Conditions for the occurrence of heat transfer deterioration in light hydrocarbons flows

Heat transfer deterioration could affect heated channel flows of supercritical pressure fluids in a number of technological applications. Aim of the present study is to analyze the phenomenon onset and to investigate its dependence on the pressure, for three light hydrocarbons: methane, ethane and propane. To this goal a parametric numerical analysis is carried out on uniformly heated straight channels varying, for each different species, the inlet reduced pressure and the enforced heat flux. A parabolized Navier-Stokes solver is used to carry out the simulations, together with Helmholtz energy equation of state and accurate models for the transport properties. Results lead to an unambiguous definition of the threshold value for the ratio between heat flux and specific mass flow rate which identifies the boundary for heat transfer deterioration onset. On the basis of this definition, for assigned inlet reduced temperature, a correlation for the threshold parameter in terms of reduced pressure is presented for the considered species.