JP3970412B2 - Air conditioner for electric vehicles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air conditioner for an electric vehicle that does not have a hot water heat source for heating, and in particular, in a heat pump type that heats a vehicle interior by using condensation heat generated when a refrigerant condenses, the outside air temperature is The present invention relates to an air conditioner for an electric vehicle that can improve heating performance when the temperature is low.
[0002]
[Prior art]
An electric vehicle whose traveling drive source is an electric motor has less heat energy as a heat source for heating compared to a gasoline engine vehicle that can use high-temperature engine coolant. Therefore, conventionally, as an air conditioner for an electric vehicle, an air conditioner system has been developed that can perform dehumidifying heating by performing cycle operation using a refrigerant for both cooling and heating, and heating the vehicle interior while preventing fogging of windows. (For example, see JP-A-5-201243).
[0003]
As shown in FIG. 3, this air conditioner has a duct 2 for sending the air taken in by the blower device 1 toward the passenger compartment, and as an heat exchanger, the evaporator 3 is sequentially installed in the duct 2 from the upstream side. And a sub capacitor 4 that mainly works during the heating operation, and a main capacitor 5 that mainly works during the cooling operation is arranged outside the duct 2.
[0004]
The refrigeration cycle is configured by connecting a compressor 6, a main condenser 5, a sub condenser 4, a liquid tank 7, an expansion valve 8, and an evaporator 3 with refrigerant piping, and enclosing the refrigerant therein. An accumulator 9 is provided at the suction port of the compressor 6 in order to prevent the refrigerant from returning to the compressor 6 in a liquid state. In addition, a four-way valve 10 for switching the refrigerant flow is provided at the inlet of the main capacitor 5 in order to switch the capacitors 4 and 5 that function between the heating operation and the cooling operation. The four-way valve 10 is connected to a bypass pipe 11 that bypasses the main condenser 5 and a refrigerant recovery pipe 12 that mainly returns the refrigerant remaining in the main condenser 5 to the suction side of the compressor 6. The bypass pipe 11 is connected to a pipe 13 that connects the outlet of the main capacitor 5 and the inlet of the sub capacitor 4.
[0005]
A condenser fan device 14 for supplying air for heat exchange to the main condenser 5 is disposed on the back surface of the main condenser 5. An air mix door 15 is rotatably attached upstream of the sub-capacitor 4 in order to adjust the temperature of the air blown into the passenger compartment.
[0006]
During the cooling operation, the refrigerant discharged from the compressor 6 is guided to the main condenser 5 side by the four-way valve 10, and the path of the compressor 6 → the main condenser 5 → the sub condenser 4 → the liquid tank 7 → the expansion valve 8 → the evaporator 3 → the compressor 6. The refrigerant flows through. Thereby, in the evaporator 3, heat exchange is performed between the liquid refrigerant and the intake air, and the liquid refrigerant evaporates and cools the intake air that passes around the refrigerant passage, so that the vehicle interior is cooled. Further, in the main condenser 5, the heat taken by the evaporator 3 is released to the outside by heat exchange with the outside air, and the gas refrigerant is cooled and condensed. In this case, the sub capacitor 4 hardly functions as a heat exchanger.
[0007]
On the other hand, during the heating operation, the refrigerant discharged from the compressor 6 is guided to the bypass pipe 11 side by the four-way valve 10, bypasses the main condenser 5, and the compressor 6 → the sub condenser 4 → the liquid tank 7 → the expansion valve 8 → the evaporator. The refrigerant flows through the route 3 → compressor 6. As a result, the gas refrigerant discharged from the compressor 6 is condensed and liquefied by the sub-capacitor 3 to dissipate heat, so that the air cooled and dehumidified by the evaporator 3 is heated and blown into the vehicle interior. Is dehumidified and heated. Note that the temperature of the air blown into the vehicle interior is controlled by adjusting the opening of the air mix door 15.
[0008]
However, in such a conventional air conditioner for an electric vehicle, when the outside air temperature is low (for example, −10 ° C. or lower), the heating performance tends to be insufficient. In this case, the refrigerant in the evaporator 3 Since the evaporation is not performed sufficiently, the evaporation of the refrigerant is not completed at the outlet of the evaporator 3, and the liquid refrigerant may return to the compressor 6. In order to prevent this, the accumulator 9 is provided. However, since the capacity of the accumulator 9 is also limited, when a large amount of liquid refrigerant flows out of the evaporator 3, the accumulator 9 supplies the liquid refrigerant. There is a possibility that liquid refrigerant cannot be stored and liquid refrigerant is sent out to the compressor 6. When the liquid refrigerant returns to the compressor 6, the compressor 6 may be damaged by liquid compression.
[0009]
In order to prevent such a situation, the sub-evaporator 30 is provided in the conventional air conditioner for an electric vehicle. The sub-evaporator 30 heats the liquid refrigerant to prevent the compressor 6 from being damaged by liquid compression. Yes. A sheathed heater 32 is provided inside the sub-evaporator 30 and heats the LLC 33 as a heat medium to transfer heat to the liquid refrigerant.
[0010]
In order to efficiently perform this heat transfer, a water pump 44 is provided, and the LLC 33 can be efficiently circulated by the water pump 44, and good heat transfer can be achieved. The position where the water pump 44 is installed is outside the sub-evaporator 30. The heated high-temperature LLC 33 is led out from the sub-evaporator 30, circulated by the water pump 44, and returned to the sub-evaporator 30 again.
[0011]
[Problems to be solved by the invention]
However, at the position where the water pump inside the sub-evaporator with the conventional configuration is installed, there is a risk that the material of the water pump may be altered and deformed due to high temperature LLC, and it has normal temperature resistance performance in terms of reliability. The water pump could not be used.
[0012]
In addition, in order to use a water pump with improved heat resistance, it becomes expensive in terms of cost, and even if it is newly developed, it requires enormous development costs, Invite to rise.
[0013]
The present invention has been made paying attention to the above problems in a heat pump type air conditioner that does not have a hot water heat source for heating, and relates to a sub-evaporator that realizes an improvement in heating performance when the outside air temperature is low. An object of the present invention is to provide an air conditioner for an electric vehicle equipped with a sub-evaporator that can use a conventional product for the water pump that circulates the used LLC and that is low in cost and reliable. .
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention connects a compressor, an exterior condenser, an interior condenser, an expansion valve, and an interior evaporator that constitute a refrigeration cycle in this order by refrigerant piping, and is discharged from the compressor. Refrigerant flow path switching provided in a bypass pipe for bypassing the refrigerant outside the passenger compartment to guide the refrigerant to the passenger compartment condenser and a refrigerant pipe downstream of the compressor for switching the refrigerant flow path discharged from the compressor And the refrigerant discharged from the compressor is introduced into the vehicle exterior condenser by the refrigerant flow switching means during the cooling operation, and directly through the bypass pipe by the refrigerant flow switching means during the heating operation. In an air conditioner for an electric vehicle that is introduced into an indoor capacitor, A heat exchanger disposed between a refrigerant outlet of a vehicle interior evaporator and a refrigerant suction port of the compressor, wherein the refrigerant is circulated therein and performs heat exchange between the refrigerant and a heat transfer medium; and the heat exchanger A temperature sensing cylinder of the expansion valve provided at the refrigerant outlet, a sheathed heater that generates heat by power supply from an in-vehicle power source, a heater tank that houses a heat transfer medium and the sheathed heater, and a heater tank A hose for deriving a heated heat transfer medium, circulating it to the heat exchanger and circulating it again to the heater tank, and the hose through which the heat transfer medium after heat exchange returning from the heat exchanger to the heater tank flows of a water pump provided in the middle, it has a, when the refrigerant temperature detected by the temperature sensing tube rises, the expansion valve, characterized Rukoto increasing the flow rate of the coolant And electric vehicle air-conditioning system with a solution means to be.
[0015]
In this invention, the heat generated from the sheathed heater is transferred to the external surface of the heat exchanger via the surrounding heat transfer medium, and then transferred to the refrigerant in the heat exchanger. At this time, in order to forcibly generate convection, an inlet and an outlet for the heat transfer medium are opened in the container, and a water pump is used as a circulation means for circulating the internal heat transfer medium through the inlet / outlet.
[0016]
This water pump is provided at the downstream outlet from which the heat transfer medium after heat transfer flows out, and is a portion having a relatively low temperature. Therefore, a conventional water pump having normal heat resistance can be used.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a schematic configuration diagram of an air conditioner for an electric vehicle according to an embodiment of the present invention.
This air conditioner for an electric vehicle has the same basic configuration as a conventional heat pump type air conditioner, and has a duct 2 for sending air (inside air or outside air) taken in by the blower device 1 toward the vehicle interior. As a heat exchanger, a main evaporator 3 as a vehicle interior evaporator and a sub-condenser 4 as a vehicle interior capacitor mainly working during heating operation are disposed in the duct 2 in order from the upstream side. Is provided with a main capacitor 5 as a condenser outside the vehicle, which mainly works during cooling operation. An intake door 16 for selectively taking in the inside air or outside air is rotatably attached to one end of the duct 2.
[0019]
An air mix door 15 is rotatably attached upstream of the sub-capacitor 4 in order to adjust the temperature of the air blown into the passenger compartment. The air mix door 15 adjusts the ratio of the hot air that has passed through the sub-capacitor 4 and the cold air that bypasses the air to create air at a desired temperature in the downstream area of the sub-capacitor 4 or air flows through the sub-capacitor 4. I try not to.
[0020]
Further, in the air conditioner of the present embodiment, a sub-evaporator 30 serving as an evaporator outside the vehicle compartment is disposed between the refrigerant outlet of the main evaporator 3 and the refrigerant inlet of the compressor 6. The sub-evaporator 30 has a built-in sheathed heater 32 that generates heat by supplying power from the in-vehicle power supply 31, and has a function of heating the refrigerant flowing from the main evaporator 3 using heat generated from the sheathed heater 32. Yes. The structure and operation of the sub-evaporator 30 will be described in detail later.
[0021]
The refrigeration cycle which this air conditioner comprises includes the sub-evaporator 30 and connects the compressor 6, main capacitor 5, sub-capacitor 4, liquid tank 7, expansion valve 8, main evaporator 3, and sub-evaporator 30 with refrigerant piping. And it is comprised by enclosing a refrigerant | coolant in it. Here, an accumulator 9 is further provided at the suction port of the compressor 6 so that only the gas refrigerant is always sent to the compressor 6. Moreover, in order to switch the capacitors 4 and 5 to function between the heating operation and the cooling operation, a four-way valve 10 for switching the refrigerant flow is provided on the inlet side of the main capacitor 5 as a refrigerant flow switching means. ing.
[0022]
Connected to the four-way valve 10 are a bypass pipe 11 that bypasses the main condenser 5 and a refrigerant recovery pipe 12 that returns so-called stagnation refrigerant that mainly stays in the main condenser 5 to the suction side of the compressor 6. Yes. The bypass pipe 11 is connected to a pipe 13 that connects the outlet of the main capacitor 5 and the inlet of the sub capacitor 4. Reference numerals 20 and 21 denote check valves. A condenser fan device 14 for supplying heat exchange air to the main condenser 5 is disposed on the back surface of the main condenser 5.
[0023]
For example, the four-way valve 10 is provided with one inlet port and three outlet ports in a sealed case, and a slide member that communicates two outlet ports among the three outlet ports in the case. An outlet port other than the outlet port selected by the communication port is configured to communicate with the inlet port. Therefore, an outlet port that communicates with the inlet port is selected according to the position of the slide member.
[0024]
Here, the inlet port of the four-way valve 10 is connected to the discharge side of the compressor 6, and the three output ports of the four-way valve 10 are the inlet of the main condenser 5, the suction side (refrigerant recovery pipe 12) of the compressor 6, and the main, respectively. It is connected to the outlet (bypass pipe 11) of the capacitor 5. The four-way valve 10 switches between a cooling circuit that guides the refrigerant discharged from the compressor 6 to the main condenser 5 and a heating circuit that guides the refrigerant discharged from the compressor 6 to the bypass pipe 11 of the main condenser 5.
[0025]
The cooling circuit has a path indicated by a broken-line arrow in the drawing, that is, a path of compressor 6 → main capacitor 5 → sub capacitor 4 → liquid tank 7 → expansion valve 8 → main evaporator 3 → sub evaporator 30 → accumulator 9 → compressor 6. It consists of That is, during cooling operation, the four-way valve 10 is set at a position connecting the discharge side of the compressor 6 and the inlet of the main condenser 5 (not shown), and the refrigerant discharged from the compressor 6 is led to the main condenser 5 side. , Forming a cooling cycle in which the refrigerant circulates along the path.
[0026]
In this circulation process, the main evaporator 3 evaporates the liquid refrigerant by heat exchange and cools the intake air passing around the refrigerant passage, thereby cooling the vehicle interior. Further, the main condenser 5 releases the heat taken away by the main evaporator 3 to the outside by heat exchange with the air, thereby cooling the gas refrigerant and condensing it. At this time, the sheathed heater 32 in the sub-evaporator 30 does not generate heat (OFF). Further, the sub capacitor 4 hardly functions as a heat exchanger.
[0027]
On the other hand, the heating circuit is configured by a path indicated by a solid line arrow in the figure, that is, a path of the compressor 6 → the sub capacitor 4 → the liquid tank 7 → the expansion valve 8 → the main evaporator 3 → the sub evaporator 30 → the accumulator 9 → the compressor 6. Has been. That is, during the heating operation, the four-way valve 10 is set at the position shown in the figure connecting the discharge side of the compressor 6 and the bypass pipe 11, and the refrigerant discharged from the compressor 6 is guided to the bypass pipe 11 side so that the refrigerant passes through the path. Form a heating cycle that circulates along
[0028]
In this circulation process, the gas refrigerant discharged from the compressor 6 is condensed and liquefied by the sub-capacitor 4 to dissipate heat, so that the air cooled and dehumidified by the main evaporator 3 is heated and blown out into the vehicle interior. The vehicle interior is dehumidified and heated. At this time, the temperature of the air blown into the vehicle interior is controlled by adjusting the opening of the air mix door 15.
[0029]
As described above, the sub-evaporator 30 includes the sheathed heater 32 that generates heat by supplying power from the on-vehicle power supply 31, and uses the heat generated from the sheathed heater 32 to heat the refrigerant flowing from the main evaporator 3. It has a function.
[0030]
More specifically, the sub-evaporator 30 is configured by being housed in a hermetically sealed container 34. The components housed in the container 34 are a heater tank 51 housing a sheathed heater 32 and a heat transfer medium 33 enclosed in the heater tank 51 at the same time. During the heating operation, the heat transfer medium 33 is heated by the sheathed heater 32, and the heated heat transfer medium 33 is led out from the heater tank 51 by the hose 43 and is circulated through the heat exchanger 35.
[0031]
On the other hand, the heat exchanger 35 is provided with a refrigerant tube through which the refrigerant flows, and the outer skin of the refrigerant tube and the heat transfer medium 33 come into contact with each other to exchange heat. As a result, the low-temperature and low-pressure refrigerant circulating in the refrigerant tube is heated to improve the heating performance.
[0032]
Note that the heat transfer medium 33 that has become low temperature after heat exchange is returned to the heater tank 51 from the heat exchanger 35 by the hose 43. A water pump 44 is provided in the middle of a so-called downstream hose 43 that flows out of the heat exchanger 35, and the heat transfer medium 33 is circulated by the water pump 44.
[0033]
By providing such a sub-evaporator 30, the refrigerant is not sufficiently evaporated in the main evaporator 3 because the outside air temperature is low, so that an appropriate degree of superheat is not secured at the outlet of the main evaporator 3 or the main evaporator 3. Even if the liquid refrigerant flows out of the sub-evaporator 30, the refrigerant effectively takes in heat from the sheathed heater 32 and is heated by heat exchange with the heat transfer medium 33 heated by the sheathed heater 32. Therefore, it is possible to give a moderate degree of superheat at the outlet of the sub-evaporator 30.
[0034]
Then, since the moderately heated refrigerant is sucked into the compressor 6 and compressed again, the refrigerant discharged from the compressor 6 becomes a higher temperature refrigerant and is supplied to the sub capacitor 4. Become. As a result, the air that is heat-exchanged by the sub-capacitor 4 has a higher temperature, so that higher heating performance is exhibited and so-called immediate warming is improved. In addition, when the temperature sensing cylinder of the expansion valve 8 is provided at the outlet of the sub-evaporator 30 as described above, the refrigerant flow rate is adjusted by the temperature of the refrigerant after being heated by the sub-evaporator 30, and thus the sub-evaporator 30. During operation (that is, when the heating element 32 is operated), a larger amount of refrigerant circulates, thereby further improving the heating performance.
[0035]
That is, since the heating performance (heat dissipation capability) of the sub-capacitor 4 is related to the temperature and flow rate of the refrigerant, higher heating performance is exhibited by increasing the temperature of the discharged refrigerant and increasing the flow rate. become. In addition, since such a tendency is amplified with the passage of time, so-called immediate warming property is also improved. In addition to the improvement in heating performance, the heat exchange can complete evaporation at least at the outlet of the sub-evaporator 30, so that the liquid refrigerant does not return to the compressor 6 and there is no possibility of damage to the compressor 6 due to liquid compression. The durability of the compressor 6 is improved.
[0036]
The sub-evaporator 30 is disposed outside the indoor duct 2, for example, in the engine room. For this reason, use of a high voltage is possible.
[0037]
FIG. 2 is a partial cross-sectional front view showing a configuration example of the sub-evaporator 30.
[0038]
This sub-evaporator 30 is provided with a sheathed heater 32 as a heating element inside a heater tank 51 in a sealed container 34 and a heat exchanger 35 through which the refrigerant flows, and heat generated from the sheathed heater 32 is transferred to the heat exchanger 35. As a heat transfer medium to be transmitted to, for example, an LLC (Long Life Coolant) 33 which is a coolant that can be used for a long time is enclosed.
[0039]
Connection pipes 35a and 35b are attached to both ends of the heat exchanger 35, respectively. For example, one connection pipe 35a is connected to the outlet side of the main evaporator 3, and the other connection pipe 35b is connected to the suction side of the compressor 6 (more precisely, the inlet side of the accumulator 9).
[0040]
The sheathed heater 32 is a heating element in which a heating wire (for example, a coiled nichrome wire) is placed in a protective tube (sheath) and is filled with a heat-resistant insulating material in the middle. Has been. Two lead terminal portions (not shown) are connected to both ends of the sheathed heater 32. As will be described later, for example, one lead terminal portion is connected to a vehicle power source, and the other lead terminal portion is grounded via a relay.
[0041]
The heater tank 51 is provided with an inlet 36 for injecting the LLC 33 into the container 34. The inlet 36 has a mechanical protection circuit that operates when the temperature of the internal LLC 33 becomes high. A cap mechanism 37 is attached.
[0042]
Further, a temperature sensor 50 (described later) for detecting the temperature of the enclosed LLC 33 is disposed in the heater tank 51 as a temperature detecting means at an appropriate position. As will be described later, ON / OFF control of the sheathed heater 32 is performed according to the detection value of the temperature sensor.
[0043]
With this configuration, the heat generated from the sheathed heater 32 is transmitted to the external surface of the heat exchanger 35 via the surrounding LLC 33, and then transmitted to the refrigerant in the heat exchanger 35 and absorbed. . At this time, since the LLC 33 has a large heat capacity, heat exchange using a heat transfer medium having such a large heat capacity reduces the temperature fluctuation when the sheathed heater 32 is turned on and off, thereby reducing the refrigeration cycle (and thus the blowing temperature). Occurrence of hunting is suppressed. As a result, the heating performance is stabilized.
The sheathed heater 32 is a kind of resistor, and the sheathed heater 32, which is such a resistor, is inserted in the electric circuit. 31 (high voltage system) can be directly connected, and low-voltage light electrical components (relays, harnesses, etc.) can be used for the other lead terminal portion, thereby reducing the cost.
[0044]
The LLC 33 heated by the sheathed heater 32 has the highest temperature near the outlet of the sheathed heater 32 of the hose 43 from the portion heated by the sheathed heater 32. Since a thermal load is applied to the other parts including the hose 43 in this high temperature part, a reliable part in heat resistance is used.
This high-temperature LLC 33 contacts the surface of the heat exchanger 35 and transfers heat to the refrigerant, where the temperature of the LLC 33 is lowered. This low temperature LLC 33 returns to the sheathed heater 32 from the outlet of the sub-evaporator 30 of the hose 43 through which the LLC 33 flows out from the section in contact with the heat exchanger 35 and is reheated.
[0045]
The water pump 44 used in the sub-evaporator 30 of the automotive air conditioner to which the present invention is applied is provided on the downstream outlet side of the hose 43 from which the LLC 33 having a temperature lower than that of the sub-evaporator 30 flows out. On the downstream outlet side from the sub-evaporator 30, the temperature of the LLC 33 is lower than the temperature of the upstream LLC 33 for the above reason, and the water pump 44 is not required to have high heat resistance.
[0046]
For this reason, since the conventional water pump 44 with a track record of use can be used as it is, it is not necessary to use an expensive pump with improved heat resistance. In addition, since it is not necessary to prepare a newly designed pump that takes heat resistance into consideration, it is possible to simultaneously achieve the proven reliability and low cost of conventional products.
[0047]
The embodiment described above is described in order to facilitate understanding of the present invention, and is not described in order to limit the present invention. Therefore, each element disclosed in the above embodiment includes all design changes and equivalents belonging to the technical scope of the present invention.
[0048]
【The invention's effect】
According to the present invention, a conventional actual product can be used for a water pump that circulates a heated LLC in a sub-evaporator, and the sub-evaporator is low-cost and reliable. It is possible to provide an air conditioner for an electric vehicle including
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an air conditioner for an electric vehicle according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of an air conditioner for an electric vehicle according to an embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of a conventional air conditioner for an electric vehicle.
[Explanation of symbols]
3 ... Main evaporator (vehicle compartment evaporator)
4 ... Sub capacitor (in-vehicle capacitor)
5 ... Main condenser (condenser outside the passenger compartment)
6 ... Compressor 7 ... Liquid tank 8 ... Expansion valve 9 ... Accumulator 10 ... Four-way valve (refrigerant flow path switching means)
11 ... Bypass pipe 30 ... Sub-evaporator (Evaporator outside the passenger compartment)
31 ... Vehicle power supply (car power supply)
32 ... Seeds heater (heating element)
33 ... LLC (Heat Transfer Medium)
35 ... heat exchanger 43 ... hose (circulation means)
44 ... Water pump (circulation means)
51 ... Heater tank

Claims (1)

The compressor (6), the vehicle exterior condenser (5), the vehicle interior condenser (4), the expansion valve (8), and the vehicle interior evaporator (3) constituting the refrigeration cycle are connected in this order by refrigerant piping, and the compressor A bypass pipe (11) for guiding the refrigerant discharged from (6) to bypass the vehicle exterior condenser (5) to the vehicle interior condenser (4), and the flow of refrigerant discharged from the compressor (6) Refrigerant flow switching means (10) provided in refrigerant piping downstream of the compressor (6) for switching the path,
The refrigerant discharged from the compressor (6) is introduced into the outdoor condenser (5) by the refrigerant flow switching means (10) during the cooling operation, and the refrigerant flow switching means (10) by the refrigerant flow switching means (10) during the heating operation. In the air conditioner for an electric vehicle introduced directly into the vehicle interior condenser (4) through the bypass pipe (11),
Between the refrigerant outlet of the vehicle interior evaporator (3) and the refrigerant inlet of the compressor (6), the refrigerant is circulated to exchange heat between the refrigerant and the heat transfer medium (33). A heat exchanger (35) to perform;
A temperature sensing cylinder of the expansion valve (8) provided at the refrigerant outlet of the heat exchanger (35);
A sheathed heater (32) that generates heat by power supply from an in-vehicle power supply (31), a heater tank (51) that houses therein a heat transfer medium (33) and the sheathed heater (32), and the heater tank (51 ) A heated heat transfer medium (33) from the hose (43) that is circulated to the heat exchanger (35) and circulated again to the heater tank (51);
A water pump (44) provided in the middle of the hose (43) through which the heat transfer medium (33) after heat exchange returning from the heat exchanger (35) to the heater tank (51) flows. and, when the refrigerant temperature detected by the temperature sensing tube rises, the expansion valve, an electric car air-conditioning system according to claim Rukoto increasing the flow rate of the refrigerant.

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