| Abstract: | The influence of the grain size of metallic surfaces on nucleate boiling was investigated experimentally. Surfaces of electrodeposited copper, nickel, brass and chromium were studied with particular emphasis on copper (146 grains per inch to 1678 grains per inch). The pool boiling heat transfer studies were conducted by transferring heat produced electrically through a 6-in. diameter heating surface to a pool of boiling water contained in a glass boiler. A log-log plot of the Q/A versus δTm data showed a definite effect of the grain size of the surface on nucleate boiling heat transfer, the heat transferred at a given δTm increasing as the grain size increased. For copper plated surfaces, the Rohsenow Equation for nucleate pool boiling gave values for Cst and r, which showed a linear relationship when plotted separately against the number of grains per unit length of the surface. A slightly modified form of the Rohsenow correlation has been proposed which takes into account the influence of the grain size of the surface metal for predicting boiling heat transfer. |
