Numerical investigation of heat transfer and friction factor in ribbed triangular duct solar air heater using Computational fluid dynamics (CFD)

Journal of Mechanical Science and Technology - The Computational fluid dynamics (CFD) based analysis is carried out to investigate the thermal and hydraulic performance of circular rib roughened...     

Experimental investigations on heat transfer and frictional characteristics of a turbulator roughened solar air heater duct

An experimental investigation has been carried out to study the heat transfer coefficient and friction factor by using artificial roughness in the form of specially prepared inverted U-shaped turbulators on the absorber surface of an air heater duct. The roughened wall is uniformly heated while the remaining three walls are insulated. These boundary conditions correspond closely to those found in solar air heaters.The experiments encompassed the Reynolds number range from 3800 to 18000; ratio of turbulator height to duct hydraulic mean diameter is varied from, e/D_h = 0.0186 to 0.03986 (D_h = 37.63 mm and e = 0.7 to 1.5 mm) and turbulator pitch to height ratio is varied from, p/e = 6.67 to 57.14 (p = 10 to 40 mm). The angle of attack of flow on turbulators, α = 90° kept constant during the whole experimentation. The heat transfer and friction factor data obtained is compared with the data obtained from smooth duct under similar geometrical and flow conditions. As compared to the smooth duct, the turbulator roughened duct enhances the heat transfer and friction factor by 2.82 and 3.72 times, respectively. The correlations have been developed for area averaged Nusselt number and friction factor for turbulator roughened duct.     

Determination of view factors by contour integral technique

This paper presents the application of contour integral technique to derive the diffuse radiation view factor expressions (analytical) for elements of nuclear reactor fuel bundle. The cases considered are: (i) view factor between two cylindrical rods of equal diameter and finite length, (ii) view factor between two cylindrical rods with interference by another rod and (iii) view factor between a cylindrical rod and a non-concentric cylindrical enclosure. The contour integral method is significantly more accurate than the area-integration method. The view factor results based on the analytical expressions derived for these finite length geometries are compared with that of the exact expressions available in the literature for infinite length. It is observed that the use of infinite length approximations in finite length cases can lead to significant errors.     

Local configuration factors for radiant interchange between cylindrical surfaces in rod bundle geometry

The aim of this study is to obtain configuration factor expressions for the diffuse interchange of radiant energy between two parallel cylindrical rods by contour integral technique. The contour integral approach for diffuse configuration factors has been derived by Sparrow (1963). It replaces the usual area integrals by more tractable contour (i.e., line) integrals, which simplifies analytical calculation of configuration factors. The advantages of this representation are associated with the reduced order of the integrals (i.e., double reduced to single, quadruple reduced to double) which must be evaluated to calculate the angle factor. For the numerical or analytical evaluation of configuration factors, the reduction in the order of the integrals has a great practical utility. In the literature, contour integral technique has been stated to appreciably be the more precise method than the area integration method.The cases studied are for elemental ring areas of (i) two cylindrical rods/tubes, (ii) two cylindrical rods with interference from a third rod and (iii) cylindrical rod within a cylindrical enclosure. The results of present configuration factor expressions meant for the ring elements of finite length geometries have been compared with values using exact algebraic expressions available in the literature for infinite length, analytical configuration factor expressions for equal finite lengths and with numerical results available in the literature. Contour integral technique has been observed to be a simple method that yields realistic results. This study has application in the analysis of fin-tube radiators, boiler tubes, nuclear fuel rod bundle, etc.     

Credit Scoring Models Using Ensemble Learning and Classification Approaches: A Comprehensive Survey

Wireless Personal Communications - Credit scoring models are developed to strengthen the decision-making process specifically for financial institutions to deal with risk associated with a credit...