Experimental Research On Heat Transfer Characteristic Of Plate-Fin Microchannel Heat Exchanger And Development Of Three-Dimensions Parametric Design Platform

More and more attention has been paid to energy issues.As an important part of refrigeration and air-conditioning field,energy-saving optimization design of heat exchanger has also been widely concerned and studied.Enhanced heat transfer is an important direction of heat exchanger optimization research.As an efficient and compact heat exchanger,plate-fin heat exchanger has been widely used in energy and power,petrochemical,aerospace,refrigeration and air-conditioning industries.In view of the shortcomings of microchannel heat exchanger in the application of evaporator and heat pump,a new fin structure was developed and optimized.The reliability of the structure design was verified by experiments.At the same time,the design and calculation correlations of the new fins are fitted by the method of simulation and experiment,and embedded in the design and calculation software.Finally,a three-dimensional parametric design platform for microchannel heat exchangers is developed,which integrates the design and calculation with the selection of parts and drawings,and greatly improves the work efficiency.The main contents of this paper are as follows:(1)A wind tunnel monomer test rig for microchannel heat exchanger was designed and built to study the heat transfer and pressure drop characteristics of fins.The basic structure of the test rig,experimental equipment,experimental instruments and experimental operation process were introduced.A large number of experiments were carried out on heat exchangers with different fin types and fin spacing on the test bench,and the influence trend of fin structure parameters on air side flow and heat transfer was obtained.At the same time,according to the experimental results,the initial conditions and calculation structure of the simulation calculation are corrected,and the reliability of the simulation calculation is verified.The empirical correlations of heat transfer factor J and friction factor F for different fins are fitted by the corrected simulation results.(2)Aiming at the deficiency of microchannel heat exchanger under drainage and frosting conditions,microchannel heat exchanger with plate-fin was applied to heat pump air conditioning of R32 system.The system was tested and the data was compared with the results of the tube-fin heat exchanger,conducting to preliminarily discuss the characteristic of plate-fin microchannel heat exchangers for heat pump systems.On the premise of the same size and operation conditions of heat exchangers,two different heat exchanger contrivances of 16 series and 20 series were experimented respectively and the annual average heat transfer and APF were taken as comprehensive evaluation indexes.The method of APF for the inverter accord with real usage of air-conditioners as it takes cooling and heating into account,the heat transfer capacity and energy efficiency under normal cooling,middle cooling,normal heating and middle heating were used to calculated it.The results show that the charge of 20 series of the plate-fin heat exchangers was reduced by 25% and the capacity was increased by 1.5%.,the EER increased by 0.4% on the normal cooling condition and reduced by 1.7% on the middle cooling condition,the COP increased by 1.1% and increased by 0.9% on the middle heating,eventually the APF through the year increased by 0.3%.About the 16 series,the capacity increased by 2.5%,the energy efficiency mentioned above has increased by 1.7%,-0.3%,3.5%,3.2%respectively and the APF increased by 3.2%.On this basis the fin structure and the arrangement of the pipe has been further optimized,such as changing the direction of wind blowing through the heat exchanger and the way refrigerant flows inside the heat exchanger and ultimately the average capacity under frosting condition has been raised to 95.06% from 78.6% of the tube-fin heat exchanger.That thrust plate-fin heat exchanger has the feasibility and advantages when applied to the heat pump system,and has a certain development prospects.(3)A three-dimensional parameterized design platform for microchannel heat exchangers is built,which links the design calculation of heat exchangers with the establishment of models and the generation of Engineering drawings.Standardize drawing process,establish standard parts database,use C # language to redevelop SolidWorks software,shorten the design cycle of heat exchanger,improve work efficiency,and realize collaborative design.