Study on Heat Transfer Enhancement of Oscillating-Flow Heat Pipe for Drying

Abstract

The application of oscillating-flow heat pipe (OFHP) in drying is of great potential. In this article, two methods are proposed to enhance the heat transfer of OFHP: (1) pulse heating is adopted instead of conventional continuous heating; and (2) a tube with a nonuniform cross section is introduced. Experiments on the effects of these two methods have been studied in comparison with ordinary OFHP. Experimental results indicate that using the pulse heating and the nonuniform cross section channel can improve the oscillating process and the heat transport performance in the OFHP. The heat transfer rate of pulse heating OFHP is higher than that of the continuous by 15–38%, and the effective thermal conductivity is higher by 12–63% at the same heating power. The effective thermal conductivity and the heat transfer rate of the nonuniform cross section heat pipe are also higher than that of the uniform cross section heat pipe when the heating power is more than 100 W.

Keywords:

• Drying
• Nonuniform cross section
• Oscillating-flow heat pipe
• Pulse heating

ACKNOWLEDGEMENTS

This work is supported by project No. 50606011 of the Chinese National Science Foundation and the Beijing Key Laboratory of Energy Safety and Clean Utilization.