Carbon dioxide supercritical heating system and heating control method

Abstract

A carbon dioxide supercritical heating system and a heating control method. The heating system comprises: a heat exchanger, a gas-liquid separation device, a throttling device, an evaporator, a compressor unit and a first flow control valve, wherein a refrigerant inlet of the heat exchanger is in communication with an output end of the compressor unit, and a refrigerant outlet of the heat exchanger is in communication with a refrigerant inlet of the gas-liquid separation device, the heat exchanger being used for heat exchange between a refrigerant and a substance to be heated, thereby heating said substance; a gaseous refrigerant outlet of the gas-liquid separation device is in communication with a first end of the first flow control valve, and a second end of the first flow control valve is in communication with a first input end of the compressor unit; and a liquid refrigerant outlet of the gas-liquid separation device is in communication with a first end of the throttling device, a second end of the throttling device is in communication with a first end of the evaporator, and a second end of the evaporator is in communication with a second input end of the compressor unit. The carbon dioxide supercritical heating system and the heating control method in the present application can fully meet the heating requirements for a substance to be heated.

Description

Carbon dioxide supercritical heating system and heating control method TECHNICAL FIELD

[0001] The present application relates to the technical field of heating devices, in particular to a carbon dioxide supercritical heating system and a heating control method. BACKGROUND

[0002] At present, crude oil collection and transportation mostly use electric heating or gas heating schemes to increase its temperature to reduce the flow viscosity. Electric heating has high energy consumption, and gas heating has environmental pollution problems, etc. Therefore, the air source heat pump heating scheme which is energy-saving and environmentally friendly has become the development trend of crude oil heating.

[0003] However, the traditional air source heat pump has low energy efficiency in low temperature environment, and the heating temperature cannot meet the requirement of crude oil heating temperature.

[0004] Therefore, it is necessary to make improvements to at least partially solve the above problems.

[0005] SUMMARY

[0006] A series of simplified concepts are introduced in the summary section, which will be further described in detail in the specific embodiment section. The summary section of the present application does not mean to attempt to limit the key features and necessary technical features of the claimed technical solution, nor to determine the protection scope of the claimed technical solution.

[0007] In order to at least partially solve the above problems, according to the first aspect of the present application, a carbon dioxide supercritical heating system is provided, comprising: a heat exchanger, a gas-liquid separation device, a throttling device, an evaporator, a compressor unit and a first flow control valve;

[0008] The refrigerant inlet of the heat exchanger is in communication with the output end of the compressor unit, and the refrigerant outlet of the heat exchanger is in communication with the refrigerant inlet of the gas-liquid separation device, wherein the heat exchanger is used for heat exchange between refrigerant and a to-be-heated substance to heat the to-be-heated substance, and the refrigerant comprises carbon dioxide;

[0009] The gaseous refrigerant outlet of the gas-liquid separation device is in communication with the first end of the first flow control valve, and the second end of the first flow control valve is in communication with the first input end of the compressor unit;

[0010] The liquid refrigerant outlet of the gas-liquid separation device is in communication with the first end of the throttling device, the second end of the throttling device is in communication with the first end of the evaporator, and the second end of the evaporator is in communication with the second input end of the compressor unit;

[0011] The compressor unit comprises a parallel mode and a parallel mode;

[0012] the compressor unit is in a parallel mode when the first flow control valve is open;

[0013] the compressor unit is in a parallel mode when the first flow control valve is closed.

[0014] exemplarily, the compressor unit comprises a first compressor, a second compressor and a three-way control valve;

[0015] an output end of the first compressor and an output end of the second compressor are both in communication with a refrigerant inlet of the heat exchanger;

[0016] a first end of the three-way control valve is in communication with a second end of the first flow control valve, a second end of the three-way control valve is in communication with an input end of the second compressor, and a third end of the three-way control valve is in communication with an input end of the first compressor and a second end of the evaporator;

[0017] the first end of the three-way control valve and the second end of the three-way control valve are conducted when the compressor unit is in the parallel mode;

[0018] the second end of the three-way control valve and the third end of the three-way control valve are conducted when the compressor unit is in the parallel mode.

[0019] exemplarily, the heating system further comprises a regenerator, a second flow control valve, a third flow control valve and a fourth flow control valve;

[0020] the regenerator comprises a first heat exchange pipeline and a second heat exchange pipeline, a refrigerant outlet of the heat exchanger is in communication with a refrigerant inlet of the gas-liquid separation device through the first heat exchange pipeline, and the second end of the first flow control valve is in communication with the first end of the three-way control valve through the second heat exchange pipeline;

[0021] the second end of the evaporator is in communication with the third end of the three-way control valve and the input end of the first compressor through the second flow control valve;

[0022] a first end of the third flow control valve is in communication with a first end of the second flow control valve, and a second end of the third flow control valve is in communication with the second end of the first flow control valve;

[0023] a first end of the fourth flow control valve is in communication with the first end of the three-way control valve, and a second end of the fourth flow control valve is in communication with the third end of the three-way control valve.

[0024] exemplarily, the gas-liquid separation device comprises a tank body, a coil pipe and a throttling device;

[0025] The coil is partially located inside the tank, and both the first and second ends of the coil are connected to the outside of the tank.

[0026] The throttling device is located outside the tank body, with its first end connected to the second end of the coil and its second end connected to the interior of the tank body.

[0027] The first end of the coil is the refrigerant inlet of the gas-liquid separation device, and the bottom and top of the tank are respectively provided with the liquid refrigerant outlet and the gaseous refrigerant outlet.

[0028] For example, the evaporator includes a first refrigerant line and a second refrigerant line, and the heating system further includes a fifth flow control valve;

[0029] The first end of the first refrigerant pipeline is connected to the second end of the throttling device, and the second end of the first refrigerant pipeline is connected to the first end of the second flow control valve;

[0030] The first end of the fifth flow control valve is connected to the refrigerant inlet of the heat exchanger, the second end of the fifth flow control valve is connected to the second input end of the compressor unit, and the second end of the second refrigerant pipeline is connected to the refrigerant inlet of the gas-liquid separator.

[0031] The first refrigerant pipeline exchanges heat with the second refrigerant pipeline.

[0032] For example, the heating system further includes a liquid reservoir;

[0033] The refrigerant outlet of the heat exchanger is connected to the refrigerant inlet of the gas-liquid separator through the liquid receiver, and the second end of the second refrigerant pipeline is connected to the refrigerant inlet of the gas-liquid separator through the liquid receiver.

[0034] According to a second aspect of the present invention, a heating control method is provided, which is applied to the heating system described above, the heating control method comprising:

[0035] Obtain the outlet temperature of the substance to be heated;

[0036] When the outlet temperature is greater than the preset temperature, the first flow control valve is opened, and the compressor unit is in the parallel mode.

[0037] For example, the heating control method further includes:

[0038] When the outlet temperature is less than or equal to the preset temperature, the heating load of the substance to be heated is obtained;

[0039] when the temperature increasing load is less than a preset load, controlling the first flow control valve to open, and the compressor unit is in the parallel mode;

[0040] when the temperature increasing load is greater than or equal to the preset load, controlling the first flow control valve to close, and the compressor unit is in the parallel connection mode;

[0041] wherein, when the compressor unit is in the parallel mode, a first end of the three-way control valve and a second end of the three-way control valve are conducted;

[0042] when the compressor unit is in the parallel mode, the second end of the three-way control valve and a third end of the three-way control valve are conducted.

[0043] exemplarily, when the compressor unit is in the parallel mode, the second flow control valve is opened, and the third flow control valve and the fourth flow control valve are closed;

[0044] when the compressor unit is in the parallel connection mode, the third flow control valve and the fourth flow control valve are opened, and the second flow control valve is closed.

[0045] exemplarily, the heating control method further comprises:

[0046] when the compressor unit is in the parallel connection mode, obtaining a frost layer thickness on the evaporator;

[0047] when the frost layer thickness is greater than a preset thickness, opening a fifth flow control valve.

[0048] exemplarily, the heating control method further comprises:

[0049] when the compressor unit is in the parallel connection mode, obtaining a temperature increasing rate of the to-be-heated substance;

[0050] when the temperature increasing rate is less than a preset rate value within a preset time, increasing a power of a first compressor of the compressor unit, and / or, increasing a power of a second compressor of the compressor unit, and / or, increasing an opening degree of the throttling device.

[0051] According to the carbon dioxide supercritical heating system and the heating control method, the switching between the parallel mode and the parallel connection mode can be realized by controlling the opening and closing of the first flow control valve, in the parallel mode, the compressor unit can compress the refrigerant from the gaseous refrigerant outlet of the gas-liquid separator and the refrigerant from the evaporator, thereby improving the circulation efficiency of the system, in the parallel connection mode, the compressor unit only compresses the refrigerant from the evaporator, thereby effectively improving the heat supply capacity of the heat exchanger to the heated substance and significantly improving the temperature of the heated substance. Therefore, the carbon dioxide supercritical heating system and the heating control method can achieve better heating effect on the heated substance such as crude oil. BRIEF DESCRIPTION OF DRAWINGS

[0052] The following drawings of the present application are hereby incorporated into the present application as part of the present application for the purpose of understanding the present application. The embodiments of the present application and the description thereof shown in the drawings are used to explain the devices and principles of the present application. In the drawings,

[0053] Fig. 1 is a structural schematic diagram of a carbon dioxide supercritical heating system according to a first embodiment of the present application;

[0054] Fig. 2 is a structural schematic diagram of a carbon dioxide supercritical heating system according to a second embodiment of the present application;

[0055] Fig. 3 is a structural schematic diagram of a gas-liquid separation device;

[0056] Fig. 4 is a structural schematic diagram of an evaporator;

[0057] Fig. 5 is a refrigerant flow direction schematic diagram when the compressor unit of the second embodiment is in the parallel mode;

[0058] Fig. 6 is a refrigerant flow direction schematic diagram when the compressor unit of the second embodiment is in the parallel connection mode;

[0059] Fig. 7 is a refrigerant flow direction schematic diagram when the compressor unit of the second embodiment is in the parallel connection mode and defrosting is performed;

[0060] Fig. 8 is a flow chart of a heating control method according to an embodiment of the present application. 100 - compressor unit, 1 - first compressor, 2 - second compressor, 3 - one-way valve, 4 - heat exchanger, 401 - inlet of substance to be heated, 402 - outlet of substance to be heated, 5 - regenerator, 6 - first flow control valve, 7 - liquid accumulator, 8 - second flow control valve, 9 - gas-liquid separation device, 91 - coil, 92 - tank, 93 - throttling device, 10 - throttling device, 11 - evaporator, 111 - first refrigerant line, 1111 - first end of first refrigerant line, 1112 - second end of first refrigerant line, 112 - second refrigerant line, 1121 - first end of second refrigerant line, 1122 - second end of second refrigerant line, 12 - fan, 13 - three-way control valve, 1301 - first end of three-way control valve, 1302 - second end of three-way control valve, 1303 - third end of three-way control valve, 14 - third flow control valve, 15 - fourth flow control valve, 16 - fifth flow control valve. DETAILED DESCRIPTION

[0061] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. It will be apparent, however, to one skilled in the art that the present application can be practiced without one or more of these specific details. In other instances, well-known techniques have not been described in detail in order to avoid unnecessarily obscuring the present application.

[0062] It should be understood that, although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present application.

[0063] Referring to Fig. 1, a carbon dioxide supercritical heating system according to a first embodiment of the present application is schematically illustrated.

[0064] The heating system comprises a heat exchanger 4, a gas-liquid separation device 9, a throttling device 10, an evaporator 11, a compressor unit 100 and a first flow control valve 6.

[0065] The heat exchanger 4 is configured to exchange heat between the refrigerant and the substance to be heated, so as to heat the substance to be heated. The heat exchanger 4 has a refrigerant inlet, a refrigerant outlet, a substance-to-be-heated inlet 401 and a substance-to-be-heated outlet 402, and has a refrigerant pipeline and a substance-to-be-heated pipeline in the heat exchanger 4. The two ends of the refrigerant pipeline are the refrigerant inlet and the refrigerant outlet, respectively. The two ends of the substance-to-be-heated pipeline are the substance-to-be-heated inlet 401 and the substance-to-be-heated outlet 402, respectively. The refrigerant in the refrigerant pipeline exchanges heat with the substance to be heated in the substance-to-be-heated pipeline in the heat exchanger 4. The refrigerant inlet of the heat exchanger 4 is in communication with the output end of the compressor unit 100, and the refrigerant outlet of the heat exchanger 4 is in communication with the refrigerant inlet of the gas-liquid separation device 9. The compressed refrigerant in the high-temperature and high-pressure state from the compressor unit 100 exchanges heat with the substance to be heated entering the substance-to-be-heated pipeline from the substance-to-be-heated inlet 401 in the heat exchanger 4, so as to heat the substance to be heated. The heat exchanger 4 can be a double-pipe heat exchanger, a shell-and-tube heat exchanger or a plate heat exchanger.

[0066] The gas-liquid separation device 9 is configured to separate the refrigerant from the heat exchanger 4 into gas and liquid. The gaseous refrigerant outlet of the gas-liquid separation device 9 is in communication with the first end of the first flow control valve 6, and the second end of the first flow control valve 6 is in communication with the first input end of the compressor unit 100. The liquid refrigerant outlet of the gas-liquid separation device 9 is in communication with the first end of the throttling device 10, and the second end of the throttling device 10 is in communication with the first end of the evaporator 11. The second end of the evaporator 11 is in communication with the second input end of the compressor unit 100. The throttling device 10 can be a thermal expansion valve, an electronic expansion valve or the like. In some embodiments, the throttling device 10 can be a device capable of throttling the refrigerant, such as an expander.

[0067] Referring to FIG. 3, in the embodiment, the gas-liquid separation device 9 comprises a tank 92, a coil 91 and a throttling device 93. The coil 91 is partially located in the tank 92, i.e., the main body of the coil 91 is located inside the tank 92 and at the upper portion of the tank 92. The first end and the second end of the coil 91 are both in communication with the outside of the tank 92. The first end of the coil 91 is the refrigerant inlet of the gas-liquid separation device 9 and is in communication with the refrigerant outlet of the heat exchanger 4. The throttling device 93 is located outside the tank 92. The first end of the throttling device 93 is in communication with the second end of the coil 91, and the second end of the throttling device 93 is in communication with the inside of the tank 92. The throttling device 93 can be a capillary tube or an expansion valve. The bottom and the top of the tank 92 are respectively provided with a liquid refrigerant outlet and a gaseous refrigerant outlet. Thus, the refrigerant entering the gas-liquid separation device 9 from the first end of the coil 91 is first exchanged with the gaseous refrigerant in the tank 92 in the coil 91 to increase the supercooling degree and improve the refrigeration capacity after throttling, and then throttled by the throttling device 93. The throttled refrigerant is in a gas-liquid mixed state and enters the inside of the tank 92. Under the action of gravity, the liquid refrigerant accumulates at the bottom of the tank 92 and can flow to the throttling device 10 through the liquid refrigerant outlet at the bottom of the tank 92. The gaseous refrigerant accumulates at the upper portion of the tank 92 and is exchanged with the refrigerant in the coil 91 and can flow to the first flow control valve 6 through the gaseous refrigerant outlet at the top of the tank 92.

[0068] In other embodiments, the gas-liquid separation device 9 can also be other types of gas-liquid separators known to those skilled in the art, such as a cyclone separator.

[0069] The compressor unit 100 is used to compress the refrigerant from the first flow control valve 6 and the evaporator 11. The compressor unit 100 comprises a parallel mode and a parallel connection mode. When the first flow control valve 6 is open, the compressor unit 100 is in the parallel mode. In the parallel mode, the compressor unit 100 can respectively compress the refrigerant from the first flow control valve 6 and the refrigerant from the evaporator 11. The two compression processes can be relatively independent and do not affect each other, which can improve the system cycle efficiency. When the first flow control valve 6 is closed, the compressor unit 100 is in the parallel connection mode. In the parallel connection mode, the compressor unit 100 only compresses the refrigerant from the evaporator 11. At this time, the temperature of the refrigerant output by the compressor unit 100 can be effectively compressed, and the heating effect on the substance to be heated can be improved.

[0070] In the embodiment, the compressor unit 100 comprises a first compressor 1, a second compressor 2 and a three-way control valve 13. The output end of the first compressor 1 and the output end of the second compressor 2 are both in communication with the refrigerant inlet of the heat exchanger 4; the first end 1301 of the three-way control valve 13 is in communication with the second end of the first flow control valve 6, the second end 1302 of the three-way control valve 13 is in communication with the input end of the second compressor 2, and the third end 1303 of the three-way control valve 13 is in communication with the input end of the first compressor 1 and the second end of the evaporator 11.

[0071] When the compressor unit 100 is in the parallel mode, the first end 1301 of the three-way control valve 13 and the second end 1302 of the three-way control valve 13 are in conduction, at this time, the refrigerant from the first flow control valve 6 can enter the second compressor 2 through the three-way control valve 13, and the refrigerant from the evaporator 11 can enter the first compressor 1. The first compressor 1 is the main compressor, which provides the main heating capacity for the system, and the second compressor 2 is the auxiliary compressor. The second compressor 2 compresses the medium-throttled refrigerant, and the first compressor 1 compresses the twice-throttled refrigerant. The suction positions and state points of the two compressors are relatively independent and do not affect each other, which will not cause mixing loss. The displacement and capacity of the main compressor can be higher than that of the auxiliary compressor, and the two compressors can be operated at high-efficiency operating points, and the system cycle efficiency is higher. Further, by adjusting the compressor frequency and the opening of the throttling device 10, the supercooling degree of the carbon dioxide refrigerant out of the gas cooler can be increased, and the cycle efficiency of the system can be improved.

[0072] When the compressor unit 100 is in the parallel mode, the second end 1302 of the three-way control valve 13 and the third end 1303 of the three-way control valve 13 are in conduction. At this time, the refrigerant from the evaporator 11 can enter the first compressor 1 and can enter the second compressor 2 through the three-way control valve 13, and the first compressor 1 and the second compressor 2 both compress the twice-throttled refrigerant, so that the temperature of the refrigerant entering the heat exchanger 4 can be significantly improved, and the heating capacity for the material to be heated can be improved.

[0073] In the embodiment, the first temperature sensor, the first pressure sensor and the first flow sensor are arranged at the inlet 401 of the heat exchanger 4 for the substance to be heated, and the second temperature sensor is arranged at the outlet 402 of the heat exchanger 4 for the substance to be heated. The first temperature sensor, the first pressure sensor, the first flow sensor and the second temperature sensor are respectively used to detect the temperature T3, the pressure P2 and the flow Q of the substance to be heated entering the heat exchanger 4 and the outlet temperature T4 of the substance to be heated from the outlet of the heat exchanger 4. The temperature rise load φ of the substance to be heated can be calculated according to the temperature T3, the pressure P2, the flow Q and the set outlet temperature T5, wherein the set outlet temperature T5 is the temperature to which the substance to be heated needs to be heated. The temperature rise load φ of the substance to be heated is QxCx(T5-T3), wherein C is the specific heat capacity of the substance to be heated entering the heat exchanger 4, which is a function of the pressure P2, C=f(P2). Thus, the switching between the parallel mode and the series mode can be performed according to the outlet temperature T4 of the substance to be heated and the temperature rise load φ.

[0074] In the embodiment, the refrigerant includes carbon dioxide, and the refrigerant can be only carbon dioxide or a mixture of carbon dioxide and other refrigerants known to those skilled in the art. Carbon dioxide is used as the refrigerant, which is safe, non-polluting, good in flowability, low in circulation loss and high in heat transfer efficiency. The substance to be heated can be crude oil or other gaseous or liquid substances to be heated. After entering the compression unit 100 (i.e., the first compressor 1 and the second compressor 2), the carbon dioxide is compressed to a supercritical state and then enters the heat exchanger 4 to exchange heat with the substance to be heated. The supercritical carbon dioxide has a higher heat exchange coefficient and heat exchange efficiency, and can better heat the substance to be heated.

[0075] The carbon dioxide supercritical heating system according to the second embodiment of the present application is exemplarily described with reference to FIG. 2. The heating system of the second embodiment further includes a regenerator 5, a second flow control valve 8, a third flow control valve 14 and a fourth flow control valve 15 on the basis of the heat exchange system of the first embodiment.

[0076] The regenerator 5 includes a first heat exchange pipeline and a second heat exchange pipeline. The refrigerant outlet of the heat exchanger 4 is communicated with the refrigerant inlet of the gas-liquid separation device 9 through the first heat exchange pipeline, and the second end of the first flow control valve 6 is communicated with the first end 1301 of the three-way control valve 13 through the second heat exchange pipeline. The refrigerant in the first heat exchange pipeline exchanges heat with the refrigerant in the second heat exchange pipeline.

[0077] The second end of the evaporator 11 is communicated with the third end 1303 of the three-way control valve 13 and the input end of the first compressor 1 through the second flow control valve 8.

[0078] The first end of the third flow control valve 14 is in communication with the first end of the second flow control valve 8, and the second end of the third flow control valve 14 is in communication with the second end of the first flow control valve 6.

[0079] The first end of the fourth flow control valve 15 is in communication with the first end 1301 of the three-way control valve 13, and the second end of the fourth flow control valve 15 is in communication with the third end 1303 of the three-way control valve 13.

[0080] When the compressor unit 100 is in the parallel mode, the second flow control valve 8 is opened, and the third flow control valve 14 and the fourth flow control valve 15 are closed. At this time, the low-temperature refrigerant from the first flow control valve 6 can enter the second heat exchange pipeline and exchange heat with the high-temperature refrigerant from the refrigerant outlet of the heat exchanger 4 entering the first heat exchange pipeline, thereby increasing the temperature of the refrigerant entering the second compressor 2 and keeping the second compressor 2 at a certain suction superheat.

[0081] When the compressor unit 100 is in the parallel mode, the third flow control valve 14 and the fourth flow control valve 15 are opened, and the second flow control valve 8 is closed. At this time, the refrigerant from the evaporator 11 can enter the second heat exchange pipeline through the third flow control valve 14, exchange heat with the high-temperature refrigerant from the refrigerant outlet of the heat exchanger 4 entering the first heat exchange pipeline, and then enter the first compressor 1 and the second compressor 2 through the fourth flow control valve 15 and the three-way control valve 13, thereby effectively increasing the temperature of the refrigerant entering the first compressor 1 and the second compressor 2 and keeping the first compressor 1 and the second compressor 2 at a certain suction superheat.

[0082] Referring to FIGS. 2 and 4, in the present embodiment, the evaporator 11 includes a first refrigerant pipeline 111 and a second refrigerant pipeline 112, and the heating system further includes a fifth flow control valve 16.

[0083] The first end 1111 of the first refrigerant pipeline 111 is in communication with the second end of the throttling device 10, and the second end 1112 of the first refrigerant pipeline 111 is in communication with the second input end of the compressor unit 100, i.e., in communication with the input end of the first compressor 1 through the second flow control valve 8, i.e., in communication with the first end of the second flow control valve 8. The refrigerant in the first refrigerant pipeline 111 exchanges heat with air and is evaporated by absorbing heat. The first end of the fifth flow control valve 16 is in communication with the refrigerant inlet of the heat exchanger 4, the second end of the fifth flow control valve 16 is in communication with the first end 1121 of the second refrigerant pipeline 112, and the second end 1122 of the second refrigerant pipeline 112 is in communication with the refrigerant inlet of the gas-liquid separation device 9. The first refrigerant pipeline 111 exchanges heat with the second refrigerant pipeline 112, specifically, the first refrigerant pipeline 111 and the second refrigerant pipeline 112 can exchange heat through fin connection. It should be noted that the first end of the evaporator 11 and the second end of the evaporator 11 mentioned above refer to the first end of the first refrigerant pipeline 111 and the second end of the first refrigerant pipeline 111.

[0084] In the present embodiment, the heating system further comprises a fan 12 for providing heat exchange air volume for the evaporator 11, and the second refrigerant pipeline 112 is arranged between the first refrigerant pipeline 111 and the fan 12. Thus, the air blown by the fan 12 first passes through the second refrigerant pipeline 112 and then passes through the first refrigerant pipeline 111, which can efficiently and uniformly provide the heat released by the second refrigerant pipeline 112 to the first refrigerant pipeline 111 to defrost the first refrigerant pipeline 111. In some embodiments, the fan 12 can not be arranged in the heating system, and the first refrigerant pipeline 111 and the second refrigerant pipeline 112 are configured to exchange heat only through fins.

[0085] When the evaporator 11 needs to be defrosted, i.e., the first refrigerant pipeline 111 needs to be defrosted, the fifth flow control valve 16 can be opened. When the fifth flow control valve 16 is opened, the high-temperature and high-pressure refrigerant from the compressor unit 100 can enter the second refrigerant pipeline 112 through the fifth flow control valve 16 and release heat in the second refrigerant pipeline 112 to defrost the first refrigerant pipeline 111.

[0086] In other embodiments, the second refrigerant pipeline 112 can not be arranged in the evaporator 11, and the fifth flow control valve 16 can not be arranged in the heating system, and the evaporator 11 is defrosted by other means known to those skilled in the art.

[0087] In the embodiment, the heating system further comprises a liquid reservoir 7 for storing the refrigerant which does not participate in the circulation. The refrigerant outlet of the heat exchanger 4 is in communication with the refrigerant inlet of the gas-liquid separator 9 through the first heat exchange pipeline of the regenerator 5 and the liquid reservoir 7 in sequence, that is, the refrigerant from the refrigerant outlet of the heat exchanger 4 first enters the first heat exchange pipeline of the regenerator 5 for heat exchange, then enters the liquid reservoir 7 after the heat exchange, and then enters the refrigerant inlet of the gas-liquid separator 9 from the liquid reservoir 7. The second end of the second refrigerant pipeline 112 is in communication with the refrigerant inlet of the gas-liquid separator 9 through the liquid reservoir 7, that is, the refrigerant from the second refrigerant pipeline 112 first enters the liquid reservoir 7, and then enters the refrigerant inlet of the gas-liquid separator 9 from the liquid reservoir 7.

[0088] In the embodiment, the compressor unit 100 further comprises a one-way valve 3, the output end of the second compressor 2 is in communication with the output end of the first compressor 1 and the refrigerant inlet of the heat exchanger 4 through the one-way valve 3, that is, the inlet end of the one-way valve 3 is in communication with the output end of the second compressor 2, and the outlet end of the one-way valve 3 is in communication with the output end of the first compressor 1 and the refrigerant inlet of the heat exchanger 4 at the same time. The one-way valve 3 is used to protect the second compressor 2 from being impacted by the refrigerant from the outlet of the first compressor 1.

[0089] Referring to FIG. 5, when the compressor unit 100 is in the parallel mode, the first flow control valve 6 and the second flow control valve 8 are opened, the third flow control valve 14, the fourth flow control valve 15 and the fifth flow control valve 16 are closed, and the three-way control valve 13 is in a conducting state between the first end 1301 and the second end 1302. At this time, the flow direction of the refrigerant is: the heat exchanger 4→the first heat exchange pipeline of the regenerator 5→the liquid reservoir 7→the gas-liquid separator, and the refrigerant is divided into two paths in the gas-liquid separator. One path (i.e., the flow direction of the gaseous refrigerant from the gas-liquid separator) is: the gas-liquid separator→the first flow control valve 6→the second heat exchange pipeline of the regenerator 5→the three-way control valve 13→the second compressor 2→the one-way valve 3→the heat exchanger 4. The other path (i.e., the flow direction of the liquid refrigerant from the gas-liquid separator) is: the gas-liquid separator→the throttling device 10→the first refrigerant pipeline 111 of the evaporator 11→the second flow control valve 8→the first compressor 1→the heat exchanger 4.

[0090] Referring to Fig. 6, when the compressor unit 100 is in parallel mode, the first flow control valve 6, the second flow control valve 8 and the fifth flow control valve 16 are closed, the third flow control valve 14 and the fourth flow control valve 15 are opened, and the three-way control valve 13 is connected to its second end 1302 and third end 1303. At this time, the flow direction of the refrigerant is: the heat exchanger 4→the first heat exchange pipeline of the heat regenerator 5→the accumulator 7→the gas-liquid separator→the throttling device 10→the first refrigerant pipeline 111 of the evaporator 11→the third flow control valve 14→the second heat exchange pipeline of the heat regenerator 5→the fourth flow control valve 15. The refrigerant from the fourth flow control valve 15 is divided into two paths. One path is: the fourth flow control valve 15→the first compressor 1→the heat exchanger 4. The other path is: the fourth flow control valve 15→the second compressor 2→the one-way valve 3→the heat exchanger 4.

[0091] Referring to Fig. 7, when the compressor unit 100 is in parallel mode and the evaporator 11 needs to be defrosted, the fifth flow control valve 16 is opened. The flow direction of the refrigerant is further based on the parallel mode and includes: the first compressor 1 and the one-way valve 3→the fifth flow control valve 16→the first refrigerant pipeline 111 of the evaporator 11→the accumulator 7→the gas-liquid separator.

[0092] In the present embodiment, the first refrigerant pipeline 111 is provided with an ambient temperature sensor, a pipeline temperature sensor and an air pressure sensor, which are respectively used to detect the ambient temperature T1 outside the first refrigerant pipeline 111, the temperature T2 of the outer wall of the first refrigerant pipeline 111 and the leeward air pressure P1 of the first refrigerant pipeline 111. The frost thickness h of the first refrigerant pipeline 111 is a function of the ambient temperature T1, the temperature T2 of the outer wall of the first refrigerant pipeline 111 and the leeward air pressure P1 of the first refrigerant pipeline 111, h=f(T1, T2, P1). Exemplarily, h=(T1-T2)*a1+P1*a2, wherein a1 and a2 are fitting data obtained by trial test. Thus, the frost thickness h can be determined according to the ambient temperature T1, the temperature T2 of the outer wall of the first refrigerant pipeline 111 and the leeward air pressure P1 of the first refrigerant pipeline 111. Further, whether defrosting is needed, i.e., whether the fifth flow control valve 16 needs to be opened, can be determined according to the frost thickness.

[0093] In the embodiment, the first temperature sensor, the first pressure sensor and the first flow sensor are arranged at the inlet 401 of the heat exchanger 4 for the substance to be heated, and the second temperature sensor is arranged at the outlet 402 of the heat exchanger 4 for the substance to be heated. The first temperature sensor, the first pressure sensor, the first flow sensor and the second temperature sensor are respectively used to detect the temperature T3, the pressure P2 and the flow Q of the substance to be heated entering the heat exchanger 4 and the outlet temperature T4 of the substance to be heated from the outlet of the heat exchanger 4. The temperature rise load φ of the substance to be heated can be calculated according to the temperature T3, the pressure P2, the flow Q and the set outlet temperature T5, wherein the set outlet temperature T5 is the temperature to which the substance to be heated needs to be heated. The temperature rise load φ of the substance to be heated is QxCx(T5-T3), wherein C is the specific heat capacity of the substance to be heated entering the heat exchanger 4, which is a function of the pressure P2, C=f(P2). Thus, the switching between the parallel mode and the parallel-connection mode can be performed according to the outlet temperature T4 of the substance to be heated and the temperature rise load φ.

[0094] The heating control method according to an embodiment of the present application will be exemplarily described below with reference to FIG. 8. The heating control method can be applied to the carbon dioxide supercritical heating system of the above-described embodiments.

[0095] The heating control method comprises:

[0096] S100: obtaining an outlet temperature of the substance to be heated.

[0097] Specifically, the outlet temperature of the substance to be heated is the temperature of the substance to be heated when the substance to be heated exits the heat exchanger 4 from the refrigerant outlet 402 of the heat exchanger 4. Exemplarily, the outlet temperature of the substance to be heated can be obtained by the second temperature sensor arranged at the outlet 402 of the heat exchanger 4 for the substance to be heated.

[0098] S200: when the outlet temperature is greater than a preset temperature, controlling the first flow control valve 6 to open, and the compressor unit 100 is in the parallel mode.

[0099] Specifically, the preset temperature is the temperature to which the substance to be heated needs to be heated. When the outlet temperature is greater than the preset temperature, it indicates that the heating system can fully meet the heating demand of the substance to be heated. At this time, the first flow control valve 6 is controlled to open, and the compressor unit 100 is in the parallel mode, so that the system efficiency is high. For the heating system of the first embodiment, when the compressor unit 100 is in the parallel mode, the first end 1301 of the three-way control valve 13 and the second end 1302 of the three-way control valve 13 are conducted. For the heating system of the second embodiment, when the compressor unit 100 is in the parallel mode, the first end 1301 of the three-way control valve 13 and the second end 1302 of the three-way control valve 13 are conducted, and the second flow control valve 8 is opened, and the third flow control valve 14, the fourth flow control valve 15 and the fifth flow control valve 16 are closed.

[0100] When the outlet temperature is less than or equal to the preset temperature, referring to FIG. 8, the heating control method further comprises:

[0101] S300: When the outlet temperature is less than or equal to the preset temperature, obtaining the temperature load of the to-be-heated substance.

[0102] Specifically, the temperature T3, the pressure P2 and the flow Q of the to-be-heated substance entering the heat exchanger 4 can be obtained by the first temperature sensor, the first pressure sensor and the first flow sensor arranged at the to-be-heated substance inlet 401 of the heat exchanger 4, and then the temperature load φ of the to-be-heated substance is calculated according to the temperature T3, the pressure P2, the flow Q and the set outlet temperature T5. The set outlet temperature T5 is the temperature to which the to-be-heated substance needs to be heated, that is, the preset temperature. The temperature load φ of the to-be-heated substance is QxCx(T5-T3), wherein C is the specific heat capacity of the to-be-heated substance entering the heat exchanger 4, which is a function of the pressure P2, C=f(P2). The temperature load is the heat load required for the to-be-heated substance to be heated to the preset temperature.

[0103] S400: When the temperature load is less than the preset load, controlling the first flow control valve 6 to open, and the compressor unit 100 is in the parallel mode.

[0104] Specifically, the preset load is the maximum heat load that can be provided to the to-be-heated substance when the compressor unit 100 is in the parallel mode. When the temperature load is less than the preset load, it indicates that sufficient heat load can be provided by the parallel mode to heat the to-be-heated substance to the preset temperature. At this time, the first flow control valve 6 is controlled to open, and the compressor unit 100 is in the parallel mode.

[0105] S500: When the temperature load is greater than or equal to the preset load, controlling the first flow control valve 6 to close, and the compressor unit 100 is in the parallel mode.

[0106] Specifically, when the temperature load is greater than or equal to the preset load, it indicates that it is difficult to provide sufficient heat load by the parallel mode to heat the to-be-heated substance to the preset temperature. At this time, the first flow control valve 6 is controlled to close, and the compressor unit 100 is in the parallel mode to increase the heating capacity to heat the to-be-heated substance to the preset temperature. For the heating system of the first embodiment, when the compressor unit 100 is in the parallel mode, the second end 1302 of the three-way control valve 13 and the third end 1303 of the three-way control valve 13 are conducted. For the heating system of the second embodiment, when the compressor unit 100 is in the parallel mode, the second end 1302 of the three-way control valve 13 and the third end 1303 of the three-way control valve 13 are conducted, and the third flow control valve 14 and the fourth flow control valve 15 are opened, and the second flow control valve 8 and the fifth flow control valve 16 are closed.

[0107] Further, for the heating system of the second embodiment, when the compressor unit 100 is in the parallel mode, referring to FIG. 8, the heating control method further comprises:

[0108] S600: obtaining the frost thickness on the evaporator 11;

[0109] Specifically, the frost thickness on the evaporator 11 is the frost thickness at the first refrigerant pipeline 111. The ambient temperature T1 outside the first refrigerant pipeline 111, the temperature T2 of the outer wall of the first refrigerant pipeline 111, and the leeward air pressure P1 of the first refrigerant pipeline 111 can be obtained by the ambient temperature sensor, the pipeline temperature sensor, and the air pressure sensor arranged at the first refrigerant pipeline 111. The frost thickness h at the first refrigerant pipeline 111 is a function of the ambient temperature T1, the temperature T2 of the outer wall of the first refrigerant pipeline 111, and the leeward air pressure P1 of the first refrigerant pipeline 111, h = f(T1, T2, P1). Exemplarily, h = (T1-T2)*a1+P1*a2, wherein a1 and a2 are fitting data obtained by trial test. Thus, the frost thickness h can be determined according to the ambient temperature T1, the temperature T2 of the outer wall of the first refrigerant pipeline 111, and the leeward air pressure P1 of the first refrigerant pipeline 111.

[0110] S700: opening the fifth flow control valve 16 when the frost thickness is greater than the preset thickness.

[0111] Specifically, after the fifth flow control valve 16 is opened, the high-temperature and high-pressure refrigerant from the compressor unit 100 can enter the second refrigerant pipeline 112 through the fifth flow control valve 16, heat in the second refrigerant pipeline 112, and defrost the first refrigerant pipeline 111.

[0112] Further, for the heating system of the first embodiment and the second embodiment, when the compressor unit 100 is in the parallel mode, referring to FIG. 8, the heating control method further comprises:

[0113] S800: obtaining the temperature rising rate of the to-be-heated substance.

[0114] Specifically, the outlet temperature of the to-be-heated substance can be obtained in real time by the second temperature sensor arranged at the to-be-heated substance outlet 402 of the heat exchanger 4, and the temperature rising rate of the to-be-heated substance can be determined according to its relationship with time.

[0115] S900: increasing the power of the first compressor 1 of the compressor unit 100, and / or increasing the power of the second compressor 2 of the compressor unit 100, and / or increasing the opening degree of the throttling device 10 when the temperature rising rate is less than the preset rate value within the preset time.

[0116] Specifically, when the temperature rising rate is less than the preset rate value within the preset time, it indicates that the heat supply to the material to be heated is insufficient, and the heat supply needs to be further increased. At this time, the power of the first compressor 1 of the compressor unit 100 can be increased, and / or the power of the second compressor 2 of the compressor unit 100 can be increased, and / or the opening degree of the throttling device 10 (that is, the throttling capacity of the throttling device 10) can be increased, so as to increase the heat supply to the material to be heated, and meet the heating demand of the material to be heated.

[0117] According to the heating system of the present application, the compressor unit 100 has a parallel mode and a parallel connection mode. During normal heating operation, the parallel mode is adopted, and in the parallel mode, the supercooling degree of the system can be maintained by adjusting the frequency of the second compressor 2 and adjusting the opening degree of the throttling device 10, and the system has high operating efficiency. In the working condition that the parallel mode cannot meet the heating demand of the material to be heated, the parallel connection mode can be switched to, the heat supply capacity of the system to the outside is increased, and the heating demand of the material to be heated is ensured. In the parallel connection mode, when the frost layer thickness of the evaporator 11 is greater than the preset thickness, the fifth flow control valve 16 can be opened for defrosting, and the evaporation effect of the evaporator 11 is ensured. According to the heating system of the present application, the system can always operate in a high-efficiency state on the basis of maintaining the heat supply capacity to the outside.

[0118] Although example embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the example embodiments are only exemplary and are not intended to limit the scope of the present application. Those of ordinary skill in the art can make various changes and modifications without departing from the scope and spirit of the present application. All such changes and modifications are intended to be included within the scope of the present application as claimed in the appended claims.

[0119] Those skilled in the art can understand that, except for the mutual exclusivity between features, all features disclosed in the present specification (including the accompanying claims, abstract and drawings) and all processes or units of any method or device disclosed in the same can be combined in any combination. Unless explicitly stated otherwise, each feature disclosed in the present specification (including the accompanying claims, abstract and drawings) can be replaced by an alternative feature that provides the same, equivalent or similar purpose.

Claims

1. A supercritical carbon dioxide heating system, characterized by, The heat exchanger, the gas-liquid separation device, the throttling device, the evaporator, the compressor unit and the first flow control valve are included. The refrigerant inlet of the heat exchanger is communicated with the output end of the compressor unit, and the refrigerant outlet of the heat exchanger is communicated with the refrigerant inlet of the gas-liquid separation device, wherein the heat exchanger is used for heat exchange between the refrigerant and the to-be-heated substance to heat the to-be-heated substance, and the refrigerant includes carbon dioxide. The gaseous refrigerant outlet of the gas-liquid separation device is communicated with the first end of the first flow control valve, and the second end of the first flow control valve is communicated with the first input end of the compressor unit. The liquid refrigerant outlet of the gas-liquid separation device is communicated with the first end of the throttling device, the second end of the throttling device is communicated with the first end of the evaporator, and the second end of the evaporator is communicated with the second input end of the compressor unit. The compressor unit includes a parallel mode and a parallel connection mode. When the first flow control valve is opened, the compressor unit is in the parallel mode. When the first flow control valve is closed, the compressor unit is in the parallel connection mode.

2. The carbon dioxide supercritical heating system according to claim 1, wherein The compressor unit includes a first compressor, a second compressor and a three-way control valve. The output end of the first compressor and the output end of the second compressor are both communicated with the refrigerant inlet of the heat exchanger. The first end of the three-way control valve is communicated with the second end of the first flow control valve, the second end of the three-way control valve is communicated with the input end of the second compressor, and the third end of the three-way control valve is communicated with the input end of the first compressor and the second end of the evaporator. When the compressor unit is in the parallel mode, the first end of the three-way control valve and the second end of the three-way control valve are conducted. When the compressor unit is in the parallel connection mode, the second end of the three-way control valve and the third end of the three-way control valve are conducted.

3. The carbon dioxide supercritical heating system according to claim 2, wherein The heating system further includes a regenerator, a second flow control valve, a third flow control valve and a fourth flow control valve. The regenerator includes a first heat exchange pipeline and a second heat exchange pipeline, the refrigerant outlet of the heat exchanger is communicated with the refrigerant inlet of the gas-liquid separation device through the first heat exchange pipeline, and the second end of the first flow control valve is communicated with the first end of the three-way control valve through the second heat exchange pipeline. The second end of the evaporator is communicated with the third end of the three-way control valve and the input end of the first compressor through the second flow control valve. The first end of the third flow control valve is communicated with the first end of the second flow control valve, and the second end of the third flow control valve is communicated with the second end of the first flow control valve. The first end of the fourth flow control valve is communicated with the first end of the three-way control valve, and the second end of the fourth flow control valve is communicated with the third end of the three-way control valve.

4. The carbon dioxide supercritical heating system according to any one of claims 1-3, wherein The gas-liquid separation device includes a tank body, a coil pipe and a throttling device. ​ The coil is partially located in the tank, and both the first end and the second end of the coil are in communication with the outside of the tank; The throttling device is located outside the tank, the first end of the throttling device is in communication with the second end of the coil, and the second end of the throttling device is in communication with the inside of the tank; The first end of the coil is the refrigerant inlet of the gas-liquid separation device, and the bottom and the top of the tank are respectively provided with the liquid refrigerant outlet and the gaseous refrigerant outlet.

5. The supercritical carbon dioxide heating system according to any one of claims 1-3, wherein the evaporator comprises a first refrigerant pipeline and a second refrigerant pipeline, and the heating system further comprises a fifth flow control valve; The first end of the first refrigerant pipeline is in communication with the second end of the throttling device, and the second end of the first refrigerant pipeline is in communication with the second input end of the compressor unit; The first end of the fifth flow control valve is in communication with the refrigerant inlet of the heat exchanger, the second end of the fifth flow control valve is in communication with the first end of the second refrigerant pipeline, and the second end of the second refrigerant pipeline is in communication with the refrigerant inlet of the gas-liquid separation device; The first refrigerant pipeline and the second refrigerant pipeline exchange heat.

6. The supercritical carbon dioxide heating system according to claim 5, wherein the heating system further comprises a liquid accumulator; The refrigerant outlet of the heat exchanger is in communication with the refrigerant inlet of the gas-liquid separation device through the liquid accumulator, and the second end of the second refrigerant pipeline is in communication with the refrigerant inlet of the gas-liquid separation device through the liquid accumulator. The heating control method is applied to the supercritical carbon dioxide heating system according to any one of claims 1-6, and the heating control method comprises: acquiring an outlet temperature of the to-be-heated substance; 7. A heating control method characterized by, when the outlet temperature is greater than a preset temperature, controlling the first flow control valve to be opened, and the compressor unit to be in the parallel mode.

8. The heating control method according to claim 7, wherein the heating control method further comprises: when the outlet temperature is less than or equal to the preset temperature, acquiring a temperature rise load of the to-be-heated substance; when the temperature rise load is less than a preset load, controlling the first flow control valve to be opened, and the compressor unit to be in the parallel mode; when the temperature rise load is greater than or equal to the preset load, controlling the first flow control valve to be closed, and the compressor unit to be in the parallel mode; when the compressor unit is in the parallel mode, the first end of the three-way control valve and the second end of the three-way control valve are conducted; when the compressor unit is in the parallel mode, the second end of the three-way control valve and the third end of the three-way control valve are conducted.

9. The heating control method according to claim 8, wherein when the compressor unit is in the parallel mode, the second flow control valve is opened, and the third flow control valve and the fourth flow control valve are closed; when the compressor unit is in the parallel mode, the third flow control valve and the fourth flow control valve are opened, and the second flow control valve is closed.

10. The heating control method according to claim 8, wherein ​ ​ ​ ​ The heating control method further comprises: acquiring a frost thickness on the evaporator when the compressor unit is in the parallel mode; opening a fifth flow control valve when the frost thickness is greater than a preset thickness.

11. The heating control method according to claim 8, characterized in that, The heating control method further comprises: acquiring a temperature rising rate of the substance to be heated when the compressor unit is in the parallel mode; increasing a power of a first compressor of the compressor unit and / or increasing a power of a second compressor of the compressor unit when the temperature rising rate is less than a preset rate value within a preset time, and / or increasing an opening degree of the throttling device. ​

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