Laminar Boundary Layer Heat Transfer Research Articles

Non-Newtonian laminar boundary-layer heat transfer in stirred tanks

A laminar boundary-layer heat transfer in a jacketed, stirred tank with non-Newtonian fluids has been experimentally and theoretically examined. Heat transfer rates from jacket to process liquid through the stirred tank wall were measured for different large-scale impeller designs and rheological properties. On the basis of the laminar boundary-layer theory, we developed a theoretical correlation for non-Newtonian laminar tank-side film heat transfer coefficients in stirred tanks. The correlation was derived using von Karman's integral technique. Satisfactory agreement between the predictions of the proposed correlation and the present experimental data for viscous Newtonian and non-Newtonian laminar heat transfer in stirred tanks was obtained.

Laminar Boundary Layer Heat Transfer to Power Law Fluids: An Approximate Analytical Solution.

Based on the integral momentum and energy balance equations, the laminar boundary layer heat transfer is studied between a plane surface and a power law medium. The analysis presented herein encompasses both types of boundary conditions imposed on the surface, i.e., constant temperature and constant heat flux. Analytical expressions have been developed for the local values of heat transfer coefficients. The approximate results presented herein are in good agreement with the previously available scant results.

Enhancement of Laminar Boundary Layer Heat Transfer by a Vortex Generator

The enhancement of heat transfer caused by the presence of a single vortex generator in a laminar boundary layer was experimentally investigated. The local heat transfer coefficients just down stream of the vortex generator and the mean and fluctuation components of velocity were measured. The influence of the height, angle of attack and geometry of the vortex generator on heat transfer was investigated

Enhancement of laminar boundary layer heat transfer by a vortex generator.

The enhancement of heat transfer caused by the presence of a single vortex generator in a laminar boundary layer was experimentally investigated. The local heat transfer coefficients just downstream of the vortex generator and the mean and fluctuation component of velocity were measured. A substantial increase in the heat transfer was noticed, with a maximum improvement of the heat transfer coefficient of 80 %, even in regions where the laminar structure was clearly predominant. It was observed that the heat transfer coefficient presents two peaks in the spanwise direction, each one associated with different vortices. The corner longitudinal vortex, which arose in the generator's front corner, was found to be associated with one of these peaks. The effects on the heat transfer of varying the generator's size, angle of attack and geometry were clarified.

Heat transfer from a rotating cone or disk to fluids of any prandtl number

Abstract A new similarity variable is proposed for the analysis of laminar boundary-layer heat transfer from a rotating cone or disk to fluids of any Prandtl number. Very accurate similarity solutions for both the isothermal and uniform-flux cases are obtained over a very wide range of Prandtl number from 0.001 to infinity. Dimensionless temperature profiles in this range of Prandtl number are very similar. A heat transfer correlation equation of high accuracy for all Prandtl numbers is given.

Laminar boundary layer heat transfer along a moving plate with suction or blowing

Abstract The effects of suction or blowing on the laminar boundary layer flow and heat transfer along a horizontal continuously moving plate are analyzed by a local similarity method and a local nonsimilarity method. The cases of prescribed surface temperature and prescribed wall heat flux are considered. The effects of surface suction or blowing on the boundary layer friction factor and heat transfer rate are studied in detail. It is shown that the local nonsimilarity solution gives more accurate results than the local similarity solution.

Flow Transition Phenomena and Heat Transfer Over the Pressure Surfaces of Gas Turbine Blades

Detailed examination of flow measurements over concave pressure surfaces suggests that interaction of Taylor-Goertler vorticity with mainstream turbulence exerts only limited influence in enhancing laminar boundary-layer heat transfer. While transition is primarily controlled by the Launder laminarisation criterion, the Goertler number at which it subsequently occurs is not solely determined by turbulence intensity. Adoption of K≥2.5.10 – 6 as a design criterion for the pressure surfaces of turbine blades would appear to have significant advantages in terms of reduced heat transfer, increased lift, and lower aerodynamic drag.

Instant Nonsimilarity Solutions of Unsteady Laminar Boundary-Layer Heat Transfer

Instant Nonsimilarity Solutions of Unsteady Laminar Boundary-Layer Heat Transfer

Buoyancy effects on the laminar boundary layer heat transfer along vertically moving cylinders

Abstract The effects of buoyancy forces on the laminar boundary layer flow and heat transfer along vertically moving cylinders are analyzed for the cases of prescribed surface temperature and prescribed wall heat flux in power of streamwise distance. Local similarity solutions are obtained to show the effects of buoyancy parameters and the transverse curvature of the cylinder on the surface friction and heat transfer rate.

BUOYANCY EFFECTS ON THE FORCED CONVECTION ALONG VERTICALLY MOVING SURFACES

Abstract The buoyancy effects on the laminar boundary layer heat transfer from vertically moving flat plate and cylinder are studied by a coordinate perturbation method for the cases of prescribed surface temperature and prescribed wall heat flux. Universal expressions are given to show the temperature distributions and the increase of heat transfer rate with the increase of the buoyancy force parameter.

Laminar boundary layer heat transfer along static and moving cylinders

Abstract Local similarity solutions are obtained for the laminar boundary layer heat transfer along static and moving cylinders with prescribed surface temperature or wall heat flux. The effects of normalized streamwise distance and Prandtl number on the temperature distribution and heat transfer rate are studied in detail. The comparison with perturbation solutions is given. It is shown that the local similarity solutions are more useful for large normalized streamwise distance where the perturbation solutions are not valid.

Laminar forced convection in wedge flow with separation

Abstract A perturbation method is used to study the steady and unsteady laminar boundary layer heat transfer from a wedge with separation for a step‐discontinuity in the surface temperature. The analytic solutions obtained can be used to calculate the steady and unsteady heat transfer rate with arbitrary surface temperature. The effects of the Prandtl number on the temperature distribution and the heat transfer rate are discussed in detail. The solution is valid for large or moderate Prandtl number.

Extensions of Merk's method to the calculation of laminar boundary layer heat transfer from a non-isothermal surface

The Merk's method for calculating non-similar boundary layer heat transfer from an isothermal surface is extended to the case with non-isothermal surface and the reliability of the method is checked in detail. It is shown that except for some small ranges of β (pressure gradient parameter) and γ (wall temperature distribution parameter), the present method yields accurate heat transfer results. Examples of application of the present method are given for a flow around a circular cylinder and for that past a flat plate. The calculations are performed in the limits Pr→∞ and Pr→0, and the results are compared with those derived from the exact asymptotic theories for these limits.

An approximate method of computing the heat transfer in laminar boundary-layer

An approximate method of computing the heat transfer in laminar boundary-layer without pressure gradient is described. The energy equation is written in an approximate form which, through a change of variables, becomes identical to the momentum equation. The method described in a preceding paper is then applied to determine the heat transfer for arbitrary initial conditions. The procedure is then extended to the flow with pressure gradient and the results compare well with the exact similar solutions.

Laminar boundary-layer heat transfer in low- thrust rocket nozzles.

Laminar boundary-layer heat transfer in low- thrust rocket nozzles.

Laminar Boundary-Layer Heat Transfer from a Partially Ionized Monatomic Gas

Laminar boundary-layer heat transfer from a partially ionized monatomic gas to a highly cooled wall with no applied external electric or magnetic fields is analyzed by the similarity solution approach. The gas is assumed to be electrically neutral with ambipolar diffusion by ion-electron pairs. In addition, equal electron and atom-ion temperatures are assumed, and sheath effects are not considered. From existing perfect gas similarity solutions, the number of parameters that need to be investigated is reduced to those directly related to ionization effects. Solutions for the limiting cases of a large diffusion rate compared to the net production rate of ions and for local equilibrium are obtained for a range of Prandtl and Lewis numbers. An approximate prediction method that includes variable property considerations is then suggested to account for variable free-stream velocity and ionization effects in a flow over a highly cooled wall.

Prediction of Heat Transfer From Laminar Boundary Layers, With Emphasis on Large Free-Stream Velocity Gradients and Highly Cooled Walls

Laminar boundary-layer heat transfer and shear-stress predictions from existing similarity solutions are extended in an approximate way to perfect gas flows with a large free-stream velocity gradient parameter β and variable density-viscosity product ρμ across the boundary layer resulting from a highly cooled wall. The dimensionless enthalpy gradient at the wall gw′, to which the heat flux is related, is found not to vary appreciably with β. Thus the application of similarity solutions on a local basis to predict heat transfer from accelerated flows to an arbitrary surface may be a reasonable approximation involving a minimum amount of calculation time. Unlike gw′, the dimensionless velocity gradient at the wall fw″, to which the shear stress is related, is strongly dependent on β.

Laminar boundary layer heat transfer with an arbitrary surface heat flux

Laminar boundary layer heat transfer with an arbitrary surface heat flux

Further note on an approximate method for calculating heat transfer in laminar boundary-layers with constant wall temperature

Further note on an approximate method for calculating heat transfer in laminar boundary-layers with constant wall temperature