Heat Transfer From Electrically Heated Nichrome Wires to Boiling Water at Different Pressures

Abstract

Boiling curves for nucleate and film boiling have been drawn for nichrome of three sizes in distilled and degasified water at saturation temperatures under five different sub-atmospheric vapour pressure. It has been observed that (i) for the same Q/A (heat transfer), Delta Theta (excess of wire temperature over saturation point of water) decreases with pressure in both nucleate and film boiling ranges, (ii) Both Q/A max. and Delta Theta/SubC show a rapid decrease with pressure but these variations become more gradual at higher pressures, and (iii) Q/A max. and Delta Theta/SubC increase with wire size at all pressures; increase in Delta Theta/SubC however, becomes less conspicuous at higher pressures approaching one atmosphere.