Measurement Of Thermal-pressure Conversion Effect Of Liquid Contained In Rigid Loops And Analysis On Heat Transfer

With the development of new and high technology,electronic device is more and more compact and efficient.The traditional electronic device cooling methods such as conduction heat transfer,natural convection and forced convection heat transfer already can't meet the requirement of the high heat flux cooling.Recently,a high heat flux technology has been found,while the heat transfer mechanism of it is still uncertain.According to the preliminary results of the experiment research about it,it can be caused by the thermal-pressure conversion effect,that is to say,the boundary sudden heat input will cause the intense pressure wave in the sealed cavity filled liquid working medium inside,and the pressure wave propagation in the working medium with the speed of sound,then transfer the energy quickly to the working medium.In order to verify the hypothesis,this paper sets up a super short pulse heating test system,and then explores its heat transfer mechanism.In this paper,the liquid R134a in the closed-loop circuit is studied by the combination of experiment and numerical calculation.In experimental study,we set up a single pulse heat test bed,the quantitative measurement of the effect of heat pressure conversion in liquid is realized.A high power pulse power can transmit a square voltage signal,whose pulse width is 300 ?s and pulse power can reach up to 40 V,through the high frequency LabVIEW control program to control the pressure and temperature signal synchronization and acquisition,and the sampling frequency reach up to 20 kHz.The experimental results show:through power pulse power source,the pressure waves can be produced,whose velocity is similar to the sound velocity.Further,as the heating power increases,the amplitude of pressure wave is larger.And the efficiency of heat pressure conversion is less than 1%,which is highest near the saturated liquid line.In the future,the thermal pressure conversion effect and corresponding measurement of higher intensity are expected to be achieved by improving the experimental system.In numerical calculation,the thermal-pressure conversion effect in the two-dimensional loop filled the liquid R134a and the piston effect of superheated liquid caused by thermal-pressure conversion is simulated.Calculation results show that:the thermal-pressure conversion effect also exists in the liquid working medium.In the superheat liquid R134a,with the same conditions,the equivalent thermal conductivity of piston effect is tripe to the pure heat conduction,and the higher of ratio of the superheat,the stronger of the piston effect.Moreover,the heat transfer of piston effect can be capable of with a long distance.