Department of Mechanical Engineering, IIT Kharagpur, West Bengal-721302, India
School of Energy Science & Engineering, IIT Kharagpur, West Bengal, India- 721302
Sukanta Kumar Dash
School of Energy Science & Engineering, IIT Kharagpur, West Bengal, India- 721302; Department of Mechanical Engineering, IIT Kharagpur, West Bengal, India- 721302
The current study examines the combined effects of surface radiation and natural convection heat transfer from a solid isothermal helical coil that is vertically orientated. A finite-volume technique (FVM) based computational fluid dynamics (CFD) solver is used for numerical simulations in the laminar regime for Rayleigh number (Ra) in the range of 104 to 108. The discrete-ordinate radiation model is used for modeling the surface radiation heat transfer. In this study, the heat transfer coefficient is a strong function of the cooling efficiency, which in turn depends on the design parameters like pitch (P), diameter (D), and length (L) of the helical coil. The influence of Ra and surface emissivity on convective and radiative heat transfer and the effect of surface radiation on the heat transfer from the helical coil, are discussed. The temperature contours as a function of Ra are graphically elucidated. Under various operating parameters, the relative strength of radiation was determined and compared to the relative strength of convection. The relative magnitude of radiation diminishes with an increase in the Ra at a particular surface emissivity. In contrast, convection has a stronger effect at higher Ra.