THERMAL-HYDRAULICS OF HELICAL-TYPE HELIUM HELIUM INTERMEDIATE HEAT-EXCHANGERS (IHX) FOR NUCLEAR PROCESS HEAT APPLICATIONS OF HIGH-TEMPERATURE GAS-COOLED REACTORS (HTR) - FUNDAMENTAL RESEARCH AND LARGE-SCALE TESTS

The influence of the yaw angle on heat transfer and pressure drop was studied by testing tube banks of straight tubes at different angles between the flow direction and the tube axis in the range 15-degrees less-than-or-equal-to phi less-than-or-equal-to 90-degrees (cross flow) for subcritical Reynolds numbers from 2 x 10(3) to 10(5). Thermal-hydraulic advantages caused by an opposite inclination of neighbouring tube layers are shown. Results from the fundamental work on straight tube banks were checked at a semiexperimental helical-type heat exchanger for a nuclear process heat application, which is characterized by a large thread pitch and opposite-sense coiling of the tubes.