Kyaw Zin Htoo†*, Phuoc Hien Huynh‡, Keishi Kariya†† and Akio Miyara††‡‡

†Graduate School of Science and Engineering, Saga University 1 Honjo-machi, Saga, 840-8502, Japan

‡Ho Chi Minh City University of Technology – VNU – HCM (HCMUT) 268 Ly Thuong Kiet, Ho Chi Minh City, Vietnam ††Department of Mechanical Engineering, Saga University 1 Honjo-machi, Saga, 840-8502, Japan

‡‡International Institute for Carbon-Neutral Energy Research, Kyushu University Nishi-ku, Motooka, Fukuoka, 819-0395, Japan

*Corresponding Author Email: [email protected]

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Loop heat pipe (LHP), a naturally operated heat transfer device with exceptionally flexible and simple in construction, has been paid interest by many researchers and scientists. Additionally, the effectiveness of using LHP as a heat exchanging device can be seen by transmitting heat load at high rates over considerable distances with extremely small temperature drop. In this paper, instead of using the traditional method of the gravity-assisted orientation, the experiment is set up in horizontal condition. Water and ethanol are selected as two types of working fluids in this operation. Experimental results of horizontal orientation using water as a working fluid have already been reported. The present experimental set up is shown that the operation can be carried out a wider range of temperatures up to 124 ºC at the surface of the heating block whereas the contribution of the previous set up is only up to 95 ºC. For the comparison of the working fluids, the performance of the water LHP is by far superior to the ethanol. Unlike the ethanol LHP which have a stable, limited operation up to 57 W, the water LHP can be able to perform a considerable range of the heat load of 41 W to 244 W while the surface temperature of the heating block raised from 63 ºC to 124 ºC in the water LHP.