The pressure drop characteristics of R134a flow boiling in micro scale single and multi-channels were investigated.The heat flux ranged from 3.54 W·cm-2 to 40.7 W·cm-2,Reynolds number varied from 278 to 6502,and vapor quality in outlet was at the range of 0 to 1.At the same experimental conditions,pressure drop in single channel was lower than that in multi-channels.With the increase of heat flux and mass flux rate,the pressure drop range in multichannel was lower than that in the single channel.With visual observation,flow instability was the main reason for higher pressure drop in multichannels.The reasons for flow instability and high pressure drop were analyzed.

To meet the need of electronic equipment work at lower temperature,experiment study on PHP charged with R141b and R600a.Experimental results indicate that low-boiling point fluid pulsating heat pipes start up more quickly and start-up temperature is lower compared with acetone at different heat power.During operation low-boiling pulsating heat pipe has smaller temperature difference、lower heating-surface temperature and smaller thermal resistance.Low-boiling point fluid improve PHP heat transfer performance,with R600a as working fluid,the shortest start-up time is 12 s,during operation,the smallest temperature difference is 0.8℃ with R141b as working fluid.