ISSN Online: 2379-1748
ISBN Flash Drive: 978-1-56700-431-1
ISBN Online: 978-1-56700-430-4
First Thermal and Fluids Engineering Summer Conference
EXPERIMENTAL STUDY OF FORCED CONVECTION HEAT TRANSFER DURING UPWARD AND DOWNWARD FLOW OF HELIUM AT HIGH PRESSURE AND HIGH TEMPERATURE
要約
Fundamental high pressure/high temperature forced convection experiments have been conducted in support
of the development of a Very High Temperature Reactor (VHTR) with a prismatic core. The experiments
utilize a high temperature/high pressure flow test facility constructed for forced convection and natural
circulation experiments. The test section has a single 16.8 mm ID flow channel in a 2.7 m long, 108 mm OD
graphite column with four 2.3kW electric heater rods placed symmetrically around the flow channel. This
experimental study presents the role of buoyancy forces in enhancing or reducing convection heat transfer
for helium at high pressures up to 70 bar and high temperatures up to 873 °K. Wall temperatures have been
compared among 10 cases covering the inlet Re numbers ranging from 500 to 3,000. Downward flows
display higher and lower wall temperatures in the upstream and downstream regions, respectively, than the
upward flow cases due to the influence of buoyancy forces. In the entrance region, convection heat transfer
is reduced due to buoyancy leading to higher wall temperatures, while in the downstream region, buoyancy-induced mixing causes higher convection heat transfer and lower wall temperatures. However, their
influences are reduced as the Reynolds number increases. This experimental study is of specific interest to
VHTR design and validation of safety analysis codes.