JPS6054600B2 - Temperature control method for heat pipe heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control method for a heat pipe heat exchanger, and in order to protect the heat pipe used in the heat exchanger, the operating temperature of the heat pipe is kept within the operating limit, and damage to the pipe body is prevented. This is to prevent a sudden drop in heat transfer characteristics.

Generally, a heat pipe heat exchanger is called a heater or a cooler depending on the purpose of use, but there are many types, and the following explanation will be given using an example of heat exchange that heats a low-temperature gas or liquid with a high-temperature gas.

Although the heat pipe is a heat transfer element having extremely high thermal conductivity, it has the following drawbacks (a) to (c).

(a) The operating temperature range is limited by the heat medium, and if the operating temperature range is exceeded, the operating pressure will increase, leading to damage to the tube. (b) When operated at a temperature above a certain temperature, the heat transfer medium decomposes or reacts with the pipe material, generating non-condensable gas, resulting in a sudden drop in performance.

(c) A single heat medium cannot cover a wide temperature range.

Due to the above-mentioned drawbacks, heat pipes have been mainly used in heat exchangers for air conditioning, where the high temperature side fluid inlet temperature of the heat exchanger is lower than the maximum operating temperature of the heat pipe.

By the way, if the above-mentioned drawbacks can be successfully overcome and some or all of the heat pipe can be used even when the maximum operating temperature of the heat pipe is below the high temperature side fluid inlet temperature, high heat transfer performance can be achieved. You can make a heat exchanger.

As shown in FIG. 1, such a heat exchanger includes a first heat exchanger 1 and a second heat exchanger 2, and a heat exchanger that penetrates a partition plate 3 between these heat exchangers 1 and 2. A large number of heat pipes 4a, 4b, . A method using a heat medium B having a relatively low temperature is known. Code 5a in the figure
, 5b are the inlet and outlet of the heat exchanger 1, 6a and 6b, respectively.
does not show the inlet and outlet of heat exchanger 2. Further, arrow A indicates the flow direction of the low-temperature side fluid, and arrow B indicates the flow direction of the high-temperature side fluid.・Second
The figure shows the operating temperatures of the heat pipes 4a, 4b, . . . , 4g. The one in Figure 1 above combines several groups of heat pipes with the optimal heat medium for each operating temperature range,
Although there are heat pipes that cover a wide temperature range, the heat pipe body (or operating temperature) can be set to an arbitrary value between the high-temperature side fluid inlet temperature and the low-temperature side fluid inlet/inlet temperature, and the exhaust gas can be used to inject fuel oil. When heating, the temperature of the tube is kept below the flash point of the fuel, or when heating water with exhaust gas, the temperature of the tube is kept above the acid dew point. The conventional heat exchanger described above has no problems when used under the planned usage conditions, but if the flow rate of the low-temperature fluid decreases or the temperature of the high-temperature fluid increases, part or all of the heat vibrator becomes overheated. This results in the above-mentioned drawbacks (a) and (b). For this reason, heat-vib heat exchangers have not been used much in the past for industrial waste heat recovery and the like. On the other hand, as a method for preventing overheating of a heat-vib heat exchanger, there is also known a method of detecting a decrease in the flow rate of a low-temperature fluid and shutting off a high-temperature fluid, as shown in FIG.

In FIG. 3, 7 is a heat-vib heat exchanger, 8 is a flow rate sensor, 9 is a heating side fluid cutoff valve, and 10 is a controller, and the flow rate of the cooling side fluid flowing in the direction of arrow C is detected by the sensor 8. The cutoff valve 9 is controlled by the controller 10 based on this detected value, and the heating side fluid is cut off by this control. Note that arrow D indicates the direction of flow of the heating fluid. The one shown in FIG. 3 above had the following drawbacks. (a) It is not possible to deal with overheating of the heat vibrator due to a decrease in heat transfer performance on the cooling side due to dirt or the like.

(b) It is not possible to cope with overheating of the heat vibrator due to a rise in temperature of the high-temperature fluid.

(c) It is not possible to cope with overheating of the heat vibrator due to an increase in the flow rate of the high temperature fluid.

(d) It is not possible to respond in detail to the individual conditions of each group of heat vibrators with different heat media.

The present invention eliminates the above-mentioned drawbacks and provides a temperature control method for a heat vibrator heat exchanger that can prevent overheating of the heat vibrator.

First, the basic configuration of the present invention will be explained in detail with reference to FIG.

In FIG. 4, 11 is a heat vibrator heat exchanger, and 12 is a heat vibrator, which are well known. 13 is a tube body temperature detection sensor provided in the heat vibrator 12;
4 is a controller, and 15 is a heating side fluid flow rate control valve.

In a heat exchanger having such a configuration, the sensor 13 detects the tube body temperature of the heat vibrator 12, and based on this detected value, the controller 14 drives the control valve 15, which controls the flow rate of the high-temperature fluid. , Heat Vibe 1
In order to prevent overheating of the heat vibrator 2, the temperature of the tube body of the heat vibrator 12 is kept within the operating limit. As schematically shown in FIG. 5, the sensor 13 may be attached to the first heat vibrator counted from the high temperature fluid inlet 16 side among the many heat vibrators 12. In FIG. 5, the same reference numerals as in FIGS. 3 and 4 indicate the same elements. The heat exchanger 11 shown in FIG. 5 is composed of one group of heat vibrators 12, but if it is composed of two or more groups of heat vibrators 12a, 12b as shown in FIG. heat vibe 12a,
12b, the tube body temperature j of the heat vibrator having the highest operating temperature may be detected. In FIG. 6, the same reference numerals as in FIGS. 3 and 4 indicate the same elements. Additionally, the mounting position of the sensor 13 in the heat vibes 12a and 12b is basically the boundary between the high temperature side and the low temperature side (operating temperature), which is known to approximate the internal temperature of the working fluid of the heat vibe. Although it is preferable that the temperature be on the high-temperature side or the low-temperature side, it does not matter. Sensor 13
If it is installed on the high temperature side, it will detect a temperature higher than the operating temperature, so it is safe, but if it is installed on the low temperature side, the indicated value will be lower than the operating temperature at that time, so be careful. . In FIG. 4, the flow rate of the fluid is controlled according to the detected temperature, but the heat transfer area of the tube may be changed according to the detected temperature. An embodiment of the present invention will be described below.

In this embodiment, the heat exchanger 11 shown in FIG.
The control valve 1 is controlled via the controller 14 according to the detected temperature.
5 was driven, and was applied to preheating fuel gas in a soaking furnace at a steelworks, and the exhaust gas flow rate was controlled so that the tube body temperature of the heat vibrator 12a, 12b was below the maximum operating temperature of each heat vibrator. Arrow E indicates the flow direction of so-called M gas, which is a mixture of blast furnace gas and coke oven gas, and arrow F indicates the flow direction of exhaust gas. In this example, (1) Exhaust gas type Soaking furnace combustion exhaust gas
Flow rate 0~2000Nd/h Temperature 5500C~80(1)0C'' (2)
Fuel gas Type M gas (2500Kca1/Nd)
Flow rate 0~2000N/h Temperature 20C (3) Dowsome heat pipe operating temperature MA x 320・
c (4) Water heat vibrator operating temperature MA x 200℃ (5
) Number of rows of heat vibes 7 rows of water heat vibes 17 rows of dowsome heat pipes (6) Thermocouple (sensor) mounting position...
・At the boundary between the heating side and the heated side, the temperature change was as shown in Figure 8.

FIG. 9 shows a heat-vib type hot water heater as another embodiment, in which the heat-transfer area is controlled so that the temperature of the exhaust gas-side tube body of the water heat-vibe 12 is equal to or higher than the acid dew point temperature. Control heat area.

The hot water of this hot water heater is for general refueling, and is 61℃ → 7℃.
There is a flow rate of 1.3 t/h at a temperature of 6°C. In FIG. 9, 17 is an exhaust gas passage, through which exhaust gas at a temperature of 600°C to 900°C passes. 18 is a tank disposed with a partition plate 19 between it and the passage 17, and 20 indicates water in the tank. The heat vibes 12 are disposed between the passage 17 and the tank 18, each of these heat vibes 12 is covered with a cutoff tube 21 made of oak, and the cutoff tubes 21 are connected to a drive section 22. There is. This drive section 2
2 is controlled via the controller 10 based on the temperature detected by the sensor 13 provided on the heat vibrator 12, and the cutoff tube 21 is controlled according to the temperature of the heat vibrator 12.
is moved up and down, thereby changing the contact area between the heat vibrator 12 and the water 20, and controlling the heat transfer area. This control made it possible to maintain the temperature of the exhaust gas side tube body at 20 degrees Celsius despite temperature fluctuations in the exhaust gas (600 degrees Celsius to 900 degrees Celsius). The movable range of the cutoff tube 21 relative to the heat vibrator 12 was 0 to 200 wR. With respect to the temperature change of the exhaust gas in this water heater, the temperature of the gas side tube wall of the heat vibrator was as shown in FIG. 10. The present invention is as described above,
Since the heating fluid is directly controlled by the temperature of the tube body of the heat vibe, it is possible to completely prevent the heat vibe from overheating.

Furthermore, it becomes possible to maintain the target value of the tube body temperature at an arbitrary value (within the usage limit), and fine temperature control of the heat exchanger becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional example, FIG. 2 is a diagram showing temperature characteristics of the one shown in FIG. 1, FIG. 3 is a block diagram showing another conventional example, and FIG. 4 is a block diagram of the present invention. FIG. 5 is a schematic diagram of the main part of FIG. 4, FIG. 6 is a schematic diagram showing a modification of the one in FIG. 5, and FIG. 7 is a configuration diagram of a heat exchanger used in an embodiment of the present invention. Fig. 8 is a diagram showing the temperature characteristics of the one shown in Fig. 7, Fig. 9 is a diagram showing the configuration of a water heater used in another example, and Fig. 10 is a diagram showing the temperature characteristics of the one shown in Fig. 9. . 12, 12a, 12b...chemical pipe, 15.
... Control valve, 21 ... Shutoff cylinder.

Claims (1)

[Claims] 1 Detect the temperature of the heat pipe body on the heating fluid inlet side,
A method for controlling the temperature of a heat pipe heat exchanger, characterized in that the flow rate of a fluid or the heat transfer area of the tube body is changed so that the temperature of the heat pipe tube body is below the operating temperature limit.