water side is connected to the hot water heating pipeline;

[0025] The carbon dioxide transcritical compressor is used to compress the input low-temperature, low-pressure first refrigerant steam and output the high-temperature, high-pressure first refrigerant steam in the transcritical region; the air cooler is used to use the high-temperature, high-pressure first refrigerant steam to heat the primary high-temperature water input by the heating diversion pipeline; the air cooling valve is used to reduce the pressure of the high-temperature, high-pressure first refrigerant steam to the subcritical superheated steam region to obtain the medium-temperature, medium-pressure first refrigerant steam; the intermediate heat exchanger is used to evaporate the low-temperature, low-pressure second refrigerant in a gas-liquid mixed state by the heat released by the condensation of the medium-temperature, medium-pressure first refrigerant steam to obtain the low-temperature, low-pressure second refrigerant steam and the medium-temperature, medium-pressure first refrigerant solution; the carbon dioxide expansion valve is used to reduce the pressure of the medium-temperature, medium-pressure first refrigerant solution to obtain the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state; the evaporator is used to evaporate the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state to obtain the low-temperature, low-pressure first refrigerant steam; The high-temperature compressor is used to compress the low-temperature and low-pressure second refrigerant vapor to obtain high-temperature and high-pressure second refrigerant vapor; the condenser is used to heat the low-temperature water input by the heating circulation pump and the hot water circulation pump through the heat released by the condensation of the high-temperature and high-pressure second refrigerant vapor to obtain primary high-temperature water and a high-temperature second refrigerant solution; the high-temperature expansion valve is used to reduce the pressure of the high-temperature second refrigerant solution to obtain a low-temperature and low-pressure second refrigerant in a gas-liquid mixed state; the heating circulation pump is used to pump the low-temperature water in the heating return water pipe into the condenser; the hot water circulation pump is used to pump the low-temperature water in the hot water return water pipe into the condenser; the first heating water supply pipe is used to transport the primary high-temperature water to the target heating user; the hot water intermediate pipe is used to transport the primary high-temperature water to the air cooler for heating; the hot water heating pipe is used to transport the secondary high-temperature water output by the air cooler to the target water supply user.

[0026] The present invention discloses the following technical effects:

[0027] The present invention provides a carbon dioxide cascade heat pump system and an implementation method thereof. Through an air cooler and an air cooling valve, the system solves the problem that the existing system cannot operate in transcritical and subcritical states at the same time and the heat exchange efficiency of carbon dioxide is low, and the carbon dioxide transcritical compressor outputs steam to operate in transcritical and subcritical states at the same time and utilizes the temperature glide characteristics of carbon dioxide to perform secondary heating of primary high-temperature water. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 A structural diagram of a carbon dioxide cascade heat pump system provided by an embodiment of the present invention;

[0030] Figure 2 A structural diagram of a carbon dioxide cascade heat pump system for simultaneously supplying water and heat provided by an embodiment of the present invention;

[0031] Description of reference numerals:

[0032] 1-CO2 transcritical compressor, 2-air cooler, 3-air cooling valve, 4-intermediate heat exchanger, 5-CO2 expansion valve, 6-evaporator, 7-high temperature compressor, 8-condenser, 9-high temperature expansion valve, 10-heating circulation pump, 11-heating return water pipe, 12-first heating water supply pipe, 13-heating diversion pipe, 14-second heating water supply pipe, 15-hot water circulation pump, 16-hot water return pipe, 17-hot water intermediate pipe, 18-hot water heating pipe. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The purpose of the present invention is to provide a carbon dioxide cascade heat pump system and its implementation method, which realizes the carbon dioxide transcritical compressor outputting steam in transcritical and subcritical operation at the same time through an air cooler and an air cooling valve, and utilizes the temperature glide characteristics of carbon dioxide to perform secondary heating of primary high-temperature water, thereby improving the hot water production efficiency and the heat exchange efficiency of carbon dioxide.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 The structure diagram of the carbon dioxide cascade heat pump system provided by the embodiment of the present invention is as follows: Figure 1 As shown, the present invention provides a carbon dioxide cascade heat pump system, including: a heat pump subsystem and a water-side heat exchange subsystem; the heat pump subsystem includes: a carbon dioxide transcritical compressor 1, an air cooler 2, an air cooling valve 3, an intermediate heat exchanger 4, a carbon dioxide expansion valve 5, an evaporator 6, a high-temperature compressor 7, a condenser 8 and a high-temperature expansion valve 9; the water-side heat exchange subsystem includes: a heating circulation pump 10, a heating return water pipeline 11, a heating water supply first pipeline 12, a heating diversion pipeline 13, and a heating water supply second pipeline 14;

[0037] The carbon dioxide transcritical compressor 1, the air cooler 2, the air cooling valve 3, the intermediate heat exchanger 4, the carbon dioxide expansion valve 5 and the evaporator 6 are connected in sequence; the high-temperature stage compressor 7, the condenser 8, the high-temperature stage expansion valve 9 and the intermediate heat exchanger 4 are connected in sequence; the output end of the carbon dioxide transcritical compressor 1 is connected to the input end of the first refrigerant side of the air cooler 2; the output end of the first refrigerant side of the air cooler 2 is connected to the input end of the air cooling valve 3; the output end of the air cooling valve 3 is connected to the input end of the first refrigerant side of the intermediate heat exchanger 4; the output end of the first refrigerant side of the intermediate heat exchanger 4 is connected to the input end of the carbon dioxide expansion valve 5; the output end of the carbon dioxide expansion valve 5 is connected to the input end of the evaporator 6; the output end of the evaporator 6 is connected to the input end of the carbon dioxide transcritical compressor 1; the output end of the second refrigerant side of the intermediate heat exchanger 4 The end is connected to the input end of the high-temperature compressor 7; the output end of the high-temperature compressor 7 is connected to the input end of the second refrigerant side of the condenser 8; the output end of the second refrigerant side of the condenser 8 is connected to the input end of the high-temperature expansion valve 9; the output end of the high-temperature expansion valve 9 is connected to the input end of the second refrigerant side of the intermediate heat exchanger 4; the input end of the heating circulation pump 10 is connected to the heating return water pipe 11; the input end of the water side of the condenser 8 is connected to the output end of the heating circulation pump 10; the output end of the water side of the condenser 8 is connected to the first heating water supply pipe 12; the first heating water supply pipe 12 is connected to the heating shunt pipe 13 and the second heating water supply pipe 14 in turn according to the water supply direction; the heating shunt pipe 13 is connected to the input end of the water side of the air cooler 2; the output end of the water side of the air cooler 2 is connected to the second heating water supply pipe 14;

[0038] The carbon dioxide transcritical compressor 1 is used to compress the input low-temperature, low-pressure first refrigerant vapor and output the high-temperature, high-pressure first refrigerant vapor in the transcritical area; the air cooler 2 is used to use the high-temperature, high-pressure first refrigerant vapor to heat the primary high-temperature water input by the heating shunt pipe 13; the air cooling valve 3 is used to reduce the pressure of the high-temperature, high-pressure first refrigerant vapor to the subcritical superheated steam zone to obtain the medium-temperature, medium-pressure first refrigerant vapor; the intermediate heat exchanger 4 is used to evaporate the low-temperature, low-pressure second refrigerant in a gas-liquid mixed state through the heat released by the condensation of the medium-temperature, medium-pressure first refrigerant vapor to obtain the low-temperature, low-pressure second refrigerant vapor and the medium-temperature, medium-pressure first refrigerant solution; the carbon dioxide expansion valve 5 is used to reduce the pressure of the medium-temperature, medium-pressure first refrigerant solution to obtain the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state; the evaporator 6 is used to evaporate the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state to obtain the low-temperature, low-pressure first refrigerant steam; the high-temperature compressor 7 is used to compress the low-temperature and low-pressure second refrigerant vapor to obtain high-temperature and high-pressure second refrigerant vapor; the condenser 8 is used to heat the low-temperature water input by the heating circulation pump 10 through the heat released by the condensation of the high-temperature and high-pressure second refrigerant vapor to obtain primary high-temperature water and a high-temperature second refrigerant solution; the high-temperature expansion valve 9 is used to reduce the pressure of the high-temperature second refrigerant solution to obtain a low-temperature and low-pressure second refrigerant in a gas-liquid mixed state; the heating circulation pump 10 is used to pump the low-temperature water in the heating return water pipe 11 into the condenser 8; the first heating water supply pipe 12 is used to transport the primary high-temperature water to the air cooler 2 for heating through the heating diversion pipe 13 according to a preset ratio; the second heating water supply pipe 14 is used to transport the primary high-temperature water heated by the air cooler 2 to the first heating water supply pipe 12 to obtain mixed high-temperature water, and transport the mixed high-temperature water to the target heating users.

[0039] Preferably, when the working fluid of the system is carbon dioxide, the high temperature range is: 80 to 130°C; the medium temperature range is: 15 to 80°C; the low temperature range is: -20 to 0°C; the high pressure range is: 80 to 120bar; the medium pressure range is: 45 to 72bar; the low pressure range is: 14 to 33bar.

[0040] Furthermore, a method for implementing a carbon dioxide cascade heat pump comprises:

[0041] Compressing low-temperature and low-pressure first refrigerant vapor by using the carbon dioxide transcritical compressor 1 to obtain high-temperature and high-pressure first refrigerant vapor;

[0042] The pressure of the high-temperature and high-pressure first refrigerant steam is adjusted to the subcritical superheated steam region by using the air-cooled valve 3 to obtain the medium-temperature and medium-pressure first refrigerant steam;

[0043] The heat released by condensation of the medium-temperature medium-pressure first refrigerant vapor is used by the intermediate heat exchanger 4 to evaporate the low-temperature low-pressure second refrigerant in a gas-liquid mixed state, thereby obtaining the low-temperature low-pressure second refrigerant vapor and the medium-temperature medium-pressure first refrigerant solution;

[0044] The medium-temperature and medium-pressure first refrigerant solution is depressurized by using the carbon dioxide expansion valve 5 to obtain a low-temperature and low-pressure first refrigerant in a gas-liquid mixed state;

[0045] The low-temperature and low-pressure first refrigerant in a gas-liquid mixed state is evaporated by the evaporator 6 to obtain high-temperature and high-pressure first refrigerant vapor;

[0046] The low-temperature and low-pressure second refrigerant vapor is compressed by the high-temperature stage compressor 7 to obtain the high-temperature and high-pressure second refrigerant vapor;

[0047] The heat released by condensation of the high-temperature and high-pressure second refrigerant steam is used by the condenser 8 to heat the low-temperature water input by the heating circulation pump 10 to obtain primary high-temperature water and a high-temperature second refrigerant solution;

[0048] The high-temperature expansion valve 9 is used to reduce the pressure of the high-temperature second refrigerant solution to obtain a low-temperature and low-pressure second refrigerant in a gas-liquid mixed state;

[0049] The low-temperature water in the heating return water pipe 11 is pumped into the condenser 8 by the heating circulation pump 10;

[0050] A fixed proportion of primary high-temperature water is delivered to the air cooler 2 by using the first heating water supply pipe 12 and the heating diversion pipe 13;

[0051] The high-temperature and high-pressure first refrigerant steam in the transcritical region is used to heat the primary high-temperature water, and the primary high-temperature water heated by the air cooler 2 is transported to the first heating water supply pipe 12 through the second heating water supply pipe 14 to obtain mixed high-temperature water;

[0052] The mixed high-temperature water is delivered to the target heating users by using the first heating water supply pipe 12 .

[0053] Preferably, the high-temperature, low-pressure first refrigerant vapor is carbon dioxide refrigerant.

[0054] refer to Figure 2 , a carbon dioxide cascade heat pump system for supplying water and heat at the same time, comprising: a heat pump subsystem and a water-side heat exchange subsystem; the heat pump subsystem comprises: a carbon dioxide transcritical compressor 1, an air cooler 2, an air cooling valve 3, an intermediate heat exchanger 4, a carbon dioxide expansion valve 5, an evaporator 6, a high-temperature compressor 7, a condenser 8 and a high-temperature expansion valve 9; the water-side heat exchange subsystem comprises: a heating circulation pump 10, a hot water circulation pump 15, a heating return water pipeline 11, a first heating water supply pipeline 12, a hot water return water pipeline 16, a hot water intermediate pipeline 17 and a hot water heating pipeline 18;

[0055] The carbon dioxide transcritical compressor 1, the air cooler 2, the air cooling valve 3, the intermediate heat exchanger 4, the carbon dioxide expansion valve 5 and the evaporator 6 are connected in sequence; the high-temperature stage compressor 7, the condenser 8, the high-temperature stage expansion valve 9 and the intermediate heat exchanger 4 are connected in sequence; the output end of the carbon dioxide transcritical compressor 1 is connected to the input end of the first refrigerant side of the air cooler 2; the output end of the first refrigerant side of the air cooler 2 is connected to the input end of the air cooling valve 3; the output end of the air cooling valve 3 is connected to the input end of the first refrigerant side of the intermediate heat exchanger 4; the output end of the first refrigerant side of the intermediate heat exchanger 4 is connected to the input end of the carbon dioxide expansion valve 5; the output end of the carbon dioxide expansion valve 5 is connected to the input end of the evaporator 6; the output end of the evaporator 6 is connected to the input end of the carbon dioxide transcritical compressor 1; the output end of the second refrigerant side of the intermediate heat exchanger 4 is connected to the input end of the high-temperature stage compressor 7; The output end of the first-stage compressor 7 is connected to the input end of the second refrigerant side of the condenser 8; the output end of the second refrigerant side of the condenser 8 is connected to the input end of the high-temperature stage expansion valve 9; the output end of the high-temperature stage expansion valve 9 is connected to the input end of the second refrigerant side of the intermediate heat exchanger 4; the input end of the heating circulation pump 10 is connected to the heating return water pipeline 11; the input end of the hot water circulation pump 15 is connected to the hot water return water pipeline 16; the output end of the heating circulation pump 10 is connected to the first input end of the water side of the condenser 8; the output end of the hot water circulation pump 15 is connected to the second input end of the water side of the condenser 8; the first output end of the water side of the condenser 8 is connected to the first heating water supply pipeline 12; the second output end of the water side of the condenser 8 is connected to the hot water intermediate pipeline 17; the input end of the water side of the air cooler 2 is connected to the hot water intermediate pipeline 17; the output end of the water side of the air cooler 2 is connected to the hot water heating pipeline 18;

[0056] The carbon dioxide transcritical compressor 1 is used to compress the input low-temperature, low-pressure first refrigerant vapor and output the high-temperature, high-pressure first refrigerant vapor in the transcritical area; the air cooler 2 is used to use the high-temperature, high-pressure first refrigerant vapor to heat the primary high-temperature water input by the heating shunt pipe 13; the air cooling valve 3 is used to reduce the pressure of the high-temperature, high-pressure first refrigerant vapor to the subcritical superheated steam zone to obtain the medium-temperature, medium-pressure first refrigerant vapor; the intermediate heat exchanger 4 is used to evaporate the low-temperature, low-pressure second refrigerant in a gas-liquid mixed state by the heat released by the condensation of the medium-temperature, medium-pressure first refrigerant vapor to obtain the low-temperature, low-pressure second refrigerant vapor and the medium-temperature, medium-pressure first refrigerant solution; the carbon dioxide expansion valve 5 is used to reduce the pressure of the medium-temperature, medium-pressure first refrigerant solution to obtain the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state; the evaporator 6 is used to evaporate the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state to obtain the low-temperature, low-pressure first refrigerant vapor; The first stage compressor 7 is used to compress the low-temperature and low-pressure second refrigerant vapor to obtain the high-temperature and high-pressure second refrigerant vapor; the condenser 8 is used to heat the low-temperature water input by the heating circulation pump 10 and the hot water circulation pump 15 through the heat released by the condensation of the high-temperature and high-pressure second refrigerant vapor to obtain primary high-temperature water and a high-temperature second refrigerant solution; the high-temperature stage expansion valve 9 is used to reduce the pressure of the high-temperature second refrigerant solution to obtain a low-temperature and low-pressure second refrigerant in a gas-liquid mixed state; the heating circulation pump 10 is used to pump the low-temperature water in the heating return water pipe 11 into the condenser 8; the hot water circulation pump 15 is used to pump the low-temperature water in the hot water return water pipe 16 into the condenser 8; the first heating water supply pipe 12 is used to transport the primary high-temperature water to the target heating user; the hot water intermediate pipe 17 is used to transport the primary high-temperature water to the air cooler 2 for heating; the hot water heating pipe 18 is used to transport the secondary high-temperature water output by the air cooler 2 to the target water supply user.

[0057] Preferably, the heating circulation pipeline is designed as follows: the outlet of the output end of the condenser 8 is connected to the three-way diverter, the pipeline between the outlet of the output end of the condenser 8 and the three-way diverter and the pipeline from the three-way diverter to the target heating user constitute the first heating water supply pipeline 12, and the pipeline between the three-way diverter and the condenser 8 is the heating diversion pipeline 13.

[0058] Specifically, the user return water of the heating cycle is sent to the condenser 8 for heating through the heating variable frequency circulation pump. The circulating hot water out of the condenser 8 is divided into two paths, one is to the user water supply (main path, i.e. the first heating water supply pipeline 12), and the other is to the air cooler 2 for sensible heat exchange with high-temperature carbon dioxide. After further increasing the water temperature, it is merged with the main water supply to the user side, and the water supply temperature is increased to be delivered to the user.

[0059] Furthermore, when the system is in the state of heating and hot water cogeneration, high-temperature and high-pressure refrigerant steam is discharged through the exhaust port of the carbon dioxide compressor, the outlet temperature of the air cooler 2 is controlled, and the exhaust pressure is controlled to be in the supercritical region by the opening of the air cooling valve 3. After throttling, the exhaust pressure drops to the subcritical superheated steam region, and condenses and releases heat with the high-temperature refrigerant in the intermediate heat exchanger 4. After the liquid refrigerant is throttled and depressurized by the carbon dioxide expansion valve 5, it absorbs heat in the evaporator 6 to form superheated steam and returns to the compressor suction port for further compression, completing the carbon dioxide cycle. The high-temperature refrigerant is compressed by the high-temperature compressor 7 to form high-temperature and high-pressure refrigerant steam, and condenses and releases heat with the user return water in the condenser 8. After the liquid refrigerant is throttled and depressurized by the high-temperature expansion valve 9, it absorbs the condensation heat of carbon dioxide in the intermediate heat exchanger 4, forms superheated steam, and returns to the high-temperature compressor 7 suction port for further compression, completing the high-temperature cycle. The user return water of the heating cycle is sent to the condenser 8 through the heating circulation pump 10 for heating and then delivered to the target heating user. The domestic hot water is pumped into the condenser 8 for heating, and then enters the air cooler 2 for sensible heat exchange with the high-temperature carbon dioxide, and the water temperature is further increased before being delivered to the target hot water users.

[0060] This embodiment uses an air-cooled valve to control the exhaust pressure of the transcritical compressor and the outlet temperature of the air cooler, so that the carbon dioxide system can achieve transcritical and subcritical operation at the same time, realizes the secondary heating of the primary high-temperature water by utilizing the temperature glide characteristic of carbon dioxide, improves the hot water production efficiency and the heat exchange efficiency of carbon dioxide, and realizes the characteristics of the cascade system suitable for circulation heating.

[0061] The beneficial effects of the present invention are as follows:

[0062] (1) The present invention heats hot water by utilizing the large temperature glide characteristic during the heat release of the high-temperature and high-pressure first refrigerant vapor, thereby fully recovering and utilizing energy and improving the thermal efficiency of the overall system.

[0063] (2) The present invention uses carbon dioxide as a refrigerant, which has low global warming potential (GWP) and zero ozone depletion potential (ODP), and meets environmental protection requirements.

[0064] (3) The unique multi-stage heat exchange and compression design of the present invention can increase the output water temperature while ensuring system stability, adapting to more application scenarios.

[0065] (4) The system design of the present invention allows for simultaneous heating and water supply, and can be flexibly adapted to different seasons and user needs.

[0066] (5) The multi-stage circulation and exchange process of the present invention effectively improves the coefficient of performance (COP) of the heat pump system and provides a higher energy efficiency ratio.

[0067] (6) The rational arrangement and organization of the components of the present invention improves the reliability and service life of the system and reduces maintenance requirements.

[0068] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0069] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A carbon dioxide cascade heat pump system, characterized in that: include: Heat pump subsystem and water side heat exchange subsystem; The heat pump subsystem includes: a carbon dioxide transcritical compressor, an air cooler, an air cooling valve, an intermediate heat exchanger, a carbon dioxide expansion valve, an evaporator, a high-temperature compressor, a condenser and a high-temperature expansion valve; the water-side heat exchange subsystem includes: a heating circulation pump, a heating return water pipeline, a first heating water supply pipeline, a heating diversion pipeline, and a second heating water supply pipeline; The carbon dioxide transcritical compressor, the air cooler, the air cooling valve, the intermediate heat exchanger, the carbon dioxide expansion valve and the evaporator are connected in sequence; the high-temperature compressor, the condenser, the high-temperature expansion valve and the intermediate heat exchanger are connected in sequence; the output end of the carbon dioxide transcritical compressor is connected to the input end of the first refrigerant side of the air cooler; the output end of the first refrigerant side of the air cooler is connected to the input end of the air cooling valve; the output end of the air cooling valve is connected to the input end of the first refrigerant side of the intermediate heat exchanger; the output end of the first refrigerant side of the intermediate heat exchanger is connected to the input end of the carbon dioxide expansion valve; the output end of the carbon dioxide expansion valve is connected to the input end of the evaporator; the output end of the evaporator is connected to the input end of the carbon dioxide transcritical compressor; the second refrigerant side of the intermediate heat exchanger The output end of the refrigerant side is connected to the input end of the high-temperature compressor; the output end of the high-temperature compressor is connected to the input end of the second refrigerant side of the condenser; the output end of the second refrigerant side of the condenser is connected to the input end of the high-temperature expansion valve; the output end of the high-temperature expansion valve is connected to the input end of the second refrigerant side of the intermediate heat exchanger; the input end of the heating circulation pump is connected to the heating return water pipe; the input end of the condenser water side is connected to the output end of the heating circulation pump; the output end of the condenser water side is connected to the first heating water supply pipe; the first heating water supply pipe is connected to the heating shunt pipe and the second heating water supply pipe in sequence according to the water supply direction; the heating shunt pipe is connected to the input end of the water side of the air cooler; the output end of the water side of the air cooler is connected to the second heating water supply pipe; The carbon dioxide transcritical compressor is used to compress the input low-temperature, low-pressure first refrigerant steam and output the high-temperature, high-pressure first refrigerant steam in the transcritical area; the air cooler is used to use the high-temperature, high-pressure first refrigerant steam to heat the primary high-temperature water input by the heating shunt pipe; the air cooling valve is used to reduce the pressure of the high-temperature, high-pressure first refrigerant steam to the subcritical superheated steam zone to obtain the medium-temperature, medium-pressure first refrigerant steam; the intermediate heat exchanger is used to evaporate the low-temperature, low-pressure second refrigerant in a gas-liquid mixed state through the heat released by condensation of the medium-temperature, medium-pressure first refrigerant steam to obtain the low-temperature, low-pressure second refrigerant steam and the medium-temperature, medium-pressure first refrigerant solution; the carbon dioxide expansion valve is used to reduce the pressure of the medium-temperature, medium-pressure first refrigerant solution to obtain the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state; the evaporator is used to evaporate the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state to obtain the low-temperature, low-pressure first refrigerant steam steam; the high-temperature compressor is used to compress the low-temperature and low-pressure second refrigerant vapor to obtain high-temperature and high-pressure second refrigerant vapor; the condenser is used to heat the low-temperature water input by the heating circulation pump through the heat released by condensation of the high-temperature and high-pressure second refrigerant vapor to obtain the primary high-temperature water and the high-temperature second refrigerant solution; the high-temperature expansion valve is used to reduce the pressure of the high-temperature second refrigerant solution to obtain a low-temperature and low-pressure second refrigerant in a gas-liquid mixed state; the heating circulation pump is used to pump the low-temperature water in the heating return water pipe into the condenser; the first heating water supply pipe is used to transport the primary high-temperature water to the air cooler through the heating diversion pipe according to a preset ratio for heating; the second heating water supply pipe is used to transport the primary high-temperature water heated by the air cooler to the first heating water supply pipe to obtain mixed high-temperature water, and transport the mixed high-temperature water to the target heating user.

2. A method for implementing a carbon dioxide cascade heat pump, characterized in that: Applied to a carbon dioxide cascade heat pump system as claimed in claim 1, the method comprising: Compressing the low-temperature and low-pressure first refrigerant vapor by using the carbon dioxide transcritical compressor to obtain the high-temperature and high-pressure first refrigerant vapor; The air-cooled valve is used to adjust the pressure of the high-temperature and high-pressure first refrigerant steam to a subcritical superheated steam region to obtain the medium-temperature and medium-pressure first refrigerant steam; The heat released by condensation of the medium-temperature and medium-pressure first refrigerant vapor is used to evaporate the low-temperature and low-pressure second refrigerant in a gas-liquid mixed state through the intermediate heat exchanger to obtain the low-temperature and low-pressure second refrigerant vapor and the medium-temperature and medium-pressure first refrigerant solution; Using the carbon dioxide expansion valve to reduce the pressure of the medium-temperature and medium-pressure first refrigerant solution to obtain the low-temperature and low-pressure first refrigerant in a gas-liquid mixed state; Using the evaporator to evaporate the low-temperature and low-pressure first refrigerant in a gas-liquid mixed state to obtain the high-temperature and high-pressure first refrigerant vapor; Compressing the low-temperature and low-pressure second refrigerant vapor by using the high-temperature stage compressor to obtain the high-temperature and high-pressure second refrigerant vapor; The heat released by condensation of the high-temperature and high-pressure second refrigerant steam is used by the condenser to heat the low-temperature water input by the heating circulation pump to obtain the primary high-temperature water and the high-temperature second refrigerant solution; Using the high-temperature expansion valve to reduce the pressure of the high-temperature second refrigerant solution to obtain the low-temperature and low-pressure second refrigerant in a gas-liquid mixed state; Using the heating circulation pump to pump the low-temperature water in the heating return water pipe into the condenser; Using the first heating water supply pipe and the heating diversion pipe to transport a fixed proportion of the primary high-temperature water to the air cooler; The high-temperature and high-pressure first refrigerant steam in the transcritical region is used to heat the primary high-temperature water, and the primary high-temperature water heated by the air cooler is transported to the first heating water supply pipeline through the second heating water supply pipeline to obtain mixed high-temperature water; The mixed high-temperature water is delivered to target heating users by using the first heating water supply pipeline.

3. A method for implementing a carbon dioxide cascade heat pump according to claim 2, characterized in that: The high-temperature, low-pressure first refrigerant vapor is carbon dioxide refrigerant.

4. A carbon dioxide cascade heat pump system for simultaneous water and heat supply, characterized in that: include: Heat pump subsystem and water-side heat exchange subsystem; the heat pump subsystem includes: a carbon dioxide transcritical compressor, an air cooler, an air cooling valve, an intermediate heat exchanger, a carbon dioxide expansion valve, an evaporator, a high-temperature compressor, a condenser and a high-temperature expansion valve; the water-side heat exchange subsystem includes: a heating circulation pump, a hot water circulation pump, a heating return water pipeline, a heating water supply first pipeline, a hot water return water pipeline, a hot water intermediate pipeline and a hot water heating pipeline; The carbon dioxide transcritical compressor, the air cooler, the air cooling valve, the intermediate heat exchanger, the carbon dioxide expansion valve and the evaporator are connected in sequence; the high-temperature stage compressor, the condenser, the high-temperature stage expansion valve and the intermediate heat exchanger are connected in sequence; the output end of the carbon dioxide transcritical compressor is connected to the input end of the first refrigerant side of the air cooler; the output end of the first refrigerant side of the air cooler is connected to the input end of the air cooling valve; the output end of the air cooling valve is connected to the input end of the first refrigerant side of the intermediate heat exchanger; the output end of the first refrigerant side of the intermediate heat exchanger is connected to the input end of the carbon dioxide expansion valve; the output end of the carbon dioxide expansion valve is connected to the input end of the evaporator; the output end of the evaporator is connected to the input end of the carbon dioxide transcritical compressor; the output end of the second refrigerant side of the intermediate heat exchanger is connected to the input end of the high-temperature stage compressor The input end is connected; the output end of the high-temperature compressor is connected to the input end of the second refrigerant side of the condenser; the output end of the second refrigerant side of the condenser is connected to the input end of the high-temperature expansion valve; the output end of the high-temperature expansion valve is connected to the input end of the second refrigerant side of the intermediate heat exchanger; the input end of the heating circulation pump is connected to the heating return water pipeline; the input end of the hot water circulation pump is connected to the hot water return water pipeline; the output end of the heating circulation pump is connected to the first input end of the condenser water side; the output end of the hot water circulation pump is connected to the second input end of the condenser water side; the first output end of the condenser water side is connected to the first heating water supply pipeline; the second output end of the condenser water side is connected to the hot water intermediate pipeline; the input end of the air cooler water side is connected to the hot water intermediate pipeline; the output end of the air cooler water side is connected to the hot water heating pipeline; The carbon dioxide transcritical compressor is used to compress the input low-temperature, low-pressure first refrigerant steam and output the high-temperature, high-pressure first refrigerant steam in the transcritical region; the air cooler is used to use the high-temperature, high-pressure first refrigerant steam to heat the primary high-temperature water input by the heating diversion pipeline; the air cooling valve is used to reduce the pressure of the high-temperature, high-pressure first refrigerant steam to the subcritical superheated steam region to obtain the medium-temperature, medium-pressure first refrigerant steam; the intermediate heat exchanger is used to evaporate the low-temperature, low-pressure second refrigerant in a gas-liquid mixed state by the heat released by the condensation of the medium-temperature, medium-pressure first refrigerant steam to obtain the low-temperature, low-pressure second refrigerant steam and the medium-temperature, medium-pressure first refrigerant solution; the carbon dioxide expansion valve is used to reduce the pressure of the medium-temperature, medium-pressure first refrigerant solution to obtain the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state; the evaporator is used to evaporate the low-temperature, low-pressure first refrigerant in a gas-liquid mixed state to obtain the low-temperature, low-pressure first refrigerant steam; The high-temperature compressor is used to compress the low-temperature and low-pressure second refrigerant vapor to obtain high-temperature and high-pressure second refrigerant vapor; the condenser is used to heat the low-temperature water input by the heating circulation pump and the hot water circulation pump through the heat released by the condensation of the high-temperature and high-pressure second refrigerant vapor to obtain primary high-temperature water and a high-temperature second refrigerant solution; the high-temperature expansion valve is used to reduce the pressure of the high-temperature second refrigerant solution to obtain a low-temperature and low-pressure second refrigerant in a gas-liquid mixed state; the heating circulation pump is used to pump the low-temperature water in the heating return water pipe into the condenser; the hot water circulation pump is used to pump the low-temperature water in the hot water return water pipe into the condenser; the first heating water supply pipe is used to transport the primary high-temperature water to the target heating user; the hot water intermediate pipe is used to transport the primary high-temperature water to the air cooler for heating; the hot water heating pipe is used to transport the secondary high-temperature water output by the air cooler to the target water supply user.

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