JP2000130868A - Lorentz-cyclic heat pump system utilizing non-azeotropic mixed refrigerant as working fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of a system by effectively utilizing properties of a non-azeotropic mixed refrigerant, whose refrigerating capacity is also changed when its composition is changed, and always performing an optimum Lorentz-cycle according to external environmental conditions. SOLUTION: This heat pump system utilizes a non-azeotropic mixed refrigerant as a working fluid. In this case, the system is so constituted that the flow of the refrigerant is diverted by providing a fractionating path 7 bypassing a refrigerant path 6 passing through an expansion valve 5 at an intermediate portion of the refrigerant path 6 leading from a condenser 3 to an evaporator 4 through the expansion valve 5. This fractionating path is constituted in such a manner that a fractionating unit 9 is set via a pressure reducing valve 8 and that the composition of the refrigerant, which is caused to circulate in the system, is made controllable by providing control valves 10. The condenser 3 and the evaporator 4 are made to operate as water-cooled counterflow heat exchangers utilizing a secondary fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Lorentz cycle heat pump system applied to an air conditioning system and the like.

[0002]

2. Description of the Related Art In a compression heat pump system using a motor or a gas engine as a drive source, a pure refrigerant such as R-22 has been widely used as a working fluid.
Since the destruction of the ozone layer by CFCs was pointed out, alternative CFCs have been developed, and non-CFC air conditioners such as absorption have been developed. FIG. 6 schematically shows the configuration of a compression heat pump system. The condenser and the evaporator are mainly configured as air-cooled heat exchangers. At present, as an alternative CFC, R-3 with ODP of 0
A mixed refrigerant containing 2, R-125 and R-134a as components is considered to be promising as a retrofit. However, in view of easy handling, a refrigerant having the same characteristics as a pure refrigerant and having a negligible change in composition can be used. Boiling mixed refrigerant R-32 / 12
The 5, R-32 / 125 / 134a system has received attention.
In the case of a pure refrigerant or an azeotropic mixed refrigerant, the phase change is performed under isothermal and isobaric pressures. If attention is paid only to the heat exchanger, the phase change is shown in a Ts (temperature-entropy) diagram of FIG. Thus, it can be considered as an inverse Carnot cycle. In addition, R-32 / 134a system which is a non-azeotropic mixed refrigerant is also considered as an alternative chlorofluorocarbon.

[0003]

The above prior arts have the following problems. a. The pressure of the azeotropic mixed refrigerant R-32 / 125 system is high, and when applied to a conventional system, it is necessary to improve the compressor in terms of pressure resistance. b. It is difficult to control the composition of the azeotropic mixed refrigerant R-32 / 125 / 134a when the refrigerant leaks. c. The non-azeotropic refrigerant mixture R-32 / 134a changes its capacity when the composition changes, and the system becomes unstable, and b. As in the case of the above, it is difficult to control the composition when the refrigerant leaks. d. Since the heat exchangers that make up condensers and evaporators mainly use air cooling, the average temperature at the inlet and outlet of the heat exchanger becomes the output temperature,
Therefore, even if the alternative CFC is applied to the conventional system as it is, the capacity is equal to or lower than that of R-22. An object of the present invention is to solve such a problem.

[0004]

According to the present invention, there is provided a heat pump system using a non-azeotropic mixed refrigerant as a working fluid in a refrigerant path from a condenser to an evaporator through an expansion valve. A rectification path that bypasses a path that passes through the expansion valve is provided to divide the refrigerant, and a rectification device is installed in the rectification path via a pressure reducing valve and a control valve is provided to circulate the system. The composition of the refrigerant to be controlled is configured to be controllable, and the condenser and the evaporator are configured to operate as a water-cooled counter-flow heat exchanger using a secondary fluid.The cycle calculation is performed in accordance with the environmental conditions. Coefficient of performance for each cycle condition such as flow rate, temperature, pressure, etc.
Calculate exergy efficiency, heat efficiency, etc., calculate the optimum value of the cycle condition, control the heat pump system based on the calculated cycle condition, perform the operation to set the outlet temperature of the secondary fluid to the set temperature, We propose a Lorentz cycle heat pump system using a non-azeotropic refrigerant mixture as a working fluid that performs control to feed back cycle conditions in actual operation to the cycle calculation.

Further, according to the present invention, in the above configuration,
The rectification device is configured on the upstream side of the rectification path and configured to heat a mixed refrigerant to separate a high-boiling component and a low-boiling component into a first container and a first container for storing the separated components. 2,
A third container is proposed, and a control valve is provided in each of the refrigerant paths from the second and third containers.

Further, in the present invention, it is proposed that the compressor constituting the heat pump system is driven by a gas engine and the exhaust heat thereof is used as a heat source of the system.

Further, the present invention proposes that in the above-mentioned configuration, heat and cold of another process are used as heat sources of the system.

In the present invention, it is proposed that a non-azeotropic refrigerant mixture having a large difference in boiling point, such as R-32 / 134a, be selected.

According to the present invention described above, the composition of the refrigerant circulated in the system can be controlled by the rectification device in the rectification route. Therefore, in the present invention, it is possible to effectively use the property of the non-azeotropic mixed refrigerant whose capacity changes as the composition changes, and to perform an operation that maximizes the efficiency according to external environmental conditions.

In such an operation, the cycle calculation is performed according to the environmental conditions, and the coefficient of performance, exergy efficiency, heat efficiency, etc. are calculated for each cycle condition such as the composition and flow rate of the refrigerant, the temperature, and the pressure. Calculate the optimal value of, control the heat pump system based on the calculated cycle conditions, perform the operation to set the outlet temperature of the secondary fluid to the set temperature,
The cycle condition in the actual operation can be controlled by feedback to the cycle calculation.

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a system explanatory diagram conceptually showing a heat pump system of the present invention. Reference numeral 1 denotes a compressor, and the compressor 1 is driven by a driving device 2 such as an electric motor or a gas engine. Reference numeral 3 denotes a condenser, 4 denotes an evaporator, and 5 denotes an expansion valve, which have a configuration similar to that of a normal compression heat pump system. Therefore, in the present invention, the refrigerant circulated through the system is, for example, a non-azeotropic mixed refrigerant such as an R-32 / 134a system, and a refrigerant path 6 from the condenser 3 to the evaporator 4 via the expansion valve 5. A rectification path 7 that bypasses the refrigerant path 6 is provided to divide the refrigerant. A rectification device 9 is connected to the rectification route 7 through a pressure reducing valve 8.
And a control valve 10 is provided. In the figure, the control valve 10 is illustrated on the upstream side of the pressure reducing valve 8 and on the downstream side of the rectification device 9, but the installation position and the number of the control valves 10 are appropriate.

In the above configuration, the non-azeotropic mixed refrigerant discharged from the compressor 1 reaches the refrigerant path 6 via the condenser 3, a part of the refrigerant flows toward the expansion valve 5, and the other part is a rectification path 7. Flows through. The flow rate ratio of the non-azeotropic mixed refrigerant flowing through the rectification path 7 can be adjusted by the control valve 10. The non-azeotropic mixed refrigerant flowing through the rectification path 7 in this way is
After reaching the rectification device 9 via the pressure reducing valve 8, the composition is controlled by the rectification device 9, the rectification device 9 joins the refrigerant path 6, mixes with the non-azeotropic mixed refrigerant passed through the expansion valve 5, and flows into the evaporator 4. To the compressor 2 via. As described above, in the present invention, by controlling the composition and flow rate of the non-azeotropic mixed refrigerant flowing through the rectification path 7 by the rectification device 9, the composition of the non-azeotropic mixed refrigerant flowing through the system can be changed, Therefore, the ability can be adjusted.

FIG. 2 shows an embodiment of the rectification device 9 which is arranged upstream of the rectification path 7 and heats the mixed refrigerant to produce a low-boiling component and a high-boiling component. A first container 11 for separating the components and second and third containers 12 and 13 for storing the separated components. The first and second containers reach the refrigerant path 6 from the second and third containers. The control valves 10a and 10b are provided in the respective paths. And the first
The container 11 is provided with a refrigerant heating means 14h,
The second and third containers 12 and 13 are provided with a cooling means 14c for the refrigerant.
Is provided.

In the above configuration, the non-azeotropic mixed refrigerant flowing from the refrigerant passage 6 and flowing to the rectification passage 7 flows into the first container 11 via the pressure reducing valve 8 and accumulates. The non-azeotropic mixed refrigerant accumulated in the first container 11 is heated by the heating means 14h to evaporate the low-boiling component, and the low-boiling component flows into the second container 12 via the control valve 10c. Here, it is cooled by the cooling means 14c and liquefied and accumulated. on the other hand,
The high-boiling components that have not evaporated in the first container 11 are introduced into the third container 13 and accumulated therein, and are cooled by the cooling means 14c as required. The low-boiling component and the high-boiling component thus rectified are supplied to the second and third vessels 1 respectively.
By adjusting the ratio and amount of components passing through the respective paths by adjusting valves 10a and 10b stored in the paths from the respective containers 12 and 13 to the refrigerant path 6, the expansion valve 5 is controlled. The composition when mixed with the passed non-azeotropic refrigerant mixture can be controlled.

Next, returning to FIG. 1, in the present invention,
The condenser 3 and the evaporator 4 are operated as a water-cooled counter-flow heat exchanger in which the non-azeotropic refrigerant mixture and the secondary fluid exchange heat in counter-flow. Such an operation is performed, as shown in FIG. 3, by focusing on the heat exchanger, Ts (temperature-entropy).
The temperature difference between the secondary fluid and the non-azeotropic mixed refrigerant, that is, the pinch temperature is controlled to be constant, and each heat exchanger (condenser 3, evaporator 4) of the secondary fluid is controlled. ) Can be used as an output temperature in air conditioning or the like. At this time, by controlling the control elements of the system, the optimal Lorentz cycle can always be performed according to the environmental conditions, and the system efficiency is improved as compared with the conventional system.
Effective use of energy can be achieved. For example, by minimizing the area of a portion surrounded by oblique lines in the figure, it is possible to control the compressor power to a minimum. As described above, the condenser 3 and the evaporator 4 operate as a water-cooled counter-flow heat exchanger in which the non-azeotropic mixed refrigerant and the secondary fluid exchange heat in the counter-flow. It can be used as a process in a large-scale plant.

Next, a control method in the heat pump system of the present invention will be described. FIG. 4 is a schematic diagram showing an example of a control method according to the present invention, in which a portion surrounded by a broken line indicates a control means such as a computer. First, in this control, cycle calculation is performed according to environmental conditions throughout the year, which change depending on the outside temperature, and the composition and flow rate of the refrigerant,
The coefficient of performance, exergy efficiency, heat efficiency, and the like are calculated for each cycle condition such as temperature and pressure, and the optimum value of the cycle condition is calculated. Then, the heat pump system is controlled based on the cycle conditions to perform an operation in which the outlet temperature of the secondary fluid is set to a set temperature, and the cycle conditions in the actual operation are fed back to the cycle calculation. Specifically, by such a control method, the power of the compressor 2 is reduced as much as possible based on the environmental conditions, and the cycle conditions are changed so that the coefficient of performance and the exergy efficiency in the heat exchanger are maximized. This is mainly performed, but control can be performed by an appropriate algorithm according to the condition of what is actually given priority.

Next, FIG. 5 shows an embodiment of the heat pump system of the present invention including each secondary fluid and the heat source such as the rectification device 9 in the above description, and has the same configuration as the components of FIG. Elements are given the same reference numerals, and duplicate description is omitted. In this embodiment, the driving device 2 for driving the compressor 1 is a gas engine, and a supercooler 15 is provided on the refrigerant path 6 on the upstream side of the expansion valve 5 and on the downstream side of the evaporator 4. A superheater 16 is provided. In this embodiment, as the heat source (including the cold heat source) of the rectification device 9, the supercooler 15, the superheater 16, and the secondary fluid in this embodiment, the exhaust heat of the gas engine as the driving device 2 and the like The heat (including cold heat) of the other process 17 is used. That is, a dashed line with an arrow in the figure indicates the flow of a fluid having cold heat, and a broken line with an arrow indicates the flow of a fluid having heat. In this way, by using the exhaust heat or the cold heat of itself or another process as the heat source of the system, equipment such as a cooling tower is not required, and a more energy-efficient, high-efficiency, and low-cost system can be configured.

[0018]

As described above, the present invention has the following effects. a. By effectively utilizing the properties of non-azeotropic mixed refrigerants whose capacity also changes as the composition changes, and always performing an optimal Lorentz cycle in accordance with external environmental conditions, system efficiency is improved over the past, and energy consumption is improved. Effective utilization can be achieved. b. As a retrofit device for the pure refrigerant R-22, it is only necessary to add a rectification route having a rectification device and its control means to an existing system, so that high performance can be achieved at low cost, space saving, and low cost. c. Since the composition of the non-azeotropic refrigerant mixture circulating in the system can be controlled by the rectifying device, it is not necessary to consider the performance degradation due to the composition change as in the related art. d. Replenishment at the time of refrigerant leakage is easy because maintenance can be performed because the refrigerant of each component may be filled in a container for storing each component of the rectification device. e. The heat exchanger constituting the condenser or the evaporator can be used as a process in a large-scale plant such as a district heating and cooling system by operating as a water-cooled counter-flow heat exchanger.

[Brief description of the drawings]

FIG. 1 is a system explanatory view conceptually showing a heat pump system of the present invention.

FIG. 2 is a system explanatory diagram showing an embodiment of a rectification device.

FIG. 3 Ts focusing on a heat exchanger of a non-azeotropic mixed refrigerant
It is a (temperature-entropy) diagram.

FIG. 4 is a schematic diagram illustrating an example of a control method according to the present invention.

FIG. 5 is a system explanatory diagram showing an embodiment of a heat pump system of the present invention including a heat source such as a secondary fluid and a rectification device.

FIG. 6 is a system explanatory view conceptually showing a conventional compression heat pump system.

FIG. 7 is a Ts (temperature-entropy) diagram focusing on a heat exchanger of a pure refrigerant and an azeotropic mixed refrigerant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Drive device 3 Condenser 4 Evaporator 5 Expansion valve 6 Refrigerant path 7 Rectification path 8 Pressure reducing valve 9 Rectification apparatus 10 (10a, 10b, 10c) Control valve 11 1st container 12 2nd container 13 Third container 14h Heating means 14c Cooling means 15 Subcooler 16 Superheater 17 Other process

Claims (5)

[Claims] In a heat pump system using a non-azeotropic mixed refrigerant as a working fluid, a refrigerant path from a condenser to an evaporator through an expansion valve is provided with a rectification path that bypasses a path passing through the expansion valve. In the rectification path, a rectification device is installed via a pressure reducing valve and a control valve is provided to control the composition of the refrigerant circulated through the system, and a condenser and an evaporator are provided. Is configured to operate as a water-cooled counter-flow heat exchanger using a secondary fluid, performs cycle calculations according to environmental conditions, and calculates the coefficient of performance and exergy efficiency for each cycle condition such as the composition and flow rate of the refrigerant, temperature, and pressure. Calculate the thermal efficiency and the like, calculate the optimal value of the cycle condition, control the heat pump system based on the calculated cycle condition, perform the operation to set the outlet temperature of the secondary fluid to the set temperature, A Lorentz cycle heat pump system using a non-azeotropic mixed refrigerant as a working fluid, wherein control is performed to feed back the cycle conditions in the actual operation to the cycle calculation. 2. A rectification apparatus, comprising: a first container configured on an upstream side of a rectification path to heat a mixed refrigerant to separate the mixture into a high-boiling component and a low-boiling component; 2. A non-azeotropic mixed refrigerant according to claim 1, comprising a second container and a third container for storing the refrigerant, and a control valve provided in each of the refrigerant paths from the second and third containers. Lorentz cycle heat pump system using oil as working fluid 3. The non-heat pump according to claim 1, wherein a compressor constituting the heat pump system is driven by a gas engine, and the exhaust heat thereof is used as a heat source of the system. Lorentz cycle heat pump system using azeotropic mixed refrigerant as working fluid 4. A Lorentz cycle using a non-azeotropic refrigerant mixture as a working fluid according to claim 1, wherein heat and cold heat of another process are used as a heat source of the system. Heat pump system 5. The heat pump system according to claim 1, wherein the non-azeotropic mixed refrigerant is a mixed refrigerant having a large difference in boiling point.