A disc-type ultra-low temperature evaporator with enhanced natural convection

Abstract

The present invention discloses a disc-shaped ultra-low temperature evaporator with enhanced natural convection, relating to the technical field of refrigerator evaporators. The evaporator comprises a spiral coil, a temperature-equalizing base plate, and straight fins with inter-slotted holes. The upper surface of the temperature-equalizing base plate is connected to the spiral coil, and the lower surface of the temperature-equalizing base plate is provided with multiple rows of straight fins with inter-slotted holes. This invention can reduce the contact thermal resistance between the evaporating tube and the temperature-equalizing base plate in small biological sample storage refrigerators, enhance the heat exchange capacity between the air and the evaporator, reduce the thermal gradient of the air below the temperature-equalizing base plate, and provide excellent sealing performance.

Description

Technical Field

[0001] The invention relates to the technical field of refrigerator evaporators, and in particular to a disc-type ultra-low temperature evaporator for enhancing natural convection. Background Art

[0002] High-quality biological samples are a crucial source for basic and clinical research, and the material foundation for translational medicine and precision medicine. They are also listed as a key development area in the 14th Five-Year Plan for Bioeconomic Development. Most biological samples require an extremely low temperature of -80°C ± 5°C for long-term storage.

[0003] In traditional ultra-low temperature refrigerators, the evaporator is typically located on the inner wall's insulation, with the evaporation piping attached to the inner wall. Heat is transferred from the air inside the refrigerator to the inner wall, where the heat is transferred to the evaporator. The refrigerant inside the evaporator then carries the heat out of the unit. Due to the multi-layer heat exchange between the refrigerant and the air inside the refrigerator, thermal resistance is high and heat transfer efficiency is low, necessitating a larger temperature difference. To achieve the same cooling effect, a lower evaporation temperature is required, and the evaporation pressure must also be reduced. This increases the pressure difference between the evaporator and condenser, reducing both the cooling efficiency and the cost-effectiveness (COP) of the entire system.

[0004] At the same time, the distance between the lower part and the top of the small biological sample storage refrigerator is far, making it difficult to meet the extremely low temperature requirements for storage. The temperature field of the refrigerator is unevenly distributed, with large temperature differences at different positions. The air circulation at the top of the evaporator is blocked, and the heat exchange capacity is poor.

[0005] A literature search of the prior art revealed that there is a utility model patent with patent number CN216845217U, entitled "A Ultra-Low-Temperature Biological Sample Cold Storage Evaporator." This patent comprises multiple groups of copper tubes on two upper and lower layers and multiple groups of loop U-shaped evaporation tubes to form an ultra-low-temperature biological sample cold storage evaporator with excellent thermal conductivity. However, due to the multi-row tube design, the evaporator is relatively high, and the upper part is prone to poor heat exchange and may have a local temperature gradient that is too large. In addition, the existing evaporators suitable for low-temperature biological sample libraries are all rectangular in structure and are not suitable for installation in the cylindrical main area of a small sample library.

[0006] Therefore, technicians in this field are committed to developing a disc-type ultra-low temperature evaporator with enhanced natural convection, which can reduce the contact thermal resistance between the evaporation tube and the temperature-uniform bottom plate in the cylindrical main body area of a small sample library and enhance the heat exchange capacity between the air and the evaporator. Summary of the Invention

[0007] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to reduce the thermal resistance of a small biological sample storage refrigerator and improve the heat exchange efficiency.

[0008] To achieve the above-mentioned objectives, the present invention provides a disc-type ultra-low temperature evaporator with enhanced natural convection, characterized in that it includes a spiral coil, a temperature-uniform bottom plate and straight fins with holes between slots, wherein the upper surface of the temperature-uniform bottom plate is connected to the spiral coil, and the lower surface of the temperature-uniform bottom plate is provided with multiple rows of straight fins with holes between slots.

[0009] Furthermore, the spiral coil is an equidistant spiral tube, and the pipe of the spiral coil is an elliptical flat tube or a rectangular tube.

[0010] Furthermore, the upper surface of the temperature-averaging bottom plate is provided with a groove equidistant from the spiral coil, and the spiral coil is matched with the groove and then connected by welding, so that the spiral coil is tightly fitted to the upper surface of the temperature-averaging bottom plate.

[0011] Furthermore, the lower surface of the temperature uniform base plate is provided with grooves, the inter-groove opening straight fins are formed between the grooves, and the roots of the inter-groove opening straight fins are provided with through holes.

[0012] Furthermore, the spiral coils are connected in parallel in two groups. The refrigerant of the first spiral coil enters from the center of the spiral coil and flows out from the edge. The refrigerant of the second spiral coil enters from the edge of the spiral coil and flows out from the center.

[0013] Furthermore, the spiral coil is connected to the capillary tube outlet at one end where the refrigerant flows in, and is connected to the compressor inlet at one end where the refrigerant flows out. The spiral coil is connected to the capillary tube outlet and the compressor inlet by welding.

[0014] Furthermore, the disc-type ultra-low temperature evaporator further includes a support plate and a cover plate, the support plate is connected to the temperature uniformity bottom plate by bolts, and the support plate and the cover plate are connected by welding.

[0015] Furthermore, the space between the temperature-uniform bottom plate, the cover plate and the support plate is formed into a heat-insulating layer by polyurethane foaming.

[0016] Furthermore, the disc-type ultra-low temperature evaporator further includes an annular sealing strip, which is installed at a position where the cover plate and the support plate are connected.

[0017] Furthermore, the annular sealing strip is an M-shaped silicone rubber ring.

[0018] Compared with the existing small biological sample storage refrigerator evaporator, the present invention has the following advantages:

[0019] 1. The contact thermal resistance between the existing evaporator coil and the temperature equalizing plate is too large; the present invention opens a semi-elliptical groove or rectangular groove of the same size as the spiral coil on the top of the temperature equalizing base plate, and the two are connected by welding. The different shrinkage rates of the temperature equalizing aluminum plate and the copper coil under low temperature conditions make the two fit closely during operation, reducing the gap and contact thermal resistance, thereby significantly reducing the contact thermal resistance between the spiral coil and the temperature equalizing base plate, and the maximum temperature difference between the two is less than 0.5K.

[0020] 2. The existing heat exchange capacity between the bottom of the temperature equalizing plate and the air is poor, and the thermal gradient of the air at the bottom of the temperature equalizing plate is large; the present invention opens grooves at the bottom of the temperature equalizing plate, forms fins between the grooves, and opens through circular holes at the roots of the fins. The grooves have a guiding effect on the air, and the fins between the grooves also increase the heat exchange area on the air side, enhance the natural convection of hot air and reduce accumulation. The through circular holes at the root allow the air in different grooves to be mixed, reducing the thermal gradient of the air and making the air flow in an orderly manner. The heat exchange capacity between the air and the evaporator is greatly enhanced, and the air temperature gradient on the surface of the temperature equalizing plate is significantly reduced.

[0021] 3. When the air circulates naturally in the sample storage cylinder, it absorbs heat and rises from the middle. The heat exchange capacity required by the temperature equalizing plate along the radial direction is larger in the middle and smaller at the edge. The present invention adopts equidistant spiral elliptical flat tubes or rectangular tubes as evaporating tubes. The refrigerant of one tube enters from the middle and flows out from the edge. The flow direction of the other tube is opposite, and the refrigerant enters from the edge and flows out from the middle. The grooves and fins at the bottom of the temperature equalizing base plate are not equidistantly distributed, but are non-equidistantly distributed in a "dense-sparse-dense" manner. Since the heat exchange capacity of the refrigerant is strongest at medium dryness and weaker at low and extremely high dryness, the opposite flow directions of the refrigerants in the two tubes can compensate for each other's heat exchange capacity. The fins with denser centers and edges enhance the heat exchange effect at the center and outermost edge of the temperature equalizing base plate, and the matching of the overall heat exchange capacity of the temperature equalizing base plate and the load is enhanced.

[0022] 4. The temperature difference between the internal environment and the outside world is extremely large. Air infiltration will cause frost on the cylinder and evaporator, affecting the heat exchange effect. The present invention adopts an "M"-shaped annular sealing strip at the connection between the evaporator support plate and the cover plate. The gap in the middle of the annular sealing strip clamps the edge of the cylinder body of the sample storage cylinder. The weight of the evaporator presses on the annular sealing strip and transmits it to the cylinder wall, achieving sealing on the upper side. The two sides of the "M" shape isolate the air inside the cylinder from the outside air, achieving sealing on both sides. The internal cold air does not seep out and the external hot air does not seep in. There is no risk of frost and the internal temperature fluctuation is small.

[0023] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a bottom view of the overall assembly of a disc-type ultra-low temperature evaporator with enhanced natural convection according to a preferred embodiment of the present invention;

[0025] Figure 2 This is a cross-sectional view of a temperature-uniform bottom plate and bottom hole fins of a disc-type ultra-low temperature evaporator for enhancing natural convection according to a preferred embodiment of the present invention;

[0026] Figure 3 This is a top view of a preferred embodiment of a disc-type ultra-low temperature evaporator with enhanced natural convection after the spiral coil and the temperature uniforming bottom plate are matched;

[0027] Figure 4 This is a partially enlarged bottom view of the bottom of the temperature-uniform base plate and the straight fins with holes between the slots of a disk-type ultra-low temperature evaporator with enhanced natural convection according to a preferred embodiment of the present invention;

[0028] Figure 5 This is a top view of the overall assembly of a disc-type ultra-low temperature evaporator with enhanced natural convection according to a preferred embodiment of the present invention;

[0029] Figure 6 1 is a schematic diagram of the overall structure of a spiral coil of a disk-type ultra-low temperature evaporator with enhanced natural convection according to a preferred embodiment of the present invention;

[0030] Figure 7 1 is a cross-sectional view of an annular sealing strip of a disk-type ultra-low temperature evaporator with enhanced natural convection according to a preferred embodiment of the present invention;

[0031] Figure 8 1 is a schematic diagram of the structure of the cooperation between the annular sealing strip and the sample storage cylinder of a disk-type ultra-low temperature evaporator with enhanced natural convection according to a preferred embodiment of the present invention;

[0032] Among them, 1- spiral coil, 2- temperature-averaging bottom plate, 3- straight fins with holes between slots, 4- support plate, 5- cover plate, 6- annular sealing strip, 7- load-bearing ring, 8- sample storage cylinder body. DETAILED DESCRIPTION

[0033] The following describes several preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0034] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0035] like Figure 6 As shown, the present invention is a disc-type ultra-low temperature evaporator structural design for improving heat transfer efficiency, which is characterized in that the evaporating tube of the evaporator is an equidistant spiral coil 1, the pipeline is an elliptical flat tube or a rectangular tube, the middle of the spiral coil 1 is the refrigerant inlet, and the outer side is the outlet. Since the hot air rises from the middle and the cold air falls from the edge, this design makes the area corresponding to the heat exchange between the hot air and the uniform temperature bottom plate 2 mainly the refrigerant with a large heat transfer coefficient in the medium dryness area, and the cooling effect is good.

[0036] like Figure 2 As shown, the horizontally mounted disc-type ultra-low temperature evaporator temperature-averaging base plate 2 includes: a groove on the upper surface equidistant from the spiral coil 1 and having a depth of half the short semi-axis (the pipe is an elliptical flat pipe) or the pipe height (the pipe is a rectangular pipe) of the spiral coil 1, which is used to fix the position of the evaporation pipe; and a lower surface including multiple rows of straight fins 3 with holes opened between the grooves.

[0037] like Figure 3 As shown, the spiral coil 1 is matched with the groove above the temperature-averaging base plate 2 and then connected by welding, so that the spiral coil 1 and the temperature-averaging base plate 2 fit tightly together to form an integrated device, reducing the air gap to achieve the purpose of reducing local thermal resistance. The temperature-averaging base plate 2 is an aluminum plate and the spiral coil 1 is a copper tube. The shrinkage rates of the two are different under low temperature conditions, so that the two fit tightly together during operation, reducing the gap and contact thermal resistance. The spiral coil 1 is connected to the capillary outlet at the refrigerant inlet end and to the compressor inlet at the refrigerant outflow end. The connection is made by welding, and the connecting pipe diameter does not exceed 10mm. The spiral coil 1 is connected in two groups in parallel. The refrigerant of the first coil enters from the center and flows out from the edge, and the refrigerant of the second coil enters from the edge and flows out from the center. The heat exchange capacities compensate each other. When starting up or at extremely high loads, the two refrigeration system groups can be turned on at the same time. At medium and low loads, only one group can be turned on.

[0038] like Figure 4 As shown, a hole is punched in the middle of the temperature-uniform bottom plate 2 so that the rotating shaft of the placement rack can pass through and play a positioning role; the spacing of the bottom fins of the temperature-uniform bottom plate 2 can be adjusted according to different refrigerants, generally adopting a "dense-sparse-dense" arrangement from the center to the edge. The dense fins enhance the heat transfer effect in the low-dryness and extremely high-dryness areas, and the fins increase the air-side heat exchange area and improve the heat exchange performance; the channels between the fins play a guiding role, and the through circular holes at the roots of the fins allow the cold and hot air in different channels to mix with each other, reducing temperature unevenness.

[0039] like Figure 1 and Figure 5As shown, the support plate 4 and the cover plate 5 are connected into one piece by welding, and an annular sealing strip 6 is put on the connection; the integral evaporator after the spiral coil 1 and the temperature-averaging base plate 2 are matched and connected to form an integrated structure with the support plate 4 and the cover plate 5 installed and connected on the base plate; the space formed between the temperature-averaging base plate 2, the cover plate 5 and the support plate 4 is formed by polyurethane foaming to form an insulation layer; the temperature-averaging base plate 2 and the support plate 4 are connected by bolts below the temperature-averaging base plate 2, and the pressure is dispersed to the entire base plate through the load-bearing ring 7; the connected integral evaporator is installed on the top of the outer shell of the placement area of the small biological sample library, and the annular sealing strip 6 is used to achieve internal and external isolation to reduce heat leakage and prevent frost; the large hole of the temperature-averaging base plate 2 and the small hole of the cover plate 5 are concentric holes, and the shaft shoulder fits with the top plate to achieve sealing.

[0040] like Figure 7 As shown, the structure of the annular sealing strip 6 is an "M"-shaped silicone rubber ring, which can work normally even in ultra-low temperature environments.

[0041] like Figure 8 As shown, the edge of the sample storage cylinder body 8 is stuck in the gap in the middle of the annular sealing strip 6, isolating the inside and outside air, preventing frost, and achieving fit and sealing.

[0042] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A disc-type ultra-low temperature evaporator with enhanced natural convection, characterized in that: The heat dissipation device is a heat dissipation device, and the heat dissipation device is a heat dissipation device. The heat dissipation device is a heat dissipation device, and the heat dissipation device is a heat dissipation device. The heat dissipation device is a heat dissipation device, and the heat dissipation device is a heat dissipation device. The upper surface of the heat dissipation device is connected to the spiral coil, the upper surface of the heat dissipation device is provided with a groove equidistant from the spiral coil, and the spiral coil is connected to the groove by welding, and the spiral coil is tightly fitted into the upper surface of the temperature uniformity base plate; the lower surface of the temperature uniformity base plate is provided with a plurality of rows of straight fins with holes between the slots, the lower surface of the temperature uniformity base plate is provided with a groove, the grooves of the grooves form the straight fins with holes between the slots, and the roots of the straight fins with holes between the slots are provided with through holes; the disc-type ultra-low temperature evaporator also includes a support plate and a cover plate, the support plate is connected to the temperature uniformity base plate by bolts, the support plate and the cover plate are connected by welding, the space between the temperature uniformity base plate, the cover plate and the support plate is formed with polyurethane foam to form an insulation layer, and the disc-type ultra-low temperature evaporator also includes an annular sealing strip, which is installed at the position where the cover plate is connected to the support plate.

2. The disc-type ultra-low temperature evaporator with enhanced natural convection according to claim 1, characterized in that: The spiral coil is an equidistant spiral tube, and the pipe of the spiral coil is an elliptical flat tube or a rectangular tube.

3. The disc-type ultra-low temperature evaporator with enhanced natural convection according to claim 1, characterized in that: The spiral coils are connected in parallel in two groups. The refrigerant of the first spiral coil enters from the center of the spiral coil and flows out from the edge. The refrigerant of the second spiral coil enters from the edge of the spiral coil and flows out from the center.

4. The disc-type ultra-low temperature evaporator with enhanced natural convection according to claim 3, characterized in that: The spiral coil is connected to the capillary tube outlet at one end where the refrigerant flows in, and is connected to the compressor inlet at one end where the refrigerant flows out. The spiral coil is connected to the capillary tube outlet and the compressor inlet by welding.

5. The disc-type ultra-low temperature evaporator with enhanced natural convection according to claim 1, characterized in that: The annular sealing strip is an M-shaped silicone rubber ring.

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