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Experimental studies have revealed that both downstream and upstream pointing V-shaped ribs result in better heat transfer enhancement than transverse straight ribs of the same geometry. Secondary flows induced by the angled ribs are believed to be responsible for this higher heat transfer enhancement. Further investigations are needed to understand this. In the present study, the heat and fluid flow in V-shaped-ribbed ducts is numerically simulated by a multi-block 3D solver, which is based on solving the Navier-Stokes and energy equations in conjunction with a low-Reynolds number k-ε turbulence model. The Reynolds turbulent stresses are computed with an explicit algebraic stress model (EASM), while turbulent heat fluxes are calculated with a simple eddy diffusivity model (SED). Firstly, the simulation results of transverse straight ribs are validated against the experimental data, for both velocity and heat transfer coefficients. Then, the results of different rib angles (45° and 90°) and Reynolds number (15,000–30,000) are compared to determine the goodness of different rib orientations. Detailed velocity and thermal field results have been used to explain the effects of the inclined ribs and the mechanisms of heat transfer enhancement.

This paper presents the results of an investigation on prediction of local and mean thermal-hydraulic characteristics in rib-roughened ducts of square cross section. the Navier–Stokes and energy equations together with two low-Re k–ε turbulence models are solved numerically. The Reynolds turbulent stress tensor is calculated by two methods, namely, an eddy viscosity model (EVM) and an explicit algebraic stress model (EASM). The pressure–velocity coupling is handled by the SIMPLEC algorithm and calculations were carried out on a collocated grid. The convection–diffusion terms were calculated using the hybrid scheme (the changes in the results obtained by the other schemes, e.g., QUICK and Van Leer, were not significant). The considered ribbed duct configuration is identical to that in an experimental study and comparisons between the predictions and experimental results are provided. A discussion of the capabilities of the two methods (EVM and EASM) is presented.

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Numerical analysis of the instantaneous flow and heat transfer has been carried out for offset strip fin geometries in self-sustained oscillatory flow. The analysis is based on the twodimensional solution of the governing equations of the fluid flow and heat transfer with the aid of appropriate computational fluid dynamics methods. Unsteady calculations have been carried out. The obtained time-dependent results are compared with previous numerical and experimental results in terms of mean values, as well as oscillation characteristics. The mechanisms of heat transfer enhancement are discussed and it has been shown that the fluctuating temperature and velocity second moments exhibit non-zero values over the fins. The creation processes of the temperature and velocity fluctuations have been studied and the dissimilarity between these has been proved. U i = Mean velocity components (i = 1,2,3) U m = Mean velocity u i = Fluctuating part of velocity components (i = 1,2,3) = Kinematic viscosity = DensityThe current issue and full text archive of this journal is available at http://www.emerald-library.com/ft Financial support from the Swedish Energy Administration (STEM) is kindly acknowledged.

A technique for determining the heat transfer on the far surface of a wall based on measuring the heat transfer and temperature on the near wall is presented. Although heat transfer measurements have previously been used to augment temperature measurements in inverse heat conduction methods, the sensors used alter the heat flow through the surface, disturbing the very quantity that is desired to be measured. The ideal sensor would not alter the boundary condition that would exist were the sensor not present. The innovation of this technique in that it has minimal impact on the wall boundary condition. Since the sensor is placed on the surface of the wall, no alteration of the wall is needed. The theoretical basis for the experimental technique as well as experimental results showing the heat flux sensor performance is presented.

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This paper presents a discussion of the role of intercoolers in low to medium power gas turbine systems and combined thermal processes for production of electricity. Available literature is cited and various types of intercoolers are presented. Means to improve the performance are discussed and opportunities to achieve more compact intercoolers are presented. An analysis of a specific enhanced surface intended for the air-side is presented. The volume goodness factor is defined and used as the performance is evaluated.