An Experimental Study on the Energy and Exergy Performance of an Air-Type PVT Collector with Perforated Baffle

BIPV (Building Integrated Photovoltaic) system is a building envelope technology that generates energy by converting solar energy into electricity. However, after producing electrical energy, the remaining solar energy is transferred as heat, raising the temperature at the rear of the BIPV module, and reducing electrical efficiency. On the other hand, a PVT (Photovoltaic Thermal) collector is a device that generates electricity from a PV module and at the same time uses the heat transferred to the air layer inside the collector. In general, the performance of air-type PVT collectors is based on energy analysis using the first law of thermodynamics. Since this performance does not take into account the loss amount, it is not the actual amount of power generation and preheat of the collector that can be used. Therefore, an exergy analysis based on the second law of thermodynamics considering the amount of energy loss must be performed. In this paper, an air-type PVT collector to which perforated baffles were applied was tested through outdoor experiments based on ISO 9806 standard. The total energy (thermal and electrical characteristics) and exergy according to the flow rate (100, 150, and 200 m3/h), solar radiation, and rear temperature of the PV module of the air-type PVT collector were analyzed. As a result, the total exergy efficiency of the air-type PVT collector with perforated baffles was 24.8–30.5% when the total energy efficiency was 44.1–63.3%.

A CFD study on hydrocarbon mean residence time in a horizontal oil–water separator

This study presents computational fluid dynamics analyses on oil–water flow characteristics in a horizontal separator. The performance of these vessels are inferred from mean residence time and cumulative residence time distribution of the hydrocarbon phase inside the separator. The authors model a separator used by previous researchers and evaluate mean residence time of the hydrocarbon phase in a two-phase mixture of oil and water. Three different water-cuts of 21%, 32%, and 57% are used. Additional analyses are done to assess how certain geometric features of the separator influence hydrocarbon mean residence time. The results show that the addition of a second perforated baffle plate does not improve the hydrocarbon mean residence time significantly. However, introducing a downward slanting throat section between the primary zone and the gravity separation zone improves the hydrocarbon mean residence time at 21% and 32% water-cuts. The results suggest oil–water separators with a throat section may be more efficient than regular horizontal separators without the throat section at low water-cuts.

A Perforated Baffle Design to Improve Mixing in Contact Tanks

In this study, a perforated baffle design is proposed to improve mixing in contact tanks. Turbulent flow through the perforated baffle is studied at the perforation hole scale. The contribution of jets emerging from the perforations to the mixing process is evaluated in terms of standard mixing indexes for various perforation parameters, such as the solidity ratio and hole diameter. Based on numerical simulation results, the two sets of perforated baffles that yielded the highest performance were manufactured from polycarbonate and tracer studies were conducted on a laboratory model. Comparison of numerical and experimental results demonstrates that the numerical model developed is reliable in simulating the flow through the perforated baffles and the associated mixing level in the contact tank. Numerical simulations indicate that the jet flow structure through the perforated baffle penetrates to the recirculation zones in the neighboring chambers and turns the dead zones into active mixing zones. Furthermore, large scale turbulent eddies shed by the perforations contribute to the mixing process in the chambers of the tank. With the use of the perforated baffle design, it is shown that the hydraulic efficiency of the tank can be improved from average to superior according to the baffling factor, and the associated mixing in the proposed design can be improved by 31% according to the Morrill index.

Three-dimensional analysis of heat transfer in a channel provided with solid baffle, single and double perforation

Purpose The purpose of this paper is to present a three-dimensional (3D) analysis of the laminar flow of air and the conjugate heat transfer in a pipe of rectangular cross-section with a solid or perforated deflector inserted on the lower wall. Design/methodology/approach To this end, by using the finite volume method, the conservation equations for mass, momentum and energy are solved numerically. Two cases of “single and double” perforation were studied and compared with that of the solid case for a range of Reynolds numbers ranging from 140 to 840. The velocity and temperature profiles were plotted and interpreted on three different sections placed sequentially upstream, mid-stream and downstream of the deflector. Total heat exchange at the bottom wall, outlet fluid temperature, perforated PFE deflector performance and pressure loss is presented for different cases studied and for different Reynolds numbers. Findings The results show that although the perforated deflector improves the heat transfer, it also results in additional pressure losses; the study also showed the existence of a limiting velocity beyond which the perforation effect on the improvement of the heat exchange decreases until the same performance of the solid deflector is achieved. Originality/value The main originality of this work is to show a 3D analysis for a perforated baffle as heat exchanger application.