CFD modeling and performance evaluation of multipass solar air heaters

This article investigates the impacts of flow configurations on the thermal performance of a solar heater system. Recycled aluminum cans (RACs) have been utilized as turbulators with a double pass single duct solar air collector. The CFD software of COMSOL Multiphysics V5.3a is used to model three designs: Cocurrent (model A), countercurrent (model B), and U-shape (model C). The numerical results reveal that the U-shape design offers a greater thermal performance of 5.4% and 6.5%, respectively, compared with the cocurrent and countercurrent flow models. Furthermore, an outdoor experiment is performed based on the numerical modeling of flow configurations. The experimental setup is examined for three configurations of model C, namely, solar air heater (SAH) without RAC model C-I (plain model), SAH with in-line RAC layout (model C-II), and SAH with staggered RAC layout (model C-III). We found the double pass single duct solar air collector (model C) design is in a good agreement with the experimental data, and model C-III has a better thermal efficiency of 60.2%, compared to those of model C-II, 53.1%, and model C-I, 49.4%

Performance Evaluation of Roughened Solar Air Heaters for Stretched Parameters

Artificial roughness applied to a Solar Air Heater (SAH) absorber plate is a popular technique for increasing its total thermal efficiency (ηt−th). In this paper, the influence of geometrical parameters of V-down ribs attached below the corrugated absorbing plate of a SAH on the ηt−th was examined. The impacts of key roughness parameters, including relative pitch p/e (6–12), relative height e/D (0.019–0.043), angles of attack α (30–75°), and Re (1000–20,000), were examined under real weather conditions. The SAH ηt−th roughened by V-down ribs was predicted using an in-house developed conjugate heat-transfer numerical model. The maximum SAH ηt−th was shown to be 78.8% as predicted under the steady-state conditions of Re = 20,000, solar irradiance G = 1000 W/m2, p/e = 8, e/D = 0.043, and α = 60. The result was 15.7% greater efficiency compared to the default smooth surface. Under real weather conditions, the ηt−th of the roughened SAH with single- and double-glass covers were 17.7 and 20.1%, respectively, which were higher than those of the smooth SAH

CFD analysis of a one-pass photovoltaic/thermal air system with and without offset strip fins

The focus on managing PV panel temperature has undergone a remarkable development in the last two decades. Specifically, in countries with moderate weather temperature and high insolation, the problem of keeping the PV cell temperature in an optimal range has been managed by use of PV/T collectors. In this work, a single pass PV/T collector using laminar air flow has been assessed. Two PV/T collector designs are utilised, one with and one without offset strip fins. COMSOL Multiphysics v5.3a has been used for the analysis of the thermal and electrical performances. Two assumptions were implemented in order to reduce the computational time from 95 hours to 7 hours, namely ignoring radiative effects between the fins and the wall channels, and representing thin layers as 2D boundaries, whilst ensuring a high level of conformity (4%),. Monocrystalline silicon PV cells were used with a power temperature coefficient of 0.41%. A validation against work in the literature was made, showing a good consistency. The objective of this work is to verify the performance of the air PV/T collector with offset strip fins compared to an unfinned air PV/T collector. The results reveal that the use of offset strip fins has a noticeable impact on both the electrical and thermal efficiencies of the system. In addition, the maximum combined efficiency (ηC o ) for the finned PV/T system is 84.7% while the unfinned PV/T system is 51.2%

Current Status and Potential of Tire Pyrolysis Oil Production as an Alternative Fuel in Developing Countries

Current status and potential of tire pyrolysis oil production as an alternative fuel in developing countrie

Modelling of automotive fuel droplets heating and evaporation - mathematical tools and approximations

New mathematical tools and approximations developed for the analysis of automotive fuel droplet heating and evaporation are summarised. The approach to modelling biodiesel fuel droplets is based on the application of the Discrete Component Model (DCM), while the approach to modelling Diesel fuel droplets is based on the application of the recently developed multi-dimensional quasi-discrete model. In both cases, the models are applied in combination with the Eective Thermal Conductivity/Eective Diusivity model and the implementation in the numerical code of the analytical solutions to heat transfer and species diusion equations inside droplets. It is shown that the approximation of biodiesel fuel by a single component leads to under-prediction of droplet evaporation time by up to 13% which can be acceptable as a crude approximation in some applications. The composition of Diesel fuel was simpli ed and reduced to only 98 components. The approximation of 98 components of Diesel fuel with 15 quasi-components/components leads to under-prediction of droplet evaporation time by about 3% which is acceptable in most engineering applications. At the same time, the approximation of Diesel fuel by a single component and 20 alkane components leads to a decrease in the evaporation time by about 19%, compared with the case of approximation of Diesel fuel with 98 components. The approximation of Diesel fuel with a single alkane quasi-component (C14:763H31:526) leads to under-prediction of the evaporation time by about 35% which is not acceptable even for qualitative analysis of the process. In the case when n-dodecane is chosen as the single alkane component, the above-mentioned under-prediction increases to about 44%