JPS591998A - Heat medium pressure control device for waste heat restrieving device - Google Patents

Abstract

PURPOSE:To restrict the over-rising of the heat medium pressure by a method wherein the heat medium pressure in an enclosed pipeline is detected by a specified means and the flow amount of a heated fluid is controlled based on a signal therefrom. CONSTITUTION:When a pressure switch 8 or a thermosetting member 9 has detected a phenomenon wherein the amount of heat, retrieved from exhaust gas by a retrieving side heat exchanger 2, is large, a steam pressure in the enclosed pipeline 5 is exceeding a set value and the temperature is increasing to a value higher than a predetermined temperature, a fan 23 is rotated by a controller 27, a normally closed valve 26 is opened and a normally opened solenoid valve 13 is closed. When the solenoid valve 13 is closed, condensed water is reserved at the upstream side of the valve 13, the supply of the condensed water to the heat exchanger 2 is stopped, generation of steam is stopped and the pressure in the enclosed pipeline 5 is reduced. By starting the fan 23 to increase the flow amount of cooling water for a heat demanding part 3, the heat exchanging capacity of the heat transmitting side heat exchanger 4 is increased and the steam, increased in the pressure thereof, is cooled and condensed to reduce the steam pressure quickly. When the pressure and the temperature of the steam are reduced, the operation of the fan 23 is stopped by the controller 27, the valve 13 is opened, the valve 26 is closed and the heat medium pressure in the enclosed pipeline 5 is regulated and controlled by increasing the pressure and temperature of the steam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an exhaust heat recovery device that supplies engine exhaust heat to a heat demand section through a closed pipe line filled with a heat medium.

An example of a conventional automotive heating system using this type of exhaust heat recovery device is shown in FIG. 1 (disclosed in Japanese Utility Model Application No. 56-140705).

In the figure, a recovery side heat exchanger 2 installed in an engine exhaust passage 1 and a heat transfer side heat exchanger 4 installed in a heat demand section 3 that leads engine cooling water to a heater core (not shown) are connected in a closed pipe line 5. connected. For example, superheated steam is sealed in the closed pipe line 5 as a heat medium, and is circulated within the closed pipe line 5 by a fan 7 driven by a motor 6.

The steam circulating in the closed pipe line 5 transfers the engine exhaust heat recovered by the recovery side heat exchanger 2 from the heat transfer side heat exchanger 4 to the heat demand section 3.
heat is transferred to and supplied to the cooling water (heater water) flowing through the water. In this way, exhaust heat is applied to the cooling water flowing from the heat demand unit 3 to the heater core to heat it, thereby exchanging heat in the heater core, increasing the temperature of the hot air blown into the vehicle interior, and increasing heating efficiency. There is.

Here, the means for controlling the pressure of the heat medium in the closed pipe line 5 is configured as follows. That is, the closed pipe line 5 is provided with a pressure switch 8 and a thermocouple 9 as a temperature switch.
Signals from these switches are input to the controller 10. Based on these, when the controller 1 detects that the steam pressure in the closed pipe line 5 has increased abnormally, it closes the closed pipe line 5.
The purge valve 11 installed in the closed pipe line 5 is driven open to discharge a part of the heat medium to lower the pressure, and after the heat medium is discharged by the purge valve 11, the injection valve installed in the closed pipe line 1
2 is driven to replenish the heat medium into the closed pipe line 5 and adjust the amount of heat medium.

However, in such a conventional device, in order to adjust the pressure in the closed pipe line 5, the heat medium in the closed pipe line 5 must be controlled by taking it in and out using a purge valve and an injection valve, and the heat medium for supply must be controlled by 1llJ. There is a problem in that it is necessary to always have the heat medium on hand, and that only a safe heat medium can be used because it is discharged to the outside.

The present invention has been made in view of such conventional problems, and is a method of temporarily increasing the flow rate of fluid flowing through a heat demand section in which a heat transfer side heat exchanger is installed when the pressure in a closed pipe line increases excessively. It is an object of the present invention to provide a heat medium pressure control device for an exhaust heat recovery device that solves the conventional problems as a configuration in which a flow rate control means is provided.

However, in the following figures, the same components as in the prior art are given the same reference numerals and explained.

The present invention will be explained below based on illustrated embodiments.

In FIG. 2 showing one embodiment, a recovery side heat exchanger 2 is installed in the engine exhaust passage 1, and a heat transfer side heat exchanger 4 is installed in the heat demand section 3 that supplies engine cooling water to the heater core. The connection via the closed pipe line 5 is the same as in the conventional case. Water as a heat medium is sealed in the closed pipe line 5, and the exhaust heat is absorbed by the recovery side heat exchanger 2, turned into steam, and supplied to the heat transfer side heat exchanger 4, where it is heated to the engine. After giving heat to the cooling water and turning it into condensed water, it is returned to the recovery side heat exchanger 2. That is, the closed pipe line 5 functions as a loop-type thermosiphon type heat vibrator and circulates naturally, so that the motor and fan for circulating the heat medium shown in FIG. 1 are unnecessary. however,
The present invention is not directly concerned with this, but can also be applied to a forced circulation type closed pipe line in which superheated steam is sealed.

Further, in the closed pipe line 5, a pressure switch 8 and a thermocouple 9 are provided at the upstream side of the recovery side heat exchanger 2, and an electromagnetic on-off valve 13 is provided at the downstream side of the recovery side heat exchanger 2.

Here, in the present invention, means for temporarily increasing the fluid flow rate to the heat demand section 3 when the heat medium pressure in the closed pipe line 5 rises excessively is provided as follows. That is, in this embodiment, the heat demand section 3
A fan blade driven by a motor 22 is interposed in the engine cooling water passage 21 on the upstream side.

However, an engine may be used as the power source instead of the motor 22.

On the other hand, the engine cooling water passage on the downstream side of the heat demand section 3 is branched into two, a main passage 24 that passes through the heater core, and a bypass passage 25 that bypasses the heater core and radiates heat from the cooling water.
In addition, an on-off valve 26 is provided in the bypass passage 25.

A controller 27 is provided to input signals from the pressure switch 8 and thermocouple 9, and the controller 27
The motor 22, the on-off valve 26, and the electromagnetic on-off valve 13 are controlled as follows. That is, if the amount of heat recovered from the exhaust gas by the recovery side heat exchanger 2 is large and the steam pressure in the closed pipe line 5 exceeds a certain set value, or if it becomes superheated steam and increases to a predetermined temperature or higher, The pressure is detected by the pressure switch 8 and thermocouple 9, and the output of the controller 27 drives the motor 22 to rotate the fan, and at the same time opens the closed on-off valve 13 via an actuator or the like, and opens the normally open solenoid on-off valve 13. close.

As a result, the flow rate of cooling water to the heat demand section 3 increases due to the rotation of the fan, and the heat transfer coefficient hw from the heat transfer side heat exchanger 4 to the engine cooling water increases, so that the steam in the heat exchanger 4 increases. The heat transfer rate K from the cooling water to the cooling water increases.

In particular, in this case, since the heat transfer coefficient hw on the heat demand section 3 side acts dominantly on the heat transfer rate, K also increases significantly as hw increases.

Therefore, if the temperature difference between the cooling water temperature Tw in the heat demand section 3 and the steam temperature TV in the heat transfer side heat exchanger 4 is the same, the amount of heat q transferred to the heat demand section 3 is q = K (Tv - Tw ), the amount of transferred heat q increases by the increase in the heat transfer rate, and the amount of steam condensed increases, making it possible to lower the steam pressure.

Also, at the same time as the fan 23 starts, the electromagnetic on-off valve 1 of the closed pipe line 5
3 is closed and the condensed water is stored upstream of the electromagnetic on-off valve 13, and the supply of condensed water to the recovery side heat exchanger 2 is stopped, so the generation of steam is stopped and the pressure in the closed pipe line 5 is reduced. . Specifically, the electromagnetic on-off valve 13 is closed, and the heat transfer side heat exchanger 4 is closed.
When the supply of the cooled condensed water to the recovery-side heat exchanger 2 is stopped, the water remaining in the recovery-side heat exchanger 2 is initially sufficiently overheated at a high temperature to reach or be close to saturation. As evaporation is promoted, vapor pressure temporarily increases. However, if this steam is cooled in the heat exchanger 4 on the heat transfer side and becomes condensed water, the amount of steam decreases and the steam pressure decreases as described above.

That is, when the electromagnetic on-off valve 13 is closed, the pipe line 5 is closed.
However, with the normal heat exchange capacity of the heat transfer side heat exchanger 4, the steam whose pressure has temporarily increased will not be cooled down quickly and it will take time for the pressure to decrease, resulting in problems such as durability, etc. This causes problems in terms of

However, in the present invention, as described above, by increasing the flow rate of cooling water to the heat demand section 3, the heat exchange capacity of the heat transfer side heat exchanger 4 is increased, and the steam whose pressure has increased is quickly cooled and condensed. By doing so, the steam pressure can be quickly reduced.

On the other hand, by increasing the cooling water flow rate of the heat demand section 3 in this way, the amount of heat recovered from the heat transfer side heat exchanger 4 to the cooling water increases, but since the on-off valve 26 is also opened at the same time,
When the bypass passage 5 is opened, the cooling water that has recovered heat flows through both the main passage 24 via the heater core and the bypass passage section, so the flow rate of the cooling water to the main passage 24 can be kept at the same level as normal. This prevents excessive heat supply to the heater core, prevents overheating of the hot air that exchanges heat with the heater core, and maintains stable and comfortable heating.

In addition, a bypass passage that bypasses the heat exchanger on the heat transfer side and an on-off valve that opens and closes the bypass passage are provided, and when the amount of cooling water increases, the bypass passage is also opened, and the cooling water whose heat is recovered by the heat exchanger on the heat transfer side and the bypass passage are provided. A configuration may also be adopted in which overheating of the hot air is prevented by mixing the cooling water that has been cooled by heat dissipation and guiding the mixture to the heater core. Steam pressure from such control,
When the temperature drops below a certain level, the controller 27 stops driving the motor 23, opens the electromagnetic on-off valve 13, and closes the on-off valve 26 to return to the normal state and raise the steam pressure and temperature. In this way, the pressure of the heat medium in the closed pipe line 5 can be adjusted and controlled without introducing or removing the heat medium to the outside, so there is no need to replenish the heat medium, and it is possible to use a heat medium that cannot be discharged to the outside, such as an organic body. I can do it.

FIG. 3 shows another embodiment of the invention. In the figure, the closed pipe line 5 is constructed in the same manner as in the embodiment shown in FIG. An accumulator 33 and a bypass passage 34 that bypasses the accumulator 33 are provided with a plunger 32 in the engine cooling water passage 31 on the upstream side of the heat demand section 3 in which the heat transfer side heat exchanger 4 is interposed. Bypass passage 3
4 is provided with an on-off valve 35, and on-off valves 36 and 37 are also provided at the inlet and outlet of the accumulator 33, respectively.

Then, these on-off valves 35, 36, 37, the electromagnetic on-off valve 13, the on-off valve 26 and the plunger 32 which are interposed in the bypass passage device of the heater core on the downstream side of the heat demand section 3,
Based on the signals from the pressure switch 8 and thermocouple 9, the controller 38 controls as follows. Normally, the on-off valves 36 and 37 are closed and the on-off valve 35 is open, while the electromagnetic on-off valve 13 is open and the on-off valve 26 is closed. Further, the plunger 32 is held at a position pushed up from the accumulator 33. Therefore, the cooling water is exclusively supplied to the heat demand section 3 through the passage 34, and the entire amount is supplied to the heater core through the main passage 24, thereby performing normal heating control. On the other hand, the steam pressure or temperature in the closed pipe line 5 is
If it becomes higher than each set value, pressure switch 8 or thermocouple 9
Based on the signal, the controller 3 closes the on-off valve 36,
The on-off valve 37 is opened, and the plunger 32 is driven and pushed down via an actuator (not shown) to push out the cooling water stored in the accumulator 33 from the outlet. On the other hand, the on-off valve 35 of the passage 34 is held open and the cooling water flows through the passage 34 as usual, so the flow rate of the cooling water in the heat demand section 3 increases by the amount pushed out from the accu-mulator 33.

Therefore, as in the previous embodiment, the condensing capacity of the heat transfer side heat exchanger 4 increases, the amount of steam in the closed pipe line 5 decreases, and the pressure can be lowered.

At the same time, the on-off valve 13 installed in the closed pipe line 5 is closed, so that, as in the previous embodiment, the temporary rise in steam pressure is quickly reduced by controlling the increase in the flow rate of cooling water from the accumulator 33. After that, the pressure can be lowered by reducing the amount of steam ordered.

Next, when the steam pressure and temperature drop below a certain level due to such control, the controller 38 controls the on-off valve 35 based on signals from the pressure switch 8 and thermocouple 9, which detect this.
．． 37 is closed and the on-off valve 36 is opened, the plunger 32 is simultaneously driven upward in the figure, thereby causing the accumulator 3 to open.
3. Cooling water is sucked in from the inlet and stored.

As shown in FIG. 4, the bypass passage of the accumulator 33 is omitted, and the on-off valves 41 and 42 provided at the inlet and outlet of the accumulator 33 are opened during normal times, and the on-off valves 41 and 42 provided at the inlet and outlet of the accumulator 33 are opened when steam pressure and temperature rise excessively. 41 and open the on-off valve 42 to push down the plunger 32. When storing cooling water in the accumulator 33, open the on-off valve 41 and open the on-off valve 42.
It may be configured to close and push down the plunger 32.

If a pump-type flow rate increasing means using a plunger or diaphragm is provided, the response delay caused by the start-up time of the motor, etc. can be eliminated, and the heat medium flow rate can be increased in steps to quickly generate steam, especially in an emergency. Pressure can be reduced.

As explained above, according to the present invention, by temporarily increasing the flow of the heat demand section fluid, the heat exchange rate between the heat transfer side heat exchanger and the heat demand section fluid is increased. Because the structure suppresses excessive rise in the heating medium pressure, the heating medium pressure in the closed pipe can be controlled without introducing or removing the heating medium, eliminating the need for replenishment of the heating medium, and using an organic fluid as the heating medium. It is also possible to use a substance that cannot be leaked to the outside.

[Brief explanation of drawings]

Figure 1 is a configuration diagram showing an example of a conventional exhaust heat recovery device;
The figure is a block diagram showing one embodiment of the present invention, FIG. 3 is a block diagram showing a second embodiment of the present invention, and FIG. 4 is a block diagram of a third embodiment in which a part of the second embodiment is modified. FIG. 3 is a configuration diagram showing main parts. ■...Exhaust passage 2...Recovery side heat exchanger 3.
... Heat demand section 4 ... Heat transfer side heat exchanger 5 ...
Closed pipe line 8...Pressure switch 9...Thermocouple 2
1.31...Engine cooling water passage 22...Motor Rule...Fan 27.38...Controller
32...Plunger 33...Accumulator
34...Aisle 35.36°37, 41.42.
...On-off valve patent applicant Nissan Motor Co., Ltd. Patent attorney Fujio Sasashima

Claims (1)

[Claims] a recovery side heat exchanger installed in the exhaust passage of the engine;
A closed pipe is formed by connecting a heat transfer side heat exchanger installed in a heat demand section through which the fluid to be heated flows, and a heat medium sealed in the closed pipe is circulated to transfer heat from the recovery side heat exchanger. In an exhaust heat recovery device that heats a fluid to be heated by supplying the recovered exhaust heat from a heat transfer side heat exchanger to a heat demand unit,
A means for detecting the heat medium pressure in the closed pipe line; and a flow rate control means for temporarily increasing the flow rate of the heated fluid flowing through the heat demand part when the heat medium pressure rises excessively based on the signal from the detecting means. 1. A heat medium pressure control device for an exhaust heat recovery device, characterized in that the device is configured by: