JP3855860B2 - Vapor compression refrigerator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vapor compression refrigerator that moves low-temperature heat to a high-temperature side, and is effective when applied to a hot-water supply device or a heating device that uses warm heat.
[0002]
[Prior art and problems to be solved by the invention]
For example, in a hot water supply apparatus that heats hot water using a vapor compression refrigerator, heat is absorbed from outside air by an evaporator that forms a low-temperature side heat exchanger, the refrigerant is evaporated, and the vapor phase refrigerant that has been evaporated is compressed by the compressor. Thus, the amount of heat absorbed from the outside air is given to the hot water supply by raising the temperature.
[0003]
At this time, in winter when the outside air temperature is low, the refrigerant evaporating temperature is often below freezing in order to absorb a sufficient amount of heat from the outside air, so frost adheres to the surface of the evaporator. And if frost adheres to the surface of the evaporator, the heat absorption capacity is lowered. Usually, in the winter where the outside air temperature is low, the evaporator does not depressurize the high-temperature refrigerant (hot gas) periodically discharged from the compressor. The defrosting operation is performed to melt and remove the frost adhering to the surface of the evaporator.
[0004]
However, this defrosting method requires a bypass passage that guides the hot gas to the evaporator without reducing the pressure, and a valve that controls the communication state of the bypass passage, which increases the number of components of the vapor compression refrigerator. The structure becomes complicated, leading to an increase in assembly man-hours and an increase in manufacturing costs.
[0005]
In view of the above points, the present invention firstly provides a novel vapor compression refrigerator that is different from the conventional one, and secondly, it is intended to perform a defrosting operation with simple means.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides, in the invention described in claim 1, a vapor compression refrigerator that moves low-temperature heat to a high-temperature side, and a compressor (10) that compresses a refrigerant; A high pressure side heat exchanger (20) that dissipates the heat of the high pressure refrigerant, a decompression means (40) that decompresses and expands the high pressure refrigerant, a low pressure side heat exchanger (30) that absorbs heat by evaporating the low pressure refrigerant, and a compression The gas-liquid separator (50) is provided on the refrigerant suction side of the machine (10) and separates the flowing refrigerant into a gas phase refrigerant and a liquid phase refrigerant and supplies the gas phase refrigerant to the suction side of the compressor (10). ), And the decompression means decompresses and expands the high-pressure refrigerant in an isentropic manner and can change the throttle opening , and the booster (42, 42) that converts the enthalpy reduced during the decompression and expansion into pressure energy. is composed of the ejector (40) having a 43) The refrigerant that has flowed out of the ejector (40) flows into the gas-liquid separator (50), and further, directly from the gas-liquid separator (50) to the low-pressure side heat exchanger (30) by the pump action of the ejector (40). In the defrosting operation for removing frost adhered to the surface of the low pressure side heat exchanger (30), the throttle opening of the nozzle (41) is compared with that before performing the defrosting operation. And increasing the pressure of the low-pressure refrigerant.
[0007]
As a result, the defrosting operation can be performed by a simple means such as increasing the throttle opening of the nozzle (41), so that the number of parts of the vapor compression refrigerator is increased, the structure is complicated, and the number of assembling steps is increased. Can be prevented. In its turn, it can be obtained and the monitor can be achieved reducing manufacturing costs of the vapor compression type refrigerator, an unconventional new vapor compression refrigerator.
[0010]
And the frost adhering to the surface of a gas-liquid separator (50) can also be thawed and removed as well as the frost adhering to the surface of the low-pressure side heat exchanger (30).
[0012]
The invention according to claim 2 is characterized in that, in the operation mode other than the defrosting operation, the throttle opening degree of the nozzle (41) is controlled according to the heat load.
[0013]
The invention according to claim 3 is characterized in that the pressure of the low-pressure refrigerant during the defrosting operation is a pressure at which the saturation temperature of the refrigerant becomes 0 ° C. or higher.
[0014]
The invention according to claim 4 is characterized in that the pressure of the high-pressure refrigerant is equal to or higher than the critical pressure of the refrigerant.
[0015]
The invention according to claim 5 is characterized in that carbon dioxide is used as the refrigerant.
[0016]
Incidentally, the reference numerals in parentheses of each means described above are an example showing the correspondence with the specific means described in the embodiments described later.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
In the present embodiment, the vapor compression refrigerator according to the present invention is applied to a water heater device, and FIG. 1 is a schematic view of the water heater device according to the present embodiment.
[0018]
The compressor 10 sucks and compresses refrigerant, and the radiator 20 is a high-pressure side heat exchanger that cools the refrigerant by exchanging heat between the refrigerant discharged from the compressor 10 and hot water and heating the hot water. is there.
[0019]
Here, the compressor 10 is driven by an electric motor (not shown), and when the heating capacity of the radiator 20 is increased, the refrigerant discharged from the compressor 10 by increasing the rotation speed of the compressor 10. On the other hand, when the heating capacity is reduced, the rotational speed of the compressor 10 is decreased to reduce the flow rate of the refrigerant discharged from the compressor 10.
[0020]
In this embodiment, carbon dioxide is used as the refrigerant, and the compressor 10 pressurizes the refrigerant to a critical pressure or higher so that the refrigerant temperature at the refrigerant inlet of the radiator 20 is 80 ° C. to 90 ° C. or higher. ing.
[0021]
Incidentally, since the pressure in the radiator 20 is equal to or higher than the critical pressure, the refrigerant reduces the enthalpy while decreasing the refrigerant temperature from the refrigerant inlet side toward the refrigerant outlet side without condensing the refrigerant in the radiator 20. I will let you.
[0022]
The evaporator 30 is a low-pressure heat exchanger that evaporates the refrigerant by heat-exchanging the outdoor air and the liquid-phase refrigerant to evaporate the liquid-phase refrigerant and absorbs heat from the outdoor air. The ejector 40 decompresses the refrigerant. The gas phase refrigerant that is expanded and evaporated in the evaporator 30 is sucked, and the expansion energy is converted into pressure energy to increase the suction pressure of the compressor 10. Details of the ejector 40 will be described later.
[0023]
The gas-liquid separator 50 is a gas-liquid separator that stores the refrigerant by flowing the refrigerant flowing out from the ejector 40 into the vapor-phase refrigerant and the liquid-phase refrigerant. 50, the gas phase refrigerant outlet is connected to the suction side of the compressor 10, and the liquid phase outlet is connected to the inlet side of the evaporator 30 side.
[0024]
Next, the structure of the ejector 40 will be described.
[0025]
As shown in FIG. 2, the ejector 40 converts the pressure energy of the flowing high-pressure refrigerant into velocity energy to cause the refrigerant to be isentropically decompressed and expanded, and the entraining action of the high-speed refrigerant flow ejected from the nozzle 41. While mixing the vapor-phase refrigerant evaporated in the evaporator 30 by the mixing unit 42 for mixing the refrigerant flow ejected from the nozzle 41, the refrigerant ejected from the nozzle 41 and the refrigerant sucked from the evaporator 30 are mixed. However, it comprises a diffuser 43 or the like for increasing the pressure of the refrigerant by converting velocity energy into pressure energy.
[0026]
In the mixing unit 42, since the sum of the momentum of the refrigerant flow injected from the nozzle 41 and the momentum of the refrigerant flow sucked into the ejector 40 from the evaporator 30 is preserved, the mixing unit 42 However, the static pressure of the refrigerant increases. On the other hand, in the diffuser 43, the dynamic pressure of the refrigerant is converted into a static pressure by gradually increasing the passage cross-sectional area. Therefore, in the ejector 40, the refrigerant pressure is increased by both the mixing unit 42 and the diffuser 43. . Therefore, the mixing unit 42 and the diffuser 43 are collectively referred to as a boosting unit.
[0027]
That is, in the ideal ejector 40, the refrigerant pressure increases so that the sum of the momentums of the two refrigerant flows is stored in the mixing unit 42, and the refrigerant pressure increases so that energy is stored in the diffuser 43. In this way, it is desirable to recover enthalpy that has been reduced during expansion under reduced pressure as pressure energy.
[0028]
The nozzle 41 is a Laval nozzle (see Fluid Engineering (Tokyo University Press)) having a throat portion 41a having the smallest passage area in the middle of the passage and a divergent portion 41b in which the inner diameter gradually increases after the throat portion 41a. The throttle opening of the nozzle 41 is variably controlled by displacing the needle valve 44 within the nozzle 41 by the actuator 45 in the axial direction of the nozzle 41.
[0029]
In the present embodiment, an electrical actuator such as a stepping motor using a screw mechanism or a linear solenoid is employed as the actuator 45.
[0030]
Next, the characteristic operation and effect of the hot water supply apparatus according to the present embodiment will be described.
[0031]
1. Normal operation (endothermic operation) mode (see Fig. 3)
This mode is an operation mode in which the hot water is heated by absorbing heat from the outside air.
[0032]
Specifically, the pressure in the evaporator 30, that is, the pressure corresponding to a predetermined temperature equal to or lower than the outside air temperature, and the pressure detected by a pressure sensor (not shown) that detects the refrigerant pressure on the high pressure side. The throttle opening degree of the nozzle 41 is controlled so that becomes a predetermined pressure.
[0033]
As a result, hot water having a predetermined temperature or higher can be supplied to the hot water storage tank regardless of the heat load (outside air temperature).
[0034]
The macroscopic refrigerant behavior in this operation mode is as follows.
[0035]
That is, the refrigerant discharged from the compressor 10 is cooled while the hot water is heated by the radiator 20. Then, the refrigerant cooled by the radiator 20 is isentropically decompressed and expanded at the nozzle 41 of the ejector 40 and flows into the mixing unit 42 at a speed equal to or higher than the speed of sound.
[0036]
The refrigerant evaporated in the evaporator 30 is sucked into the mixing part 42 by the pump action accompanying the entrainment action of the high-speed refrigerant flowing into the mixing part 42, so that the low-pressure side refrigerant is evaporated from the gas-liquid separator 50 → evaporation. It circulates in the order of the vessel 30 → the ejector 40 (pressure increase unit) → the gas-liquid separator 50 and absorbs heat from the outside air.
[0037]
On the other hand, the refrigerant sucked from the evaporator 30 (suction flow) and the refrigerant blown out from the nozzle 41 (driving flow) are mixed by the mixing unit 42 and the dynamic pressure thereof is converted into static pressure by the diffuser 43. Return to the liquid separator 50.
[0038]
2. Defrosting operation mode (see Fig. 4)
This mode is an operation mode for removing frost adhering to the surface of the evaporator 30.
[0039]
Specifically, the throttle opening of the nozzle 41 is increased before the defrosting operation mode, that is, compared with the normal operation mode, so that the refrigerant saturation temperature in the evaporator 30 is reduced to a pressure at which the refrigerant saturation temperature becomes 0 ° C. or higher. Increase refrigerant pressure. The refrigerant flow is the same as in the normal operation mode.
[0040]
At this time, immediately after the start of the defrosting operation mode, the hot gas does not flow directly into the evaporator 30, so that the temperature of the refrigerant flowing into the evaporator 30 remains at a low temperature equal to or lower than the outside air temperature. The frost that adheres to the surface cannot be melted.
[0041]
However, the pressure at which the pressure in the evaporator 30 becomes 0 ° C. or higher in addition to the fact that the throttle opening of the nozzle 41 is increased and the temperature of the refrigerant injected from the nozzle 41 is higher than that in the normal operation mode. Therefore, the temperature of the refrigerant in the gas-liquid separator 50 gradually increases, and the temperature of the refrigerant flowing into the evaporator 30 becomes 0 ° C. or higher.
[0042]
Therefore, the frost adhering to the surface of the evaporator 30 and the frost adhering to the surface of the gas-liquid separator 50 are melted and removed.
[0043]
As described above, in the present embodiment, the throttle opening of the nozzle 41 is increased without providing a bypass passage for guiding the hot gas to the evaporator 30 without reducing the pressure and a valve for controlling the communication state of the bypass passage. Since the defrosting operation can be performed by simple means such as, it is possible to prevent an increase in the number of parts, a complicated structure, and an increase in the number of assembly steps of the vapor compression refrigerator. As a result, it is possible to reduce the manufacturing cost of the vapor compression refrigerator, that is, the hot water supply apparatus.
[0044]
(Second Embodiment)
In the first embodiment, an ejector is used as the decompression means 40. However, in this embodiment, as shown in FIG. 5, an expansion valve that decompresses and expands the refrigerant is enthalpy is adopted as the decompression means 40. .
[0045]
FIG. 5 shows an accumulator cycle in which the gas-liquid separator 50 is provided on the suction side of the compressor 10, but the present embodiment is not limited to this, and the gas-liquid separator 50 is connected to the radiator 20. It goes without saying that a receiver cycle provided on the outlet side may be used.
[0046]
(Other embodiments)
In the above-described embodiment, the refrigerant is carbon dioxide and the high-pressure side pressure is increased to the critical pressure or more. However, the present invention is not limited to this, and for example, the refrigerant is the refrigerant in the radiator 20 using the refrigerant (R134a). The pressure may be lower than the critical pressure of the refrigerant.
[0047]
In the first embodiment, a Laval nozzle is used, but a tapered nozzle may be used.
[0048]
Further, the actuator 45 is not limited to that shown in the above-described embodiment. For example, a mechanical one using a gas pressure of an inert gas or a non-electromagnetic power electric type using a piezo element. It may be.
[0049]
In the above-described embodiment, the vapor compression refrigerator according to the present invention is applied to the hot water supply apparatus. However, the application of the present invention is not limited to this, and is also applied to an air conditioner, a freezer, a refrigerator, and the like. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a vapor compression refrigerator according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram of an ejector according to the first embodiment of the present invention.
FIG. 3 is an operation explanatory diagram of the vapor compression refrigerator according to the first embodiment of the present invention.
FIG. 4 is an operation explanatory diagram of the vapor compression refrigerator according to the first embodiment of the present invention.
FIG. 5 is a schematic diagram of a vapor compression refrigerator according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Compressor, 20 ... Radiator (water-refrigerant heat exchanger), 30 ... Evaporator,
40 ... ejector, 50 ... gas-liquid separator.

Claims (5)

A vapor compression refrigerator that moves the heat on the low temperature side to the high temperature side,
A compressor (10) for compressing the refrigerant;
A high-pressure side heat exchanger (20) that dissipates the heat of the high-pressure refrigerant;
Decompression means (40) for decompressing and expanding the high-pressure refrigerant;
A low pressure side heat exchanger (30) that absorbs heat by evaporating the low pressure refrigerant ;
Gas-liquid separation is provided on the refrigerant suction side of the compressor (10) and separates the flowing refrigerant into a gas phase refrigerant and a liquid phase refrigerant and supplies the gas phase refrigerant to the suction side of the compressor (10). A vessel (50) ,
The decompression means has a nozzle (41) that can expand and decompress the high-pressure refrigerant in an isentropic manner, and a pressure-increasing section (42, 43) that converts enthalpy that has decreased during decompression expansion into pressure energy. Consists of ejector (40) ,
The refrigerant that has flowed out of the ejector (40) flows into the gas-liquid separator (50), and further, from the gas-liquid separator (50) to the low-pressure side heat exchanger (30) by the pump action of the ejector (40). ) Is directly supplied with refrigerant,
During the defrosting operation for removing frost adhering to the surface of the low pressure side heat exchanger (30), the throttle opening degree of the nozzle (41) is made larger than that before the defrosting operation to increase the pressure of the low pressure refrigerant. A vapor compression refrigerator that raises the pressure. Wherein in the operating mode other than the defrosting operation, throttle opening degree of the nozzle (41) is a vapor compression type refrigerator according to claim 1, characterized in that it is controlled according to the heat load. The vapor compression refrigerator according to claim 1 or 2 , wherein the pressure of the low-pressure refrigerant during the defrosting operation is a pressure at which the saturation temperature of the refrigerant becomes 0 ° C or higher. The vapor compression refrigerator according to any one of claims 1 to 3 , wherein the pressure of the high-pressure refrigerant is equal to or higher than the critical pressure of the refrigerant. The vapor compression refrigerator according to any one of claims 1 to 4 , wherein carbon dioxide is used as the refrigerant.

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