Experimental study on condensing flow and heat transfer characteristics in minichannels under mechanical vibration conditions

Minichannel heat exchangers are often used in the condensers of vehicle air conditioners, and vibration is inevitable in vehicle driving. However, the influence of mechanical vibration on the characteristics of mini- channel condensing flow and heat transfer has been rarely studied. Therefore, the experimental study of condensing flow and heat transfer in minichannels under mechanical vibration was carried out in this paper. With R134a as the working medium, the condensation heat transfer coefficient, frictional pressure drop and flow pattern images were measured in the saturation temperature of 40 degrees C, mass flux density of 200 kg/(m2 & sdot;s), 2 & sdot; s), vapor quality range of 0-1, vibration frequency of 15-50 Hz and amplitude of 0-2.4 mm. For annular flow, intermittent flow and bubble flow, the vibration can enhance the wave of gas-liquid interface, and promote the breakup of long bubbles and the polymerization of small bubbles. Vibration enhances heat transfer in most cases, but weakens heat transfer in some specific cases. The frictional pressure drops under vibration conditions are greater than those under static conditions, which indicates that the influence mechanism of vibration on heat transfer and pressure drop is different. This paper attempts to analyze the complex mechanism of vibration affecting minichannel condensing heat transfer and pressure drop, which provides theoretical support for further study of condenser optimization design under vibration conditions.