Two-cycle PVT heat pump water heating system based on gravity-fed liquid supply

Abstract

This invention provides a gravity-fed, two-cycle PVT heat pump water heating system, comprising a compressor, a condenser, a receiver, an expansion valve, a shut-off valve, a PVT module, a gas-liquid separator, a check valve, and an inverter. The compressor exhaust port is connected to the condenser refrigerant inlet and the check valve outlet; the condenser refrigerant outlet is connected to the receiver inlet; one end of the expansion valve and shut-off valve connected in parallel is connected to the receiver outlet, and the other end is connected to the gas-liquid separator inlet; the gas-liquid separator outlet is connected to the PVT module heat exchange tube inlet; the PVT module heat exchange tube outlet is connected to the gas-liquid separator return port; and the gas-liquid separator outlet is connected to the check valve inlet and the compressor suction port; the photovoltaic cells in the PVT module are connected to the inverter. This invention's PVT heat pump water heating system can operate in both vapor compression and thermosiphon gravity circulation modes. The refrigerant in the PVT module is supplied by gravity, requiring no additional work input, resulting in low power consumption, uniform PVT module temperature, and high power generation efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar heat pump, more particularly, to a two-cycle PVT heat pump hot water system based on gravity liquid supply. BACKGROUND

[0002] The international solar photovoltaic-thermal comprehensive utilization technology is called PVT technology (Photovoltaic-thermal), which can generate electricity and heat and has high solar comprehensive utilization efficiency. The combination of PVT technology and heat pump technology forms a PVT heat pump. In the PVT heat pump, the photovoltaic cell in the PVT assembly works under the condition of low temperature with the evaporation of refrigerant, which has high power generation efficiency. At the same time, the heat pump cycle takes the heat collecting component under solar radiation as the evaporation heat source, which also significantly improves the heating performance coefficient. Therefore, the PVT heat pump has great development and application potential.

[0003] The existing PVT heat pump hot water system adopts direct expansion refrigerant supply. The gas-liquid mixture from the expansion valve enters from one end of the heat exchange pipe, the liquid part evaporates to absorb the heat of the photovoltaic cell to become gas, and when it reaches the other end of the heat exchange pipe, it is all gasified and sucked into the compressor. The PVT heat pump hot water system has the following disadvantages when using this supply method:

[0004] 1. Low PVT evaporator heat exchange rate. The refrigerant entering the PVT assembly is a gas-liquid mixture, the gas part forms a heat exchange resistance in the heat exchange pipe, the liquid part has low wetness, the supply method is single compressor-driven supply, and the refrigerant flow rate is low, which limits the overall heat exchange efficiency of the PVT assembly.

[0005] 2. Not suitable for medium and large PVT heat pump hot water systems. The medium and large PVT heat pump hot water systems contain multiple PVT arrays, each array has multiple PVT assemblies, and the total number of PVT assemblies is large. The refrigerant flowing out from the expansion valve and entering each PVT array is a gas-liquid two-phase flow, which is easy to cause uneven liquid distribution, uneven supply between PVT assemblies, and obvious difference in photovoltaic current and voltage in PVT assemblies, which causes uneven temperature distribution in PVT arrays and cannot fully utilize PVT arrays.

[0006] 3. Heating interruption under high temperature and high light intensity conditions. In hot summer with high light intensity, the refrigerant pressure in the PVT assembly is high, the compressor cannot start under high evaporation pressure, the photovoltaic cell cannot be cooled, the power generation efficiency of the photovoltaic cell is reduced, and the condenser of the heat pump hot water system is interrupted. SUMMARY

[0007] The present application aims at the technical defects in the prior art, and provides a PVT heat pump hot water system which can realize both refrigerant vapor compression gravity-fed liquid cycle and refrigerant siphon gravity-fed liquid cycle.

[0008] The technical scheme adopted by the present application to achieve the above-mentioned purpose is as follows:

[0009] The schematic diagram of the two-cycle PVT heat pump hot water system based on gravity-fed liquid of the present application is shown in Figure 1 The system comprises a compressor, a condenser, a liquid accumulator, an expansion valve, a stop valve, a PVT assembly, a gas-liquid separator, a one-way valve and an inverter. The discharge port of the compressor is connected with the refrigerant inlet of the condenser and the outlet of the one-way valve, and the refrigerant outlet of the condenser is connected with the inlet of the liquid accumulator. The expansion valve is connected with one end of the stop valve in parallel, and the other end is connected with the liquid inlet of the gas-liquid separator. The liquid outlet of the gas-liquid separator is connected with the inlet of the heat exchange tube of the PVT assembly, and the outlet of the heat exchange tube of the PVT assembly is connected with the gas return port of the gas-liquid separator. The gas outlet of the gas-liquid separator is connected with the inlet of the one-way valve and the suction port of the compressor. The photovoltaic cell in the PVT assembly is connected with the inverter.

[0010] The two-cycle PVT heat pump hot water system based on gravity-fed liquid of the present application can be divided into two cycles, i.e. a refrigerant vapor compression gravity-fed liquid PVT heat pump cycle and a refrigerant siphon gravity-fed liquid PVT heat pump cycle, according to the ambient temperature and the light intensity.

[0011] When the ambient temperature is not high and the light intensity is not large, the two-cycle PVT heat pump hot water system based on gravity-fed liquid of the present application operates in the vapor compression gravity-fed liquid PVT heat pump cycle. The stop valve is closed, the opening of the expansion valve is controlled according to the liquid level of the gas-liquid separator, and the photovoltaic cell in the PVT assembly generates electricity under the sunlight, which is converted into electricity that can be used by users through the inverter.

[0012] When the ambient temperature is high and the light intensity is large, the refrigerant in the PVT assembly and the gas-liquid separator is in a high pressure state at this time, and the compressor cannot be started due to pressure protection. The heat pump hot water system of the present application operates in the refrigerant siphon gravity-fed liquid PVT heat pump cycle. The stop valve is opened, and the photovoltaic cell in the PVT assembly generates electricity under the sunlight, which is converted into electricity that can be used by users through the inverter.

[0013] In the two-cycle PVT heat pump hot water system based on gravity-fed liquid of the present application, the installation height of the gas-liquid separator is greater than the highest position of the PVT assembly, the installation height of the liquid accumulator is greater than the highest position of the gas-liquid separator, and the installation height of the condenser is greater than the highest position of the liquid accumulator.

[0014] The PVT assembly is any one of a flat box type, a tube plate type, a blow molding plate type and a flat plate type.

[0015] The compressor is any one of a scroll compressor, a rotary compressor, a screw compressor and a piston compressor.

[0016] The condenser is a plate heat exchanger, a double-pipe heat exchanger, a shell-and-tube heat exchanger or a plate-and-shell heat exchanger.

[0017] The expansion valve is an electronic expansion valve, a thermal expansion valve, a capillary or an orifice throttling device.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] 1. When the two-cycle PVT heat pump water heating system based on gravity liquid supply operates in the PVT heat pump cycle of refrigerant vapor compression, the refrigerant entering the PVT assembly is saturated liquid, the gas in the tube is partially liquid, the liquid volume ratio is large, the tube is well wetted. In addition, the liquid supply is gravity-driven multiple liquid supply, and the refrigerant flow rate in the tube is high. The high wetness and high flow rate of the refrigerant side increase the heat transfer coefficient of the refrigerant side. The temperature difference between the refrigerant and the photovoltaic cell is small, and the comprehensive utilization rate of solar energy of the PVT assembly is high.

[0020] 2. The flow and heat exchange of the refrigerant in the PVT assembly of the two-cycle PVT heat pump water heating system based on gravity liquid supply are completely driven by the gravity of the refrigerant itself, without the need for inputting additional power, so the system consumes less electricity.

[0021] 3. The two-cycle PVT heat pump water heating system based on gravity liquid supply operates in the PVT heat pump cycle of refrigerant vapor compression or refrigerant thermal siphon gravity liquid supply, and the PVT assembly is supplied with pure liquid at a uniform temperature, which is more suitable for medium and large PVT heat pump water heating systems with a large number of PVT assemblies. The liquid distribution between the PVT assemblies is more uniform, the overall temperature distribution of the PVT assemblies is more uniform, the voltage and current difference in the photovoltaic assembly is small, and the power generation efficiency is higher.

[0022] 4. The two-cycle PVT heat pump water heating system based on gravity liquid supply operates in the PVT heat pump cycle of refrigerant thermal siphon gravity liquid supply under extremely high temperature conditions, realizes uninterrupted heating of the condenser without starting the compressor, and can also realize forced high-speed liquid supply of the PVT assembly, which continuously cools the photovoltaic cell, and the power generation efficiency of the PVT assembly is high.

[0023] 5. The two-cycle PVT heat pump water heating system based on gravity liquid supply can be operated in two cycles of refrigerant vapor compression and refrigerant thermal siphon gravity liquid supply according to the ambient temperature and the light intensity. The two-cycle operation is flexible, and the equipment utilization rate is high. Attached Figure Description

[0024] Figure 1 The diagram shown is a schematic of the two-cycle PVT heat pump water heating system based on gravity-fed liquid supply according to the present invention.

[0025] Figure 2 The diagram shown is a schematic of the PVT heat pump circulation operation principle of the two-cycle PVT heat pump water heating system based on gravity supply of refrigerant vapor compression gravity supply according to the present invention.

[0026] Figure 3 The diagram shown is a schematic of the PVT heat pump circulation operation principle of the two-cycle PVT heat pump water heating system based on gravity supply of refrigerant using a refrigerant siphon gravity supply according to the present invention.

[0027] Figure 4 The diagram shown is a schematic of the gas-liquid separator interface in the gravity-fed two-cycle PVT heat pump water heating system of the present invention.

[0028] In the diagram: 1 Compressor; 2 Condenser; 3 Liquid receiver; 4 Expansion valve; 5 Shut-off valve; 6 PVT assembly; 7 Gas-liquid separator; 7-1 Gas outlet; 7-2 Liquid inlet; 7-3 Liquid outlet; 7-4 Gas return port; 8 Check valve; 9 Inverter. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0030] The schematic diagram of the gravity-fed two-cycle PVT heat pump water heating system of this invention is shown below. Figure 1 As shown, the system includes a compressor 1, a condenser 2, a liquid receiver 3, an expansion valve 4, a shut-off valve 5, a PVT assembly 6, a gas-liquid separator 7, a one-way valve 8, and an inverter 9. The discharge port of the compressor 1 is connected to the refrigerant inlet of the condenser 2 and the outlet of the one-way valve 8; the refrigerant outlet of the condenser 2 is connected to the inlet of the liquid receiver 3; one end of the expansion valve 4 connected in parallel with the shut-off valve 5 is connected to the outlet of the liquid receiver 3, and the other end is connected to the liquid inlet of the gas-liquid separator 7; the liquid outlet of the gas-liquid separator 7 is connected to the inlet of the heat exchange tube of the PVT assembly 6; the outlet of the heat exchange tube of the PVT assembly 6 is connected to the return port of the gas-liquid separator 7; the gas outlet of the gas-liquid separator 7 is connected to the inlet of the one-way valve 8 and the suction port of the compressor 1; the photovoltaic cells in the PVT assembly 6 are connected to the inverter 9.

[0031] The present invention relates to a two-cycle PVT heat pump hot water system based on gravity-fed liquid supply, which can be divided into two types of cycle operation according to ambient temperature and light intensity: PVT heat pump cycle with refrigerant vapor compression gravity-fed liquid supply and PVT heat pump cycle with refrigerant siphon gravity-fed liquid supply.

[0032] When the ambient temperature is not high and the light intensity is not large, the two-cycle PVT heat pump water heating system based on gravity liquid supply of the application operates in a vapor compression gravity liquid supply PVT heat pump cycle, the stop valve 5 is closed, and the opening degree of the expansion valve 4 is controlled according to the gas-liquid separation liquid level. The refrigerant thermodynamic process: the compressor 1 inhales low-pressure saturated refrigerant gas from the gas outlet of the gas-liquid separator 7, and the gas is compressed to become high-pressure superheated gas which is discharged into the condenser 2. The superheated gas is condensed into high-pressure liquid refrigerant in the condenser 2 by heat exchange with water on the other side, and flows into the liquid accumulator 3. The liquid refrigerant flowing out of the liquid outlet of the liquid accumulator 3 is expanded and decompressed by the expansion valve 4 to become a low-pressure gas-liquid two-phase mixture in a saturated state, and the mixture enters the gas-liquid separator 7 for gas-liquid separation. The separated saturated liquid refrigerant flows out of the liquid outlet of the gas-liquid separator 7 under the action of gravity and enters the PVT assembly 6. Part of the liquid refrigerant evaporates to become saturated gas after absorbing the heat of the photovoltaic cell in the PVT assembly 6, and the gas-liquid two-phase fluid composed of the part of the saturated gas and the unevaporated liquid returns to the gas-liquid separator 7. The unevaporated saturated liquid is deposited at the bottom of the gas-liquid separator 7 and performs the next cycle of liquid supply, and the evaporated saturated gas is sucked into the compressor 1 together with the gas in the gas-liquid two-phase mixture from the expansion valve 4 after passing through the first one-way valve 8, completing the refrigerant cycle. The photovoltaic cell in the PVT assembly 6 generates electricity under sunlight, which is adjusted by the inverter 9 to become electricity that can be used by users.

[0033] When the ambient temperature is high and the light intensity is large, the refrigerant in the PVT assembly 6 and the gas-liquid separator 7 is in a high-pressure state at this time, and the compressor 1 cannot be started due to pressure protection. The heat pump water heating system of the application operates in a refrigerant siphon gravity liquid supply PVT heat pump cycle, and the stop valve 5 is opened. The refrigerant thermodynamic process: the liquid in the gas-liquid separator 7 flows out of the liquid outlet under the action of gravity and enters the PVT assembly 6. Part of the high-pressure saturated liquid refrigerant evaporates to become high-pressure saturated gas after absorbing the heat of the photovoltaic cell in the PVT assembly 6, and the gas-liquid two-phase refrigerant fluid composed of the part of the saturated gas and the unevaporated liquid returns to the gas-liquid separator 7. The unevaporated saturated liquid is deposited at the bottom of the separator and performs the next cycle. The saturated gas in the gas-liquid separator 7 enters the condenser 2 under the action of siphon, exchanges heat with water on the other side in the condenser 2, and is condensed into liquid refrigerant which flows into the liquid accumulator 3. The liquid in the liquid accumulator 3 flows out of the liquid outlet under the action of gravity, returns to the gas-liquid separator 7 through the stop valve 5, and completes the refrigerant cycle. The photovoltaic cell in the PVT assembly 6 generates electricity under sunlight, which is adjusted by the inverter 9 to become electricity that can be used by users.

[0034] The present application is based on the installation height of the gas-liquid separator 7 being greater than the highest position of the PVT assembly 6, the installation height of the liquid reservoir 3 being greater than the highest position of the gas-liquid separator 7, and the installation height of the condenser 2 being greater than the highest position of the liquid reservoir 3 in the two-cycle PVT heat pump hot water system with gravity liquid supply.

[0035] The above description is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should be considered as the protection scope of the present application.

Claims

1. A two-cycle PVT heat pump hot water system based on gravity feed, characterized in that, The PVT heat pump hot water system comprises a compressor, a condenser, a liquid accumulator, an expansion valve, a stop valve, a PVT assembly, a gas-liquid separator, a one-way valve and an inverter; the compressor exhaust port is connected with the condenser refrigerant inlet and the one-way valve outlet respectively, and the condenser refrigerant outlet is connected with the liquid accumulator inlet; the expansion valve is connected with the liquid accumulator outlet at one end and connected with the gas-liquid separator liquid inlet at the other end, the gas-liquid separator liquid outlet is connected with the PVT assembly heat exchange pipe inlet, the PVT assembly heat exchange pipe outlet is connected with the gas-liquid separator gas return port, the gas-liquid separator gas outlet is connected with the one-way valve inlet and the compressor suction port respectively; the photovoltaic cell in the PVT assembly is connected with the inverter.

2. The two-cycle PVT heat pump water heating system based on gravity feed according to claim 1, wherein, The PVT assembly is any one of a flat box type, a tube plate type, a blow plate type and a flat plate type.

3. The two-cycle PVT heat pump water heating system based on gravity feed according to claim 1, wherein, The compressor is any one of a scroll compressor, a rotor compressor, a screw compressor and a piston compressor.

4. The two-cycle PVT heat pump water heating system based on gravity feed according to claim 1, wherein, The condenser is a plate heat exchanger, a double-pipe heat exchanger, a shell-and-tube heat exchanger or a plate-and-shell heat exchanger.

5. The two-cycle PVT heat pump water heating system based on gravity feed according to claim 1, wherein, The expansion valve is an electronic expansion valve, a thermal expansion valve, a capillary or a orifice throttling device.

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