Optimization Of Marine Plate Heat Exchanger Based On Pulsating Flow Enhanced Heat Transfer

In order to reduce the energy consumption of Marine cooling water system and improve the performance of the system,the pulsating flow enhanced forced convection heat transfer was applied to the Marine cooling water system.A pulsation generator based on solenoid valve was designed,and a one-dimensional transient simulation model was established by Flomaster.According to the simulation results,the influences of different operating parameters of the pulsation generator,such as solenoid valve switching frequency,solenoid valve switching duty ratio and regulating valve opening on the pulsation flow were studied.As a pulsating source,the pulsating flow produced by solenoid valve is shorter in the declining stage of flow and pressure than in the rising stage in the pulsating cycle.Pulsation frequency depends on the solenoid valve switching frequency.Lower solenoid valve switching frequency can obtain higher average flow rate and higher pulsation amplitude in the pulsation cycle.Increasing the opening of the regulating valve can increase the average flow rate in the pulsating cycle,reduce the flow pulsating amplitude and reduce the pressure peak at the moment of closing the valve.An experimental device for pulsating flow intensification based on brazed plate heat exchanger was established to study the influence of working parameters of pulsating generator on heat transfer performance of heat exchanger.The enhanced heat transfer ratio was defined to characterize the enhanced heat transfer effect of pulsating flow relative to steady flow.The most important factor affecting the heat transfer performance of the plate heat exchanger is the Reynolds number.For the same Reynolds number working condition,changing the working parameters of the pulsation generator can only affect the total heat transfer coefficient in a small range.For the solenoid valve in the range of switching frequency from0.5Hz to 2.5Hz,the heat transfer enhancement effect is unstable when the pulsation frequency is low;in some working conditions,the heat transfer enhancement is weakened when the pulsation frequency is low;and the heat transfer enhancement is more stable when the pulsation frequency is high.Change the control valve opening is 25%,50% and 100%,the control valve opening condition of 50% and 25% of the enhanced heat transfer ratio is higher than the control valve opening condition of 100%,the control valve opening condition of 25% and the control valve opening condition of 50%,does not show obvious advantages.The duty ratio of the solenoid valve switch is changed to 25%,50% and 75%,respectively.In the condition of low pulsation frequency,the enhanced heat transfer ratio of the pulsating flow increases with the increase of the duty ratio.In the condition of high pulsation frequency,the enhanced heat transfer ratio of the pulsation flow is higher in the condition of 50% duty ratio than in the condition of75% duty ratio.For a series of experimental conditions,the pulsation frequency is 2.5Hz,the duty ratio is50%,and the opening of the regulating valve is 25%.Under different Reynolds numbers,the enhanced heat transfer effect is relatively stable,with the lowest enhanced heat transfer ratio of 105% and the highest enhanced heat transfer ratio of 125%.The three-dimensional transient simulation model of the plate heat exchanger in the experimental device was established by FLUENT,and the one-dimensional transient simulation model of the pipeline connected by the plate heat exchanger in the experimental device was established by Flomaster,and the coupling simulation of the two parts of the model was realized by MPCCI.Different parameters of the pulsation generator were set in the one-dimensional simulation model.According to the simulation results,the effect of different working parameters of the pulsation generator on the heat transfer enhancement of the heat exchanger was basically consistent with the experimental results.The heat transfer enhancement ratio in the simulation results was slightly lower than that in the experimental results in the corresponding conditions.The simulation method can be used as a feasible method to study the heat transfer enhancement law of plate heat exchanger with pulsating flow.