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In this paper, a curved wavy channel was proposed to further enhance the thermal performance of the conventional wavy channel. A three-dimensional model of the curved wavy channel was established with defining the overall curvature. The flow behavior and heat transfer in the wavy and curved wavy channels were numerically investigated under various wave amplitudes. The mechanism behind the observed phenomena was revealed by analyzing the synergy between velocity and temperature fields. The results indicated that the Nusselt numbers in curved wavy channels with amplitudes of 0.40 mm and 0.80 mm can be raised by 44.3% and 15.3% compared to those in conventional wavy channels. The parametric study showed that the flow resistance is more sensitive to the wavelength. For a given amplitude, curved wavy channels always show a better field synergy than conventional wavy channels. In addition, an inferior field synergy was observed near the suction side in both types of wavy channels, which indicates that the purposive improvement needs to apply to these locations. This study also found that the field synergy angle has limitations in characterizing the heat transfer intensity in the channel with small wavelengths. This is because that extremely chaotic flow patterns caused by small wavelengths result in a negative dot product of temperature gradient and velocity over a large area.

Fluid flow with phase change heat transfer in a three-dimensional porous channel with asymmetrically heating from one side is numerically studied in this paper. The “modified” Kirchhoff method is used to deal with the spatial discontinuity in the thermal diffusion coefficient in the energy equation. The velocity and temperature fields, as well as the liquid saturation field on the heated section of the wall with different Peclet and Rayleigh numbers are investigated. The results show that the liquid flow bypasses the two-phase zone, while the vapor flows primarily to the interface between the sub-cooled liquid zone and the two-phase zone. An increase in the Peclet number decreases the two-phase region while an increase in the Rayleigh number helps to spread the heat to a larger region of the domain. The distribution of the liquid saturation on the heated section of the wall indicates that the minimum liquid saturation increases with the increase of both the Peclet and Rayleigh numbers.

Fluid flow and heat transfer characteristics in a channel with staggered porous blocks were numerically studied in this paper. The Navier–Stokes and Brinkman–Forchheimer equations were used to model the fluid flow in the open and porous regions, respectively. Coupling of the pressure and velocity fields was resolved using the SIMPLER algorithm. The local thermal equilibrium model was adopted in the energy equation to evaluate the solid and fluid temperatures. The effect of Darcy number, Reynolds number, porous block height and width on the velocity field were studied. In addition, the effects of the above parameters as well as the thermal conductivity ratio between the porous blocks and the fluid on the local heat transfer were analyzed. The pressure drops across the channel for different cases were discussed. The results show that the flow behavior and its associated local heat transfer are sensitive to the variation of the above parameters. It is predicted by the present study that an increase in the thermal conductivity ratio between the porous blocks and the fluid results in significant enhancement of heat transfer at the locations of the porous blocks.

Forced convection heat transfer in a channel with different configurations of graphite foams is experimentally and numerically studied in this paper. The physical properties of graphite foams such as the porosity, pore diameter, density, permeability and Forchheimer coefficient are determined experimentally. The local temperatures at the surface of the heat source and the pressure drops across different configurations of graphite foams are measured. In the numerical simulations, the Navier–Stokes and Brinkman–Forchheimer equations are used to model the fluid flow in the open and porous regions, respectively. The local thermal non-equilibrium model is adopted in the energy equations to evaluate the solid and fluid temperatures. Comparisons are made between the experimental and simulation results. The results showed that the solid block foam has the best heat transfer performance at the expense of high pressure drop. However, the proposed configurations can achieve relatively good enhancement of heat transfer at moderate pressure drop.

Open-cell metal foams are often used in heat exchangers and absorption equipment because they exhibit large specific surface area and present tortuous coolant flow paths. However, published research works on the characteristics of fluid flow in metal foams are relatively scarce, especially for the flow oscillation condition. The present experimental investigation attempts to uncover the behavior of steady and oscillating flows through metal foams with a tetrakaidecahedron structure. In the experiments, steady flow was supplied by an auto-balance compressor and flow oscillation was provided by an oscillating flow generator. The pressure drop and velocity were measured by the differential pressure transducer and hot-wire sensor, respectively. The friction factor of steady flow in metal foam channel was analyzed through the permeability and inertia coefficient of the porous medium. The results show that flow resistance in the metal foams increases with increasing form coefficient and decreasing permeability. The empirical equation obtained by the present study indicates that the maximum friction factor of oscillating flow through the tested aluminum foams with specific structure is governed by the hydraulic ligament diameter-based kinetic Reynolds number and the dimensionless flow amplitude.