Leidenfrost Phenomenon and Rewetting of Hot Vertical Tubes by Bottom Flooding Using Nanofluids

摘要

Leidenfrost (LF) and rewetting (RWT) phenomenon are both closely related and involved for the cooling of a very hot object utilizing a suitable cooling agent. The present study focusses on the influence of different parameters on both LF and RWT phenomenon of vertical tubes by bottom flooding. The various parameters primarily include the quantity or injection rate of the coolant (CLNT), type of CLNT and initial temperature of the heated substrate. For both the phenomena, a critical comparison of the findings between nanofluids (NFs) and water has been presented. In case of the LF phenomenon, as a small mass of liquid comes into contact with a heated solid, the dynamics of the vapor layer formed in between the solid and the liquid governs the rate of evaporation of the liquid. The vapor layer vibration leads to the formation of different shapes which are orderly random in occurrence and has been investigated in details. In another event, during the RWT phenomenon, as the CLNT enters the heated solid, different flow regimes are observed to form which has been investigated in details. The temperature responses of the vertical tubes have been utilized to construct the boiling curves from which the surface heat flux can be easily estimated.