Experimental study on heat transfer characteristics of a high-temperature gas-gas heat exchanger with helically coiled tube bundles

An experimental study was carried out to investigate the heat transfer characteristics of an intermediate heat exchanger of the HTTR, using a full-size partial model and air as the fluid. The test model has 54 helically coiled tubes separated into three layer bundles and surrounding the center pipe. Radiate plates are installed between each bundle to promote heat transfer by radiation. A hot air (primary coolant), up to 300 C, flows upward on the shell side, and a cold air (secondary coolant) flows downward in the tubes. The heat transfer of the tube outside, due to forced convection, was obtained as a function of Re0.56 Pr0.3, and the ratio of the radiation heat transfer to the total transfer changed from 5 to 13% according to the temperatures, flow rates and the location of the tube bundles. The friction factor, depending on the tube arrangement, was proportional to Re-0.14