Research On Fluid Flow Distribution And Heat Transfer In Plate-fin Heat Exchangers Based On Joint Simulation

Plate-fin heat exchanger(PFHE)is widely used in LNG field as important thermodynamic equipment.While fluid flow maldistribution which causes the deterioration of heat exchanger's efficiency is a common phenomenon,so how to improve the fluid flow distribution in order to enhance the efficiency of PFHE attracts lots of researchers' attention.Because of the structural complexity,such as its tens of thousands of small channels,only entrance structure has been analyzed in numerical simulation study.Though heat exchanger can be studied in experimental study,phase change heat transfer cannot be researched because of the limitation of measuring technique.In order to reduce the limitations in numerical simulation and experimental research,this paper uses automatic co-simulation method to study the flow an heat transfer(phase change)features in complete PFHE(including entrance tube,entrance seal,420 small channels,outlet seal and outlet pipe).And the main research contents and results are as follows:(1)It is the first time to study in co-simulation with FLUENT,MATLAB and REFPROP in ISIGHT.In the co-simulation FLUENT is applied to calculate the flow features in entrance and outlet of PFHE steadily;MATLAB is applied to calculate the heat transfer and pressure in 420 small channels,where REFPROP is integrated to calculate the properties and determine the phase state,and different experience correlations are used to calculate the heat exchanger and pressure drop;ISIGHT is applied to transmit data among different software.(2)Flowing features,flow distribution and resistance characteristics are studied with co-simulation,the results show that: Flowing features in the horizontal and vertical are different,three kinds of small channels are determined by its flow path,Jet area,eddy current area and high pressure area respectively.There are two symmetric vortices vertically,which experiences formation,rupture and disappearance;The maldistribution is more serious in the horizontal than vertical,where the parameter of maldistribution in the horizontal is 7-8 times than in the vertical;Among the total pressure drop,the entrance pressure drop has the minimum proportion.And the correlations between the parameter of maldistribution and Re/length of PFHE have been obtained.(3)This paper studies the flow distribution and outlet temperature distribution of natural gas and cryogen of propane based on the operating condition of field in PFHE that is used to pre-cooling natural gas with liquid propane.The change regulation of fluid properties,temperature and heat exchange are also presented.The calculation result declared that: maldistribution is more serious in propane,as the phase of propane changes during heat exchange which results the increase of radio of core and outlet pressure drop.And the maldistribution of outlet temperature is used to measure the deterioration of heat exchanger performance,the results show that optimal structure can reduce the temperature maldistribution parameter by about 20%.(4)The original idea that change the numbers of entrance and outlets in order to improve the flow distribution is put forward for the first time.The results show that the parameter of maldistribution in gas phase reduces 47.6~50%,and 46.6~48.8% in liquid phase.