Low Prandtt number distributor

Abstract

The utility model relates to a low Prandtt number distributor which comprises a bottom plate, an inner partition plate, a flow guide plate, an accelerator plate, a speed reducing plate and end plates, the bottom plate, the inner partition plate, the flow guide plate, the accelerator plate and the speed reducing plate are sequentially arranged between the two end plates which are arranged left and right from bottom to top, a plurality of accelerator plate holes are evenly distributed in the accelerator plate, and a plurality of speed reducing plate holes are evenly distributed in the speed reducing plate. The inner partition plate, the flow guide plate and the two end plates form a flow guide cavity, the flow guide plate, the acceleration plate and the two end plates form an acceleration cavity, the flow guide cavity is communicated with the acceleration cavity, and the acceleration plate, the deceleration plate and the two end plates form a deceleration cavity. According to the utility model, a gas-liquid two-phase mixture with a low Prandtt number is created by changing the flow speed and the macroscopic flow state of the refrigerant, and the heat exchanger has the advantages that the refrigerant is uniformly distributed, the utilization rate of a heat exchange area is improved, the heat transfer performance is improved, the refrigerant uniformly and stably flows out, and the erosive wear of the refrigerant to the heat exchange tube bundle is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of heat exchangers, and particularly relates to a low Prandtl number distributor. Background Art

[0002] In the evaporator of refrigeration and air-conditioning equipment, when there is no distributor, the design concept of the distributor is wrong, or the structural design of the distributor is unreasonable, the refrigerant will be unevenly distributed when entering the heat exchange tube, and the refrigerant will be unevenly distributed outside the heat exchange tube bundle and cannot fully wet or immerse the tube bundle, so that the heat exchange area cannot be fully utilized, resulting in poor heat transfer efficiency, reduced evaporation temperature, and unsatisfactory refrigerant evaporation effect; a large amount of the gas phase of the refrigerant entering the evaporator is separated from the liquid phase, resulting in insufficient convective heat transfer, a large amount of refrigerant to be charged, a lot of refrigerant loss, and high product material cost; the flow rate of the local refrigerant is too large, causing erosion of the heat exchange tube bundle, and easily causing the problem of liquid carry-over at the evaporator outlet, resulting in local high-concentration accumulation of the lubricating oil entering the evaporator, which will affect the service life of the heat exchange product and the safe operation of the entire unit over time. Therefore, solving the refrigerant distribution problem is a crucial factor in the design process of tube heat exchangers. Summary of the Utility Model

[0003] The purpose of the utility model is to overcome the above deficiencies. By creating a two-phase mixture with a flow pattern of intermittent flow or annular flow, the Prandtl number of the pure liquid is changed to be close to the Prandtl number of the mixture of the gas phase, and a low Prandtl number distributor is provided for the refrigerant distribution of a shell-and-tube heat exchanger with external evaporation of the tube bundle. Its special internal structure has the advantages of evenly distributing the refrigerant, improving the utilization rate of the heat exchange area, reasonably managing the high-concentration oil accumulation area, thereby realizing flow strengthening and improving the heat transfer performance, greatly reducing the refrigerant filling amount, and reducing the erosion and wear of the refrigerant on the heat exchange tube bundle.

[0004] The purpose of the utility model is realized as follows:

[0005] A low Prandtl number distributor is installed at the bottom inside the evaporator, and includes a bottom plate, an inner partition plate, a guide plate, an acceleration plate, a deceleration plate and an end plate. The bottom plate, the inner partition plate, the guide plate, the acceleration plate and the deceleration plate are sequentially arranged from bottom to top between the two end plates arranged left and right. A plurality of acceleration plate holes are evenly distributed on the acceleration plate, and a plurality of deceleration plate holes are evenly distributed on the deceleration plate. The inner partition plate, the guide plate and the two end plates form a guide cavity, the guide plate, the acceleration plate and the two end plates form an acceleration cavity, the guide cavity and the acceleration cavity are communicated, the acceleration plate, the deceleration plate and one end plate form a deceleration cavity, the guide cavity and the acceleration cavity are distributed at unequal intervals, and the cavity intervals of the two decrease sequentially from bottom to top. The inner partition plate, the guide plate, the acceleration plate and the deceleration plate are all in a ∧ shape and are integrally bent and formed, and the bending angles are kept consistent.

[0006] Preferably, one end of the guide plate is welded to the end plate on the corresponding side, and the other end leaves a fluid turning gap with the corresponding end plate, so that the acceleration chamber and the guide chamber arranged above and below are connected, and the fluid in the guide chamber turns and flows to the acceleration chamber.

[0007] Preferably, the bending angles of the inner partition, guide plate, acceleration plate and deceleration plate are 45°, 60°, 90° or 120°.

[0008] Preferably, the acceleration plate hole and the deceleration plate hole are staggered.

[0009] Preferably, the bottom plate, inner baffle and left and right guide baffles constitute a feed chamber, the two guide baffles are arranged on the inner sides of the two end plates, the bottom of the feed chamber formed by the bottom plate is provided with a bottom plate hole, and the top of the feed chamber formed by the inner baffle is provided with an inner baffle with a hole section.

[0010] Preferably, pads are provided between the inner partition and the guide plate, between the guide plate and the accelerator plate, and between the accelerator plate and the decelerator plate, so as to support adjacent plates through the pads.

[0011] Preferably, the bottom plate is in an arc shape coaxial with the evaporator cylinder.

[0012] The beneficial effects of the utility model are:

[0013] The use of the distributor allows the refrigerant to be evenly distributed in the tube, and the Bernoulli equation principle is used to change the speed and pressure of the refrigerant, change the refrigerant flow rate and macroscopic flow state, etc., to create a gas-liquid two-phase mixture. The Prandtl number of the gas-liquid two-phase mixture is much lower than that of the liquid phase (taking R134a with a saturation temperature of 5°C as an example, the Prandtl number of pure liquid is 3.77, and the Prandtl number of pure gas is 0.84. The gas-liquid two-phase flow created by the distributor and the flow-equalizing tube / mixing orifice plate in the tube bundle has a Prandtl number between 1.47 and 0.88), which can fully contact the area of ​​the heat exchange tube bundle to achieve efficient heat exchange and improve heat transfer performance; low Prandtl number operation is achieved, and the refrigerant filling amount is greatly reduced while ensuring the required cooling capacity. The refrigerant filling amount is reduced by 40~60% compared with the traditional flooded evaporator, which reduces costs, can reduce the erosion damage of the refrigerant to the equipment to a certain extent, reduce the wear of the heat exchange tube bundle, and extend the service life of the equipment. It has great application market prospects in the field of refrigeration and heat exchangers. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The utility model is a schematic diagram of the assembly structure of a low Prandtl number distributor.

[0015] Figure 2 This is a front view of a low Prandtl number distributor of the utility model.

[0016] Figure 3 forFigure 2 A-A cross-sectional view.

[0017] Figure 4 is Figure 3 B-B cross-sectional view.

[0018] Figure 5 is Figure 4 Partial enlarged view.

[0019] Wherein: bottom plate 1; bottom plate hole 1.1; inner partition plate 2; perforated section of inner partition plate 2.1; flow guide plate 3; acceleration plate 4; acceleration plate hole 4.1; deceleration plate 5; deceleration plate hole 5.1; end plate 6; flow guide partition plate 7; flow guide cavity 8; acceleration cavity 9; deceleration cavity 10; spacer 11. Specific implementation mode

[0020] See Figures 1-5 , the utility model relates to a low Prandtl number distributor, which is installed at the bottom in an evaporator and comprises a bottom plate 1, an inner partition plate 2, a flow guide plate 3, an acceleration plate 4, a deceleration plate 5, an end plate 6 and a flow guide partition plate 7. A bottom plate 1, an inner partition plate 2, a flow guide plate 3, an acceleration plate 4 and a deceleration plate 5 are sequentially arranged from bottom to top between two left-and-right end plates 6. A plurality of acceleration plate holes 4.1 are evenly distributed on the acceleration plate 4, and a plurality of deceleration plate holes 5.1 are evenly distributed on the deceleration plate 5. The inner partition plate 2, the flow guide plate 3 and the two end plates 6 form a flow guide cavity 8. The flow guide plate 3, the acceleration plate 4 and the two end plates form an acceleration cavity 9. The flow guide cavity 8 and the acceleration cavity 9 are communicated. The acceleration plate 4, the deceleration plate 5 and one end plate 6 form a deceleration cavity 10.

[0021] The deceleration cavity 10 is open, so that the distributor has an oil concentration management function. As Figure 4 and Figure 5 shown, the deceleration cavity 10 is composed of the acceleration plate 4, the deceleration plate 5 and the right end plate 6. A gap is left between the left end plate 6 and the deceleration plate 5. Through this design, a high oil concentration is gathered on the side far from the evaporator outlet, which is convenient for recovering the refrigeration oil from the evaporator.

[0022] The bottom plate 1, the inner partition plate 2 and the left-and-right flow guide partition plates 7 form a feed cavity. The two flow guide partition plates 7 are arranged inside the two end plates 6. A bottom plate hole 1.1 is arranged at the bottom of the feed cavity formed by the bottom plate 1, and the bottom plate hole 1.1 is used for connecting a refrigerant inlet pipe. A perforated section 2.1 of the inner partition plate is arranged at the top of the feed cavity formed by the inner partition plate 2. Since the flow rate and impact pressure of the just-entered refrigerant are very high, the refrigerant entering the feed cavity from the refrigerant inlet pipe passes through the perforated section 2.1 of the inner partition plate under the constraint of the left-and-right flow guide partition plates 7. Using Bernoulli's equation principle: , the velocity of the fluid passing through the aperture is inversely proportional to the size of the aperture. The increase of the velocity makes the pressure of the fluid decrease at this place and the height By reducing the pressure and height, the erosion and deformation of the guide plate 7 in the acceleration chamber by the refrigerant is reduced, and the service life of the distributor is extended.

[0023] One end of the guide plate 3 is welded to the end plate 6 on the corresponding side, and the other end has a fluid turning gap with the end plate 6 on the corresponding side, so that the guide chamber 8 and the acceleration chamber 9 arranged above and below are connected, and the fluid in the guide chamber turns and flows to the acceleration chamber. The guide chamber 8 and the acceleration chamber 9 are distributed at unequal intervals, and the cavity spacing decreases from bottom to top, from 18.5mm→15.7mm. This increases the refrigerant flow rate, increases the engineering turbulence effect, and achieves complete mixing and consistency of the speeds of the gas and liquid media. By reasonably calculating and setting the inter-plate gap (cavity spacing) between the guide chamber and the acceleration chamber, the guide chamber can achieve intermittent flow or annular flow, and the fluid can be evenly distributed to each acceleration plate hole, so that the acceleration chamber maintains a certain pressure drop (should be no less than 100KPA), so that the fluid can be ejected from the acceleration plate hole evenly and at high speed. According to the Reynolds number formula , ( Fluid density, V average flow velocity, D pore diameter, The Reynolds number (dynamic viscosity of the fluid) is related to the macroscopic flow velocity, fluid geometry and fluid physical properties. The cavity increases the turbulent flow of the two-phase body, so that the refrigerant can be mixed more evenly, forming a low-density two-phase mixture whose Prandtl number is much lower than that of the liquid phase.

[0024] The surface of each plate of the distributor needs to be smooth and burr-free. The bottom plate 1 is in an arc shape coaxial with the evaporator cylinder and can be completely fitted to the bottom of the evaporator cylinder. The inner partition 2, the guide plate 3, the accelerator plate 4 and the decelerator plate 5 are all in a ∧ shape. The distributor is triangular as a whole and has a stable characteristic. The inner partition 2, the guide plate 3, the accelerator plate 4 and the decelerator plate 5 are all formed by integral bending, and the bending angle is consistent. The bending angle can be 45°, 60°, 90° or 120°.

[0025] The bottom plate hole 1.1, the acceleration plate hole 4.1, and the deceleration plate hole 5.1 can be circular, square, diamond, hexagram, elliptical, etc. according to the use conditions and the processing form requirements, and the total cross-sectional area of ​​the corresponding apertures meets The accelerating plate hole 4.1 and the decelerating plate hole 5.1 are staggered, that is, the projections of the accelerating plate hole 4.1 and the decelerating plate hole 5.1 on the bottom plate 1 do not overlap, so as to prevent the refrigerant from escaping directly from the decelerating plate hole 5.1 after being accelerated by the accelerating chamber 9 and the accelerating plate 4. The decelerating plate hole 5.1 increases the resistance and reduces the injection force.

[0026] The deceleration plate 5 is tightly fitted with the heat exchange tube bundle support plate in the evaporator cylinder. The refrigerant entering the distributor from the bottom plate hole 1.1 is evenly distributed by the distributor and then contacts the heat exchange tube bundle in the evaporator cylinder with sufficient area for efficient heat exchange.

[0027] A spacer block 11 is also provided between the inner partition plate 2 and the flow guide plate 3, between the flow guide plate 3 and the acceleration plate 4, and between the acceleration plate 4 and the deceleration plate 5. The adjacent plate members are supported by the spacer block so that each chamber can obtain sufficient rigidity.

[0028] Working principle:

[0029] The refrigerant enters the distributor through the bottom plate hole 1.1, passes through the perforated section 2.1 of the inner partition plate under the constraint of the left and right flow guide partitions 7 on both sides, and sequentially enters the flow guide chamber 8 and the acceleration chamber 9. After being guided and accelerated to increase the turbulence, it passes through the acceleration plate hole 4.1 of the acceleration plate 4, realizing the uniform mixing of gas and liquid at the same speed, creating a low Prandtl number medium with a Prandtl number much lower than that of the liquid phase and as close as possible to that of the gas phase, which can well improve the heat transfer performance. Under the condition of ensuring the same heat exchange quantity, the heat exchange efficiency is increased; then it flows through the deceleration chamber 10 and stably flows out from the deceleration plate hole 5.1. The refrigerant passing through the acceleration chamber 9 and the acceleration plate 4 in the early stage has a very high flow rate. Directly flowing into the evaporator cylinder and exchanging heat with the heat exchange tubes is likely to cause the problem of erosion of the heat exchange tube bundle due to excessive flow rate. At the same time, the excessive flow rate of the refrigerant will lead to insufficient heat exchange, resulting in waste. The application of the deceleration chamber 10 and the deceleration plate 5 in the low Prandtl number distributor enables the refrigerant to flow out evenly and stably, improves the heat exchange performance of the product, and enables the efficient utilization of the refrigerant.

[0030] The use of this distributor enables the refrigerant to be evenly distributed in the pipe, and using the principle of Bernoulli's equation , the refrigerant changes in speed and pressure, changes the flow rate and macroscopic flow state of the refrigerant, etc., creating a gas-liquid two-phase mixture. The Prandtl number of this mixture is much lower than that of the liquid phase, and it can fully contact the area of the heat exchange tube bundle, realizing efficient heat exchange and improving the heat transfer performance. In engineering applications, we preferably choose fluids with a small Prandtl number, which have the characteristics of small viscosity, small specific heat capacity, and large thermal conductivity. The special structure of the distributor can make the refrigerant have the characteristics of a low Prandtl number and can be evenly distributed, improving the heat transfer performance.

[0031] In addition to the above embodiments, the present invention also includes other implementation manners. Any technical solutions formed by equivalent transformation or equivalent substitution shall fall within the protection scope of the claims of the present invention.

Claims

1. A low Prandtl number distributor, which is installed at the bottom of the evaporator, characterized in that: It includes a bottom plate, an inner baffle, a guide plate, an acceleration plate, a deceleration plate and an end plate. The bottom plate, the inner baffle, the guide plate, the acceleration plate and the deceleration plate are arranged in sequence from bottom to top between the two end plates arranged on the left and right. The acceleration plate is evenly distributed with a number of acceleration plate holes, and the deceleration plate is evenly distributed with a number of deceleration plate holes. The inner baffle, the guide plate and the two end plates form a guide cavity. The guide plate, the acceleration plate and the two end plates form an acceleration cavity. The guide cavity and the acceleration cavity are connected. The acceleration plate, the deceleration plate and an end plate form a deceleration cavity. The guide cavity and the acceleration cavity are distributed at unequal intervals, and the cavity spacing between the two decreases from bottom to top. The inner partition, guide plate, acceleration plate and deceleration plate are all ∧-shaped and are formed by integral bending, and the bending angle remains consistent.

2. A low Prandtl number distributor according to claim 1, characterized in that: One end of the guide plate is welded to the end plate on the corresponding side, and the other end leaves a fluid turning gap with the end plate on the corresponding side, so that the acceleration chamber and the guide chamber arranged above and below are connected, and the fluid in the guide chamber turns and flows to the acceleration chamber.

3. A low Prandtl number distributor according to claim 1, characterized in that: The bending angles of the inner partition, guide plate, acceleration plate and deceleration plate are 45°, 60°, 90° or 120°.

4. A low Prandtl number distributor according to claim 1, characterized in that: The holes of the acceleration plate and the holes of the deceleration plate are staggered.

5. A low Prandtl number distributor according to claim 1, characterized in that: The bottom plate, inner baffle and left and right guide baffles form a feed cavity. The two guide baffles are arranged on the inner sides of the two end plates. The bottom of the feed cavity formed by the bottom plate is provided with a bottom plate hole, and the top of the feed cavity formed by the inner baffle is provided with an inner baffle with a hole section.

6. A low Prandtl number distributor according to claim 1, characterized in that: Pads are provided between the inner partition and the guide plate, between the guide plate and the accelerator plate, and between the accelerator plate and the decelerator plate, and the adjacent plates are supported by the pads.

7. A low Prandtl number distributor according to claim 1, characterized in that: The bottom plate is in an arc shape coaxial with the evaporator cylinder.

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