<p>A Very High Temperature Reactor (VHTR) is one of the next generation nuclear reactor systems. These is a need for a passive method in which the cooling system operates even when all power is lost in the accident of a nuclear power plant. The gas cooling system with natural circulation is considered as a candidate for the Pressure Vessel Cooling System (VCS) of the VHTR. The Japan Atomic Energy Agency (JAEA) is pursuing design and development of commercial systems such as the 300MWe gas turbine high temperature reactor GTHTR300C (Gas Turbine High Temperature Reactor 300 for Cogeneration). In the VCS of the GTHTR300C, many rectangular flow channels are formed around the reactor pressure vessel (RPV). A cooling panel utilizing natural convection of air has been proposed. However, the amount of removed heat is considered to be inferior to that of cooling by forced convection. Hence, we propose a method of inserting a porous material into the heating surface to promote heat transfer. We have already found the amount of removed heat varies from -14 to 44% when a porous material is inserted into a vertical rectangular flow channel with a square cross section in which one surface is heated. For this reason, we believe that this heat transfer promotion method is effective. In this study, we performed 2 types of experiments. First, we used an experimental apparatus that simulated the cooling panel of the VCS. The experimental apparatus is a U-shaped flow channel, and the heating surface side is a vertical rectangular flow channel. Air was used as a working fluid. Fine copper wire was used as a porous material. The porosity was varied from 0.996 to 0.999. We carried out an experiment to investigate the heat transfer and fluid flow characteristics by natural convection in a vertical rectangular channel heated on one side. For comparison, we also conducted experiment on a smooth surface. Second, we used an experimental apparatus that a porous material was inserted into a horizontal channel. In the experiment, we measured the pressure drop by forced convection in order to obtain an empirical formula for the loss coefficient. As a result, an empirical formula was formulated from changes in Reynolds number, porosity, and fine wire diameter.</p>

Heat Transfer and Fluid Flow Characteristic of U-Shaped Flow Channel for Applications of VHTR

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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