Showing papers in "Journal of Heat Transfer-transactions of The Asme in 1971"

Local non- similarity thermal boundary- layer solutions

Abstract: A solution method is described and applied for treating non-similar thermal boundary layers. The solutions are locally autonomous (that is, independent of information from other streamwise locations) and are found by solving quasi-ordinary differential equations of the similarity type. All non-similar terms appearing in the conservation equations are retained without approximation, and only in derived subsidiary equations are terms selectively neglected. The accuracy of the results can be appraised from comparisons internal to the method itself. Thermal boundary-layer non-similarity arising both from velocity-field, non-similarity and from streamwise variations of surface temperature are analyzed. Numerical results for the surface heat transfer and for the boundary-layer temperature distribution are presented for various physical situations.

Laminar Film Condensation on Plane and Axisymmetric Bodies in Nonuniform Gravity

Abstract: Condensate film thickness and Nusselt number on axisymmetric vertical plates and cylinders, correcting for variable gravity and body form

An Analysis of Combined Free and Forced Convection Heat Transfer From a Horizontal Circular Cylinder to a Transverse Flow

Abstract: Combined free and forced convection heat transfer from a horizontal circular cylinder to a transverse flow is analysed for the case when the forced flow is either in the direction of the free convection flow (parallel flow) or in the direction opposite to it (counter flow). The problem is solved for two cases: (1) a specified surface temperature variation and (2) a specified wall heat flux variation along the circumference. A coordinate perturbation method is used to transform the governing set of partial differential equations into a system of ordinary differential equations, which are solved by numerical methods. The numerical work is done for the boundary conditions of constant surface temperature and constant wall heat flux. The variation of local heat transfer coefficient and wall shear stress along the circumference up to the point of separation and velocity and temperature profiles in the boundary layer are obtained for varying values of the governing parameters Gr/Re 2 in the constant temperature case (or Gr/Re 2 in the constant heat flux case) and Pr.

Experimental hydrodynamics of the accelerated turbulent boundary layer with and without mass injection

Abstract: Mean velocity-profile data are reported for blown, unblown, and sucked accelerated turbulent boundary layers. The pressure gradients investigated are those corresponding to constant values of the pressure-gradient parameter. The results obtained indicate that acceleration apparently causes an increase in the thickness of the viscous sublayer. Blowing opposes this effect, while suction enhances it. It seems evident that strong acceleration and/or strong suction will lead to a complete laminarization of the boundary layer. An empirical correlation of the data is presented in the form of a tabular correlation of the damping constant in the van Driest (1956) mixing-length hypothesis.

Turbulent Boundary Layer and Heat Transfer Measurements Along a Convergent-Divergent Nozzle

Abstract: Turbulent boundary layer and heat transfer measurements along cooled conical convergent- divergent nozzle

Combining Forced and Free Convective Equations to Represent Combined Heat-Transfer Coefficients for a Horizontal Cylinder

Abstract: An analytical correlation of superposed free and forced convection for air for a horizontal cylinder in which the forced convection and free convection forces act in the same direction is considered. A simplified method by which the ordinary formulas for forced convection and for free convection can be used together to give the Nusselt number is presented. The method proposed herein can easily be modified to work for other combinations of free and forced flow systems. The method, therefore, may have wide application because standard formulas for simple systems are easily combined to obtain formulas which are valid for complicated systems.

Boiling-Curve Measurements From a Controlled Heat-Transfer Process

Abstract: Feedback has been introduced around a boiling heat-transfer process in such a way that stable operation of the process has been obtained in all boiling regions including the transition region, in which, as is well known, the process itself is unstable. This system makes it possible to obtain much new information concerning both the steady-state and dynamic characteristics of boiling heat-transfer processes. Pool-boiling data which were obtained by the use of this system are presented. Accurate measurements of heater voltage and current were obtained by a new technique involving the use of digital instruments. These data are presented in the form of plotted experimental points in the nucleate, transition, and film boiling regions. The new measurement technique is described. Values of n in the equation q/As = CTdn are determined for all three boiling regions, where q = Btu/hr , As is heater surface area, and Td is temperature difference between heater surface and ambient liquid. The ambient liquid is distilled water maintained at saturation temperature under atmospheric pressure.