NUMERICAL SIMULATION OF ENHANCING HEAT TRANSFER BY ARRANGING CHANNEL STRUCTURES ABOVE THE BOILING SURFACE

The regulation of bubble movement above the boiling surface plays an important role in enhancing boiling heat transfer. A channel structure formed by baffles above a boiling surface is proposed in this paper. In this arrangement, the bubbles generated at the bottom merge and detach through the middle channel, and liquid flows back from two-side channels to the heating surface. A stable vapor-liquid channel separation structure is formed to fully utilize the kinetic energy of bubble buoyancy, and the passive enhanced boiling heat transfer is achieved. To investigate the effect of baffles on the heat transfer performance above the boiling surface, the numerical study is conducted on the distance between the baffles and the heating surface, as well as the width of the middle channel in the baffles. The simulation results show that the channel structure formed by the baffles above the heating surface can improve the performance of boiling heat transfer, and the arrangement of the baffles affects boiling heat transfer by the growth and detachment of bubbles. Bubble detaching from the channel that form a relatively stable circulating flow for the working fluid can enhance boiling heat transfer. For different distances between baffles and the heating surface, the average heat transfer coefficient and average wall temperature first increase and then decrease with the distance. The heat transfer performance is best when the distance is 0.2 mm and the middle channel width is 0.5 mm. Compared to the surface without baffles, the greatest improvement in the average heat transfer coefficient increases by 212.59%, and the average wall temperature decreases by 10.45 K.