JPH0245645Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to an evaporator for vaporizing low-temperature liquefied gas, and particularly to an air-heated pressurized evaporator for low-temperature liquefied gas storage tanks. [Prior Art] Storage tanks for low-temperature liquefied gas such as cold evaporators are equipped with air-heated liquefied gas evaporators (pressurized evaporators) that use air as a heat source. This is often installed under the outside of the bottom of the storage tank for evaporating a small amount of liquefied gas necessary to increase the internal pressure of the storage tank in order to send out a predetermined amount of liquefied gas from the storage tank at a predetermined pressure. This conventional air-heated pressurized evaporator was constructed by welding twelve finned U-shaped heat transfer tubes 1 to a header 2 in parallel, as shown in FIGS. 4 and 5. However, this configuration requires a large number of welding points, such as welding the heat exchanger tube 1 and header 2, welding the cap 3 at the end of the header 2, and welding the inlet/outlet flanges 4, 4', and requires a large number of manufacturing man-hours. Due to the shape of the welded portion 5 between the heat tube 1 and the header 2, thermal stress concentration due to welding is likely to occur, and at the same time, thermal stress at low temperatures also becomes excessive. In response to these stresses, since the heat exchanger tube 1 is made of an aluminum alloy and the header 2 is made of a different kind of aluminum alloy, the strength of the welded portion is relatively low, and there is a problem that cracks may occur with repeated use. Note that 6 is a heat dissipation fin. Furthermore, extremely strict quality conditions are required for the quality of semiconductor industrial gases, which have been in increasing demand in recent years, and it has become necessary for the material of the supply equipment to be made of stainless steel (hereinafter referred to as SUS). Therefore, the parts of the pressurized evaporator that come in contact with the gas are
It is becoming increasingly necessary to use SUS. Furthermore, recently, high pressure containers have come into widespread use, and as the filling pressure increases, evaporators are also required to have high pressure resistance. Furthermore, cold evaporators come in a wide variety of capacities, and the pressurized evaporators attached to them are also required to have various capacities. A pressurized evaporator of each capacity was manufactured and installed. [Problems that the invention aims to solve] As described above, conventional pressurized evaporators made of aluminum alloy have many welded parts due to their structure, which not only requires a large number of manufacturing steps, but also has the disadvantage of cracking due to use over time. In addition, from the demand side, evaporation tubes are required to be made of SUS. Furthermore, various types of pressurized evaporators are required depending on cold evaporators of various capacities, but if these were manufactured each time, the number of man-hours required for manufacturing would increase and there would be a problem in that prompt response could not be achieved. Furthermore, in conventional products, the spacing between each fin is not optimal, so
In some cases, frost adhering to the surface of the fins grows over time and covers the entire evaporator, degrading the performance of the evaporator. [Means for Solving the Problems] The present invention has been developed in view of the above-mentioned problems, and a predetermined number of rectangular heat dissipation fins made of aluminum or aluminum alloy are provided with two small holes. One evaporation tube unit is made by inserting the heat dissipation fins into the fins, which are arranged almost parallel to each other with a predetermined spacing between them, and at least two of the evaporation tube units are This is a pressurized evaporator for a low-temperature liquefied gas storage tank, characterized in that it is constructed by connecting a single tube in series. Further, the inner diameter of the small hole provided in the aluminum or aluminum alloy heat dissipation fin is shaped like the U-shape.
The feature is that a hole is bored slightly smaller than the outer diameter of the SUS pipe, the edge of the small hole is bent, and the outer circumferential surface of the SUS pipe is inserted and fitted so as to be in close contact with the bent edge, and furthermore, A pressurized evaporator for a low-temperature liquefied gas storage tank, characterized in that the distance between the heat dissipation fins is 15 mm to 25 mm, and the size (area) of the heat dissipation fins is 10 to 30 times the cross-sectional area of the SUS pipe. It is. [Operation] As mentioned above, the liquefied gas evaporator of the present invention is U-shaped.
One evaporator tube with fins is constructed by fitting multiple aluminum or aluminum alloy fins into a SUS heat transfer tube through holes smaller in diameter than the heat transfer tube.
A plurality of units are connected according to the capacity required as a pressurized evaporator, and an inlet/outlet flange is connected to the inlet and outlet of the unit, respectively, to form one pressurized evaporator. With this configuration, in the case of a pressurized evaporator consisting of a finned evaporator tube unit, there are only five pipe parts: a U-shaped SUS pipe, a connecting bend pipe, an inlet/outlet elbow, and an inlet/outlet flange. Moreover, these connections required only six welds. The conventional pressurized evaporator has 30 welding points for the same capacity, so the number of welding points can be significantly reduced and manufacturing costs reduced. In addition, by eliminating the header 2 used in conventional models and making all gas paths a single pipe, stress concentration and thermal stress caused by low temperatures are reduced, preventing damage and further reducing pressure loss. Obtained. Materials are SUS for heat transfer tubes, bend tubes, and flange parts.
By making it a manufactured product, it has high mechanical strength and pressure resistance, and can also be used as a gas evaporator for the semiconductor industry. As mentioned above, the aluminum or aluminum alloy fins were constructed by inserting the heat transfer tube into two holes with a slightly smaller diameter than the outer diameter of the SUS heat transfer tube, so that the heat transfer can be carried out with the introduction of low-temperature liquefied gas. Both heat tubes and fins undergo heat shrinkage, but since aluminum shrinks approximately 1.2 times more than SUS, the fitting part of the fins fits better at low temperatures than at room temperature, improving heat transfer. That is, we focused on the difference in the materials of the heat exchanger tubes and fins, and developed a method of fixing the heat exchanger tubes and fins that is simple to manufacture and has good heat transfer properties without requiring welding, brazing, etc. Furthermore, the area of each fin was conventionally 40 mm x 240 mm, but this was changed to 110 mm x 300 mm, the total heat transfer area was made equal, the number of fins was reduced, and the pitch between the fins was widened. That is, based on the findings from experiments in Examples described later,
The conventional model had a fin pitch of 10mm.
It was set to 15mm. By widening the fin pitch, it was possible to prevent the deterioration of heat transfer performance due to frost adhesion. This prevents the conventional model's fin pitch of 10 mm, which caused frost adhering to the fins to combine with frost adhering to the adjacent fins, resulting in a decrease in heat transfer area and deterioration of heat transfer properties. It is. [Example] An example of the present invention will be explained with reference to FIG.
11, 11' are SUS heat exchanger tubes, 12 are aluminum or aluminum alloy fins, 13, 1
3' is an inlet/outlet flange. 14 is a heat exchanger tube 13,
Bend pipes 13' are connected to each other, and elbows 15, 15' are elbows that connect the heat exchanger tube 11 and the inlet/outlet flanges 13, 13'. The evaporator of the present invention is composed of these five types of parts, 16a and 16b are the welded connections between the inlet and outlet flanges 13 and 13' and the elbows 15 and 15', and 16c and 16d are the welded connections between the elbows 15 and 15' and the heat exchanger tubes. A welded connection connecting 11 and 11′,
16e and 16f are welded portions that connect the heat exchanger tubes 11 and 11' and the bend tube 14. Therefore, in the evaporator of the present invention, when the minimum number of units is two heat exchanger tubes 11, 11', there are only six welding points, and the man-hours required for welding assembly are reduced from the conventional 30 hours to 20 hours.
decreased in time. In this embodiment, the SUS heat exchanger tubes 11 and 11' are U-shaped single tubes with an outer diameter of 27.2 mm, and the fins 12 are
110mm x 300mm aluminum or aluminum alloy fins, 110 pieces to 15 pieces for the above unit.
Attach at mm intervals. The total heat transfer area of these fins is ^7.2m2 , which is the same area as a conventional pressurized evaporator using 365 40mm x 240mm fins. A comparison of the specifications of both the conventional type and the type of pressurized evaporator according to the present invention is shown in Table 1. As mentioned above, the pitch of the fins is 15 mm for the conventional model compared to 10 mm for the present model, which makes it possible to prevent frost growth. Further, as shown in FIG. 2, the through-holes 17 for the U-shaped SUS heat exchanger tubes 11, 11', which are provided at two locations approximately in the center of each fin having a thickness T of approximately 0.8 mm, The hole is approximately 10 mm smaller in diameter than the outer diameter of 11', which is 27.7 mm, and as shown in the figure, the edge 1 of the through hole 17
The width W of 8 is bent by about 5 mm. The heat exchanger tubes 11, 11' are inserted through the spring force of the edges 18 of the bent fins 12 at room temperature.
Strong contact is maintained. As mentioned above, when the low-temperature liquefied gas flows through the evaporation tube and cools down, -
Since aluminum shrinks approximately 1.2 times more than SUS at 196°C, the above contact becomes stronger and heat transfer performance improves. FIG. 3 shows test results comparing the performance of the conventional evaporator and the evaporator of the present invention, the specifications of which are shown in Table 1. In the figure, curve a shows the capacity of the evaporator of the present invention,
b is a curve showing the capacity of the conventional type. Based on the above study and test results, the pitch of fin 12 should be 15 mm or more.
25mm, the size of the fins 12 is the heat exchanger tube 11, 11'
It was found that 10 to 30 times the cross-sectional area of is appropriate.

[Effect of idea]

The present invention is constructed as described above, and its effects are as follows. (i) By changing the conventional multi-tube heat exchanger tube to a single tube, the header and cap are made of bent pipes and elbows, reducing material costs and greatly reducing the number of welding points. Achieved a reduction in processing and welding man-hours. (ii) By using a single-tube heat exchanger tube without using a header, changes in shape due to temperature differences are reduced, stress concentration and distortion caused by thermal stress are reduced, and damage due to this can be prevented. Ta. (iii) In the single-tube heat exchanger tube of the present invention, the cross-sectional area of the flow path is constant, and the parts where the direction of fluid flow changes have a gentle degree of curvature. The pressure loss is much lower than that of (iv) By using a SUS tube as the heat transfer tube, it has a high pressure resistance and can be used for supplying gas to the semiconductor industry. (v) When fixing the aluminum fin to the above SUS pipe, the diameter of the small hole provided in the fin for inserting the SUS pipe was made smaller than the diameter of the SUS pipe, and the edge was bent to allow the SUS pipe to be inserted and fixed. Therefore, it is easy to manufacture and can be fixed firmly, and when low-temperature liquefied gas is supplied, it can be used with aluminum.
The difference in the degree of thermal contraction of SUS provides the effect of further improving heat conductivity. (vi) One unit is an evaporator tube consisting of one U-shaped SUS tube, and two evaporator tube units are connected in series to form a pressurized evaporator with the minimum capacity. Pressurized evaporators for low-temperature liquefied gas storage tanks with various gas supply volumes can be manufactured immediately upon request. (vii) By setting the spacing between the heat dissipation fins to 15 mm, airflow improves, heat transfer performance improves, and even if frost adheres, it becomes difficult for frost to combine with adjacent fins, making heat transfer possible. Performance deterioration is less likely to occur compared to the conventional fin pitch of 10 mm.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the evaporator of the present invention, Fig. 2 is a partially enlarged front view, Fig. 3 is a performance comparison diagram of the conventional type and the evaporator of the present invention, and Fig. 4 5 shows an example of a conventional evaporator, with FIG. 4 being a plan view and FIG. 5 being a side view. 11, 11'...heat exchanger tube, 12...fin, 1
3, 13'... Entrance/exit flange, 14... Bend pipe, 15, 15'... Elbow.

Claims (1)

[Claims for Utility Model Registration] 1. A U-shaped stainless steel tube is inserted through the small holes of a plurality of aluminum or aluminum alloy heat dissipating fins each having two small holes, and the heat dissipating fins 1. An evaporator comprising at least two single tubes connected in series in an evaporator tube unit in which a predetermined number of single tubes are arranged substantially parallel to each other at a predetermined interval. 2. A small hole provided in the aluminum or aluminum alloy heat dissipation fin is bored with an inner diameter smaller than the outer diameter of the U-shaped stainless steel tube, the edge of the small hole is bent, and the stainless steel tube is attached to the bent edge. The evaporator according to claim 1, which is a utility model, wherein the evaporator is inserted so that the outer peripheral surface of the evaporator is in close contact with the evaporator. 3. The evaporator according to claim 1, wherein the distance between the heat dissipation fins is 15 mm to 25 mm.