A study on the numerical values of the thermophysical properties for the eight single gases helium, nitrogen, oxygen, xenon, carbon dioxide, methane, tetrafluoromethane and sulfur hexafluoride at two film temperatures 300K and 600K for laminar boundary l

摘要

This paper addresses the laminar boundary layer flow of selected binary gas mixtures along a heated flat plate. To form the binary gas mixtures, light helium is the primary gas and the heavier secondary gases are nitrogen, oxygen, xenon, carbon dioxide, methane, tetrafluoromethane and sulfur hexafluoride. The central objective in the work is to investigate the potential of this group of binary gas mixtures for heat transfer intensification. From fluid physics, two thermophysical properties: viscosity and density influence the fluid flow, whereas four thermophysical properties: viscosity, thermal conductivity, density, and heat capacity at constant pressure affect the forced convective heat transfer. The heat transfer augmentation from the flat plate is pursued by stimulating the forced convection mode as a whole. Whenever there is heat transfer enhancement in a forced flow, drag force accretion seems to be inevitable. A standard formula for estimating the drag force exerted on the flat plate is available, from the fluid dynamics literature. At a film temperature 300K and 1atm, the He-SF_6 mixture delivers the absolute maximum for the relative heat transfer 16.2 at an optimal molar gas composition 0.96. When compared to the light primary He gas with a relative heat transfer rate 12.04, the He-SF_6 mixture generates a significant heat transfer enhancement of 39 percent. At a film temperature 600K and the same 1 atm, the relative heat transfer for the light primary He gas comes down to 10.77. In reference to this, the He-SF_6 mixture furnishes an absolute maximum heat transfer at an optimal molar gas composition 0.96 yielding a remarkable heat transfer enhancement of 68 percent. In the global context, the usage of exotic binary gas mixtures with light helium and heavier gases may be envisioned for special tasks in industry that demand high heat transfer rates.