Effect Of Inverse Load On Critical Heat Flux Of Steam-Water Two-Phase Flow In A Rectangular Tube

The cooling of electric and electronic devices with high heat flux stimulates the researches on the flow boiling in narrow rectangular tubes,in which some experimental results and theoretical models have been obtained.The flow characteristics in rectangular tubes are very complex,and the critical heat flux is an important parameter for the boiling heat transfer.The fluid in tubes will be subjected to different dynamic loads during the maneuver of aircraft,which increases the difficulty of the research.An experimental apparatus of flow boiling in a narrow rectangular tube was established on a rotating platform.And the experiment for obtaining the characteristics of flow boiling for different inlet temperature,mass flow rate,tube size,heating orientation and inverse load were performed.The variations of mass flow rate,wall temperature,pressure drop and heat flux of tube with time under earth gravity and inverse load were analyzed.The effects of inlet undercooling,mass flow rate,heating orientation,section size and inverse load on the critical heat flux were investigated.The results show that as the magnitudes of supercooling and the flow rate increase,the saturated boiling wall temperature and the pressure drop increase.Under the inverse load,the increase in tube pressure drop is higher,and the flow fluctuation is more obvious.The critical heat flux increases with the increases of inlet supercooling,mass flow rate and inverse load.The critical heat flux for different heating orientations changes from high to low following the order of 0°,270°,90° and 180°.The critical heat fluxes for heating orientations of 0° and 180° are obviously affected by earth gravity,and the critical heat fluxes for 90° and 270° are markedly influenced by Coriolis force.The critical heat flux increases with the increase of tube’s depth-width ratio.A dimensionless formula for predicting the critical heat flux in rectangular tubes under earth gravity and inverse load was obtained through fitting the experimental data of present work.This research can be a reference for the development of avionics cooling device.