Enhancement of pool boiling performance through an asymmetric dual V-groove microchannel structured surface

Abstract

In pool boiling, microchannels on the heated surface change the bubble dynamics and consequently improve the heat transfer. In this study, two new microchannel configurations, i.e., asymmetric dual V-groove microchannels (VM) and orthogonally intersecting asymmetric dual V-groove microchannels (OIVM) have been introduced to study enhancement in pool boiling. The heat transfer enhancement due to the modified surfaces was established by comparing the heat transfer rates from the reference flat surface. Experiments have been performed using deionized water under saturation temperature at one atmosphere to evaluate the steady state heat transfer characteristics. The bubble dynamics and interface morphology at various heat flux levels have been captured using high-speed camera. The experimental observations have revealed that both the microchannel configurations exhibit a substantial improvement in heat transfer compared to that of flat surfaces. The OIVM surface demonstrates the highest rates of heat transfer and increase of 5.3 times in the maximum heat transfer coefficient (HTC) and 2.4 times in the critical heat flux (CHF) were observed compared to that of flat surfaces. Similarly, the VM surface demonstrates an improvement of 2.2 fold in HTC and 1.7 fold in CHF compared to the flat surface. Moreover, the OIVM surface demonstrates better heat transfer rates than that of modified surfaces investigated in the past studies. The increased heat transfer rate with the OIVM surface can be ascribed to large area for heat exchange, increased bubble initiation sites, bubble motion promoted macroconvection and efficient rewetting mechanism.