CN102878842A - Novel initiative jet cooling device - Google Patents

Abstract

A novel active spray cooling device belongs to the field of long-term non-destructive storage and transportation of cryogenic liquids. It includes a shell, heat transfer tubes, fins and a forced jet pump; fins are added to the outside of the cold end of the heat transfer tubes, and the heat transfer tubes are drop-shaped symmetrical special-shaped tubes; the cross-sectional shape of the fins is consistent with the The cross-sectional shapes of the special-shaped tubes of the heat transfer tubes are the same. The invention solves the problem of low efficiency of the conventional low-temperature liquid active storage and transportation system, and has important practical significance for the long-life and non-destructive storage and transportation of cryogenic liquids (liquid hydrogen, liquid oxygen, liquid nitrogen, liquid helium), especially for The space storage of low-temperature liquid effectively solves the problem of space energy shortage, improves system performance, and prolongs the effective working cycle of the low-temperature storage system.

Description

A New Type of Active Ejection Cooling Device

technical field

The invention relates to a novel active jet cooling device, which belongs to the field of long-term non-destructive storage and transportation of cryogenic liquids, and is especially suitable for space storage of cryogenic liquids.

Background technique

With the large-scale application of cryogenic liquids in the industrial field, the requirements for long-life and non-destructive storage and transportation of cryogenic liquids are getting higher and higher. Since the acquisition of cryogenic liquid must consume a lot of energy, the long-life storage and transportation of cryogenic liquid is also an important way to achieve energy saving. As we all know, only the liquid below the ambient temperature is called cryogenic liquid, usually the temperature is below minus 150°C. Therefore, various external heat leakage from the environment will inevitably lead to the endothermic phase transition of the cryogenic liquid, resulting in the failure of the cryogenic storage tank. The pressure increases, which in turn affects the safe use of the tank. In order to avoid the mechanical damage caused by the overpressure of the low-temperature storage tank, the vaporized gaseous substances must be discharged out of the tank in time, which will inevitably result in waste of low-temperature liquid and energy.

At present, cryogenic storage tanks are divided into ground and space according to different places of use. For ground cryogenic liquid storage tanks, since the energy is relatively abundant and easy to obtain, the method of constant pressure emptying can still be adopted without considering energy waste. However, for the reality that space energy is extremely scarce and difficult to obtain, the use of constant pressure discharge not only wastes energy and reduces the effective performance of cryogenic liquids, but also increases the cost of space launches; at the same time, due to the particularity of space flight, the exhaust will interfere The flight attitude increases the difficulty of control.

Therefore, it is of great significance to realize the long-life and non-destructive storage and transportation of cryogenic liquids for improving the performance of cryogenic liquids and realizing energy saving. The long-life and non-destructive storage and transportation technology of cryogenic liquid refers to the use of advanced low-temperature refrigeration and low-temperature insulation technologies to balance the leakage heat loss of the cryogenic liquid storage tank, so that the evaporation rate of the cryogenic liquid in the storage tank is significantly reduced, or even reduced to zero, and maintained A storage method in which the internal pressure of a cryogenic liquid storage tank is constant. In 2005, NASA proposed a non-destructive storage system. This structure uses traditional cylindrical heat pipes and side mixers to enhance heat transfer and improve heat transfer efficiency. However, this structure has greater resistance and enhances heat transfer effects. poor. U.S. Patent US 2007/0193282 A1 proposes a low-temperature storage method and system for cryogenic liquids. This solution utilizes the difference in working temperature between liquid oxygen and liquefied natural gas, and uses liquefied natural gas to cool the outer wall of the liquid oxygen storage tank, thereby reducing external heat leakage At the same time, the internal refrigeration system is used to cool the liquid oxygen and reduce the average storage temperature of the liquid oxygen, so as to realize the non-destructive storage of the cryogenic liquid. However, this scheme uses two types of cryogenic liquids, the structure is complex, and the control is difficult.

Contents of the invention

For this reason, the purpose of the present invention is to solve the problem of unsatisfactory heat transfer in the flow dead zone of traditional circular heat pipes and fins in the prior art, and to improve the heat exchange of the space cryogenic liquid storage tank heat exchange elements by adopting the structure of symmetrical special-shaped tubes. Thermal efficiency, reducing the low-speed zone on the leeward side, reducing flow resistance, and improving the efficiency of the forced jet pump, thereby achieving an overall improvement in system performance.

In order to achieve the above object, the technical solution adopted by the present invention is: a novel active spray cooling device, including a shell, a heat transfer tube, fins and a forced jet pump; fins are added to the outside of the cold end of the heat transfer tube, The heat transfer tube is a symmetrical special-shaped tube; the cross-sectional shape of the fin is the same as the cross-sectional shape of the special-shaped tube of the heat transfer tube.

The axis of symmetry of the heat transfer tubes and fins is perpendicular to the centerline of the outlet of the forced jet pump.

The forced injection pump uses pulse or variable frequency mode injection.

The fins are slotted fins, shutters or corrugated fins.

The outer surface of the shell is wrapped with multiple layers of heat insulating material.

The present invention improves the energy efficiency of the low-temperature liquid storage tank from two aspects: (1), through the design of the drop-shaped symmetrical heat transfer tube, the flow resistance of the low-temperature liquid is reduced, the heat transfer characteristics of the heat transfer surface are improved, and the (2) Add fins to the cold end of the heat transfer tube to increase the heat transfer area, especially the corresponding symmetrical special-shaped tube structure, which further eliminates the dead zone on the leeward side and improves the heat transfer characteristics. Contribute to the improvement of system energy efficiency.

The invention solves the problem of low efficiency of conventional low-temperature liquid active storage and transportation systems, and has important practical significance for the long-life and non-destructive storage and transportation of cryogenic liquids (liquid hydrogen, liquid oxygen, liquid nitrogen, liquid helium), especially for The space storage of cryogenic liquid effectively solves the problem of space energy shortage, improves system performance, and prolongs the effective working period of the cryogenic storage system.

The structure of the invention is compact, simple and efficient, and is suitable for long-term non-destructive storage and transportation requirements of various types of cryogenic liquids.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the top view of Fig. 1;

Fig. 3 is a comparative diagram of fluid flow velocity distribution at 8 mm from the cold end of the heat pipe;

Fig. 4 is a comparison diagram of fluid temperature distribution at 8 mm from the cold end of the heat pipe;

Fig. 5 is the temperature distribution curve of the outer wall of the storage tank;

Fig. 6 is the comparison diagram of the effect of the average velocity in the storage tank;

Figure 7 is a comparison diagram of the effect of the average temperature in the storage tank.

Detailed ways

The present invention and its beneficial effects will be further described in detail below in conjunction with the accompanying drawings.

Referring to Figures 1 and 2, a new type of active spray cooling device includes a cylindrical tank shell 1 with an ellipsoidal top and bottom and a water-drop-shaped symmetrical special-shaped heat transfer tube 2 placed inside the shell 1. The water-drop-shaped symmetrical The cold end 3 of the special-shaped heat transfer tube 2 is located in the middle part of the shell 1, and fins 4 are installed on the outside of the cold end 3 to increase the heat exchange area of the heat pipe, and the cross-sectional shape of the fin 4 is consistent with that of the heat transfer tube 2. The cross-sectional shape of the special-shaped tube is the same. A forced jet pump 5 is arranged in the middle of the shell 1, and the outlet is facing the cold end 3 of the heat transfer tube, so as to strengthen the heat exchange between the cold end 3 of the heat transfer tube and the surrounding thermal fluid. There is a cooling system outside the tank shell 1 to cool the hot ends of the heat transfer tubes.

The forced injection pump 5 can achieve pulsation or variable frequency injection by changing its working frequency, so as to realize the disturbed heat transfer between the cold end of the heat transfer tube and the cryogenic liquid, which helps to reduce the boundary layer, improve the heat transfer capacity, and further achieve the effect of energy saving .

The fins 4 can adopt various reinforced fin structures, such as slotted fins, louvers, and corrugated fins, to further improve the heat transfer characteristics of the fin side to achieve energy-saving effects

The outer surface of the casing 1 is wrapped with multiple layers of heat insulating material to reduce the heat leakage from the external space to the interior of the storage tank.

The present invention not only achieves a good effect when the flow rate at the outlet of the forced jet pump 5 is high, but also has a very obvious effect when the flow rate at the outlet of the forced jet pump 5 is low. Fig. 3 and Fig. 4 are comparison diagrams of the flow and heat transfer effects of circular heat transfer tubes and drop-shaped special-shaped heat transfer tubes, under the premise of the same forced jet pump 5 outlet flow rate, the leakage heat of the storage tank wall and the same heat transfer area Below, the fluid velocity and temperature distribution curve at 8mm from the cold end of the heat transfer tube (curve L). It can be seen from Figure 3 that the fluid velocity near the drop-shaped special-shaped heat transfer tube is higher than that near the circular heat transfer tube, which ensures that the cold end of the water-drop-shaped special-shaped heat transfer tube has a higher convective heat transfer coefficient and higher heat transfer efficiency. It can be seen from Figure 4 that the temperature of the fluid near the drop-shaped special-shaped heat transfer tube is lower, which is the result of better heat exchange effect produced by the higher fluid velocity near the cold end of the heat transfer tube. Fig. 5 is the temperature distribution curve of the outer wall surface of the storage tank (curve H) under the premise of the same heat leakage, the same forced jet pump 5 outlet speed and the same heat transfer area of the drop-shaped symmetrical special-shaped and circular heat transfer tubes. In the figure, the temperature of the outer wall of the storage tank using the drop-shaped symmetrical special-shaped heat transfer tube is lower than the temperature of the outer wall of the storage tank using the traditional round heat transfer tube, which shows that the drop-shaped special-shaped heat transfer tube is better than the traditional round heat transfer tube. The thermal effect can maintain the lower temperature of the cryogenic liquid under the same heat leakage condition, which realizes the reduction of power consumption and improves the utilization rate of energy in the case of extremely scarce space energy. Figures 6 and 7 are bar graphs, respectively, of the average velocity and average temperature of the fluid inside the entire tank. It can be seen from Figure 6 that the average velocity (V=0.00392m/s) of the drop-shaped heat transfer tube is 6.6% higher than that of the cylindrical heat transfer tube (V=0.00366m/s). It can be seen from Figure 7 that the average temperature (T=31.75K) of the drop-shaped special-shaped heat transfer tube is 4.3% lower than that of the cylindrical heat transfer tube (T=33.17K). This shows that under the same pump power, the drop-shaped special-shaped heat transfer tube can achieve better mixing effect and cooling effect, that is to say, to achieve the same mixing effect and cooling effect, the use of special-shaped heat transfer tube can save pump power.

In addition, through the in-depth analysis of the flow field and temperature field, we can get the reasons for the good performance of the cryogenic liquid storage tank with drop-shaped special-shaped heat transfer tubes. When the fluid is sprayed from the outlet of the forced jet pump to the cold end of the heat pipe, the fluid forms a bypass flow, and there is a large area of low-velocity zone on the leeward side of the circular heat transfer tube. Because the flow velocity is too low, it cannot be separated from the leeward side in time to form The dead stagnation zone is eliminated, resulting in poor heat transfer effect, and the streamlined design of the drop-shaped special-shaped heat transfer tube effectively reduces the area of the low-velocity zone and increases the average flow rate near the heat transfer tube, thus significantly improving the heat transfer efficiency. In addition, when the high-temperature incoming flow flows around the round tube, the fluid will separate from the round tube earlier, but the special-shaped heat transfer tube can well keep the fluid flowing against the wall, which is helpful for improving the heat transfer efficiency of the cold end of the heat transfer tube. The important significance is also an important reason for the improvement of the heat exchange efficiency of the drop-shaped special-shaped heat transfer tube storage tank.

The working process of the present invention is as follows:

Take the space cryogenic liquid storage tank as an example: in space, due to the influence of the space thermal environment such as solar radiation, earth infrared radiation, planetary albedo, cold black background, etc., the propellant storage tank continuously leaks heat into the aircraft. The initial state of the storage tank is an initial temperature of 20K and an initial pressure of 2 atm. At this time, the external cooling system of the storage tank is not activated, and the heat transfer tube is not working. With the leakage of heat, the temperature and pressure of the propellant inside the storage tank begin to rise. After a period of time, the temperature of the propellant inside the tank reaches the saturation temperature of the propellant. At this time, the pressure inside the tank begins to rise rapidly. When the pressure reaches the set value, the cooling system outside the tank is turned on. At this time, The heat pipe starts to work and continuously removes heat from the inside of the storage tank. At the same time, the forced injection pump is turned on and sprays against the cold end of the heat transfer tube, which improves the heat exchange efficiency of the cold end and makes the fluid in the entire tank However, due to the existence of local dead zones on the wall, there is inevitably a certain range of local high-temperature regions. When the temperature and pressure of the propellant inside the tank drop to the initial value with the removal of heat, the refrigeration system and the forced injection pump are turned off. When the temperature and pressure inside the storage tank reach the set value again, the cooling system and the forced mixing pump are turned on again, thus forming a cycle. Through this design, the refrigeration system and jet pump only need to work intermittently to maintain the internal pressure of the tank and achieve zero evaporation, which not only reduces energy consumption, but also prolongs the service life of the refrigeration system and forced jet pump.

The above description is only the best specific embodiment of the present invention, but the structural features of the present invention are not limited thereto, and any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the present invention. within the scope of the patent.

Claims (5)

1. a novel active injected cool radiator cooler comprises shell (1) and heat-transfer pipe (2), fin (4) and forced jet pump (5); Described heat-transfer pipe (2) cold junction (3) installs fin (4) additional, it is characterized in that: described heat-transfer pipe (2) is symmetrical shape tube; The shape of cross section of described fin (4) is identical with the shape tube shape of cross section of described heat-transfer pipe (2).

2. a kind of novel active injected cool radiator cooler according to claim 1 is characterized in that: the symmetry axis of described heat-transfer pipe (2) and fin (4) is vertical with the center line of forced jet pump (5) outlet.

3. a kind of novel active injected cool radiator cooler according to claim 1 and 2 is characterized in that: described forced jet pump (5) employing pulsation or variable mode injection.

4. a kind of novel active injected cool radiator cooler according to claim 1, it is characterized in that: described fin (4) is wing or shutter or the ripple wing of cracking.

5. a kind of novel active injected cool radiator cooler according to claim 1 is characterized in that: described shell (1) outer surface wrapped multiple heat-barrier material.

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