The Experts below are selected from a list of 57879 Experts worldwide ranked by ideXlab platform
Kamel Hooman - One of the best experts on this subject based on the ideXlab platform.
-
experimental analysis of heat transfer of supercritical fluids in plate heat exchangers
International Journal of Heat and Mass Transfer, 2014Co-Authors: Pourya Forooghi, Kamel HoomanAbstract:Heat transfer of a supercritical refrigerant with highly variable properties close to pseudo-critical temperature was experimentally investigated in plate heat exchangers. Two different plate corrugation angles (30° and 60°) were examined while the Reynolds and the Prandtl number range from 800 to 4200 and 3.2 to 4.2, respectively. The results are found to be different from those obtained using classical Dittus–Boelter type correlations. Two possible effects were investigated: effect of wall-to-bulk Property Ratio and that of buoyancy. The former was found to be important and was accounted for in the correlation using the correction factor proposed by Jackson and Hall. The latter was found not to be significant for corrugation angle of 60°. For corrugation angle of 30°, however, buoyancy effects were found to have some influence, yet majority of the data points are found to be within 15% of those predicted using the correlation.
Pourya Forooghi - One of the best experts on this subject based on the ideXlab platform.
-
experimental analysis of heat transfer of supercritical fluids in plate heat exchangers
International Journal of Heat and Mass Transfer, 2014Co-Authors: Pourya Forooghi, Kamel HoomanAbstract:Heat transfer of a supercritical refrigerant with highly variable properties close to pseudo-critical temperature was experimentally investigated in plate heat exchangers. Two different plate corrugation angles (30° and 60°) were examined while the Reynolds and the Prandtl number range from 800 to 4200 and 3.2 to 4.2, respectively. The results are found to be different from those obtained using classical Dittus–Boelter type correlations. Two possible effects were investigated: effect of wall-to-bulk Property Ratio and that of buoyancy. The former was found to be important and was accounted for in the correlation using the correction factor proposed by Jackson and Hall. The latter was found not to be significant for corrugation angle of 60°. For corrugation angle of 30°, however, buoyancy effects were found to have some influence, yet majority of the data points are found to be within 15% of those predicted using the correlation.
Derek J Jackson - One of the best experts on this subject based on the ideXlab platform.
-
screening and correlating data on heat transfer to fluids at supercritical pressure
Journal of Nuclear Engineering and Radiation Science, 2016Co-Authors: Derek J JacksonAbstract:A simple criterion for screening experimental data on turbulent heat transfer in vertical tubes to identify those not significantly influenced by buoyancy was proposed by the author many years ago and found to work quite well for water and air at normal pressures. However, it was recognized even then that the ideas on which the criterion was based were too simplistic to be suitable for use in the case of fluids at supercritical pressure. With the passage of time and tremendous advancement in data processing capability using present-day computers, it is now possible to contemplate adopting a refined approach specifically designed to be suitable for such fluids. The present paper describes a semi-empirical model of buoyancy-influenced heat transfer to fluids at supercritical pressure, which takes careful account of nonuniformity of fluid properties. It provides a criterion for determining the conditions under which buoyancy influences are negligibly small. Thus, the extensive databases now available on heat transfer to fluids at supercritical pressure can be reliably screened to eliminate those affected by such influences. Then, the many correlation equations that have been proposed for forced convection heat transfer can be evaluated in a reliable manner. These equations mostly relate Nusselt number to Reynolds number, Prandtl number, and simple Property Ratio correction terms. Thus, they should be evaluated using only experimental data that are definitely not influenced by buoyancy. A further outcome of the present paper is that it might now prove possible to correlate the buoyancy-influenced data in such databases and fit the equation for mixed convection heat transfer yielded by the model to the correlated data. If this can be done, it will represent a major advancement in terms of providing thermal analysts with a valuable new tool.
K. L. Pillai - One of the best experts on this subject based on the ideXlab platform.
-
Thermophoresis in natural convection with variable properties
Heat and Mass Transfer, 1999Co-Authors: S. Jayaraj, K. K. Dinesh, K. L. PillaiAbstract:The present paper deals with thermophoresis in natural convection with variable properties for a laminar flow over a cold vertical flat plate. Variation of properties like density, viscosity and thermal conductivity with temperature is included in the formulation of the problem. Selection of components for the Property Ratio is made by fitting the Property values between the desired temperature limits. For a selected fluid, Prandtl number variation with temperature is neglected and the Prandtl number corresponding to film temperature is used for the analysis. Solution is carried out by finite difference method. Variation of wall concentRation and wall flux along the length of plate is studied. The effect of thermophoretic coefficient on wall concentRation is also studied. Results are presented in the form of graphs. The result is compared with similarity solution by Runge-Kutta method and found to be accurate upto second decimal place.
Heinz Herwig - One of the best experts on this subject based on the ideXlab platform.
-
Fluid friction in incompressible laminar convection: Reynolds' analogy revisited for variable fluid properties
European Physical Journal B, 2008Co-Authors: Shripad P. Mahulikar, Heinz HerwigAbstract:The Reynolds' analogy between the Stanton number (St) and the skin friction coefficient (cf) is popularly believed to hold when St increases with increasing cf, for simple situations. In this investigation, the validity of Reynolds' analogy between St and cf for micro-convection of liquids with variations in fluid properties is re-examined. It is found that the Sieder-Tate's Property-Ratio method for obtaining Nusselt number corrections is theoretically based on the validity of Reynolds' analogy. The inverse dependence of Reynolds number and skin friction coefficient is the basis for validity of the Reynolds' analogy, in convective flows with fluid Property variations. This leads to the unexpected outcome that Reynolds' analogy now results in St increasing with decreasing cf. These results and their analyses indicate that the validity of Reynolds' analogy is based on deeper foundations, and the well-known validity criterion is a special case.
