JP2018077041A - Multistage heat pump having two-stage expansion structure using co2 refrigerant, and circulation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multistage heat pump having a two-stage expansion structure using COrefrigerant, and a circulation method thereof.SOLUTION: A multistage heat pump 100 includes a compressor 110, a condenser 120, a gas-liquid separator 150, an expander and an evaporator 160, and has a two-stage expansion structure, wherein a first expansion device 140 is formed between the condenser 120 and the gas-liquid separator 150, which is configured to reduce pressure of refrigerant having passed through the condenser 120. The multistage heat pump 100 is configured to execute a two-stage expansion process of causing the first expansion device 140 to expand refrigerant from a high-pressure state to an intermediate pressure state, and causing an expansion device 142 to expand the refrigerant from the intermediate state to a low-pressure state.SELECTED DRAWING: Figure 1

Description

The following embodiment relates to a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant and a circulation method thereof, and more specifically, uses a CO ₂ refrigerant using a mixed refrigerant obtained by mixing CO ₂ and other refrigerants. The present invention relates to a multistage heat pump having a two-stage expansion structure and a circulation method thereof.

  In general, a heat pump is a device that cools or heats an indoor space through a process of compressing, condensing, expanding, and evaporating a refrigerant. The heat pump is configured to include a compressor, a condenser, an expansion valve, and an evaporator, and the refrigerant takes heat from the surroundings while evaporating in the evaporator to become a gas, which is again heated to the surroundings by the condenser. It is a cooling cycle which releases and liquefies.

Since general refrigerants such as R134a used in such heat pumps are known to be the main culprits of environmental destruction such as ozone depletion and global warming, use restrictions have been expanded to protect the environment. doing. As a result, supercritical cooling cycles using carbon dioxide (CO ₂ ) instead of such refrigerants are attracting attention.

Carbon dioxide (CO ₂ ) refrigerant has a low operating compression ratio, excellent compression efficiency, and excellent heat transfer characteristics, so that it has a temperature approach (secondary fluid air inlet temperature−refrigerant outlet). The difference in temperature) is extremely small compared to existing refrigerants, and in the case of a heat exchanger on the high-temperature and high-pressure side, heat transfer characteristics are excellent so that the temperature of the refrigerant can be lowered to the temperature of the inflowing air. There are advantages.

  Moreover, since the thermodynamic property value is excellent and the volumetric cooling capacity of carbon dioxide (capacity volume ratio = vaporization latent heat × gas density) reaches 7 to 8 times that of R134a, it constitutes a supercritical refrigeration cycle. The doubler volume ratio of the compressor can be greatly reduced.

  Furthermore, since carbon dioxide has a low surface tension, it has excellent boiling heat transfer, large specific heat, low liquid viscosity, and is advantageous over R134a in terms of pressure drop.

  However, in the supercritical refrigeration cycle using carbon dioxide as a refrigerant, not only the evaporating pressure but also the heat exchanger pressure (existing condensing pressure) on the high-temperature and high-pressure side is extremely higher than a general refrigeration cycle using R134a as a refrigerant. . That is, in the supercritical refrigeration cycle, the evaporation pressure is about 10 times higher than that of a general refrigeration cycle, and the heat exchanger pressure on the high temperature and high pressure side is about 7 times (about 120 bar).

For example, the condensing step of the high-pressure refrigerant gas in the refrigerator is frozen by air or water, but if CO ₂ is applied to the refrigerator, a high pressure of 120 to 130 bar higher than the critical point must be applied. . Thereby, about 90 degreeC warm water and a heating function come to be obtained using the heat | fever of a high voltage | pressure side.

  A device that uses such heat of condensation is called a heat pump, but the COP (coefficient of performance) indicating the refrigeration cycle efficiency of the heat pump is such that 1.0 is added to the COP of the refrigerator and the COP increases to 3-4. This means that the energy of electricity 1 is applied and 3 to 4 times the heat is used.

However, since the CO ₂ heat pump has a high pressure on the low-pressure evaporator side of about 30 bar and an evaporator vaporization temperature of about 0 ° C. is obtained, the refrigerant in the outdoor unit (evaporator) can be vaporized if the outside air is low in winter. An auxiliary heat source is required without being made. Such heat from the outdoor unit can be used for refrigeration and air conditioning, but cannot provide a sustained load.

  Patent Document 1 relates to an industrial heat pump system using such a carbon dioxide refrigerant and a performance evaluation method thereof, and an industrial heat pump using a low carbon environment-friendly carbon dioxide refrigerant and the performance of the heat pump system. Describes technology related to the evaluation method.

Korean open patent 10-2012-0055065

The embodiment describes a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant and a circulation method thereof, and more specifically, heating and mixing using a mixed refrigerant obtained by mixing CO ₂ and other refrigerants. Provide technology to increase refrigeration efficiency.

In the embodiment, by installing an expansion device between the condenser and the gas-liquid separator to expand the refrigerant that is the working fluid, the low-temperature refrigerant that can be easily evaporated even in the low outdoor air in winter by the evaporator. Provided are a multistage heat pump having a two-stage expansion structure using a CO ₂ refrigerant and a circulation method thereof.

In the embodiment, by using CO ₂ and HFC mixed refrigerants having different boiling points, the CO ₂ can be increased to 50 to 90%, thereby enabling application of a lower pressure on the high pressure side. A multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant that can also save energy by providing an effect of hot water for heating, and a circulation method thereof.

  In one embodiment of the present invention, a multi-stage heat pump having a two-stage expansion structure including a compressor, a condenser, a gas-liquid separator, an expansion device, and an evaporator, between the condenser and the gas-liquid separator The expansion device includes a first expansion device that reduces the pressure of the refrigerant that has passed through the condenser. The refrigerant is expanded from a high pressure to an intermediate pressure by the first expansion device, and the expansion device A two-stage expansion process may be performed, inflated from an intermediate pressure to a low pressure.

Here, the refrigerant may be a mixed refrigerant in which carbon dioxide (CO ₂ ) and at least one other refrigerant are mixed.

The refrigerant includes carbon dioxide (CO ₂ ) and HFC mixed refrigerants having different boiling points, and the ratio of the carbon dioxide (CO ₂ ) is increased to 50% to 90%, and the pressure at the high pressure is decreased. It will be possible to provide hot water and hot air for heating.

  The refrigerant includes two or more mixed refrigerants, and with a heat pump function that uses the heat of the condenser as heating hot water, the low temperature of the evaporator can be evaporated by outside air heat or applied to a refrigeration apparatus.

The gas-liquid separator separates a part of the carbon dioxide (CO ₂ ) as a liquid from the other refrigerant having a low boiling point by reducing the pressure of the refrigerant that has passed through the condenser by the first expansion device. The remaining carbon dioxide (CO ₂ ) may be separated as a gas.

The apparatus further includes a second precooler for freezing the refrigerant that has passed through the gas-liquid separator, and the expansion device is disposed between the gas-liquid separator and the second precooler and is discharged from the gas-liquid separator. A second expansion device that lowers the pressure of the carbon dioxide (CO ₂ ) that is in a high-pressure gas state, and a liquid that is disposed between the second precooler and the evaporator and discharged from the gas-liquid separator A third expansion device may be included in which the other refrigerant in a state and a part of the carbon dioxide (CO ₂ ) are cooled by the second precooler and then the pressure is reduced and discharged to the evaporator.

The evaporator may vaporize the other refrigerant that has passed through the third expansion device and a part of the carbon dioxide (CO ₂ ) by outside air heat.

The apparatus further includes a first precooler that connects the discharge port of the evaporator and the discharge port of the condenser, and the first precooler includes the refrigerant vaporized by the evaporator and the carbon dioxide that has passed through the condenser. After (CO ₂ ) is mixed and frozen, it may be moved to the compressor.

  It further includes an ejector or an EPR (Evaporator Pressure Regulator) that corrects a difference in pressure between the refrigerant discharged from the second precooler and the refrigerant discharged from the evaporator and sends it to the compressor. Good.

  In the evaporator, the refrigerant is expanded from a high pressure to an intermediate pressure by the first expansion device so that the heating function is performed even when the outside air temperature is low, and then the low pressure is reduced from the intermediate pressure by the third expansion device. The vaporization temperature may be lowered by the inflow of the refrigerant through the two-stage expansion process.

Further, in one embodiment, a method for circulating a multi-stage heat pump having a two-stage expansion structure, wherein refrigerant mixed with carbon dioxide (CO ₂ ) discharged from a compressor and at least one other refrigerant is condensed. The refrigerant that has been condensed in the condenser and passed through the condenser is expanded using a first expansion device to reduce the pressure, and the refrigerant that has passed through the first expansion device is utilized using a gas-liquid separator. The other refrigerant having a low boiling point and a part of the carbon dioxide (CO ₂ ) are separated as a liquid, the remaining carbon dioxide (CO ₂ ) is separated as a gas, and the high pressure discharged from the gas-liquid separator The carbon dioxide (CO ₂ ), which is in a gaseous state, is expanded using a second expansion device to lower the pressure and moved to the second precooler, and in a liquid state discharged from the gas-liquid separator The other refrigerant and the carbon dioxide After a part of the (CO ₂₎ were frozen in the second precooler, inflated using a third expander discharged to the evaporator lowering the pressure, the said other refrigerant by the evaporator A part of carbon dioxide (CO ₂ ) is vaporized by outside heat, and the carbon dioxide (CO ₂ ) passed through the second precooler, the other refrigerant vaporized by the evaporator, and the carbon dioxide (CO ₂ ) a part of which includes moving to the compressor after exchanging heat with each other.

According to one embodiment, a multi-stage heat pump having a two-stage expansion structure, the compressor compressing a mixed refrigerant containing carbon dioxide (CO ₂ ) having different boiling points and at least one other refrigerant, A condenser that is disposed next to the compressor and condenses the refrigerant that has passed through the compressor, and a first expansion device that is disposed next to the condenser and that expands the refrigerant that has passed through the condenser to lower the pressure. The other refrigerant having a low boiling point and a part of the carbon dioxide (CO ₂ ), which is disposed next to the first expansion device and lowers the pressure of the refrigerant having passed through the condenser by the first expansion device. A gas-liquid separator that separates the remaining carbon dioxide (CO ₂ ) as a gas, and a second gas-liquid separator that is disposed next to the gas-liquid separator and cools the refrigerant that has passed through the gas-liquid separator. Precooler, front Liquid is separator and disposed between the second precooler, the carbon dioxide (CO ₂₎ to be inflated second expander for reducing the pressure of the gaseous state discharged from the gas-liquid separator, said second ( ₂ ) After cooling the other refrigerant in a liquid state and a part of the carbon dioxide (CO ₂ ) disposed between the precooler and the evaporator and discharged from the gas-liquid separator with the second precooler, A third expansion device for expanding and discharging pressure to the evaporator, and a first precooler disposed between the condenser and the first expansion device and connected to the discharge port of the evaporator In addition to a heat pump function that uses the heat of the condenser as heating hot water, the mixed refrigerant can be applied to a refrigeration apparatus at a low temperature of the evaporator, and the evaporator has a heating function even when the outside air temperature is low. The refrigerant is performed by the first expansion device to perform After being expanded from high pressure to intermediate pressure, the third expansion device expands from the intermediate pressure to low pressure, and the vaporization temperature is lowered by the inflow of the refrigerant through the two-stage expansion process, and is vaporized by the evaporator. After the refrigerant and the carbon dioxide (CO ₂ ) that has passed through the second expansion device are mixed, the first precooler exchanges heat with the refrigerant that has passed through the condenser, and moves to the compressor after cooling. A multi-stage heat pump having a two-stage expansion structure is provided.

According to the embodiment, by installing an expansion device between the condenser and the gas-liquid separator to expand the refrigerant that is the working fluid, the low-temperature refrigerant that can be easily evaporated even in the low outdoor air in winter by the evaporator It is possible to provide a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant and a circulation method thereof.

According to the embodiment, by using CO ₂ and HFC mixed refrigerants having different boiling points so that CO ₂ can be increased to 50 to 90%, it becomes possible to apply a lower pressure on the high pressure side. In addition, it is possible to provide a multistage heat pump having a two-stage expansion structure using a CO ₂ refrigerant and a circulation method thereof, which can save energy by providing the effect of warm water for heating.

Furthermore, according to the embodiment, by using CO ₂ and HFC mixed refrigerants having different boiling points, it is possible to increase CO ₂ to 50 to 90%, thereby making it possible to use environmentally friendly carbon dioxide as a refrigerant. By substituting a heat pump that uses refrigerant that adversely affects the ozone layer and contributes to reducing greenhouse gas emissions, the pressure on the low-pressure evaporator side generated by the heat pump using carbon dioxide as a refrigerant Since the evaporator vaporization temperature of about 0 ° C. is high, the problem that the auxiliary heat source is necessary without the refrigerant vaporization of the outdoor unit (evaporator) can be solved if the outdoor temperature in winter is low.

In one embodiment, it is a schematic diagram illustrating a multi-stage heat pump with a two-stage expansion structure using CO ₂ refrigerant. In other embodiments, the ejector is included, it is a schematic diagram illustrating a multi-stage heat pump with a two-stage expansion structure using CO ₂ refrigerant. In one embodiment, it is a diagram for explaining the two-stage expansion step of the multi-stage heat pump with two-stage expansion structure using CO ₂ refrigerant. In one embodiment, it is a diagram for explaining the two-stage expansion step of the multi-stage heat pump with two-stage expansion structure using CO ₂ refrigerant. It is the figure which showed the COP change by the intermediate pressure of two-stage expansion in one Embodiment. In yet another embodiment, it is a flowchart illustrating a circulation process of a multi-stage heat pump with two-stage expansion structure using CO ₂ refrigerant.

  Hereinafter, embodiments will be described with reference to the accompanying drawings. However, the described embodiments may be modified in various other forms, and the scope of the present invention is not limited by the embodiments described below. In addition, embodiments are provided to more fully explain the invention to those skilled in the art. In the drawings, the shape and size of elements may be exaggerated for clarity.

In the following embodiments, an expansion device is installed between a condenser and a gas-liquid separator, and a two-stage expansion process is applied, so that the evaporator can be easily evaporated even in a low outdoor environment in winter. A multi-stage heat pump (Cascade Heat Pump) having a two-stage expansion structure using a CO ₂ refrigerant and capable of obtaining a refrigerant liquid can be provided. In addition, by using CO ₂ and HFC mixed refrigerants having different boiling points so that CO ₂ can be increased to 50 to 90%, it is possible to apply a pressure having a considerably low high-pressure side pressure. Can be provided.

This allows the application of low pressures of about 60-80 bar, where the high pressure side pressure is significantly lower than 130 bar in the CO ₂ heat pump process, and the application of two or more mixed refrigerants together with a heat pump function that uses the condenser heat as hot water The low temperature of the evaporator can be applied to refrigeration. Furthermore, even during the winter when the evaporator vaporization temperature is low and the outside air temperature is low, the outside air heat is sucked to easily vaporize and the heating function can be executed, and a high COP of 3.0 to 4.0 (coefficient of performance) By providing a process for improving the energy efficiency, an energy saving effect can be provided.

FIG. 1 is a diagram schematically showing a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant in one embodiment.

Referring to FIG. 1, a multi-stage heat pump 100 having a two-stage expansion structure using CO ₂ refrigerant in one embodiment includes a compressor 110, a condenser 120, a first expansion device 140, a gas-liquid separator 150, a second The apparatus may include an expansion device 141, a third expansion device 142, and an evaporator 160. In addition, according to the embodiment, the multistage heat pump 100 having a two-stage expansion structure using a CO ₂ refrigerant further includes at least one of the first precooler 130 and the second precooler 131. Also good.

  The compressor 110 sucks the refrigerant as the working fluid and discharges it after compressing it to a state higher than the critical point.

Here, the refrigerant may be a mixed refrigerant in which carbon dioxide (CO ₂ ) and at least one other refrigerant are mixed.

More specifically, the refrigerant includes carbon dioxide (CO ₂ ) and HFC-based mixed refrigerants having different boiling points, the ratio of CO ₂ is increased to 50% to 90% to reduce the pressure at high pressure, Hot water for heating or hot air may be provided.

  The refrigerant includes two or more mixed refrigerants, and the low temperature of the evaporator can be applied to the refrigeration apparatus together with a heat pump function that uses the heat of the condenser as heating hot water.

The condenser 120 condenses the refrigerant discharged from the compressor, and may perform heating using heat generated by the condenser. In particular, when using a refrigerant containing CO ₂ as a refrigerant, CO ₂ since higher pressure than the critical point is applied, it is possible to obtain hot water and heating function by using the high-pressure heat.

For example, when CO ₂ is applied to a heat pump, a high pressure of 120 to 130 bar higher than the critical point is applied, and hot water or a heating function of about 90 ° C. can be obtained using the heat on the high pressure side.

  In such a condenser 120, a refrigerant having a low boiling point at a predetermined pressure and a predetermined temperature may exist in a gas state above the critical point.

For example, in the condenser 120, the refrigerant CO ₂ gas and another refrigerant having a low boiling point at a pressure of 60 to 80 bar and 40 ° C. may exist in a gas state above the critical point.

  The first precooler 130 may be disposed between the condenser 120 and the first expansion device 140 and may be connected to the discharge port of the evaporator 160. Such a first precooler 130 is a device for improving performance, and may be omitted.

  The first expansion device 140 may be configured between the condenser and the gas-liquid separator, and may expand the refrigerant that has passed through the condenser to reduce the pressure.

  In this way, the first expansion device 140 performs a two-stage expansion process in which the refrigerant is expanded from a high pressure to an intermediate pressure and then is expanded from an intermediate pressure to a low pressure by another expansion device.

The gas-liquid separator 150 reduces the pressure of the refrigerant that has passed through the condenser 120 by the first expansion device 140, thereby separating another refrigerant having a low boiling point from CO _{2 as} a liquid, and the remaining CO _2. May be separated as a gas.

Unlike the existing auto multistage system, according to one embodiment, if the pressure is reduced by the first expansion device 140 after the condensation process, the other refrigerant having a low boiling point and a part of CO ₂ are liquid, and the rest CO ₂ can be obtained as a gas by the gas-liquid separator 150.

  The second precooler 131 may cool the lower refrigerant liquid of the gas-liquid separator 150.

More specifically, the second precooler 131 may cool a part of the CO ₂ and the other refrigerant in the liquid state discharged from the gas-liquid separator 150. In addition, after the CO ₂ pressure, which is a high-pressure gas discharged from the gas-liquid separator 150 by the second expansion device 141, is reduced to the final pressure, the second pre-cooler 131 may be passed.

For example, the high-pressure gas CO ₂ may be expanded to a pressure of about −20 to 12 bar to a gas of −20 ° C., and the liquid in the gas-liquid separator may be further subcooled by the second precooler.

  The expansion device may include a second expansion device 141 and a third expansion device 142.

The second expansion device 141 is disposed between the gas-liquid separator 150 and the second precooler 131 and expands carbon dioxide (CO ₂ ), which is a high-pressure gas state discharged from the gas-liquid separator 150, to increase the pressure. Can be lowered. The refrigerant that has passed through the second expansion device 141 may flow into the second precooler 131.

The third expansion device 142 is disposed between the second precooler 131 and the evaporator 160, and another refrigerant in a liquid state discharged from the gas-liquid separator 150 and a part of CO ₂ are part of the second precooler 131. After cooling, the pressure may be reduced and discharged to the evaporator 160.

The evaporator 160 may vaporize the other refrigerant that has passed through the third expansion device 142 and a part of CO ₂ by outside air heat.

  For example, the precooled refrigerant liquid may be vaporized by the outside air in the evaporator 160 while the pressure is expanded to 10 bar and the temperature drops to about −15 ° C.

  More specifically, the evaporator 160 is a two-stage expansion process in which the refrigerant is expanded from high pressure to intermediate pressure by the first expansion device 140 and then expanded from intermediate pressure to low pressure by the third expansion device 142. Since the vaporization temperature is lowered by the inflow of the refrigerant that has passed through, the evaporation easily occurs even when the outside air temperature is low, and the heating function can be performed by the condenser.

Thereafter, the refrigerant vaporized by the evaporator 160 and the CO ₂ gas that has passed through the second expansion device 141 and passed through the second precooler 131 may be mixed and moved to the compressor 110. Here, the first precooler 130 is additionally installed in the middle stage in which the refrigerant vaporized by the evaporator 160 and the CO gas that has passed through the second expansion device 141 and passed through the second precooler 131 move to the compressor 110. In this case, after passing through the first precooler 130, the compressor 110 may be moved.

  Thereafter, in the first precooler 130, heat exchange is performed between the mixed gas sucked into the compressor 110 from the evaporator 160 and the mixed refrigerant that has passed through the condenser 120. That is, the high-pressure refrigerant that has passed through the condenser 120 is cooled by the cold gas drawn from the evaporator 160 into the compressor 110.

For example, the refrigerant vaporized by the evaporator 160 may be combined with CO ₂ gas, compressed by the compressor 110 after passing through the first precooler 130, and the discharge temperature may be 120 to 130 ° C.

  In the first precooler 130, about 5 ° C. may be precooled. As an example, the outlet temperature of the evaporator 160 may be heated by 5 degrees, and the temperature of the condenser 120 may be decreased by 5 degrees.

  As described above, the present embodiment is an improvement of the auto multistage cycle, and an expansion device is temporarily installed between the condenser and the gas-liquid separator, and the expansion process can be configured in two stages. That is, it can be constituted by a two-stage expansion structure of high pressure-intermediate pressure-low pressure.

According to the embodiment, CO ₂ and HFC mixed refrigerants having different boiling points may be used in the same manner, and CO ₂ may be increased to 50 to 90%. Thereby, the high pressure side pressure can be applied at a low pressure of about 60 to 80 bar.

  Also, by applying two or more mixed refrigerants, it becomes possible to apply the low temperature of the evaporator to refrigeration together with the heat pump function that uses the condenser heat as hot water, and the vaporization temperature of the evaporator is low, so the outside air temperature is low Even in the winter, the evaporator 160 can be easily evaporated to perform the heating function, and a high COP efficiency of 3.0 to 4.0 can be obtained.

FIG. 2 is a diagram schematically illustrating a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant, including an ejector, according to another embodiment.

Referring to FIG. 2, in another embodiment, a multi-stage heat pump 200 having a two-stage expansion structure using a CO ₂ refrigerant and including an ejector includes a compressor 210, a condenser 220, a first expansion device 240, an air The liquid separator 250, the second expansion device 241, the third expansion device 242, the evaporator 260, and the ejector 270 or EPR (evaporation pressure control device) may be included. Further, according to the embodiment, the multi-stage heat pump 200 including the ejector and having the two-stage expansion structure using the CO ₂ refrigerant includes at least one of the first precooler 230 and the second precooler 231. Furthermore, you may comprise.

Here, the multi-stage heat pump 200 having the two-stage expansion structure using the CO ₂ refrigerant and including the ejector in the other embodiment is the same as the two-stage heat pump 200 using the CO ₂ refrigerant in the embodiment described with reference to FIG. Since a part of the configuration of the multi-stage heat pump having the expansion structure overlaps, a description of the overlapping configuration will be omitted, and a description will be given focusing on a different configuration.

  The ejector 270 corrects the pressure difference different from each other after the refrigerant discharged from the second precooler 231 and the refrigerant discharged from the evaporator 260 are flown into the compressor 210. You may let it flow.

As described above, in the multi-stage heat pump 200 having the two-stage expansion structure using the CO ₂ refrigerant and including the ejector and the EPR in another embodiment, the ejector 270 is additionally installed when it is desired to further reduce the temperature of the evaporator. You can do it. The ejector 270 may be used to correct small pressure differences when the pressures differ from one another.

For example, if the evaporator temperature is lowered to −20 ° C. or lower, the low-pressure side pressure becomes 6 bar, and a pressure difference that is lower than the CO ₂ gas pressure of 8 to 12 bar is generated. 270 or EPR may be applied.

As described above, the ejector 270 is for correcting a small pressure difference within 5 bar, and is greatly different from the function of the main drive high-pressure ejector of the refrigerator applied to the existing ejector-applied CO ₂ heat pump system. There is.

3a and 3b are views for explaining a two-stage expansion process of a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant in one embodiment.

Referring to FIG. 3a, a multi-stage heat pump 300 having a two-stage expansion structure using a CO ₂ refrigerant in one embodiment includes a compressor 310, a condenser 320, a first precooler 330, as described in FIG. The first expansion device 340, the gas-liquid separator 350, the second expansion device 341, the third expansion device 342, the second precooler 331, and the evaporator 360 may be included.

FIG. 3 b shows a ph diagram (pressure-specific enthalpy diagram) when the ratio of the mixed refrigerant of CO ₂ and R 143 a is 85:15.

As shown in FIGS. 3a and 3b, in the condenser, at a pressure of 70 bar and 40 ° C. (point 1), the refrigerant CO ₂ gas and another refrigerant having a low boiling point may be present in a gas state above the critical point.

  The gas at the point 1 is supercooled to the point 2 by the first precooler 330 by the energy amount at the points 11 to 12 which is the outlet gas of the evaporator 360.

  The supercooled gas (point 2) is expanded to an intermediate pressure of 25 bar (point 3) and collected in the gas-liquid separator 350. The enthalpy of the liquid in the gas-liquid separator 350 is a point 7 that is a saturated liquid, and the gas is a point 4 that is a saturated gas.

The CO ₂ gas at point 4 expands to point 5 where the final pressure is 12 bar and becomes a gas at a temperature of −13 ° C. Then, the saturated liquid at point 7 is supercooled to point 8 by the second precooler 331. However, it is heated and becomes point 6.

  The supercooled liquid at the point 8 is expanded to the point 9 by the third expansion device 342 up to the final pressure of 12 bar, and is vaporized by the outside air heat to become the saturated gas at the point 10.

  The gas at the point 11 is mixed with the superheated gas at the point 6 to become the gas at the point 11, then becomes the point 12 in the first precooler 330 and is sucked into the compressor 310.

The gas is compressed by an isentropic process up to 70 bar again by the compressor 310 and becomes a gas at a temperature of 130 ° C. at the point 13. This gas becomes a low-temperature gas at point 1 by the heat pump function of hot water or heating provided by a condenser. Here, the other refrigerant means another type of refrigerant that is not CO ₂ , and may be at least one refrigerant. For example, various alternative refrigerants such as R143A, R410A, R152A, R32, R717, R290 may be used as the other refrigerant.

Unlike the existing auto multistage system, if the pressure is reduced by the first expansion device after the condensation process, the entire other refrigerant having a low boiling point and a part of CO ₂ are liquid, and the remaining CO ₂ is gas. It can be obtained with a liquid separator.

The high-pressure gas CO ₂ may be expanded to a pressure of about −20 to 12 bar to a gas of −20 ° C., and the liquid in the gas-liquid separator may be further subcooled by a second precooler.

  In the first precooler, about 5 ° C. may be precooled. For example, the evaporator outlet temperature may be heated 5 degrees and the condenser temperature reduced 5 degrees. Here, the first precooler is a facility for improving performance and may be omitted.

As described below, the performance evaluation of the multi-stage heat pump having the two-stage expansion structure using the CO ₂ refrigerant in one embodiment can be confirmed.

  For example, the thermodynamic property values (enthalpy, entropy, pressure, temperature, etc.) and performance evaluation of the refrigerant may be calculated using EES (engineering equation solver) software or the like.

Table 1 shows a case where only CO ₂ is applied as a refrigerant to an existing CO ₂ heat pump.

Referring to Table 1, when only CO ₂ is applied as a refrigerant to an existing CO ₂ heat pump, a COP (coefficient of performance) indicating the refrigeration cycle efficiency of the heat pump at high pressure and low pressure can be confirmed.

  Here, the COP (coefficient of performance) indicating the refrigeration cycle efficiency of the heat pump may be calculated by dividing the amount of heat released by the condenser by the compression work of the compressor at high and low temperatures.

  For example, it may be indicated by COP = Qc / W of the heat pump and COP = Qe / W of the refrigeration apparatus. At this time, the heat pump may indicate the condenser heat amount / compression work, and the refrigeration device may indicate the evaporator suction amount / compression work.

Table 2 shows a case where a refrigerant different from CO ₂ is applied as a mixed refrigerant to a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant in one embodiment.

Referring to Table 2, a case where CO ₂ and R143a are applied as a mixed refrigerant at 70:30 to a multistage heat pump having a two-stage expansion structure using a CO ₂ refrigerant in one embodiment is shown. The COP (coefficient of performance) indicating the refrigeration cycle efficiency of the heat pump at the intermediate pressure and the low pressure can be confirmed.

Referring to Tables 1 and 2, when comparing the case where the high pressure / low pressure is 70 bar / 12 bar, the COP of the existing CO ₂ heat pump is 1.3725, while the CO ₂ refrigerant in one embodiment is used. The multi-stage heat pump having the two-stage expansion structure is improved by 3.3635 and 245% despite the low pressure, and it can be confirmed that the COP becomes 3.3606 even in the single-stage expansion without the two-stage expansion.

Therefore, in the multi-stage heat pump having a two-stage expansion structure using CO ₂ refrigerant in one embodiment, by applying CO ₂ and another refrigerant as a mixed refrigerant, the effect of increasing COP is greater than when using only CO _2. There is.

  FIG. 4 is a diagram illustrating a change in COP due to an intermediate pressure of two-stage expansion in one embodiment.

Referring to FIG. 4, when CO ₂ and R143a are applied as a mixed refrigerant at 70:30 to a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant in one embodiment, an intermediate expansion pressure of the two-stage expansion. Can obtain the maximum COP at 25 bar.

Therefore, when CO ₂ and another refrigerant are applied as a mixed refrigerant to the multi-stage heat pump having a two-stage expansion mechanism using a CO ₂ refrigerant in one embodiment, the maximum COP can be obtained at an intermediate pressure of the two-stage expansion. it can.

In one embodiment, when the multistage heat pump having a two-stage expansion structure using CO ₂ refrigerant is applied as a heat pump, the evaporation temperature of the evaporator, which is an outdoor unit, is as low as −10 to −15 ° C., The function of heating and hot water heat pump can be executed without a supplementary heat source even when the outside air temperature decreases in winter. Thus, an energy saving effect can be obtained by improving the COP and reducing the compression power.

FIG. 5 is a flowchart showing a circulation method of a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant in still another embodiment.

Referring to FIG. 5, in another embodiment, a circulation method of a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant includes carbon dioxide (CO ₂ ) discharged from a compressor and at least one or more The refrigerant mixed with the other refrigerant is condensed in the condenser 510, the refrigerant that has passed through the condenser is expanded using the first expansion device to reduce the pressure 520, and passes through the first expansion device. Separating the obtained refrigerant from another refrigerant having a low boiling point using a gas-liquid separator and a part of carbon dioxide (CO ₂ ) as a liquid and separating the remaining carbon dioxide (CO ₂ ) as a gas 530, Stage 540, in which the carbon dioxide (CO ₂ ), which is in a high-pressure gas state discharged from the gas-liquid separator, is expanded using the second expansion device to reduce the pressure and is transferred to the second precooler, gas-liquid Discharged from the separator After a part of the other refrigerant and carbon dioxide in a liquid state (CO ₂₎ is frozen in the second precooler, discharged to the evaporator lowering the third utilizing expander is inflated by the pressure, evaporation other refrigerant and carbon dioxide (CO ₂₎ in some step 550 is vaporized by the outdoor air heat, and passes through the second precooler carbon dioxide (CO ₂₎ and other refrigerant vaporized by the evaporator dioxide in vessel Some of the carbon (CO ₂ ) may include a stage 560 that is transferred to the compressor after heat exchange with each other.

According to the embodiment, by installing an expansion device between the condenser and the gas-liquid separator to expand the refrigerant that is the working fluid, the low-temperature refrigerant that can be easily evaporated even in the low outdoor air in winter by the evaporator A liquid can be obtained. Further, by using CO ₂ and HFC mixed refrigerants having different boiling points so that CO ₂ can be increased to 50 to 90%, it is possible to apply a lower pressure on the high pressure side, and for heating By providing the effect of warm water, energy can be saved.

Hereinafter, a circulation method of a multi-stage heat pump having a two-stage expansion structure using a CO ₂ refrigerant in still another embodiment will be described more specifically with an example.

In yet another embodiment, the circulating method of multistage pump having a two-stage expansion structure using CO ₂ refrigerant has been described in FIGS. 1-4, a multi-stage heat pump with a two-stage expansion structure using CO ₂ refrigerant This will be explained in more detail using this. Here, the multistage heat pump having a two-stage expansion structure using CO ₂ refrigerant includes a compressor, a condenser, a first expansion device, a gas-liquid separator, a second expansion device, a third expansion device, and an evaporator. May be configured. In addition, according to the embodiment, the multi-stage heat pump having a two-stage expansion structure using CO ₂ refrigerant further includes at least one of a first precooler, a second precooler, and an ejector or EPR. May be. On the other hand, the circulation method of the multi-stage heat pump with two-stage expansion structure using CO ₂ refrigerant, the refrigerant containing CO ₂ refrigerant as a working fluid may indicate how to circulate.

In step 510, the condenser may condense refrigerant mixed with CO ₂ discharged from the compressor and at least one other refrigerant.

Here, the refrigerant may be a mixed refrigerant in which carbon dioxide (CO ₂ ) and at least one other refrigerant are mixed.

More specifically, the refrigerant includes carbon dioxide (CO ₂ ) and HFC mixed refrigerants having different boiling points, and increases the ratio of CO ₂ to 50% to 90% and lowers the pressure at high pressure. This makes it possible to provide hot water for heating.

  In operation 520, the first expansion device may expand the refrigerant that has passed through the condenser to reduce the pressure.

  In this way, the refrigerant may be expanded from a high pressure to an intermediate pressure by the first expansion device, and a two-stage expansion process may be performed in which the refrigerant is expanded from the intermediate pressure to the low pressure by the third expansion device.

In step 530, the gas-liquid separator may separate the refrigerant that has passed through the first expansion device from another refrigerant having a low boiling point and a part of CO ₂ as a liquid, and separate the remaining CO ₂ as a gas.

In step 540, the second expansion device may expand the high-pressure gas state CO ₂ discharged from the gas-liquid separator to reduce the pressure and move it to the second precooler.

In step 550, the third expansion device freezes another refrigerant in a liquid state discharged from the gas-liquid separator and a part of CO ₂ with the second precooler, and then expands the pressure to lower the pressure and evaporate. You may discharge to a container.

Thereafter, another refrigerant and a part of CO ₂ may be vaporized by the outside air heat in an evaporator.

In step 560, the CO ₂ that has passed through the second precooler, the other refrigerant vaporized by the evaporator, and a portion of the CO ₂ may be exchanged with each other and transferred to the compressor.

  At this time, different pressure differences between the refrigerant discharged from the second precooler and the refrigerant discharged from the evaporator may be corrected using an ejector or EPR (evaporation pressure control device), and moved to the compressor. .

  After freezing while passing through the first precooler, it may be moved to the compressor.

In the first precooler, the refrigerant vaporized in the evaporator and the CO ₂ passing through the condenser exchange heat with each other, and the low-temperature gas sucked into the compressor further lowers the temperature of the exhaust gas from the condenser.

As described above, according to the embodiment, the expansion device is installed between the condenser and the gas-liquid separator to expand the refrigerant that is the working fluid, and CO ₂ and HFC mixed refrigerant having different boiling points are used for CO _2. Is increased to 50 to 90%, the pressure on the low-pressure evaporator side generated by the heat pump using carbon dioxide as a refrigerant is high, and the vaporization temperature of the evaporator of about 0 ° C. is obtained. If it is low, the problem that the outdoor unit (evaporator) does not vaporize the refrigerant and an auxiliary heat source is required can be solved.

  Thereby, it is possible to contribute to the reduction of greenhouse gas emissions by providing a heat pump using environmentally friendly carbon dioxide as a refrigerant and substituting it with a heat pump using a refrigerant that adversely affects the ozone layer.

  As described above, the embodiments of the present invention have been described based on the limited embodiments and the drawings, but those skilled in the art can make various modifications and variations from the above description. For example, the described techniques may be performed in a different order than the described method and / or components of the described system, structure, apparatus, circuit, etc. may be in a different form than the described method. As combined with or combined with other components or equivalents or equivalent refrigerants as opposed to or replaced by HCFC refrigerants that affect ozone instead of HFC, ammonia (R717), propane (R290), etc. Can also achieve adequate results.

  Accordingly, even different embodiments belong to the appended claims as long as they are equivalent to the claims.

100: Multi-stage heat pump 110: Compressor 120: Condenser 130: First precooler 131: Second precooler 140: First expansion device 141: Second expansion device 142: Third expansion device 150: Gas-liquid separator 160: Evaporator

Claims (11)

A multi-stage heat pump having a two-stage expansion structure including a compressor, a condenser, a gas-liquid separator, an expansion device, and an evaporator,
A first expansion device that is configured between the condenser and the gas-liquid separator and expands the refrigerant that has passed through the condenser to reduce the pressure;
The refrigerant is expanded from a high pressure to an intermediate pressure by the first expansion device, and has a two-stage expansion structure in which the refrigerant is expanded from the intermediate pressure to a low pressure by the expansion device.
A multistage heat pump having a two-stage expansion structure. The refrigerant is
It is a mixed refrigerant obtained by mixing carbon dioxide (CO ₂ ) and at least one other refrigerant,
A multi-stage heat pump having the two-stage expansion structure according to claim 1. The refrigerant is
Hot water for heating, including carbon dioxide (CO ₂ ) and HFC mixed refrigerant having different boiling points, increasing the ratio of the carbon dioxide (CO ₂ ) to 50% to 90% and reducing the pressure at the high pressure And hot air can be provided,
A multi-stage heat pump having the two-stage expansion structure according to claim 2. The refrigerant is
The low temperature of the evaporator is applicable to a refrigeration apparatus simultaneously with a heat pump function including two or more mixed refrigerants and using the heat of the condenser as heating hot water,
A multi-stage heat pump having the two-stage expansion structure according to claim 2. The gas-liquid separator is
By reducing the pressure of the refrigerant that has passed through the condenser by the first expansion device, the other refrigerant having a low boiling point and a part of the carbon dioxide (CO ₂ ) are separated as a liquid, and the remaining carbon dioxide. Separating carbon (CO ₂ ) as a gas,
A multi-stage heat pump having the two-stage expansion structure according to claim 2. A second precooler for freezing the refrigerant that has passed through the gas-liquid separator;
The expansion device is
A second expansion device that is disposed between the gas-liquid separator and the second precooler and expands the carbon dioxide (CO ₂ ) in a high-pressure gas state discharged from the gas-liquid separator to lower the pressure. And the other refrigerant that is disposed between the second precooler and the evaporator and is in a liquid state discharged from the gas-liquid separator and a part of the carbon dioxide (CO ₂ ). (2) a third expansion device that cools with a precooler and then expands and lowers the pressure to discharge to the evaporator;
A multistage heat pump having the two-stage expansion structure according to claim 5. A first precooler connecting the discharge port of the evaporator and the discharge port of the condenser;
The first precooler includes:
The refrigerant vaporized by the evaporator and the carbon dioxide (CO ₂ ) that has passed through the condenser are heat-exchanged and moved to the compressor after cooling.
A multi-stage heat pump having the two-stage expansion structure according to claim 2. An ejector or an evaporation pressure control device (EPR) that corrects a difference in pressure between the refrigerant discharged from the second precooler and the refrigerant discharged from the evaporator and sends it to the compressor
Further including
A multi-stage heat pump having the two-stage expansion structure according to claim 6. The evaporator is
A second stage in which the first expansion device expands the refrigerant from a high pressure to an intermediate pressure, and then the third expansion device expands the intermediate pressure to the low pressure so that the heating function is performed even when the outside air temperature is low. The vaporization temperature is lowered by the inflow of the refrigerant that has performed the expansion step of
A multi-stage heat pump having the two-stage expansion structure according to claim 6. A condenser that condenses carbon dioxide (CO ₂ ) discharged from the compressor and a refrigerant in which at least one other refrigerant is mixed;
The refrigerant that has passed through the condenser is expanded using a first expansion device to reduce the pressure,
The other refrigerant having a low boiling point and a part of the carbon dioxide (CO ₂ ) are separated from the refrigerant that has passed through the first expansion device as a liquid using a gas-liquid separator, and the remaining carbon dioxide Separating (CO ₂ ) as a gas;
The carbon dioxide (CO ₂ ), which is in a high-pressure gas state discharged from the gas-liquid separator, is expanded using a second expansion device to reduce the pressure and move to the second precooler,
The other refrigerant in a liquid state discharged from the gas-liquid separator and a part of the carbon dioxide (CO ₂ ) are frozen by the second precooler and then expanded using a third expansion device. The pressure is lowered and discharged to the evaporator, the other refrigerant and a part of the carbon dioxide (CO ₂ ) are vaporized by outside heat in the evaporator, and the carbon dioxide that has passed through the second precooler. (CO ₂ ), the other refrigerant vaporized by the evaporator, and a part of the carbon dioxide (CO ₂ ) are exchanged with each other and then moved to the compressor.
A circulation method of a multi-stage heat pump having a two-stage expansion structure. A multi-stage heat pump having a two-stage expansion structure,
A compressor that compresses a mixed refrigerant including carbon dioxide (CO ₂ ) having different boiling points and at least one other refrigerant;
A condenser that is arranged next to the compressor and condenses the refrigerant that has passed through the compressor;
A first expansion device that is arranged next to the condenser and expands the refrigerant that has passed through the condenser to reduce the pressure;
The other refrigerant having a low boiling point and a part of the carbon dioxide (CO ₂ ) is disposed next to the first expansion device and reduces the pressure of the refrigerant that has passed through the condenser by the first expansion device. A gas-liquid separator that separates the remainder of the carbon dioxide (CO ₂ ) as a gas,
A second precooler that is arranged next to the gas-liquid separator and freezes the refrigerant that has passed through the gas-liquid separator;
A second expansion device that is disposed between the gas-liquid separator and the second precooler, and expands the carbon dioxide (CO ₂ ) in a gaseous state discharged from the gas-liquid separator to reduce the pressure;
The second refrigerant is disposed between the second precooler and the evaporator, and the other refrigerant in a liquid state discharged from the gas-liquid separator and a part of the carbon dioxide (CO ₂ ) are used in the second precooler. A third expansion device which is cooled and then expanded to lower the pressure and discharged to the evaporator; and a third expansion device disposed between the condenser and the first expansion device and connected to a discharge port of the evaporator. Including 1 precooler,
The mixed refrigerant is
Along with a heat pump function that uses the heat of the condenser as warm water for heating, the low temperature of the evaporator is applicable to a refrigeration apparatus,
The evaporator is
A refrigerant is expanded from a high pressure to an intermediate pressure by the first expansion device and then expanded from the intermediate pressure to a low pressure by the third expansion device so that the heating function is performed even when the outside air temperature is low. The vaporization temperature is lowered by the inflow of the refrigerant that has performed the expansion process,
After the refrigerant vaporized by the evaporator and the carbon dioxide (CO ₂ ) that has passed through the second expansion device are mixed, heat exchange is performed between the refrigerant that has passed through the condenser and the first precooler to cool the refrigerant. It is moved to the compressor later,
A multistage heat pump having a two-stage expansion structure.

Images