Surface modification for enhanced condensation heat transfer of saturated humid air: A numerical investigation and evaluation model

Condensation heat transfer characteristics of moist air outside 3-D finned tubes with different wettability

Influence of surface wettability on heat transfer and pressure drop characteristics of wet air in metal foam under dehumidifying conditions

Experimental study of the flow and heat transfer of a gas–water mixture through a packed channel

The surface wettability determines the condensate mode and the adhesive force of condensate on the metal fiber surface, which can directly affect the heat transfer and pressure drop characteristics of wet air in metal foams. In the present study, the heat transfer and pressure drop characteristics of wet air in metal foams with different surface wettability under dehumidifying conditions were investigated experimentally. The tested samples include the hydrophobic, hydrophilic and uncoated metal foams, and the experimental conditions cover the inlet air temperatures of 27oC-35 °C, the inlet air relative humidity of 30%–90% and the air velocities of 0.5–1.0 m/s. The experimental results show that, the heat transfer coefficients in hydrophobic and hydrophilic metal foams are larger by 4%–33% and 3–21% than that in uncoated metal foams, respectively, and the heat transfer enhancement of the hydrophobic coating is more obvious; compared with the uncoated metal foams, the pressure drop in hydrophobic metal foams is increased by 3%–139%, while the pressure drop in hydrophilic metal foams is reduced by 1%–20%. The heat transfer and pressure drop characteristics of wet air in metal foams were evaluated by the comprehensive performance index (j·f −1/3), and the comprehensive performance of hydrophilic metal foam is better than that of hydrophobic and uncoated metal foams.

This study aims to optimize the structure of compact Plate-Fin Heat Exchangers (PFHE) by incorporating corrugated fins and validating their improved performance through numerical modeling and simulation. The results provide valuable insights for refining application-specific design guidelines and enhancing the performance of PFHEs. Using Computational Fluid Dynamics (CFD), the PFHE geometry was created in SolidWorks and Ansys Fluent, with fins modeled in three layers inside the heat exchanger both with and without a cover. To investigate the fins' performance, flow field, and heat transfer, fin thickness, entry velocities, and locations of water and air were varied across three wavelengths (10, 20, and 30) during the numerical investigation. The analysis focused on the variations in pressure, temperature, and fluid velocity within the heat exchanger. Key findings include the observation that temperature distribution is influenced by the velocities of both water and air, with the upper layer experiencing a temperature increase due to the warm fluid stream, while the opposite effect is observed near the bottom layer. Furthermore, fluid temperature variation in the depth direction is attributed to conductive heat transfer through side plates and convective heat transfer to the surroundings. The outcomes of this study have the potential to reduce the pressure difference generated during heat exchange and increase the thermal efficiency of PFHEs.

Boundary conditions and wall effect for forced convection heat transfer in sintered porous plate channels

This paper presents the structure design of four kinds of circular pipes with porous layer and the experimental results of condensation heat transfer of the moist air outside the horizontal circular pipes. By comparison with the experiments on bare pipes, it is concluded that, the designed pipes not only have good condensation heat transfer performance, but also have the ability to collect and remove condensed liquid under zero gravity. They can be applied to the thermal control system for future large spacecraft.

Condensation heat transfer characteristics of moist air outside a three-dimensional finned tube

Influence of pore density on heat transfer and pressure drop characteristics of wet air in hydrophilic metal foams

Effect of porosity on heat transfer and pressure drop characteristics of wet air in hydrophobic metal foam under dehumidifying conditions

Experimental research on convection heat transfer in sintered porous plate channels

The calculation of heat transfer in aircraft bulkheads is of vital importance to the design of aircraft cabins. In this paper, a numerical model for the fluid-solid coupled heat transfer of aircraft cabin bulkhead and air in the cabin is developed, including fluid/solid area division, network strategy, turbulence model and numerical discrete method, and the model is verified based on the experimental data. The results show that the proposed model can accurately predict the wall temperature and the air temperature of the aircraft cabin with a deviation of less than 1.02°C in the working range of -15∼25°C, and the prediction deviation for the air velocity is within ±10%. The heat transfer from the cabin to the bulkhead accounts for 7.5% of the total heat transfer. The main component of the thermal resistance of the cabin bulkhead is the thicker solid area, and the inlet air temperature is the key parameter for the design of aircraft cabin. The research results provide an important theoretical basis for the optimal design of the thermal environment of the aircraft cabin.

Mixed convection heat transfer and fluid flow of air, water or oil in enclosures have been studied extensively using experimental and numerical means for many years due to their ever-increasing applications in many engineering fields. In comparison, little effort has been given to the problem of mixed convection of nanofluids in spite of several applications in solar collectors, electronic cooling, lubrication technologies, food processing, and nuclear reactors. Mixed convection of nanofluids is a challenging problem due to the complex interactions among inertia, viscous, and buoyancy forces. In this study, mixed convection of nanofluids in a lid-driven square cavity with sinusoidal roughness elements at the bottom is studied numerically using the Navier-Stokes equations with the Boussinesq approximation. The numerical model is developed using commercial finite volume software ANSYS-FLUENT for Al2O3-water and CuO-water nanofluids inside a square cavity with various roughness elements. The effects of number and amplitude of roughness elements on the heat transfer and fluid flow are analysed for various volume concentrations of Al2O3 and CuO nanoparticles. The flow fields, temperature fields, and heat transfer rates are examined for different values of Rayleigh and Reynolds numbers. The outcome of this study provides some important insight into the heat transfer behaviour of Al2O3-water and CuO-water nanofluids inside a lid-driven rough cavity. This knowledge can be further used in developing novel geometries with enhanced and controlled heat transfer for solar collectors, electronic cooling, and food processing industries.

In the present work, experimental and numerical investigations have been performed to determine the performance of an automotive radiator using louvered–fin geometry with reference to flat-fin geometry. Four radiators specimens were designed and manufactured, three specimens with different louvered fin per inch and the other with flat fin. The experimental work was carried out on a four cylinders petrol engine (Seat-124A).The effects of engine speed, number of fins per inch (FPI), Reynolds number and radiator boundary conditions on the radiator performance were investigated at a certain louvered angle of 25o. The specific fuel consumption was also investigated experimentally. Numerical CFD investigation using finite volume discretization method was also conducted to predict the radiator performance extensively. The momentum and energy equations were solved by the second order up wind scheme. The air flow and heat transfer through the louvered fin passage were treated using the k- RNG turbulence model. For the validation of the numerical model, the numerical results were compared with corresponding experimental data. It was noticed that the level of the turbulence increases through the transition region of the louvered flowpassage which will lead to a disturbance of the boundary layer thickness and hence, the increase in the heat transfer coefficient was achieved.. The results indicated that an improvement of about 23% in the Nusselt number and a decrease of about 19% in the specific fuel consumption at full load could be achieved due to using louvered-fin geometry compared to flat-fin geometry at the same operating conditions.

Study of heat and mass transfer phenomena and entropy rate of humid air inside a passive solar still