Study Performances of Thermosyphon with Heat Source near the Top and Heat Sink at the Bottom

E. Yandri1* N. Miura1, T. Kawashima1, T. Fujisawa1, M. Yoshinaga2

1Solar Energy Research Group, Department of Vehicle System Engineering, Faculty of Creative Engineering,
Kanagawa Institute of Technology, 243-0292 Atsugi, Japan

2Department of Architecture, Faculty of Science and Technology, Meijo University, 468-8502 Nagoya, Japan

Corresponding Author, vandri@,ctr. kanagawa-it. ac. jp
Abstract

Solar energy can be converted into electricity with Photovoltaic cells and to heat with solar collectors. Especially for solar collectors, the heat collected can be utilized for both water heating and space heating applications. Solar collector researches for space and water heating has been developed and resulted many interesting designs, from simple thermosyphon systems with low maintenance to automatic operation systems which are depended so much with mechanical and electrical properties like pumps, valves, sensors, etc. Recently, a device which transfered heat from the hot reservoir near the top to the cold reservoir at the bottom was invented by Ipposhi et. al [6], called as the ITMI model. As same as the ITMI model was constructed and tested. We improved the ITMI model by proposing the IMT model. The first report was presented in SWC 2007 by comparing the performance of ITMI model and IMT model. The current experiments are completed with a digital flow mater of vapor in order to be able to calculate the heat energy transported. Some experimental parameters are varied in order to know the optimal operating condition for this IMT model. Heat input is varied for 100, 200, and 300W. Inclination angle between evaporator and top heat storage is varied for 0, 5, and 100. Level of heat store in the top heat storage are varied for 20, 110, and 200mm. Result shows that this IMT model can work better for all heat input (100, 200, 300W), and for all heat store in the top heat (20, 110, and 220mm) with inclination angle of 00, 50, 100. This model could be more interesting for water and space heating applications as more ecological approach.

Keywords: natural circulation, thermosyphon, solar energy

1. Introduction

Solar energy can be converted into electricity by Photovoltaic cells, heat by solar collectors, and both electricity and heat by hybrid photovoltaic and thermal (PV/T) panels. The collected heat can be used for Space Heating and Solar Water Heating (SWH). A typical SWH system is a combination of solar collectors, an energy transfer system and a thermal storage system. SWHs are also characterized as open loop system (direct) which circulates potable water through the collectors and closed loop system (indirect) which uses antifreeze heat-transfer fluid such as polypropylene glycol to transfer heat from the collector to the potable water in the storage tank [2]. Depend on the way to circulate the working fluid, SWHs are divided into active system which uses a pump to circulate the working fluid such as water or polypropylene glycol through the collectors and passive system which circulates the working fluid naturally by the effect of the gravitational force [2]. The passive system calls also thermosyphon which means the heat transport device that can transport a large amount of heat using body forces (gravitational and centrifugal forces). Thermosyphon has a great advantage because of no electrical energy and simple structure. That is why, the thermosyphon researches are not intended for SWH application only, but for many applications. Thermosyphon was studied as an alternative liquid cooling technique in which heat is transferred as heat of evaporation from evaporator to condenser with relatively small temperature difference [3]. Thermosyphon radiator used for domestic and office heating was studied and its performance has been tested with Freon 11, acetone, methanol and water as working fluid [1]. A model of the two-phase flow and heat transfer in the closed loop two phase thermosyphon (CLTPT) involving co-current natural circulation, which is focus for electronics cooling that exhibit complex two-phase flow patterns due to the closed loop geometry and small tube size [4]. The main reason to develop a thermosyphon with a heat source near the top and heat sink at the bottom is to solve weight problem when a thermosyphon installed on the roof [7].