The top heat mode of closed loop oscillating heat pipe with check valves at the top heat mode (THMCLOHP/CV): a thermodynamic study

Nipon Bhuwakietkumjohn,Thanya Parametthanuwat

doi:10.1186/s40712-014-0005-8

Abstract

The article reports a recent study on heat flux of the top heat mode closed looped oscillating heat pipe with check valves (THMCLOHP/CV). An experimental system was evaluated under normal operating conditions. The THMCLOHP/CV was made of a copper tube with an inside diameter of 2.03 mm. The working fluid was water, ethanol and R123 with a filling ratio of 30%, 50% and 80% with respect to the total volume of the tube. The angles of inclination were 20°, 40°, 60°, 80° and 90° from the horizontal axis. The number of turn was 40 turns and 2 check valves. Three lengths of evaporator investigated were 50, 100 and 150 mm. The operating temperatures were 45°C, 55°C and 65°C. Experimental data showed that the THMCLOHP/CV at evaporator length of 50 mm gave a better heat flux with filling ratio at 50% when using R123 as working fluid and the operating temperature of 65°C at angles of inclination of 90°. It was further found that an evaporator length of 50 mm was superior in heat flux over other length in all experimental conditions under this study. Moreover, the presence of operating temperature had clearly contributed to raise the heat flux of THMCLOHP/CV, but the heat flux had decreased when evaporator length increased.

Highlights

The closed loop oscillating heat pipe had a check valve (CLOHP/Check valve (CV))
Miyazaki et al (2000) studied the oscillating heat pipe including a check valve under normal operating conditions; the liquid and vapour are effectively separated into two parts with the liquid in the cooling region and the vapour in the heating region
The results showed that the heat transfer performance of an horizontal closed loop oscillating heat pipe (HCLOHP)/CV system could be improved by decreasing the evaporator length

Summary

Introduction

The heat transfer of this CLOHP/CV occurred because of the self-sustaining oscillatory flow using a vapour or liquid circulation cycle between the heating and cooling sections: latent heat is transferred. The liquid and vapour are effectively separated into two parts with the liquid in the cooling regions and the vapour in the heating regions. The liquid forms U-shaped columns in individual turns, and these oscillations form waves. Under such flow conditions, the effective heat transfer area is limited by the amplitude of the waves. When the amplitude of oscillatory flow is sufficient and the heat transfer area is not included in the waves, effective working fluid supply to the heat transfer area cannot be obtained and heat transfer

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