Heat transfer performance of cross-row microchannel heat exchangers
[Objective]In marine gas turbines that include intercooling cycles,the performance of the intercooler directly determines the performance of the gas turbine.Microchannel heat exchangers,characterized by their small volume,compact structure,strong heat transfer ability,high stability,have the potential to serve as the core component in intercooler heat transfer.In this study,the experimental heat transfer capabilities of a cross-row microchannel heat exchanger under low-flow conditions were investigated,and the influences of channel structure and flow parameters on the heat exchange performance of the exchanger were analyzed.[Methods]Three types of cross-row microchannel heat exchangers ME01,ME02,and ME03 were obtained through additive manufacturing and processing.ME01 and ME02 have the same channel size of 1.00 mmX 1.00 mm,but ME02 has 2.6 times more channels than ME01.The channel size of ME03 is half that of ME0 1,at 0.50 mm X 0.50 mm,and it has 4 times more channels than ME0 1,thus maintaining the same channel cross-sectional area.The effectiveness-number of heat transfer units(ε-UNTU)method was employed to assess the heat transfer performance of the cross-row microchannel heat exchanger.Using air and water as heat exchange working fluids,the effects of cold water inlet flow rate(0.15,0.30,0.50,0.70,0.90,1.10 m3/h)and hot air inlet temperature(70,80,90,100,110 ℃)on the heat transfer performance of cross-row heat exchangers were investigated.[Results]Compared with ME0 1,at the same water flow rate,the UNTU of ME02 decreased by 21.9％-50.8％,while that of ME03 increased by 106.9％-61.9％.Considering the significant impact of flow rate,under the same flow rate conditions,ME02 has an average decrease of 11.6％in UNTU compared to ME0 1.The logarithmic average temperature difference(Δtm)across the three types of cross-row microchannel heat exchangers shows a decreasing trend with water flow rate,with significant changes in ME01 and minimal changes in ME02 and ME03.As the cold side water flow rate increases,UNTU continuously increases.When the flow rate increases by 6.3 times,the UNTU of ME01 increases by 44.0％.The increase in cold side water flow rate leads to an overall increase in heat transfer capacity of the heat exchanger.The overall heat transfer capacity of ME01 increases by an average of 14.2％compared to the previous operating condition.As the inlet temperature of the hot side air increases,the Δtm of ME01 significantly increases,while the change in its heat transfer performance is not significant.The maximum difference in UNTU and total heat transfer coefficient between adjacent operating conditions are only 5.4％and 1.4％,respectively.[Conclusions]Reducing the channel size within the processing capabilities allows for the arrangement of more heat exchange channels in the cross-row heat exchanger,thus increasing the total heat exchange area and improving heat transfer performance.However,increasing the number of channels also increases the volume of the heat exchanger,resulting in negative impacts.The increase in inlet water flow rate intuitively results in an increase in the total heat transfer of the cross-row microchannel heat exchanger,which is the main reason for the enhancement of the heat transfer performance.This performance suggests that enhancing the heat transfer performance of the cross-row microchannel heat exchanger can be achieved by increasing the flow rate of the cooling water.However,the impact of inlet air temperature on the heat transfer performance of the cross-row microchannel heat exchanger is relatively minor.This is due to the complex heat transfer processes within the channels of the heat exchanger.Further experimental exploration is required to investigate these heat transfer processes at the microscale within the cross-row heat exchanger.
万方数据
维普
