Determination Of Heat Transfer Rates Research Articles

Determination of heat transfer rates of heavy-duty radiators for trucks having flattened and double-U grooved pipes with louvered fins by ANN method: an experimental study

Determination of heat transfer rates of heavy-duty radiators for trucks having flattened and double-U grooved pipes with louvered fins by ANN method: an experimental study

Determination of heat transfer rates in an industry-like spray quench system using multiple impinging water jets

Liquid jet impingement (LJI) cooling is widely employed in quench systems, the majority of which utilise multiple impinging jets. Successful design and operation of such systems require accurate data of actual heat transfer rates. The present study is concerned with the determination of heat transfer rates during rapid cooling of high temperature surfaces using multiple impinging water jets (MIWJs) in an industry-like arrangement. The effects of jet variables have been investigated. Heat transfer coefficients have been numerically calculated using inverse analysis, utilising experimentally determined temperature profiles. Comparison with heat transfer rates of immersion quenching has been considered. The present study provides important information about heat transfer rates in an industry-like water spray quench system using MIWJs. Results demonstrated that the use of MIWJs offers significant flexibility in controlling cooling rates, which renders this technique most suitable for quench operations requiring wide range of cooling rates.

ANALYSIS OF INTERFACIAL AND MASS TRANSFER EFFECTS ON FORCED CONVECTION IN GAS-LIQUID ANNULAR TWO-PHASE FLOW

In a gas-liquid annular two-phase flow one of the main factors influencing the determination of heat transfer rates is the average thickness of the liquid film. A model to accurately represent the heat transfer in such situations has to be able of determining the average liquid film thickness to within a reasonable accuracy. A typical physical aspect in gas-liquid annular flows is the appearance of interface waves, which affect heat, mass and momentum transfers. Existing models implicitly consider the wave effects in the momentum transfer by an empirical correlation for the interfacial friction factor. However, this procedure does not point out the difference between interface waves and the natural turbulent effects of the system. In the present work, the wave and mass transfer effects in the theoretical estimation of average liquid film thickness are analyzed, in comparison to a model that does not explicitly include these effects, as applied to the prediction of heat transfer rates in a thermally developing flow situation.

ANALYSIS OF INTERFACIAL AND MASS TRANSFER EFFECTS ON FORCED CONVECTION IN GAS-LIQUID ANNULAR TWO-PHASE FLOW

In a gas-liquid annular two-phase flow one of the main factors influencing
the determination of heat transfer rates is the average thickness of the liquid
film. A model to accurately represent the heat transfer in such situations has
to be able of determining the average liquid film thickness to within a
reasonable accuracy. A typical physical aspect in gas-liquid annular flows is
the appearance of interface waves, which affect heat, mass and momentum
transfers. Existing models implicitly consider the wave effects in the
momentum transfer by an empirical correlation for the interfacial friction
factor. However, this procedure does not point out the difference between
interface waves and the natural turbulent effects of the system. In the
present work, the wave and mass transfer effects in the theoretical
estimation of average liquid film thickness are analyzed, in comparison to a
model that does not explicitly include these effects, as applied to the
prediction of heat transfer rates in a thermally developing flow situation.

UPPER AND LOWER RAYLEIGH NUMBER BOUNDS FOR TWO-DIMENSIONAL NATURAL CONVECTION OVER A FINITE HORIZONTAL SURFACE SITUATED IN A FLUID-SATURATED POROUS MEDIUM

A numerical study is presented of natural convection from a heated upward facing finite horizontal surface in a fluid-saturated porous medium. The Rayleigh number range for which two-dimensional flows occur is numerically determined as 40 ≤ Ra ≤ 600. At higher Rayleigh numbers the flow is shown to become three-dimensional with multiple plume formation and growth. At lower Rayleigh numbers the transport is dominated by conduction, and there is greater uncertainty in the numerical determination of heat transfer rates by convection models. For the two-dimensional flows the correlation for the Nusselt number is obtained as Nu = 3.092Ra0.272. The fundamental physical mechanisms of convection in a vast porous medium are presented and explained with the aid of the numerical results.

An Investigation of Convective Heat Transfer in a Rotating Coolant Channel

A numerical method is presented for the determination of heat transfer rates in a cylindrical cooling duct within turbine blades that rotate about an axis orthogonal to its own axis of symmetry. The equations of motion and energy are solved in conjunction with the k–ε model of turbulence using the finite element method. The predicted results are compared with experimental data and it is clearly demonstrated that conduction in the solid boundary must be taken into account if satisfactory agreement is to be achieved. Excluding these effects can lead to an overestimation of the maximum wall temperature by approximately 50 percent.

Aerodynamic and Heat Transfer Measurements on a Transonic Nozzle Guide Vane

Experimental determination of heat transfer rates to gas turbine blading plays an important part in the improvement of both the validation of existing design methods and the development of improved design codes. This paper describes a series of tests on an annular cascade of nozzle guide vanes designed for a high-work-capacity single-stage transonic turbine. The tests were carried out in the Isentropic Light Piston Cascade at the Royal Aerospace Establishment, Pyestock, and a brief description of this new test facility is included. Measurements of local heat transfer rates and aerodynamic data around the blade surface and on the end walls are described.

A method for the prediction of Coriolis induced secondary flows and their influence on heat transfer in rotating ducts

A method is presented for the determination of heat transfer rates in cylindrical cooling ducts which rotate about an axis orthogonal to its own axis of symmetry. The equations of motion and energy are solved in conjunction with the two equation model of turbulence (k—ε) using the finite element method. The importance of employing consistent velocity and turbulence quantities is demonstrated; the former condition is particularly relevant with respect to induced secondary flows. It was also found that comparatively minor mesh refinement had a significant effect on both the flow and the increase in heat transfer rates over those obtained for the non‐rotating case.

NATURAL CONVECTION IN A VERTICAL CHANNEL: I. INTERACTING CONVECTION AND RADIATION. II. THE VERTICAL PLATE WITH AND WITHOUT SHROUDING

Numerical finite-difference solutions enabled the determination of heat transfer rates for pure natural convection and for Interacting natural convection and radiation in a vertical parallel plate channel of finite height. Attention was focused on the effect of the thermal boundary conditions and on the role of radiation as an enhancement mechanism. The results also enabled comparisons of the heat transfer from a single isothermal vertical plate with that for a plate that is shrouded by an adiabatic wall situated parallel to the plate. For pure convection and at intermediate and large Grashof numbers, the rate of heat transfer for a channel with two Isothermal equt-temperature walls exceeds by more than a factor of 2 that for a channel with one isothermal wall and one adiabatic wall (note that the ratio of active heat transfer areas for the two cases Is equal to 2). At lower Grashof numbers, the heat transfer rates differ only slightly. Radiation effects were explored for the case of a channel having one ...

Effects of internal conduction on the determination of heat transfer rates using thin film models

Effects of internal conduction on the determination of heat transfer rates using thin film models

Determination of heat-transfer rates from transient surface temperature measurements

Determination of heat-transfer rates from transient surface temperature measurements