| Parallel flow heat exchanger has advantages of high heat transfer coefficient,high surface area-volume ratio,low heat transfer temperature difference,etc.It is widely used in refrigeration,air conditioning and other industrial fields,but the uneven distribution of refrigerant in the tube seriously affects the heat exchanger performance.In this paper,the optimization design of the deflector in the header of the parallel flow heat exchanger is carried out.The even distribution of the refrigerant in the header of the parallel flow heat exchanger with the deflector under single-phase and two-phase conditions is studied through numerical simulation and test methods.(1)Through the numerical simulation method,four types of heat exchangers with no deflector,uniform aperture deflector,two-hole symmetrical and three-hole symmetrical deflector were studied.Among them,the flow distribution uniformity of the non-deflector heat exchangers structure was the worst,followed by the uniform aperture deflector structure and two-hole symmetrical,the three-hole symmetrical deflector structure heat exchanger have the best distribution uniformity.The three-hole symmetrical deflector structure has even higher fluid distribution uniformity than the uniform aperture deflector structure heat exchanger.(2)Based on the numerical simulation results,a test bench was set up to test the uniformity of single-phase fluid distribution for the four heat exchangers using water as the test fluid.The flow range is 150kg/h-250kg/h.The fluid distribution uniformity of the parallel flow heat exchanger is improved as the flow rate increases.The best is the three-hole symmetrical deflector heat exchanger.The non-uniformity S value of the three-hole symmetrical deflector heat exchanger is 9.46%-22.46% lower than the uniform aperture deflector.It can be seen that rational aperture distribution of the deflector can improve the refrigerant distribution uniformity of the heat exchanger.(3)In this paper,using the air and water as the mixed working fluid.The uniformity of fluid distribution in six kinds of heat exchanger structures with two kinds of uniform aperture,two-hole symmetrical and three-hole symmetrical were studied under the experimental conditions of the gas and liquid superficial velocity range of 2.47-3.04m/s and 0.67-0.86m/s,respectively.Including three types of deflector heat exchangers with the same total area of openings and with three different,these include three types with the same cross-sectional area of the orifices and the three types with the different of deflectors.The total flow area of the deflector with the same cross-sectional area of the orifices is the same as the flat tubes.The relationship between the open area of the deflector and the cross-sectional area of the flat tube was studied.Through experimental research,it was found that among the three types of heat exchangers with the same cross-sectional area of the deflector,the uniformity of gas-liquid fluid distribution was best in the three-hole symmetrical deflector and the distribution uniformity of the uniform aperture deflector was the worst.According to the analysis,the distribution uniformity of the gas-liquid two-phase distribution of the variable-aperture deflector with a cross-sectional area of 670.39 mm2 among the six deflectors is the best.It is considered that the size of the opening area has nothing to do with the total flow area of the flat tube. |
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