An investigation of the mechanism of heat transfer near the critical state of a fluid

Abstract

Very large heat transfer coefficients have been observed in the one phase region near the critical point of some fluids. There has been some conjecture that the increase in these coefficients might be due to the agitation caused by bubble-like aggregates of low density fluid. It was believed that these bubble-like formations might grow and collapse in much the same way as actual bubbles in nucleate boiling. The purpose of these experiments was to see if the suggested mechanism of heat transfer could be observed and if it could be related to a significant increase in the heat transfer rate. Freon 114A was chosen as the test fluid because of its relatively low critical temperature and pressure. With this fluid and with the range of variables tested, bubble-like formations were observed under some conditions. However, no definite correlation to an increase in the heat transfer rate was noted. This fact should not exclude the possibility that bubble-like activity might result in a sharp increase in heat transfer rates in other fluids or even under different operating conditions with the fluid in question.