Saturated film boiling of water over a finite size heater

Abstract

A numerical investigation was carried out on pool film boiling of water over a finite size heater at near critical conditions using a Coupled Level Set and Volume of Fluid (CLSVOF) method. For the modelling of moving contact line, a dynamic contact angle approach has been considered to capture the flow characteristics near the contact line region accurately. The effect of Jacob number on flow and heat transfer characteristics was investigated for Jacob number ranging from Jav = 1.274 to 38.205. At lower Jacob number, Jav = 1.274 (ΔTSup = 1K), discrete bubbles are released from vapour layer periodically. At the medium Jacob numbers, discrete vapour bubbles are released from the vapour layer as well as from the tips of the vapour columns. At higher Jacob number, Jav = 38.205 (ΔTSup = 30K), discrete bubbles are released predominantly from the tips of long vapour columns. Over the heater surface, the rate of vapour bubble release is low at the edges of the heaters where the contact points exist compared to other regions of the heater surface. The comparison of the time averaged Nusselt number obtained from the finite and infinite size heaters show that the heat transfer rate is the same for the low wall superheats. However, at higher wall superheat conditions, heat transfer rate is higher in the case of finite size heaters compared to that of infinite size heaters.