JP2020159611A - Heat transport system - Google Patents

Abstract

To suppress increase of the viscosity of a heat transport medium at a low temperature and prevent boiling of the heat transport medium in a transport system.SOLUTION: A transport system includes a refrigeration cycle device 10 in which a refrigerant circulates, a heat transport medium circuit 30 in which a heat transport medium circulates, a cooling heat exchanger 15 by which the refrigerant and the heat transport medium exchange heat to cool the heat transport medium, and electrical devices 33-35 which are provided in the heat transport medium circuit and whose heat is absorbed by the heat transport medium. The heat transport medium includes methanol, water. and a boiling point elevation additive. The boiling point elevation additive is compatible with both of the water and the methanol, and is a substance having a boiling point higher than that of a mixture of the water and the methanol.SELECTED DRAWING: Figure 1

Description

The present invention relates to a heat transport system that transports heat by a heat transport medium.

Patent Document 1 describes a device that cools the low-temperature cooling water by exchanging heat between the refrigerant of the refrigeration cycle and the low-temperature cooling water of the low-temperature cooling water circuit by a chiller. In this device, an aqueous ethylene glycol solution or the like is used as the low temperature cooling water.

Japanese Unexamined Patent Publication No. 2017-110898

However, since the ethylene glycol aqueous solution has a high viscosity at a low temperature, the pressure loss of the low temperature cooling water circuit becomes large. Therefore, the pump power for circulating the low-temperature cooling water is increased.

By the way, in the apparatus of Patent Document 1, when the low-temperature cooling water is heated by the heat load, the low-temperature cooling water boils, and the low-temperature cooling water in the liquid phase does not exist in a part of the low-temperature cooling water circuit (that is, dry). Out) may occur. In this case, the chiller may not stably exchange heat between the refrigerant and the low-temperature cooling water.

In view of the above points, it is an object of the present invention to suppress an increase in viscosity of the heat transport medium at a low temperature and further suppress boiling of the heat transport medium in the heat transport system.

In order to achieve the above object, the invention according to claim 1 heats a refrigerating cycle apparatus (10) in which a refrigerant circulates, a heat transport medium circuit (30) in which a heat transport medium circulates, and a refrigerant and a heat transport medium. The heat transport medium comprises a cooling heat exchanger (15) for exchanging and cooling the heat transport medium, and an electric device (33 to 35) provided in the heat transport medium circuit and absorbed by the heat transport medium. A heat transport system that is an aqueous solution of methanol containing methanol, water and a boiling point enhancer.

As described above, by using methanol, water, and an aqueous methanol solution containing a boiling point elevation agent as the heat transport medium, it is possible to suppress an increase in viscosity in a low temperature environment, and further suppress boiling of the heat transport medium.

The reference numerals in parentheses of each means described in this column and the scope of claims indicate the correspondence with the specific means described in the embodiments described later.

It is a figure which shows the structure of the heat transport system which concerns on one Embodiment. It is a front view which shows the 2nd cooler in one Embodiment. It is explanatory drawing which shows the temperature state inside the 2nd cooler. It is explanatory drawing which shows the freezing point and boiling point in Example and Comparative Examples 1-3.

Hereinafter, the most suitable embodiment to which the heat transport system of the present invention is applied will be described with reference to the drawings.

The heat transport system of the present embodiment is mounted on an electric vehicle that obtains a driving force for traveling a vehicle from a traveling electric motor. The heat transport system may be mounted on a hybrid vehicle that obtains driving force for vehicle traveling from an engine (in other words, an internal combustion engine) and an electric motor for traveling. The heat transport system of the present embodiment functions as an air conditioner for adjusting the temperature of the vehicle interior space, and also functions as a temperature control device for adjusting the temperature of the battery 33 or the like mounted on the vehicle.

As shown in FIG. 1, the heat transport system includes a refrigeration cycle device 10, a high temperature medium circuit 20 which is a high temperature side heat transport medium circuit, and a low temperature medium circuit 30 which is a heat transport medium circuit. In the high temperature medium circuit 20 and the low temperature medium circuit 30, heat is transported by the heat transport medium. The heat transport medium of the low temperature medium circuit 30 has a lower temperature than the heat transport medium of the high temperature medium circuit 20. Therefore, the heat transport medium of the high temperature medium circuit 20 is also referred to as a high temperature side heat transport medium, and the heat transport medium of the low temperature medium circuit 30 is also referred to as a low temperature side heat transport medium.

The refrigeration cycle device 10 is a vapor compression refrigerator and has a refrigerant circulation flow path 11 through which a refrigerant circulates. The refrigeration cycle device 10 functions as a heat pump that pumps the heat of the low temperature side heat transport medium of the low temperature medium circuit 30 into the refrigerant.

The refrigeration cycle apparatus 10 of the present embodiment uses a fluorocarbon-based refrigerant as the refrigerant, and constitutes a subcritical refrigeration cycle in which the high-pressure side refrigerant pressure does not exceed the critical pressure of the refrigerant. A compressor 12, a condenser 13 which is a heat exchanger for heating, an expansion valve 14, and an evaporator 15 for a heat transport medium which is a heat exchanger for cooling are arranged in the refrigerant circulation flow path 11.

The compressor 12 is an electric compressor driven by electric power supplied from the battery 33, and sucks in the refrigerant, compresses it, and discharges it. The condenser 13 is a high-pressure side heat exchanger that condenses the high-pressure side refrigerant by exchanging heat between the high-pressure side refrigerant discharged from the compressor 12 and the heat transport medium of the high-temperature medium circuit 20. In the condenser 13, the heat transport medium of the high temperature medium circuit 20 is heated by the high pressure side refrigerant of the refrigeration cycle device 10.

The expansion valve 14 is a decompression unit that depressurizes and expands the liquid phase refrigerant flowing out of the condenser 13. The expansion valve 14 is a mechanical temperature expansion valve that has a temperature sensitive portion and drives the valve body by a mechanical mechanism such as a diaphragm.

The heat transport medium evaporator 15 is a low pressure side heat exchanger that evaporates the low pressure refrigerant by exchanging heat between the low pressure refrigerant flowing out of the expansion valve 14 and the heat transport medium of the low temperature medium circuit 30. The vapor-phase refrigerant evaporated in the heat transport medium evaporator 15 is sucked into the compressor 12 and compressed.

The heat transport medium evaporator 15 is a chiller that cools the heat transport medium of the low temperature medium circuit 30 with the low pressure refrigerant of the refrigeration cycle device 10. In the heat transport medium evaporator 15, the heat of the heat transport medium of the low temperature medium circuit 30 is endothermic to the refrigerant of the refrigeration cycle device 10.

The high temperature medium circuit 20 has a high temperature side circulation flow path 21 in which the high temperature side heat transport medium circulates. Ethylene glycol-based antifreeze (LLC) or the like can be used as the high-temperature side heat transport medium. The high temperature side heat transport medium is enclosed in the piping constituting the high temperature side circulation flow path 21. The high temperature medium circuit 20 of the present embodiment is a closed type that is not provided with a pressure adjusting valve that opens when the pressure of the high temperature side heat transport medium exceeds a predetermined value. That is, the high temperature medium circuit 20 of this embodiment is sealed.

A high temperature side pump 22, a heater core 23, and a condenser 13 are arranged in the high temperature side circulation flow path 21.

The high temperature side pump 22 sucks in and discharges the heat transport medium circulating in the high temperature side circulation flow path 21. The high temperature side pump 22 is an electric pump. The high temperature side pump 22 adjusts the flow rate of the heat transport medium circulating in the high temperature medium circuit 20.

The heater core 23 is an air heating heat exchanger that heats the air blown into the vehicle interior by exchanging heat between the heat transport medium of the high temperature medium circuit 20 and the air blown into the vehicle interior. In the heater core 23, the air blown into the vehicle interior is heated by the heat transport medium.

The air heated by the heater core 23 is supplied to the vehicle interior to heat the vehicle interior. Heating by the heater core 23 is mainly performed in winter. In the heat transport system of the present embodiment, the heat of the outside air absorbed by the low temperature side heat transport medium of the low temperature medium circuit 30 is pumped up by the refrigeration cycle device 10 to the high temperature side heat transport medium of the high temperature medium circuit 20, and is used for heating the room. Used.

The low temperature medium circuit 30 has a low temperature side circulation flow path 31 through which the low temperature side heat transport medium circulates. The low temperature side heat transport medium is enclosed in a pipe constituting the low temperature side circulation flow path 31. The low temperature medium circuit 30 of the present embodiment is a closed type that is not provided with a pressure adjusting valve that opens when the pressure of the low temperature side heat transport medium exceeds a predetermined value. That is, the low temperature medium circuit 30 of this embodiment is sealed. The low temperature side heat transport medium will be described later.

A low temperature side pump 32, a heat transport medium evaporator 15, a battery 33, an inverter 34, a motor generator 35, and an outdoor heat exchanger 36 are arranged in the low temperature side circulation flow path 31. In the example shown in FIG. 1, the battery 33, the inverter 34, the motor generator 35, the outdoor heat exchanger 36, and the low temperature pump 32 are connected in this order in the flow direction of the low temperature side heat transport medium, but the connection order is limited to this. It is not something that is done. Further, in the example shown in FIG. 1, the battery 33, the inverter 34, the motor generator 35, the outdoor heat exchanger 36, and the low temperature side pump 32 are connected in series, but one or more of these devices are connected to other devices. May be connected in parallel with.

The low temperature side pump 32 sucks in and discharges the heat transport medium circulating in the low temperature side circulation flow path 31. The low temperature side pump 32 is an electric pump. The low temperature side pump 32 adjusts the flow rate of the heat transport medium circulating in the low temperature medium circuit 30.

The battery 33 is a rechargeable and dischargeable secondary battery, and for example, a lithium ion battery can be used. As the battery 33, an assembled battery composed of a plurality of battery cells can be used.

The battery 33 can charge the electric power supplied from the external power source (in other words, the commercial power source) when the vehicle is stopped. The electric power stored in the battery 33 is supplied not only to the traveling electric motor but also to various in-vehicle devices such as the electric components constituting the heat transport system.

The inverter 34 converts the DC power supplied from the battery 33 into AC power and outputs it to the motor generator 35. The motor generator 35 uses the electric power output from the inverter 34 to generate a driving force for traveling, and also generates a regenerative electric power during deceleration or downhill.

The outdoor heat exchanger 36 exchanges heat between the heat transport medium of the low temperature medium circuit 30 and the outside air. Outside air is blown to the outdoor heat exchanger 36 by an outdoor blower (not shown).

The battery 33, the inverter 34, and the motor generator 35 are electric devices that operate using electricity, and generate heat during operation. The battery 33, the inverter 34, and the motor generator 35 are devices to be cooled that are cooled by the low temperature side heat transport medium.

The low temperature side circulation flow path 31 of the present embodiment is provided with coolers 37 to 39 corresponding to the electric devices 33 to 35. The first cooler 37 corresponds to the battery 33, the second cooler 38 corresponds to the inverter 34, and the third cooler 39 corresponds to the motor generator 35.

A low temperature side heat transport medium circulates in the coolers 37 to 39. The electric devices 33 to 35 are cooled by the low temperature side heat transport medium flowing through the coolers 37 to 39.

In the first cooler 37 and the second cooler 38, the battery 33 and the inverter 34 are cooled by the low temperature side heat transport medium without using another heat transport medium. The third cooler 39 is an oil cooler that cools the oil circulating in the oil circuit 40 by the low temperature side heat transport medium. The oil flows inside the motor generator 35 to lubricate and cool the motor generator 35.

In the coolers 37 to 39, heat is absorbed from the battery 33, the inverter 34, and the motor generator 35, which are the devices to be cooled, to the low temperature side heat transport medium. In the outdoor heat exchanger 36, heat is absorbed from the outside air to the low temperature side heat transport medium. That is, the battery 33, the inverter 34, the motor generator 35, and the outdoor heat exchanger 36 are endothermic devices that absorb heat to the low temperature side heat transport medium.

Next, a specific configuration of the second cooler 38 will be described. As shown in FIG. 2, the second cooler 38 of the present embodiment is a laminated heat exchanger that cools a plurality of electronic components 340 constituting the inverter 34 from both sides.

The electronic component 340 of the present embodiment has a double-sided heat dissipation structure in which heat is dissipated from both sides. As the electronic component 340, a semiconductor module incorporating a semiconductor element such as an IGBT and a diode can be used.

The second cooler 38 includes a flow path pipe 381 and a communication portion 382. The flow path tube 381 is formed in a flat shape and constitutes a low temperature side heat transport medium flow path through which the low temperature side heat transport medium of the low temperature medium circuit 30 flows. A plurality of flow path tubes 381 are laminated so that the electronic components 340 can be sandwiched from both sides.

The communication unit 382 communicates a plurality of flow path pipes 381 with each other. The communication portion 382 is connected to both ends of the flow path pipe 381 in the longitudinal direction.

In this embodiment, two electronic components 340 are provided for each of the flat surfaces in the flow path tube 381. The two electronic components 340 provided on each flat surface are arranged in series in the flow direction of the low temperature side heat transport medium.

Here, among the plurality of flow path pipes 381, the flow path pipe 381 arranged on the outermost side in the stacking direction is referred to as the outer flow path pipe 3810. Of the two outer flow path pipes 3810 in the second cooler 38, the introduction port 383 and the discharge port 384 are provided at both ends in the longitudinal direction of one of the outer flow path pipes 3810, respectively.

The introduction port 383 is an introduction unit that introduces the low temperature side heat transport medium into the second cooler 38. The discharge port 384 is a discharge unit that discharges the low temperature side heat transport medium from the second cooler 38. The introduction port 383 and the discharge port 384 are joined to one outer flow path pipe 3810 by brazing. The flow path pipe 381, the communication portion 382, the introduction port 383, and the discharge port 384 of the present embodiment are each made of aluminum.

The low-temperature side heat transport medium introduced from the introduction port 383 flows into each flow path pipe 381 from one end in the longitudinal direction of the flow path pipe 381 through one communication portion 382, and flows into each flow path pipe 381. It flows through the inside toward the other end. Then, the low temperature side heat transport medium is discharged from the discharge port 384 through the other communication portion 382. In this way, while the low-temperature side heat transport medium flows through the flow path tube 381, heat exchange is performed between the low-temperature side heat transport medium and the electronic component 340, and the electronic component 340 is cooled.

Next, the low temperature side heat transport medium will be described. It is desirable that the low temperature side heat transport medium has low viscosity at low temperature and high boiling point.

In this embodiment, a methanol aqueous solution containing methanol, water and a boiling point elevation agent is used as the low temperature side heat transport medium. In the present embodiment, the ratio of the boiling point increasing agent to the aqueous methanol solution is less than 50%.

As the boiling point elevation agent, a substance having compatibility with both water and methanol and having a boiling point higher than that of a mixture of water and methanol can be used. Specifically, at least one of alcohol, amine, ether, and carboxylic acid can be used as the boiling point elevation agent.

As the alcohol, at least one of an alcohol having one hydroxyl group and three or more carbon atoms and an alcohol having two or more hydroxyl groups and two or more carbon atoms can be used. As the alcohol having two or more hydroxyl groups and two or more carbon atoms, for example, at least one of ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol can be used.

As the amine, at least one of formamine and methylamine can be used. As the ether, at least any one of dimethyl ether, ethyl methyl ether, diethyl ether and glycol ether can be used. As the carboxylic acid, at least one of formic acid and acetic acid can be used.

As shown in FIG. 3, the heat generated in the electronic component 340 of the inverter 34 is transferred to the low temperature side heat transport medium flowing in the flow path pipe 381 via the inner wall surface 381a of the flow path pipe 381. As a result, the temperature of the low temperature side heat transport medium that has flowed into the flow path pipe 381 rises.

At this time, the temperature of the portion of the low-temperature side heat transport medium flow path in the flow path tube 381 facing the inner wall surface 381a becomes higher than the temperature of the other portion. That is, among the low-temperature side heat transport medium flow paths in the flow path tube 381, the temperature of the portion facing the inner wall surface 381a becomes the highest. Therefore, the temperature of the inner wall surface 381a of the flow path pipe 381 is substantially the maximum temperature of the low temperature side heat transport medium. Therefore, by raising the boiling point of the low temperature side heat transport medium to be higher than the temperature of the inner wall surface 381a of the flow path tube 381, it is possible to prevent the low temperature side heat transport medium from boiling in the flow path tube 381.

In particular, in a high temperature environment such as summer, the temperature of the inverter 34 tends to rise, and the temperature of the inner wall surface 381a of the flow path pipe 381 in the second cooler 38 rises. Therefore, it is desirable that the boiling point of the low temperature side heat transport medium is equal to or higher than the temperature of the inner wall surface 381a of the flow path tube 381 (about 90 ° C. in this example) in summer. Further, the freezing point of the heat transport medium on the low temperature side is preferably −35 ° C. or lower in order to suppress freezing in a low temperature environment such as winter.

As shown in FIG. 4, anhydrous methanol as Comparative Example 1 has a freezing point of −95 ° C. and a boiling point of 65 ° C. A methanol aqueous solution containing methanol and water as Comparative Example 2 (methanol: water = 35:65) has a freezing point of −35 ° C. and a boiling point of 82 ° C.

On the other hand, in the methanol aqueous solution (methanol: water: boiling point elevation agent = 10:50:40) containing methanol, water and a boiling point elevation agent as an example, the freezing point is −35 ° C. and the boiling point is 100 ° C. .. As described above, the aqueous methanol solution containing methanol, water and a boiling point elevation agent can secure a high boiling point and a low freezing point. Then, when a methanol aqueous solution containing methanol, water, and a boiling point elevation agent as an example is sealed in the low temperature medium circuit 30 at high pressure, the boiling point of the methanol aqueous solution can be further raised.

The ethylene glycol antifreeze solution (ethylene glycol: water = 50: 50) as Comparative Example 3 has a freezing point of −35 ° C. and a boiling point of 107 ° C. However, since the kinematic viscosity of the ethylene glycol antifreeze solution at −35 ° C. is higher than that of the aqueous methanol solution, it is not possible to secure the low viscosity at a low temperature.

The low temperature side heat transport medium of the present embodiment contains a rust preventive in addition to water, methanol and a boiling point elevation agent. The rust preventive is for preventing corrosion of the pipe through which the low temperature side heat transport medium flows. The concentration of the rust inhibitor in the low-temperature side heat transport medium can be appropriately set, but can be, for example, several percent.

Examples of the rust preventive agent include aliphatic monocarboxylic acids, aromatic monocarboxylic acids, aromatic dicarboxylic acids or salts thereof, borates, silicates, silicic acids, phosphates, phosphoric acids, nitrites, and nitrates. , Molybdenate, triazole, and thiazole can be at least one selected.

As described above, in the present embodiment, an aqueous methanol solution containing methanol, water and a boiling point elevation agent is used as the low temperature side heat transport medium. As a result, it is possible to suppress an increase in viscosity in a low temperature environment as compared with an ethylene glycol antifreeze solution. Therefore, even in a low temperature environment, an increase in pressure loss in the low temperature medium circuit 30 can be suppressed, and an increase in power of the low temperature side pump 32 can be suppressed.

Further, the outdoor heat exchanger 36 can be easily miniaturized by narrowing the flow path of the low temperature side heat transport medium, and the degree of freedom in design can be improved. Further, since the flow velocity of the low temperature side heat transport medium passing through the outdoor heat exchanger 36 is improved, frost formation on the outdoor heat exchanger 36 can be suppressed.

Further, since the increase in the viscosity of the low temperature side heat transport medium in the low temperature environment can be suppressed, the flow rate of the low temperature side heat transport medium can be increased as compared with the ethylene glycol antifreeze solution. As a result, the flow velocity of the low temperature side heat transport medium can be increased, and the heat transfer coefficient of the low temperature side heat transport medium can be further improved. Further, by improving the heat transfer coefficient of the low temperature side heat transport medium, it is possible to improve the heat transfer coefficient of the entire device including the outdoor heat exchanger 36.

Further, by including the boiling point elevation agent in the low temperature side heat transport medium, the boiling point of the low temperature side heat transport medium can be raised. According to this, even if the low temperature side heat transport medium is heated by the heat load, it is possible to suppress boiling of the low temperature side heat transport medium in the low temperature medium circuit 30. Therefore, it is possible to suppress the occurrence of dryout in a state where the low temperature side heat transport medium of the liquid phase does not exist in a part of the low temperature medium circuit 30. As a result, in the heat transport medium evaporator 15, heat exchange between the low-pressure refrigerant and the low-temperature side heat transport medium can be stably performed.

Further, in the present embodiment, the low temperature medium circuit 30 is a closed type. According to this, since the low temperature side heat transport medium can be enclosed in the low temperature medium circuit 30 at high pressure, the boiling point of the low temperature side heat transport medium can be further raised.

Further, in the present embodiment, the low temperature side heat transport medium contains a rust preventive agent. According to this, since corrosion of the pipe through which the low temperature side heat transport medium flows can be suppressed, the durability of the heat transport system can be improved. Further, the boiling point raising effect can raise the boiling point of the low temperature side heat transport medium.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be variously modified as follows without departing from the spirit of the present invention.

For example, in the above embodiment, the aqueous methanol solution containing methanol, water and a boiling point increasing agent is used as the heat transport medium on the low temperature side of the low temperature medium circuit 30, but the present invention is not limited to this, and the aqueous methanol solution is used on the high temperature side of the high temperature medium circuit 20. It may be used as a heat transport medium. In this case, the heat transport medium can be shared between the high temperature medium circuit 20 and the low temperature medium circuit 30.

10 Refrigeration cycle device 15 Evaporator for heat transport medium (heat exchanger for cooling)
30 Low temperature medium circuit (heat transport medium circuit)
33 Batteries (electrical equipment)
34 Inverter (electrical equipment)
35 Motor generator (electrical equipment)

Claims (8)

Refrigerant cycle device (10) that circulates refrigerant and
The heat transport medium circuit (30) through which the heat transport medium circulates,
A cooling heat exchanger (15) that exchanges heat between the refrigerant and the heat transport medium and cools the heat transport medium.
An electric device (33 to 35) provided in the heat transport medium circuit and endothermic to the heat transport medium is provided.
The heat transport system is a heat transport system in which the heat transport medium is an aqueous solution of methanol containing methanol, water, and a boiling point elevation agent. The heat transport system according to claim 1, wherein the boiling point elevation agent is a substance that is compatible with both water and methanol and has a higher boiling point than a mixture of water and methanol. The heat transport system according to claim 2, wherein the boiling point elevation agent is at least one of alcohol, amine, ether, and carboxylic acid. The heat transport system according to any one of claims 1 to 3, wherein the ratio of the boiling point elevation agent to the aqueous methanol solution is less than 50%. The heat transport system according to any one of claims 1 to 4, wherein the methanol aqueous solution contains a rust preventive. The heat transport system according to any one of claims 1 to 5, wherein the heat transport medium circuit is sealed. A high-temperature side heat transport medium circuit (20) in which a high-temperature side heat transport medium having a temperature higher than that of the heat transport medium circulates.
A heating heat exchanger (13) for exchanging heat between the refrigerant and the high temperature side heat transport medium and heating the high temperature side heat transport medium is provided.
The heat transport system according to any one of claims 1 to 6, wherein the high temperature side heat transport medium is the aqueous methanol solution. The heat transport system according to claim 7, wherein the high temperature side heat transport medium circuit is sealed.

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