Investigation of Particles Statistics in large Eddy Simulated Turbulent Channel Flow using Generalized lattice Boltzmann Method

The interaction of spherical solid particles with turbulent eddies in a 3-D turbulent channel flow with friction Reynolds number was studied. A generalized lattice Boltzmann equation (GLBE) was used for computation of instantaneous turbulent flow field for which large eddy simulation (LES) was employed. The sub-grid-scale (SGS) turbulence effects were simulated through a shear-improved Smagorinsky model (SISM), which can predict turbulent near wall region without any wall function. Statistical properties of particles behavior such as root mean square (RMS) velocities were studied as a function of dimensionless particle relaxation time ( ) by using a Lagrangian approach. Combination of SISM in GLBE with particle tracking analysis in turbulent channel flow is novelty of the present work. Both GLBE and SISM solve the flow field equations locally. This is an advantage of this method and makes it easy implementing. Comparison of the present results with previous available data indicated that SISM in GLBE is a reliable method for simulation of turbulent flows which is a key point to predict particles behavior correctly

Evaluating assumptions of scales for subjective assessment of thermal environments – Do laypersons perceive them the way, we researchers believe?

International audienc

Optimization of window-to-wall ratio for buildings located in different climates: an IDA-Indoor Climate and Energy simulation study

This study investigates different cases to obtain optimal Window-to-Wall ratio (WWR) in seven different climate conditions based on the Köppen–Geiger climate classification. The optimal WWR was decided based on the minimum amount of total energy use (total of cooling, heating, and lighting energy use) of a building model during a complete year. The impact of overhang and automatic blinds were assessed on the optimization of WWR for a building with integrated automatic lighting control. Moreover, three different windows with different U-values and features were employed in order to analyze their effect on the energy use and WWR of the building. IDA-Indoor Climate and Energy (IDA-ICE) was used to carry out the simulations. The software has been validated based on ASHRAE Standard 140. Based on each climate condition, orientation, employed window type, and comfort conditions, an optimal range with a specific combination of window with blind, overhang, or neither was found

Experimental Electrical Assessment Evaluation of a Vertical n-PERT Half-Size Bifacial Solar Cell String Receiver on a Parabolic Trough Solar Collector

A two-trough parabolic-shaped concentrating photovoltaic solar collector with a vertical half-size ‘phosphorus-passivated emitter rear totally diffused’ bifacial cell string receiver was designed and built for household applications, with the aim of smooth the electrical ‘duck curve’. The study consisted in testing the concentrating photovoltaic solar collector outdoors, under real weather conditions, for its daily electrical peak power and efficiency, as well as for its electrical transversal and longitudinal Incidence Angle Modifier direction. The outdoor testing measurements were conducted in a parabolic trough with low concentration coupled with a central vertical half-size ‘phosphorus-passivated emitter rear totally diffused’ bifacial cell string receiver. Furthermore, the electrical transversal Incidence Angle Modifier showed to be very delicate due to the position and outline of the receiver, which led to an electrical peak efficiency close to 10% at ±25° (i.e., for an electrical power output of around 49.3 W/m2). To validate the measured parameters, a ray-tracing software has been used, where the measured Incidence Angle Modifiers have a very good agreement with the simulated Incidence Angle Modifiers (e.g., deviation of <4%). Consequently, the concentrating solar collector met the objective of lowering the Photovoltaic cell stress and high radiation intensity, by shifting the electrical peak power at normal (e.g., at 0°) to higher incidence angles (e.g., ±25°); this aids the electrical demand peak shaving, by having the highest electrical power production displaced from the highest intensity solar radiation during the day

Thermal modelling and experimental evaluation of a novel concentrating photovoltaic thermal collector (CPVT) with parabolic concentrator

In the present study, a zero-dimensional thermal model has been developed to analyze a novel low concentration photovoltaic-thermal (CPVT) collector. The model has been developed by driving heat transfer and energy balance equations for each part of the collector and then solving all the equations simultaneously. Moreover, a Monte-Carlo ray-tracing software has been used for optical stimulations of the parabolic trough solar collector. The novel CPVT collector has been experimentally tested at Gävle University (Sweden) and the model has been validated against the experimental results. The primary energy saving equivalent to the thermal-electrical power cogeneration of the CPVT collector has been determined. The effect of glass cover removal, heat transfer fluid (HTF) inlet temperature and mass flow rate on the collector performance has been investigated. The optimum HTF mass flow rates of the collector for maximum electrical yield and overall primary energy saving were determined under specified operating conditions by considering the pump consumption. The effect of mean fluid temperature on the thermal and electrical efficiencies has been studied and the characteristic equation of the thermal efficiency has been obtained. The thermal and electrical peak efficiencies of the collector have been found to be 69.6% and 6.1%, respectively

Numerical and Experimental Study of an Asymmetric CPC-PVT Solar Collector

Photovoltaic (PV) panels and thermal collectors are commonly known as mature technologies to capture solar energy. The efficiency of PV cells decreases as operating cell temperature increases. Photovoltaic Thermal Collectors (PVT) offer a way to mitigate this performance reduction by coupling solar cells with a thermal absorber that can actively remove the excess heat from the solar cells to the Heat Transfer Fluid (HTF). In order for PVT collectors to effectively counter the negative effects of increased operating cell temperature, it is fundamental to have an adequate heat transfer from the cells to the HTF. This paper analyzes the operating temperature of the cells in a low concentrating PVT solar collector, by means of both experimental and Computational Fluid Dynamics (CFD) simulation results on the Solarus asymmetric Compound Parabolic Concentrator (CPC) PowerCollector (PC). The PC solar collector features a Compound Parabolic Concentrator (CPC) reflector geometry called the Maximum Reflector Concentration (MaReCo) geometry. This collector is suited for applications such as Domestic Hot Water (DHW). An experimental setup was installed in the outdoor testing laboratory at G&amp;auml;vle University (Sweden) with the ability to measure ambient, cell and HTF temperature, flow rate and solar radiation. The experimental results were validated by means of an in-house developed CFD model. Based on the validated model, the effect of collector tilt angle, HTF, insulation (on the back side of the reflector), receiver material and front glass on the collector performance were considered. The impact of tilt angle is more pronounced on the thermal production than the electrical one. Furthermore, the HTF recirculation with an average temperature of 35.1C and 2.2 L/min flow rate showed that the electrical yield can increase by 25%. On the other hand, by using insulation, the thermal yield increases up to 3% when working at a temperature of 23 C above ambient.This research was partly supported with funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 814865 (RES4BUILD). The authors are also grateful for the support provided by the STINT mobility program and are thankful for the fruitful cooperation with the project partners. </p