Effect of internal flow patterns on heat transfer performance of a closed-end oscillating heat pipe (CEOHP) at vertical position

S. Rittidech,L. Yodluk,K. Songsorn

doi:10.3844/ajassp.2007.1071.1074

Abstract

This article describes the effects of varying bond numbers (Bo) and aspect ratios (Le/d) on flow pattern of a close-end oscillating heat-pipe (CEOHP). The CEOHPs used employed a glass tube with inside diameter of 3 mm. The length of evaporator of 100 and 150 mm (the lengths of evaporator adiabatic and condenser section were equal) were employed with 10 turns. Observation of the flow pattern was conducted at 90Â° from the horizontal plane, with bond numbers of 1.8 and 2.6 with aspect ratios of 33.3 and 50. R141b and ethanol were used as the working fluids with filling ratio of 50% of internal volume of tube. The evaporator section was heated by heater and the condenser section was cooled by distilled water. The working temperature was controlled at 50Â°C. The temperature at adiabatic section and the inlet-outlet of distilled water at condenser section were recorded. The photographs of flow patterns at specific times were recorded at evaporator section by a digital camera and video camera were used to observe the flow patterns at evaporator section condenser together with adiabatic section and total part of CEOHP. It was found that the maximum heat flux occurred with Le/d 33 and Bo 2.6 an inside phenomena occurred is a dispersed bubble flow and slug flow.

Highlights

The rapid development of practical engineering application for micro–devices, micro–systems, advanced material designs and manufacturing
Among all the analysis and the experiment of the internal flow patterns are the major problems of the research, because they are crucial means to under stand the mechanism of the heat transfer in close-end oscillating heat-pipe (CEOHP)
A heat transfer characteristic of the CEOHP is directly affected by internal flow patterns

Summary

Introduction

The rapid development of practical engineering application for micro–devices, micro–systems, advanced material designs and manufacturing (including compact heat exchangers and devices for cooling electronic equipment). The variable parameters were the inclination angle, inner diameter of the tube, number of turn, working fluid and evaporator section length. As the evaporator section length increased when latent heat of the vaporization of working fluid increased.

Results

Conclusion