Heat-transfer characteristics of a closed-loop oscillating heat-pipe with check valves.pdf

APPLIED
Applied Energy 84 (2007) 565–577 ENERGY
ate/apenergy
Heat-transfer characteristics of a closed-loop
oscillating heat-pipe with check valves
S. Rittidech *, N. Pipatpaiboon, P. Terdtoon
Faculty of Engineering, Mahasarakham University, 41/20 Khamriang Sub-District, Kantartawichai
District, Mahasarakham 44150, Thailand
Available online 8 December 2006
Abstract
The heat-transfer characteristics of this system . a CLOHP/CV, depend on the ratio of check
valves (Rcv), aspect ratio (Le/di) and the dimensionless parameters of the heat transfer. The CLOHP/
CV used employed a copper tube with inner diameters of and mm. The evaporator, adia-
batic and condenser lengths were equal to 50, 100 and 150 mm. The selected working fluids were
water (H2O), ethanol (C2H5OH) and R123 (CHCl2CF3) with a filling ratio of 50% of total volume.
The number of turns was 40. The Rcv values were 20, 8, 5 and 4. The evaporator was heated by hot
water, while the condenser section was cooled by distilled water. The inclination of the CLOHP/CV
used in the experiments was 90° to the horizontal, with a controlled working-temperature of 50 °C.
When the system reached the steady state, the temperature and the flow rate of the cooling water
were measured in order to calculate the heat-transfer rate of the CLOHP/CV. The experimental
results showed that the heat-flux increases with an increase of Rcv and decreases with an increased
aspect ratio. A correlation for predicting the heat-transfer rate for the heat-pipe in the vertical posi-
tion has been established.
Ó 2006 Elsevier Ltd. All rights reserved.
Keywords: Closed-loop oscillating heat-pipe; Check valves; Heat -transfer characteristics
1. Introduction
When a heat-transfer device for a high heat-load is considered, it is realised that con-
ventional heat-pipes have several limitations, such as the capillary limit when the diameter
* Corresponding author. Tel.: +66 43 754316; fax: +66 43 754326.
E-