| The dimple brazed plate heat exchanger(DBPHE)is a new type of plate heat exchanger developed by company D.It has the advantages of good heat transfer performance,low flow losses and high pressure endurance capacity which make it have bright prospect in engineering application.However,due to its short time of application,there are insufficient related research achievements and application cases,thus only a few references can be used to guide the design and project promotion.During use,customers find a problem that the actual pressure drop is much higher than prediction.According to the analysis,the internal pressure drop prediction formula of Company D is not suitable for the conditions of low Re.Therefore,the analysis of the resistance characteristics of this type of heat exchanger in low-Re flows and the modification of the existing pressure drop prediction formulas can not only solve the problem of company D but also provide a reference for the design and application of this heat exchanger,which is of great significance.The main purpose of this paper is to obtain the drag coefficient formulas for the 4 types of DBPHEs in low-Re flows,explain their resistance characteristics,and analyze their economic conditions from the perspective of resistance.This paper uses experimental research as a basis and combines the way of theoretical analysis.The specific work are as follows:(1)A pressure drop experiment table for heat exchangers was designed and built;(2)720 sets of pressure drop test data for 4 types of heat exchangers under the steady flow with two kinds of working fluids were measured;(3)The relationships between frictional resistance coefficient and Re of the four plate heat exchangers were calculated based on the the experimental data;(4)The resistance characteristics of the DBPHEs are explained by analysing the results of numerical simulation and comparing the obtained fitting formulas with the existing research results.The study found that Re has a power function relationship with the frictional resistance coefficient for a single plate type.In the same Re flows,the drag coefficient of this type of heat exchanger is about 30% lower than that of a chevron brazed plate heat exchanger,and about 50% higher than the theoretical solution of frictional resistance coefficient under laminar flow in circular tube.When Re is less than 15,the flow economy is poor.The dimple diameter and spacing are important parameters to friction resistance characteristics.They have a negative correlation to pressure drop according to numerical simulation results.In this paper,the analysis of resistance characteristics is more qualitative.The accuracy of numerical simulation is high but there aren't enough calculation examples under time pressure.In summary,the work in this paper has a strong reference value for engineering applications but a weaker significance for guiding design. |
PDF Full Text Request