TED-AJ03-285 IMPROVEMENT OF THE PERFORMANCE OF A NEW HEAT TRANSPORT DEVICE USING THE INTERMITTENT DISCHARGE OF ACCUMULATED VAPOR
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概要
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There are many kinds of the exhaust heat sources in the urban area, such as the outdoor unit of the air-conditioning system, the paved road and the walls of the buildings which accumulate solar radiative heat in themselves, especially in summer. The demand for recovering and removing these low-quality heat efficiently must be increased seriously to keep the environment comfortable to live in. Much additional energy consumption should be required for this demand. This consumption totally leads to a large amount of the available energy loss, because the exhaust heat recovery and transport system generally uses the electric power. The authors originally proposed a unique method for treating such exhaust heat with small available energy loss. By using this method, the heat can be transported with almost no additional power for circulating the heat transport fluid. The heat transport process was composed of the following cycle, as shown in Fig.1 : (1) accumulation of high-pressure vapor in an evaporator vessel, (2) sudden flow generation by discharging the accumulated vapor, (3) condensation of a part of the discharged vapor in the downstream condenser, (4) return of the condensate to the evaporator by vapor-liquid two-phase flow via a low-pressure reservoir. Research works on the heat transport without additional power input have been reported, the most popular examples of which were heat pipes. Compared with ordinary heat pipes, the direction of the heat transport can be selected regardless of gravity by using the present method. Compared with the specially arranged anti-gravity heat pipes, the elements constructing the present system are simple, small in number and excellent in reliability of operation. According to the previous experimental results on this proposed method, however, the following two problems should be solved for the continuous operation : (a) large amount of condensate was left in the condenser, and (b) pressure in the reservoir increased gradually, cycle by cycle during operation, due to the accumulation of the vapor. The problem (a) might lead to the shortage of the working liquid in the evaporator, and the problem (b) meant the reduction of the fluid circulating force. In the present work, the effects of the size of the condenser and the existence of the vapor by-pass flow were experimentally investigated on the heat transport characteristics. The results showed that the above two problems could be solved under some experimental conditions. The instantaneous pressure drop of the upward returning vapor-liquid two-phase flow was also examined experimentally for making a physical model to design the present system.[figure]