A heat transfer textbook

https://www.eis.hu.edu.jo/deanshipfiles/pub10311353.pdf

Numerical study of natural convection in partially heated rectangular enclosures filled with nanofluids

Correlating equations for laminar and turbulent free convection from a vertical plate

Correlating equations for laminar and turbulent free convection from a horizontal cylinder

A single comprehensive equation is developed for the rate of heat and mass transfer from a circular cylinder in crossflow, covering a complete range of Pr (or Sc) and the entire range of Re for which data are available. This expression is a lower bound (except possibly for RePr < 0.2); free-stream turbulence, end effects, channel blockage, free convection, etc., may increase the rate. In the complete absence of free convection, the theoretical expression of Nakai and Okazaki may be more accurate for RePr < 0.2. The correlating equation is based on theoretical results for the effect of Pr in the laminar boundary layer, and on both theoretical and experimental results for the effect of Re. The process of correlation reveals the need for theoretical results for the effect of Pr in the region of the wake. Additional experimental data for the effect of Pr at small Pe and for the effect of Re during the transition in the point of separation are also needed.

A Correlating Equation for Forced Convection From Gases and Liquids to a Circular Cylinder in Crossflow

Direct simulations of turbulent flow and convection constitute a new and invaluable resource but are as yet limited to only a few geometries and conditions. The accuracy and generality of correlating equations for the turbulent shear stress itself preclude the need for approximate modeling for simple flows such as in round tubes and along flat plates. For asymmetric, one-dimensional flows, such as in a circular annulus, the turbulent shear stress remains well-behaved but the eddy viscosity and the mixing length become unbounded at one point and negative over an adjacent region. The κ−e model is then invalidated as well; the κ−e− model remains valid but is truly predictive only for the turbulent core. All of these elementary models are inadequate for two-dimensional channels owing to the secondary motion. The same considerations apply to convection in turbulent flow.

A critique of predictive and correlative models for turbulent flow and convection

Essentially exact characteristics of turbulent convection in a round tube

Correlation is of direct importance to all engineersboth those who generate new information and those who wish to make use of it. The solution of theoretical models to predict behavior does not preclude the need for correlation since the output is generally a set of discrete values that differ from experimental data only by virtue of their precision and regularity. The methodologies that lead to improved correlating equations are examined in general and by means of specific examples in fluid flow and heat transfer. The identification of the optimal dimensionless groupings and the derivation and incorporation of theoretically based asymptotes are shown to be the keys to better correlation. Nonconformity to known theoretical relationships and constraints and the uncritical examination of experimental data or computed values are found to be the principal sources of miscorrelation. Correlations should be expected to evolve and to be replaced as new data are obtained and new theoretical relationships are deriv...

The Art of Correlation

The oxidation of ammonia during the combustion of ethane in a thermally stabilized burner (TS8) was studied in order to test the independence of the mechanism of fuel-NOx production on the type of nitrogen in the fuel. In a previous investigation of fuel-NOx production in the TSB using carbon-containing fuel-nitrogen compounds, nitrogen was found to be converted almost entirely to NOx at equivalence ratios near stoichiometric for post-flame residence times greater than 1.5 ms. This result was reproduced by the current study using ammonia as the fuel-nitrogen source. For fuel-rich stoichiometrics, NOx production from the ammonia was found to be a stronger function of post-flame residence time, with the peak in the concentration of NOx occurring at about 1.5-2 ms after the flame front, and a moderate reduction thereafter. These results were confirmed theoretically using a plug-flow model for the TSB coupled with reaction mechanisms for ethane and ammonia oxidation. The fractional"conversion of ammo...

NOx Production from the Combustion of Ethane Doped with Ammonia in a Thermally Stabilized Plug Flow Burner

Mixed-mean velocities were computed by numerical integration using a comprehensive correlating equation for the velocity distribution, and independently using a corresponding correlating equation for the local turbulent shear stress. As contrasted with earlier analytical integrations for grossly simplified velocity distributions, these calculations take into account the effects of the boundary layer near the wall and the wake in the central region. The resulting sets of numerical values for the mixed-mean velocity are correlated almost exactly in terms of equations with a theoretically derived structure. On the basis of the generally overlooked analogy of MacLeod, the same distributions for the velocity and the turbulent shear stress are used for both round tubes and parallel plates, but of course, the expressions for the mixed-mean velocity differ because of the different areas of integration. The analysis reveals inter alia that the hydraulic-diameter and laminar-equivalent-diameter concepts are fundamentally unsound. The correlating equations for the mixed-mean velocity are extended for the transition engendered by naturally rough surfaces using the speculation of Colebrook, and are reexpressed directly in terms of the friction factor and the Reynolds number for convenience

Improved Correlating Equations for the Friction Factor for Fully Turbulent Flow in Round Tubes and between Identical Parallel Plates, both Smooth and Naturally Rough

Stuart W. Churchill

Papers

A critique of predictive and correlative models for turbulent flow and convection

Essentially exact characteristics of turbulent convection in a round tube

The Art of Correlation

NOx Production from the Combustion of Ethane Doped with Ammonia in a Thermally Stabilized Plug Flow Burner

Improved Correlating Equations for the Friction Factor for Fully Turbulent Flow in Round Tubes and between Identical Parallel Plates, both Smooth and Naturally Rough