JPH0571882A - Porous body type heat exchanger and facilities where they are employed - Google Patents

Abstract

PURPOSE:To obtain a high efficiency heat exchanger which uses a hydrophobic porous film. CONSTITUTION:A large number of heat exchanger tubes made of a hydrophobic porous material 2, which allows the penetration of steam into the material but allows no penetration of liquid, are bundled. A low temperature fluid 1, which is liquid, is passed inside the heat exchanger tubes while a high temperature fluid 2, which is liquid or steam, is passed outside the heat exchanger tubes. It is acceptable even if this internal and external relation is opposite. When the high temperature fluid 2 is liquid, the liquid is vaporized and turned into steam, which penetrates the porous material and enters the low temperature fluid side where it is condensed and turned into liquid. The liquid itself which is a high temperature fluid is unable to penetrate the porous material. When the high temperature fluid is steam, the steam is partially condensed on the high temperature fluid side and turned into liquid drops. The liquid drops thus produced are unable to penetrate the porous material as well. In this manner, heat is transferred from the high temperature fluid 2 to the lower temperature fluid 1. The heat transfer based on thermal conduction of the porous body 2 is added to this heat transfer mechanism as well. It is, therefore, possible to inhibit the penetration with the porous material and prevent the mixture into the low temperature fluid even when there exist impurities in the fluid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly efficient porous heat exchanger using a hydrophobic porous membrane, and particularly to heat requiring high efficiency in a facility having a steam boiler such as a thermal power plant or a nuclear power plant. The present invention relates to a porous heat exchanger preferably used for an exchanger.

[0002]

2. Description of the Related Art Conventionally, heat exchangers for thermal power plants, nuclear power plants, etc. handle high-pressure fluids of 70 kg / cm ² or more, so metals with high thermal conductivity are used for heat transfer tubes, and fins are provided. Although the heat transfer characteristics have been improved by this method, it is difficult to make a dramatic improvement.

On the other hand, recently, there has been developed a liquid treatment technique using a hydrophobic porous membrane having a characteristic that vapor is permeable but liquid is not permeable. This technique is a kind of distillation method and is called a membrane distillation method. This technology is Japanese Patent Publication Sho 49-
Description will be made taking No. 45461 as an example. This example is intended for desalination of seawater and the like, and seawater of elevated temperature is brought into contact with one side of the hydrophobic porous membrane and cooled on the other side. As a result, the seawater on the high temperature side evaporates, the generated vapor diffuses and permeates the membrane surface, and condenses on the low temperature side. As a result, distilled water is obtained and desalination of seawater is achieved. In this method, by using a membrane having a large surface area such as a hollow fiber membrane, the evaporation area can be made larger than that of other distillation methods, so that the apparatus can be made compact.

On the other hand, as described in Japanese Patent Application No. 62-147870, it has been noted that the hydrophobic porous membrane has a large evaporation area and a large amount of heat transfer due to evaporation, and it is used for a refrigerator or the like. It is considered to be used for a cooling tower that radiates water to the outside air to cool it.

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention It is difficult to drastically improve heat transfer characteristics with a conventional heat exchanger using a metal heat transfer tube in a thermal power plant, a nuclear power plant, etc. On the other hand, a hydrophobic porous membrane is used. The cooling tower of the above-mentioned Japanese Patent Application is inappropriate or insufficient as a heat exchanger for thermal power and nuclear power plants.

The object of the present invention is to enable highly efficient heat transfer between a high-temperature fluid and a low-temperature fluid through a hydrophobic porous membrane, and is preferably used as a heat exchanger for thermal power and nuclear power plants. It is to provide a porous heat exchanger to be obtained. Another object of the present invention is to provide a thermal power plant, a feed water heating facility for a nuclear power plant, or a reactor water purification facility for a nuclear power plant, which uses the porous heat exchanger.

[0007]

A porous heat exchanger according to the present invention has the structure described in claim 1, claim 2, claim 3 or claim 4, and the porous heat exchanger is used. According to the present invention, there is provided the thermal power supply or the feed water heating equipment for a nuclear power plant according to claim 5 or 6.
The nuclear reactor water purification facility of a nuclear power plant of the present invention using the porous heat exchanger has the configuration according to claim 7.

[0008]

In the porous body heat exchanger, there are three combinations of the high temperature fluid and the low temperature fluid which are in contact with each other through the porous membrane as shown in FIG. As a heat exchanger, it is necessary to efficiently lower the temperature of the high temperature fluid and efficiently raise the temperature of the low temperature fluid. From this point of view, the three combinations are compared.

When both the high temperature fluid and the low temperature fluid in FIG. 5 are liquids, not only the heat transfer by heat conduction but
The high temperature fluid loses its heat of vaporization due to evaporation and its temperature drops,
On the other hand, the vaporized vapor permeates the membrane and enters the cryogenic fluid, where the vapor rises in temperature due to condensation of the vapor. Therefore, it is possible to efficiently change the temperatures of the high temperature fluid and the low temperature fluid. The liquid itself, which is a hot fluid, does not penetrate into the membrane and therefore does not impede the permeation of vapor, since the liquid itself has the property of being impermeable to liquid.

When the high temperature fluid is steam and the low temperature fluid is liquid, not only the heat is transferred by heat conduction but also the high temperature fluid vapor permeates the membrane and enters the low temperature fluid. The temperature rises due to condensation. On the other hand, on the high temperature fluid side, a part of the high temperature fluid is condensed by heat conduction. The resulting water droplets cannot penetrate the hydrophobic membrane,
Since it is removed by gravitational drop, the heat transfer surface can come into direct contact with steam, which is more efficient than ordinary heat transfer. Therefore, the temperature of the high temperature fluid can also be efficiently reduced.

When the high temperature fluid is a liquid and the low temperature fluid is a vapor, the heat of the high temperature fluid is removed by evaporation, but since it does not condense in the low temperature side fluid, the effect of increasing the temperature of the low temperature fluid is small. Therefore, another device is required to recover the heat in the cryogenic fluid.

Therefore, the method (1) is excellent as a heat exchanger from the viewpoint of temperature change. The porous heat exchanger of the present invention adopts the method of or.

[0013]

EXAMPLE An example in which the present invention is applied to a feed water heater of a BWR nuclear power plant is shown in FIG. In FIG. 2, 1 is a feed water heater comprising a porous heat exchanger according to the present invention, 10 is a reactor, 21 is a turbine, 22 is a condenser, 23 and 24 are pumps, and 25 is a conventional feed water heater. is there. The steam outlet of the nuclear reactor 10 and the high temperature fluid (steam) inlet of the feed water heater 25 are connected by a pipe 41, and the high temperature fluid (steam) outlet of the feed water heater 25 is a high temperature fluid (steam) inlet of the porous heat exchanger 1. Is connected by a pipe 42. The condenser 22 is connected to the low temperature fluid (liquid water) inlet of the porous body heat exchanger 1 via the pipe 3 and the pump 23, and the low temperature fluid (liquid water) outlet of the porous body heat exchanger 1 is a pump 24. Is connected to the low temperature fluid (liquid water) inlet of the feed water heater 25, and the low temperature fluid (liquid water) outlet of the feed water heater 25 is connected to the reactor 10.

Steam, which is a high-temperature fluid discharged from the reactor 10, has a temperature of 270 ° C. and a pressure of 70 kg / cm ² . A part of this steam enters the feed water heater 25 through the pipe 41,
In it, heat is exchanged with the low temperature fluid (liquid water coming from the pump 24) to become steam reduced to a temperature of about 150 ° C. and a pressure of about 5 kg / cm ² , and this steam is then fed to the pipe 42.
Through the heat exchanger into the porous heat exchanger, where it exchanges heat with the low temperature fluid (liquid water) coming from the pump 23. On the other hand, condensate, which is a low-temperature fluid coming from the condenser 22, is liquid water having a temperature of about 30 ° C., and this water enters the porous heat exchanger 1 from the pipe 3 via the pump 23, where it is mixed with the steam. The temperature is raised by the heat exchange of the water, then enters the feed water heater 25 via the pump 24, where it is finally heated to about 180 ° C. by the heat exchange with the steam, and then fed to the reactor 10. ..

Next, referring to FIG. 1, the porous heat exchanger 1 will be described.
The structure and action of is explained. In this porous body heat exchanger, a large number of heat transfer tubes made of a tubular porous body 2 which is a hydrophobic hollow fiber membrane shown in FIG. 1 (a) are bundled and installed as shown in FIG. 1 (b). Low temperature fluid (liquid water) F from the pump 23
1 flows in each heat transfer tube 2, while the high temperature fluid (steam) F2 coming from the pipe 42 flows outside each heat transfer tube 2. Here, the steam on the side of the high temperature fluid F2 flows through the porous body 2 into the low temperature fluid F2.
It diffuses and permeates to the first side, condenses on the low temperature fluid F1 side, and the condensed water goes to the pump 24 together with the low temperature fluid (water) F1 coming from the pump 23. At the same time, heat conduction occurs due to the porous body 2 itself. Further, also on the high temperature fluid F2 side, due to heat conduction,
Part of the water vapor condenses into water droplets, but these water droplets cannot pass through the porous body 2 that is the hydrophobic porous film to the low temperature fluid F1 side, and fall down to be collected separately.

Heat transfer coefficient H at this time (kcal / m ² h ° C.)
As a result of the experiment, it was found that is given by

H = (K / δ) · ΔP _S / ΔT Here, K is a constant (= 21 (kcal / m ² h ° C.) · (m /
atm)), δ is the thickness (m) of the porous body 2, ΔP _S is the vapor pressure difference (atm) between the high temperature fluid F2 and the low temperature fluid F1, and ΔT is the temperature difference (° C) between the high temperature fluid F2 and the low temperature fluid F1. .. A trial calculation will be made for the case of this embodiment. The inlet temperature and outlet temperature of the high temperature fluid are 150 ° C and 50 ° C, respectively, and the inlet temperature and the outlet temperature of the low temperature fluid are 30 ° C and 100 ° C, respectively.
Assuming that the vapor pressure on the low temperature fluid side can be ignored, ΔP _S = (vapor pressure at inlet temperature of high temperature fluid of 150 ° C. + vapor pressure at outlet temperature of high temperature fluid of 50 ° C.) / 2 = (4.7+
0.1) /2=2.4 atm Also, ΔT = (high temperature fluid temperature−low temperature fluid temperature) / 2 = ((15
0 ° C + 50 ° C) / 2 + (100 ° C + 30 ° C) / 2)) /
2 = 83 ° C When δ is 0.001m, the heat transfer coefficient H is 600kcal /
m ² h ° C. On the other hand, when the heat transfer tube is not a porous body as described above but a conventional metal tube, the heat transfer coefficient due to only heat conduction is 13 kcal / m ² h when other conditions are the same.
It is found that the heat transfer coefficient is about 50 times higher in the porous heat transfer tube of the embodiment of the present invention.

Next, the heat resistance of the porous body 2 will be described. The inventors' study of the material at high temperature revealed that when an organic polymer porous material is used, it is difficult to use it for a long time at a temperature higher than the glass transition temperature at which the physical properties start to change. Here, from this viewpoint, PTFE (glass transition temperature 150 ° C.) was used as the porous body 2. Although the glass transition point of PTFE is 130 ° C. in the general literature value, the molecular weight of industrial products is higher than that in the literature, and the glass transition point tends to be high.

Next, the pressure resistance of the porous body 2 will be described. The pressure resistance of the porous body is determined not only by mechanical strength but also by water resistance. The hydrophobic porous body has a property of allowing water vapor to pass therethrough, but it permeates water when the pressure of water increases. The following relationship holds for the upper limit value of the pressure at which water does not permeate the porous body (this is called the water pressure resistance of the porous body) P and the pore diameter d of the porous body.

P = -4σ cos θ / d where σ is the surface tension of the liquid (water in this case), and θ is the angle (contact angle) between the liquid and the porous material. Here, PTFE with a pore size of 0.1 μm is used as a practical range.
A membrane was used. The water pressure resistance P of this membrane can be calculated by the above formula and is 12 kg / cm ² . The operating condition of the reactor 10 is 70
Compared with kg / cm ² , the above water pressure resistance value is small.
Therefore, it is necessary to take measures for driving. As a countermeasure against this, in this embodiment, the pump 23 is provided and the discharge pressure of the pump 23 is adjusted to 5 kg / cm ² or more (to suppress boiling of the high-temperature high-pressure fluid) to 12 kg / cm ² or less. On the other hand, the boost pressure of the pump 24 is 70- (5-12) = 65.
It was adjusted to ~58kg / cm ^2, thereby, was set to obtain a pressure operating conditions serving 70 kg / cm ² of the reactor 10. As a result, the pressure in the porous body heat exchanger 1 can be set to the water pressure resistance of the porous body 2 of 12 kg / cm ² or less.

According to this embodiment, since the high heat transfer coefficient can be obtained, the size of the feed water heater can be reduced to 1/50 of that of the conventional one.
And can be made smaller. Further, when the size of the feed water heater is not changed, the thermal efficiency can be greatly improved.

Next, FIG. 3 shows an embodiment in which the present invention is applied to a reactor water purification system of a nuclear power plant. In FIG. 3, reference numeral 1 is a porous heat exchanger according to the present invention (the structure of which is shown in FIG.
10 is a reactor, 11 is a regenerative heat exchanger,
Reference numeral 12 is a non-regeneration heat exchanger, 13 is a reactor water purification device, and 14 is a pump. The high temperature fluid inlet of the reactor 10 and the regenerative heat exchanger 11 are connected by a pipe 43, and the high temperature fluid outlet of the regenerator 11 is connected to the high temperature fluid inlet of the porous heat exchanger 1 and the pipe 44.
The high temperature fluid outlet of the porous heat exchanger 1 is connected to the pipe 45.
Is connected to the high temperature fluid inlet of the non-regenerative heat exchanger 12, and the high temperature fluid outlet of the non-regenerative heat exchanger 12 is connected to the inlet of the reactor water purifying device 13. The outlet of the reactor water purifying device 13 is connected to the low temperature fluid inlet of the porous body heat exchanger 1 by the pipe 31 via the pump 14, and the low temperature fluid outlet of the porous body heat exchanger 1 is the pipe 32.
Is connected to the low temperature fluid inlet of the regenerative heat exchanger 11, and the low temperature fluid outlet of the regenerative heat exchanger 11 is connected to the nuclear reactor 10 by the pipe 33. Further, the low temperature fluid side of the non-regenerative heat exchanger 12 is connected to the cooling system (not shown) of the power plant.

The high temperature fluid (reactor water) 4 discharged from the nuclear reactor 10 is liquid water having a temperature of 270 ° C. and a pressure of 70 kg / cm ² . This is cooled by the regenerative heat exchanger 11, and the temperature is 120 to 150.
The temperature reaches ℃, and about 50% of the heat can be recovered. The pressure at this time is 70 kg / cm ² and hardly changes. The hot fluid (reactor water) 4 exiting the regenerative heat exchanger 11 enters the porous heat exchanger 1 according to the present invention, where it is further cooled. After that, the temperature passes through the non-regenerative heat exchanger 12, and the temperature drops to 30 ° C. This reactor water is then purified by the purifying device 13, and then as a low temperature fluid (liquid water) via the pump 14 and the pipe 31.
Entering the porous heat exchanger 1, the pipe 32, the regenerative heat exchanger 11
And is heated to about 180 ° C., and finally returns to the reactor 10 through the pipe 33.

Here, in the porous body heat exchanger 1, a high-temperature fluid flows outside the porous body 2, which is a hydrophobic hollow fiber membrane, and a low-temperature fluid flows inside the porous body 2 (however, the relationship may be reversed).
The heat transfer will be described in detail. In this embodiment, both the high temperature fluid and the low temperature fluid are liquid water. The heat conduction by the porous body 2 occurs, evaporation occurs in the high temperature fluid, and the evaporated water vapor diffuses and permeates the porous body 2 to the low temperature fluid side and condenses on the low temperature fluid side. The porous body 2 is hydrophobic, and water does not permeate in the form of liquid from the high temperature fluid side to the low temperature fluid side. Since only the water vapor moves through the porous body, the impurities on the high temperature fluid side do not move to the low temperature fluid side.

The heat resistance of the porous body is the same as that of the first embodiment. Further, the pressure resistance is the same as that of the first embodiment, but the pressures on the high temperature fluid side and the low temperature fluid side are almost the same as the pressure inside the reactor and there is no pressure difference (the pump 14 is Since it is for liquid transfer and has almost no role of pressurization), the water pressure resistance of the membrane will not be exceeded even if no means for adjusting the pressure is provided.

According to this embodiment, since a high heat transfer coefficient can be obtained, the size of the heat exchanger of the reactor water purification system can be reduced, and the size of the heat exchanger is not changed. The thermal efficiency can be greatly improved. Further, the size of the purification device 13 can be reduced.

In each of the above embodiments, PT which is an organic polymer is used.
Although the porous body made of the FE film is used, a heat transfer tube made of a multi-layered film may be used. FIG. 4 shows an example of the structure of a heat transfer tube having a multilayer structure. In this embodiment, a porous body 2 of a hydrophobic organic polymer is provided inside and outside a tube 6 of a porous body such as a metal having high mechanical strength. According to this embodiment,
The mechanical strength of the heat transfer tube can be increased. Further, since the hydrophobic porous bodies 2 are provided on both the inner and outer sides, water as a liquid that prevents vapor permeation does not enter the porous metal body 6.

In the above examples, the organic polymer porous body was used. However, since carbon has hydrophobicity, a porous sintered body of a carbon inorganic compound such as carbon, boron carbide or nitrogen carbide is used as the porous body. Can be used. According to this embodiment, both heat resistance and pressure resistance can be increased. In this case as well, as in FIG. 4, a heat transfer tube having a multilayer structure may be used.

[0029]

According to the present invention, a porous heat exchanger having a high heat transfer coefficient can be obtained. Therefore, by using this, a heat exchanger such as a feed water heater or a reactor water purification system heat exchanger can be obtained. The size of the vessel can be significantly reduced. Further, when the size of the heat exchanger is the same as the conventional one, the thermal efficiency can be greatly improved.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of a porous heat exchanger of the present invention.

FIG. 2 is a diagram showing an embodiment in which a porous heat exchanger according to the present invention is applied to a water supply system of a nuclear power plant.

FIG. 3 is a diagram showing an embodiment in which the porous heat exchanger according to the present invention is applied to a reactor water purification system of a nuclear power plant.

FIG. 4 is a view showing another embodiment of the porous heat exchanger according to the present invention.

FIG. 5 is an explanatory view of the combination and action of both the high temperature fluid and the low temperature fluid of the porous body heat exchanger.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Porous body heat exchanger 2 ... Porous body 6 ... Porous metal tube 10 ... Reactor 11 ... Regeneration heat exchanger 12 ... Non-regeneration heat exchanger 13 ... Reactor water purification device 21 ... Turbine 22 ... Condenser 23, 24 … Pump 25… Water heater

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshitaka Nishino 1168 Moriyama-cho, Hitachi City, Ibaraki Prefecture Hiritsu Manufacturing Co., Ltd.Energy Research Institute (72) Makoto Baba 1168 Moriyama-cho, Hitachi City, Ibaraki Prefecture Hiritsu Co., Ltd. (72) Inventor Toshio Sawa 1168 Moriyama-cho, Hitachi City, Ibaraki Pref.

Claims (7)

[Claims] 1. A high-temperature fluid in a liquid or vapor state and a low-temperature fluid in a liquid state are brought into contact with each other through a heat transfer tube made of a porous material that allows vapor to pass through but does not allow liquid to pass through. And a porous heat exchanger. 2. The porous heat exchanger according to claim 1, wherein the porous body is made of an organic polymer material having a glass transition temperature equal to or higher than the temperature of the high temperature fluid. 3. The porous heat exchanger according to claim 1, wherein the porous body is made of carbon or a carbon inorganic compound. 4. A high-temperature fluid in a liquid or vapor state and a liquid state via a heat transfer tube covering the inside and the outside of a porous tube having a high mechanical strength, which is a porous body permeable to vapor but impermeable to liquid. A heat exchanger for porous bodies, characterized in that it is configured so as to be brought into contact with the low temperature fluid. 5. In a feed water heating facility of a thermal power or nuclear power plant, the porous heat exchanger according to claim 1, 2, 3 or 4 is used as a feed water heater, and the high temperature fluid is steam generated in the power plant. , A feed water heating facility for a thermal power or nuclear power plant, characterized in that a low temperature fluid is used as the feed water. 6. The water supply pump pressure is adjusted so that the pressure difference between the high temperature fluid and the low temperature fluid is not more than the water pressure resistance of the porous body.
Water heating equipment for thermal power or nuclear power plants. 7. A reactor water purification facility for a nuclear power plant, wherein the porous heat exchanger according to claim 1 is used as a heat exchanger in the facility, and the high-temperature fluid from the reactor goes to the reactor water purification device. A reactor water purification facility for a nuclear power plant, characterized in that it is water, and low-temperature fluid is used as reactor water that exits the reactor water purification device and returns to the reactor.