Mechanism and influence factor analysis of heat transfer deterioration of transcritical methane

Abstract

A three-dimensional simulation, of transcritical flow, and heat transfer of methane, under asymmetric heating conditions, were performed. The simulation results demonstrated that the drastic changes in density at the pseudo critical temperature lead to an M-type velocity distribution, which plays a dominant role in the deterioration of heat transfer. The specific heat affects the location of the deterioration, while the thermal conductivity and viscosity affect only the wall temperature magnitude, whereas they do not affect the occurrence and location of heat transfer deterioration. The M-type velocity gradually disappears with the inlet mass flow rate increasing, indicating that heat transfer deterioration was eliminated. In addition, there is a critical inlet pressure of 10 MPa. When the inlet pressure is less than critical inlet pressure, heat transfer is improved with the inlet pressure's increase. However, when the inlet pressure is higher than critical inlet pressure, with inlet pressure increasing further, the decrease in the peak specific heat value will weaken the heat absorption capacity of methane, making the deterioration more severe. The deterioration of heat transfer will be improved by increasing the wall roughness, while the pressure drop will also be increased. The optimal wall roughness of 7 μm can be selected by using the thermal performance factor.