JPH04287710A - Heat exchanger - Google Patents

Abstract

PURPOSE:To provide a heat exchanger capable of using a general operating fluid such as water or alcohol when the temperature of a high-temperature heat source becomes high. CONSTITUTION:A two-way valve 17 switches the flow to the first evaporation section 18 and the flow to the second evaporation section 20, high-temperature steam is generated from the first evaporation section 18 to improve the quick warming performance of a heater 13 as a condenser at the time of a start, when the steam temperature of the first evaporation section 18 becomes high, it is switched to the second evaporation section 20, the temperature of an operating fluid is not increased above the limit temperature, the heat from an exhaust pipe 4 can be utilized for the heater 13 during the stationary operation, and general water or alcohol can be used for the operating fluid.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger that prevents a working fluid serving as a heat exchange medium from becoming hotter than a predetermined value.

0002

2. Description of the Related Art As a conventional heat exchanger, there is one that is applied to a vehicle heating system, for example, as shown in FIG. 5 (see Japanese Utility Model Application Publication No. 2-76509). This uses a heater 1 that circulates engine cooling water to exchange heat with the air and a loop heat pipe 2.
The heat absorbed by the evaporator 5 provided in the exhaust pipe 4 of the engine 3 is released by the condenser 6 in the vehicle interior. The amount of heat absorbed by the loop heat pipe 2 is controlled by a bypass door 7 and a choke part 8.

[0003] In the figure, reference numeral 9 is a blower fan, and reference numeral 10 is
is a liquid tank.

0004

[Problems to be Solved by the Invention] However, in such a conventional heat pipe, a heat pipe in the loop type heat pipe 2 is used to absorb heat from the exhaust pipe 4, which is a high-temperature heat source of 400°C or more, and radiate the heat into the vehicle interior. The working temperature of the working fluid is 3
The problem is that there is no suitable working fluid that can handle such operating temperatures. Therefore,
In conventional vehicle heating systems, when ordinary water or alcohol is used as the working fluid of the loop heat pipe 2, it cannot operate for a long time, so for example, it can only be used within an extremely limited period of time from the time of startup. When the engine cannot operate and the working fluid reaches a high temperature, it is necessary to use heat exchange with the engine cooling water circulating through the heater 1 to heat the interior of the vehicle.

Therefore, an object of the present invention is to provide a heat exchanger that can use a general working fluid such as water or alcohol even when the temperature of a high-temperature heat source is high.

[0006]

[Means for Solving the Problems] This invention has been made in view of this problem, and it is possible to connect an evaporator provided on the high temperature heat source side and a condenser provided on the low temperature side by a return pipe and a steam pipe. In a vehicle heating system in which the evaporator is connected in a ring to form a loop-type heat pipe, the evaporator absorbs heat from the high-temperature heat source, and the heat is radiated from the condenser by movement of a working fluid. The working fluid is divided into a plurality of evaporation sections through which the working fluid passes, and each evaporation section is set to have a different heat transfer coefficient from the high-temperature heat source, and when the temperature of the working fluid becomes higher than a predetermined value, the heat transfer coefficient becomes smaller. The heat exchanger is characterized in that the evaporator is provided with a control means for controlling the working fluid to flow to the evaporator having a high heat transfer coefficient when the temperature of the working fluid becomes lower than a predetermined value.

[0007]

[Operation] According to this means, exhaust heat from a high-temperature heat source is absorbed into the working fluid by the evaporator, and this working fluid is transferred to the condenser via the steam pipe, and the condenser radiates heat to operate. The fluid is condensed and the condensed working fluid is returned to the evaporator via a return pipe.

[0008] When such heat exchange is performed, when the temperature of the working fluid flowing from the evaporator to the condenser becomes higher than a predetermined temperature, the heat transfer coefficient from the high-temperature heat source of the plurality of evaporators is small. The evaporator is switched to the evaporator section by means of a control means. Further, when the temperature of the working fluid is lower than a predetermined temperature, the control means switches the working fluid so that it flows from the evaporating section to the evaporating section having a higher heat transfer coefficient.

[0009] By switching to an arbitrary evaporator according to the temperature of the working fluid in this manner, it is possible to prevent the working fluid from becoming higher than a predetermined temperature, so that a normal working fluid can be used.

0010

EXAMPLES The present invention will be explained below based on examples.

FIGS. 1 to 4 are diagrams showing an embodiment in which the heat exchanger of the present invention is applied to a heating system for a vehicle. Members that are the same as or equivalent to the conventional ones will be described using the same reference numerals.

First, to explain the configuration, the loop heat pipe 11 has an evaporator 12 attached around the exhaust pipe 4 as a high-temperature heat source and a heater 13 as a condenser. 13 are connected in an annular manner by a return pipe 15 and a steam pipe 16. A solenoid valve 14 and a two-way valve 17 are disposed in the middle of the return pipe 15.

The evaporator 12 is arranged around the exhaust pipe 4 extending from the engine 1, with the exhaust pipe 16 as the center.
It has a structure in which the evaporator 18, the air-tight space 19, and the second evaporator 20 are surrounded in this order. The heat transfer coefficient from the exhaust pipe 4 to the second evaporator 20 is smaller than that of the first evaporator 18 because the second evaporator 20 is not in direct contact with the exhaust pipe 4 and the space 19 is present.

The return pipe 16 and the steam pipe 16 are branched into two near the evaporator 12 and connected to a first evaporator 18 and a second evaporator 20. The two-way valve 17 is arranged at a branch point of the return pipe 16.

[0015] Furthermore, the heater 13 is installed in the vehicle interior,
After a portion of the air flow generated by the blower 21 passes through the condenser 22, it is taken in by opening and closing the damper 23.

Furthermore, the surface of the second evaporator 20, the evaporator 12
An evaporator sensor 24, an outlet sensor 25, and a heater sensor 26 are attached to the outlet and the heater 13, respectively, and signals from these sensors 24, 25, and 26 are input to a control device 27 as a control means. This control device 27 controls the two-way valve 17 and the solenoid valve 14 as follows.

Next, the operation of the above embodiment will be explained.

A working fluid circulates inside the loop heat pipe 11, and as the evaporator 12 absorbs exhaust heat from the engine 1, the working fluid turns into steam and moves from the evaporator 12 to the heater 13. . Here, heat is released into the air sent from the blower 21 and the air is condensed into liquid. The condensed liquid passes through the solenoid valve 14 and the two-way valve 17 via the return pipe 15, returns to the evaporator 12, and returns to the evaporator 12 again.
Heat transport is repeated by absorbing heat. In the loop heat pipe 11, heat is transported from the evaporator 12 to the heater 13 at the vapor velocity, so the heater 13 has excellent thermal response and can improve rapid heating performance during heating.

In such a case, the steam temperature T at the outlet of the evaporator 12
2 is detected by the outlet sensor 25, and the second evaporator 20
(second evaporator temperature T3) is detected by the evaporator sensor 24. This signal is then sent to the control device 27,
The two-way valve 17 is controlled by the control device 27, and the flow is switched between flow A flowing into the first evaporation section 18 and flow B flowing into the second evaporation section 20 as appropriate.

The first evaporator 18 directly surrounds the exhaust pipe 4 and has excellent heat transfer characteristics to the working fluid inside, so the working fluid that flows into the first evaporator 18 boils violently and reaches a high temperature. It becomes heated steam and flows out from the first evaporation section 18. In addition, since heat is transferred to the second evaporator 20 through the first evaporator 18 and the space 19 filled with air with poor heat transfer characteristics, the working fluid that has flowed into the second evaporator 20 is transferred to the second evaporator 20 . The amount of heating is suppressed, and the steam generated in the second evaporator 20 does not become high-temperature steam like the first evaporator 18, so the condensation temperature in the heater 13 does not become high.

Switching of the two-way valve 17 is performed based on a control flow as shown in FIG. That is, after startup, in step 100, the second evaporator temperature T3 reaches the set temperature Tse.
If it is higher than t1, the process proceeds to step 103, and if the second evaporator temperature T3 is equal to or lower than Tset1, the process proceeds to step 101.
Proceed to. In step 101, the two-way valve 17 is switched to flow A.

In step 102, the steam temperature T2 at the outlet of the evaporator 12 and the second evaporator temperature T3 are detected, and the condition is that the steam temperature T2 is higher than the set temperature Tset2, or the second evaporator temperature T3 is set. If the condition that the temperature is higher than Tset1 is satisfied, the process proceeds to step 103. In step 103, the two-way valve 17 is switched to the B direction.

Up to this point, the two-way valve 17 is switched at the time of startup, and the two-way valve 17 is set to flow A until the temperature of the steam generated in the evaporator 12 becomes high, thereby achieving rapid heating during heating. Improved performance.

In step 104, the steam temperature T2 at the outlet of the evaporator 15 is detected, and if this becomes lower than the set temperature Tset3, the process proceeds to step 105. This set temperature Tset3 is set lower than the set temperature Tset2. In step 105, the two-way valve 17 is switched to flow A. In step 106, the steam temperature T2 at the outlet of the evaporator 12 is detected, and if this is higher than the set temperature Tset2, the two-way valve 17 is switched to flow B in step 107.

As described above, when the working fluid flowing from the evaporator 12 toward the heater 13 becomes higher than the predetermined temperature,
Switching is made to the second evaporator 20, which has a lower heat transfer coefficient from the exhaust pipe 4. Moreover, when the temperature of the working fluid is lower than a predetermined temperature, switching is made to the first evaporation section 18 having a higher heat transfer coefficient.

In this way, depending on the temperature of the working fluid, the first
, the second evaporator 18, 20, it is possible to prevent the working fluid from becoming higher than a predetermined temperature, so that a normal working fluid can be used.

When using an organic substance as the working fluid, it is necessary to control the two-way valve 17 and the like so that the temperature of the generated steam is below the temperature at which thermal decomposition occurs.

On the other hand, switching (opening and closing) of the solenoid valve 14 is performed based on the control flow shown in FIG. This solenoid valve 1
The switching (opening/closing) of No. 4 is performed to control the temperature of the heater 13, so it is performed based on the heater temperature T1 of the heater 13 measured by the heater sensor 26.

That is, after starting, the heater temperature T1 of the heater 13 is detected, and if it is higher than the set temperature Tset4,
The process proceeds to step 121, and if the temperature is equal to or lower than the set temperature Tset4, the process proceeds to step 126. In step 121, the solenoid valve 14 is closed.

In step 122, the heater temperature T1 of the heater 13 is detected, and if it is below the set temperature Tset3, the process proceeds to step 123. This set temperature Tset3 is set lower than the set temperature Tset4. Step 12
3, the solenoid valve 14 is opened.

In step 124, the heater temperature T1 of the heater 13 is detected, and if it is higher than the set temperature Tset4, the process proceeds to step 125. In step 125, the solenoid valve 14 is closed.

On the other hand, in step 126, the solenoid valve 14 is opened. In step 127, the temperature T1 of the heater 6 is detected, and if it is higher than the set temperature Tset4, step 127 is performed.
Proceed to step 8. In step 128, the solenoid valve 14 is closed. In step 129, the temperature T1 of the heater 6 is detected,
If the temperature is below the set temperature Tset3, the process proceeds to step 130. In step 130, the solenoid valve 14 is opened.

Further, in the present invention, the steam temperature T2 at the outlet of the evaporator 12 is used to control the two-way valve 17, but it goes without saying that the temperature of the heater 13 may also be used. Further, in the above embodiment, the evaporation section 12 is divided into two, but it may be divided into more than that.

[0034]

As explained above, according to the present invention, the evaporator is divided into a plurality of evaporation sections through which the working fluid passes, and the temperature of the heat transferred from the high-temperature heat source to each evaporation section is adjusted. By setting the working fluid to be different and providing a control means that changes the flow so that it passes through any evaporator section depending on the temperature of the working fluid passing through the evaporator, the evaporator section with a good heat transfer rate is activated at startup. The rapid heating performance of the condenser is improved by passing fluid through it to generate steam, and when the steam temperature in this evaporator section becomes high, the working fluid is switched to an evaporator section with a lower heat transfer coefficient. Since the temperature does not rise above the limit temperature, it is possible to utilize heat from a high-temperature heat source even in steady state, and it also has the practical advantage of being able to use common water or alcohol as the working fluid. Demonstrate.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a heat exchanger of the present invention.

FIG. 2 is an explanatory cross-sectional view of the evaporator of the same embodiment.

FIG. 3 is a flow chart diagram showing a two-way valve of the same embodiment.

FIG. 4 is a flow chart diagram of the electromagnetic valve of the same embodiment.

FIG. 5 is a schematic diagram corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

4 Exhaust pipe (high temperature heat source) 11 Loop type heat pipe 12 Evaporator 13 Heater (condenser) 15 Return pipe 16 Steam pipe 18 First evaporation section 20 Second evaporation section 27 Control device (control means)

Claims (1)

[Claims] 1. An evaporator provided on the high-temperature heat source side and a condenser provided on the low-temperature side are connected in an annular manner by a return pipe and a steam pipe to form a loop-type heat pipe, and the evaporator provides the high-temperature A vehicle heating device that absorbs heat from a heat source and radiates the heat from the condenser by movement of a working fluid,
The evaporator is divided into a plurality of evaporation sections through which the working fluid passes, each evaporation section is set to have a different heat transfer coefficient from the high temperature heat source, and when the temperature of the working fluid becomes higher than a predetermined value, A heat sink characterized in that a control means is provided for controlling the working fluid to flow into the evaporating section having a low heat transfer coefficient and to flow to the evaporating section having a large heat transfer coefficient when the temperature of the working fluid becomes lower than a predetermined value. exchanger.