Mathematical model of bent-flattened sintered-grooved heat pipe with concept of receding-and-excessing fluid

Abstract

A mathematical model that uses the concept of evaporation and condensation to explain the process of heat and mass transfer within the bent, flattened heat pipe has been established to predict its wall temperature and thermal resistance. When the heat pipe was bent and flattened in the application, the wick was damaged, resulting in less liquid being returned. It caused the wick to become unsaturated at the evaporator section. It can be determined that the liquid-vapor interface will gradually recede into the wick. This is defined as the “Receding” model (R). In the condenser section, the remaining condensate was collected as excess fluid. This is referred to as the “Excess Fluid” model (EF). It was observed that the low thermal conductivity of the unsaturated wick decreased the effective thermal conductivity at the evaporator section. The effective thermal conductivity at the condenser section also decreased due to the low thermal conductivity of the liquid film. The low effective thermal conductivity resulted in higher evaporator temperatures and lower condenser temperatures, resulting in higher thermal resistance. The established “REF” model has been validated in the same conditions by the experimental results and provides accurate predictions for the heat transfer performance of heat pipes.

Keywords

• Sintered-grooved wick
• Miniature heat pipe
• Numerical simulation
• Bending and flattening
• Cryogenic