Experimental Device Improvement And Numerical Simulation For Heat Transfer Characteristics Of Slot Jet Impinging With Periodic Signals

Jet impingement heat transfer is one of the most effective ways to enhance heat transfer,because it has a high local heat transfer efficiency,and has been widely concerned and studied.Based on the comprehensive consideration of both the periodic jet signal and the slot nozzle jet,the heat transfer enhancement of periodic slot jet impingement has carried on the preliminary study in this paper.Firstly,this paper designs the experiment system of the jet impinging,including hardware system design and software system design.The heat exchange plate is jet impingement experiments hardware system development focus,mainly from the heat exchange plate wiring,electrical properties and performance estimation of three aspects of heat exchange plate design.The design of external circulating bath provides a constant temperature environment for the calibration experiment of the heat exchange plate,the key from the circulating bath performance estimation,pressure loss calculation and design.Secondly,the impact of different nozzle cross sectional face on the Nu number was analyzed by slot jet impingement heat transfer experiment on the experimental bench.Experimental study shows that under the steady jet,slot jet impingement to transfer heat effect on the whole is more uniform,and circular and square for effect of heat almost overlap;in the better effect of heat transfer near the stagnation point of a square jet,and the circular second,slot the worst.At last,the numerical simulation investigation is performed to the duty cycle and chamfer of the double nozzles impinging jet heat transfer enhancement.For different duty cycle slot nozzle jet,studies show that compared to heat transfer characteristics of the steady jet,the phase difference of adjacent two nozzles makes velocity stagger.When the stagger of velocity has no interactions or mutual influence is small,heat transfer enhancement achieves the best effect.Heat transfer performance with duty cycle of 0.5 is worse above the threshold frequency of 50 Hz,while the effect of jet frequency on the heat transfer with a duty cycle of 0.25 is less than the former within the frequency of 0 ~ 100 Hz.For different chamfer double slot nozzles jet,studies have shown that reducing the chamfer angle to some extent increase the turbulence intensity,which can strengthen the effect of heat transfer;and the increase of chamfer lengths makes a wider range of turbulence intensity.