King-Leung Wong

Heat transfer characteristics of an insulated regular polygonal pipe by using a wedge thermal resistance model

The relation of the critical and neutral thicknesses and heat transfer characteristics for an insulated regular polygonal pipe are investigated by using a new wedge thermal resistance model based on its varying pipe surface area. It is found that the dimensionless heat transfer characteristics of the insulated polygonal pipes are the same as those of an insulated circular pipe. It is also found that the conventional constant surface area plate model cannot be used to analyse the insulated regular polygonal pipes, especially at the situations of small to medium pipe sizes and/or with a greater insulation thickness.

Heat transfer characteristics of an insulated regular polyhedron by using a regular polygon top solid wedge thermal resistance model

The relation of the critical and the neutral thickness and heat transfer characteristics for an insulated regular polyhedron are investigated by using a new regular polygon top solid wedge thermal resistance (RPSWT) model obtained from a solid angle concept. It is found that the dimensionless heat transfer characteristics of the insulated polyhedrons are the same as those of an insulated sphere even though their actual heat transfer rates are different. It is also found that the conventional constant surface area plate model cannot be used to analyze the insulated polyhedrons, especially in situations of small to medium body size and/or with a greater insulation thickness. The single RPSWT model should also be applied to the heat transfer problem of the wedge block with a regular polygon top.

Heat transfer characteristics of an insulated regular cubic box by using a solid wedge thermal resistance model

Abstract A new solid wedge thermal resistance model is developed in this investigation and used to solve the relation of the critical and the neutral thickness and heat transfer characteristics for an insulated regular cubic box based on its varying surface area. It is found that the dimensionless heat transfer characteristics of the insulated cubic box are the same as those of an insulated sphere. It is also found that the conventional constant surface area plate model cannot be used to analyse the insulated cubic box, especially at the situations of small to medium box sizes and or with a greater insulation thickness. The solid wedge thermal resistance model should also be applied to the heat transfer problem of the block having a shape similar to a solid wedge.

Finite element solutions for laminar flow and heat transfer around a square prism

Abstract The finite element solutions of Navier‐Stokes and energy equations for steady laminar flow and heat transfer around square prisms, with attack angles of 0° and 45° have been obtained for a gas of Pr=0.7. The variations of surface shear stress, local pressure and Nusselt number are obtained over the entire prism surface including the zone beyond the point of separation. The predicted values of drag coefficients, the location of. separation, the average Nusselt number and the plots of velocity flow fields and isotherms are also presented. The trend of the present numerical results seems reasonable.

The critical heat transfer characteristics of an insulated or compound sphere considering heat radiation

Critical heat transfer from an insulated or compound sphere happen in ambient air with natural convection. Thus, heat radiation in such a situation must be considered because natural convection has only a small effect. It is found that the critical heat transfer characteristics considering heat radiation are very different from those neglecting heat radiation. The conventional critical heat transfer characteristics neglecting heat radiation only depend on sphere size, external convection heat transfer coefficient, and insulation conductivity. In addition to the above parameters, the critical heat transfer characteristics considering heat radiation are also related to the surface emissivities of the sphere and the insulation, the surrounding temperature, and the internal convection heat transfer coefficient.