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. INTRODUCTIONThe energy consumption of drying shares a big proportion of industrial energy consumption, [1] and paper drying takes about 33% of the total energy consumption of paper producing. [2] Therefore, saving energy in the drying industry is very important. Efforts can be made in two ways: (1) It is common knowledge that increasing the drying efficiency by improving the heat and mass transfer of drying process can reduce the energy usage, and (2) saving energy consumption of a drying system can accomplish the same purpose. Concretely, for general convective dryers, it is reasonable to increase the heat transfer

Theoretical evaluation of a simple cooling pad for inducing hypothermia in the spinal cord following traumatic injury

“…The heat transfer rate is affected by changes in the boundary layer thickness, fluid mixing, and a lowered thermal resistance [16,23]. Several previous studies in engineering design applications have concluded that the presence of an oscillating flow can enhance heat transfer by 15-40% and increase the effective thermal conductivity by 10-60% [16, 21,30,31,53,56]. It has been suggested that this enhancement is mainly due to the fact that oscillations promote fluid mixing and create vortices around the cylinder because the laminar-turbulent transition may be a major mechanism that enhances heat transfer in zero-mean oscillating flow [28,31].…”

Effectiveness of using acoustic oscillations of ultrasonic frequency on the process of removing moisture from porous material

“…The experimental data obtained will make it possible to develop specialized drying equipment that provides optimal modes and conditions that maximize the drying process. Also, based on the results of the research, the requirements for sources of acoustic impact will be determined and existing ultrasonic emitters will be developed and/or modified to form the required distribution of oscillations in a gaseous medium [10].…”