Experimental study on condensation heat transfer of high pressure flowing steam on a bundle of coiled tubes

MasterThe coiled tube is used as a heat exchanger in various industries such as refrigeration and air conditioning, chemical plants, and small reactor systems, and is composed of a spiral wound heat exchanger (SWHX). It is used as an evaporator in the field of refrigeration and air conditioning, a reactor in a chemical plant, and a steam generator in a SMR. In addition, in the event of an accident with a SMR, it may be used as a condenser as a part of the residual heat removal system (RHRS) that removes superheated steam generated from reactor core under accident condition. When used as a condenser, condensation occurs on the shell side where the flow of condensate water and steam is free. In case of an accident, film condensation occurs on the tube because it is a high heat flux condition. Several researchers have studied the external condensation of the coiled tube under static steam conditions. Depending on the ratio of the curvature of the coiled tube and the diameter of the tube, acceleration forces due to gravity and centrifugal forces that are not found in the horizontal tube are generated, and the shape of the film thickness changes due to the forces generated. It is reported that the heat transfer coefficient is higher than that of the horizontal tube depending on the degree of change. However, this study did not consider the steam flow required for industrial applications. In addition, since the coiled tube is close to the form of a bundle tube in which several tubes are arranged, the bundle effect should be considered. Therefore, in this study, experiments were conducted under the conditions of two vapor mass flux (7.2kg/m^2 s,12.0kg/m^2 s) and two pressures (1.0MPa, 2.0 MPa) to confirm how the mass flux of steam is reflected in the coiled tubes, and the heat transfer coefficient for each row. By measuring, it was verified how the tube bundle shape affects the heat transfer coefficient in the coiled tube