Abstract
A numerical investigation of the heat transfer deterioration (HTD) phenomena is performed using the low-Re k-ωturbulence model. Steady-state Reynolds-averaged Navier-Stokes equations are solved together with equations for the transport of enthalpy and turbulence. Equations are solved for the supercritical water flow at different pressures, using water properties from the standard IAPWS (International Association for the Properties of Water and Steam) tables. All cases are extensively validated against experimental data. The influence of buoyancy on the HTD is demonstrated for different mass flow rates in the heated pipes. Numerical results prove that the RANS low-Re turbulence modeling approach is fully capable of simulating the heat transfer in pipes with the water flow at supercritical pressures. A study of buoyancy influence shows that for the low-mass flow rates of coolant, the influence of buoyancy forces on the heat transfer in heated pipes is significant. For the high flow rates, buoyancy influence could be neglected and there are clearly other mechanisms causing the decrease in heat transfer at high coolant flow rates.
Highlights
High performance light water reactor (HPLWR) is one of the six Gen-IV reactor concepts, based on the existing boiling and pressurized water reactors
Two different experiments are numerically simulated with Ansys CFX-11.0 computational software, using the stress transport (SST) turbulence model in order to examine the influence of buoyancy on the heat transfer
The experiment by Ornatskij et al [3] is performed for very high-coolant flow rate, where the buoyancy force should have no effect on the heat transfer according to (7)
Summary
High performance light water reactor (HPLWR) is one of the six Gen-IV reactor concepts, based on the existing boiling and pressurized water reactors. The heat transfer coefficient decreases causing the increase in wall temperature. As shown by several experiments (Shitsman [1], Kirillov et al [2], or Ornatskij et al [3]), the increase in wall temperature is not as rapid as in case of boiling crisis in classical light water reactors. Due to the relatively mild increase in wall temperature, the onset of HTD is not well defined. Koshizuka et al [4] defined the onset of HTD as the following ratio: Dr. where α0 is the heat transfer coefficient calculated numerically by Jones-Launder’s k-ε model using constant properties at bulk liquid temperature. For the present study the exact definition is not relevant, as all the simulations are performed in the highly deteriorated region
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