Solar Engineering Of Thermal Processes

Entropy Generation Minimization

Energy and exergy analysis of solar air heater having new design absorber plate with conical surface

Solar simulators are used to test components and systems under controlled and repeatable conditions, often in locations with unsuitable insolation for outdoor testing. The growth in renewable energy generation has led to an increased need to develop, manufacture and test components and subsystems for solar thermal, photovoltaic (PV), and concentrating optics for both thermal and electrical solar applications. At the heart of any solar simulator is the light source itself. This paper reviews the light sources available for both low and high-flux solar simulators used for thermal applications. Criteria considered include a comparison of the lamp wavelength spectrum with the solar spectrum, lamp intensity, cost, stability, durability, and any hazards associated with use. Four main lamp types are discussed in detail, namely argon arc, the metal halide, tungsten halogen lamp, and xenon arc lamps. In addition to describing the characteristics of each lamp type, the popularity of usage of each type over time is also indicated. This is followed by guidelines for selecting a suitable lamp, depending on the requirements of the user and the criteria applied for selection. The appropriate international standards are also addressed and discussed. The review shows that metal halide and xenon arc lamps predominate, since both provide a good spectral match to the solar output. The xenon lamp provides a more intense and stable output, but has the disadvantages of being a high-pressure component, requiring infrared filtering, and the need of a more complex and expensive power supply. As a result, many new solar simulators prefer metal halide lamps.

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Light source selection for a solar simulator for thermal applications: A review

The recent studies on thermal performance enhancement of the flat plate solar air collectors are critically reviewed primarily regarding the absorber surface modifications, multiple-passes of air, porous absorbers, air-jet impingement on absorber surface, integration of heat storage materials, dual-purpose hybrid collectors and hybrid photovoltaic/thermal solar collectors. The formation of a laminar viscous layer over the surface causes poor heat transfer to airflow. Enhanced heat transfer surface area and residence time of air are vital factors for heat transfer augmentation using baffles, turbulators, roughness, and obstacles. The streamwise pitch ratio of the jet plate has the maximum contribution to friction and, subsequently, the heat transfer. The thermal efficiency of finned and porous absorber varies from 71.4% to 93%. The integration of phase change material and fins with solar air collector enhance daily thermal efficiency by 0.1%–4%, increasing further with honeycomb and porous structures. The application of agriculture waste as sensible heat storage material is an effective alternative to replace conventional materials. Electrical and thermal efficiencies of hybrid solar collector increased with the addition of thermal energy storage by 9% and 5%, which further enhanced by 3% with the addition of fins into the phase change materials. Thermo-economic performance of the dual-purpose collector and hybrid photovoltaic/thermal solar air collector is comparatively cost-effective with environmental benefits. This review article provides an insight into the recent critical findings on the thermal performance enhancement of the flat plate solar air collector to stimulate further developments towards the betterment of sustainable development.

A review on recent developments in thermal performance enhancement methods of flat plate solar air collector

An indoor standard test procedure is developed to experimentally investigate the steady state energy and exergy performance of single-pass flat plate solar air heater (SPFPSAH), roughened plate dual-pass solar air heater (RPDPSAH), finned plate dual-pass solar air heater (FPDPSAH) and wire mesh dual-pass solar air heater (WMDPSAH) at varied mass flow rates and solar intensities. The analytical solution of the energy balance equations for various elements of the SPFPSAH, RPDPSAH, FPDPSAH and WMDPSAH is determined using a MATLAB 8.1 program and correlated with experimental findings. The analytical and experimental results show that the energy and exergy performance of WMDPSAH is superior to FPDPSAH, RPDPSAH and SPFPSAH. The pressure drop of WMDPSAH is higher than that of FPDPSAH, RPDPSAH and SPFPSAH. From the economic analysis, WMDPSAH is found economically viable within the opted conditions compared with FPDPSAH and RPDPSAH. The analytical and experimental results are in fairly good agreement.

Energy and Exergy Analysis of Solar Air Heaters with Varied Geometries

In this paper, a mathematical model based on the energy balance equations is developed to study the energy and exergy performances of single, double, and triple pass solar air heaters The energy and exergy performances of solar air heaters are determined by simulation using Matlab-81 The influence of mass flow rate on the rise in air temperature, energy efficiency, improvement efficiency, exergy efficiency, and irreversibility are studied The energy and exergy performance of the triple pass is higher than the single and the double pass conditions The results obtained from the analytical models are in good agreement with experimental data reported by earlier researchers

Energy and Exergy Analysis of Multi-Pass Flat Plate Solar Air Heater—An Analytical Approach

In this study, an attempt is made to improve the energy and exergy performance of solar air heater by employing double pass with different absorber surface geometries (roughened, finned, and v-corrugated wire mesh) in the second pass, and also by mounting longitudinal fins in the back side of the absorber plate (first pass). The effect of varied mass flow rate and solar intensity on temperature rise of air, energy efficiency, exergy gain and pressure drop at steady state condition was determined for different types of solar air heaters utilizing an indoor solar simulator. The temperature rise of air, thermal efficiency and exergy gain depends on mass flow rate, surface geometries of absorber and solar intensity, whereas the pressure drop depends on mass flow rate and surface geometries of absorber.

Energy and exergy analysis in double-pass solar air heater

In this study, thermal performance of double- and triple-pass solar air heater with longitudinal fins is mathematically evaluated. The effects of parameters, viz. mass flow rate, solar intensity and inlet temperature upon outlet temperature, thermal efficiency and increments in efficiency, power consumption are presented. The analytical solution for the mathematical model involving energy balance equations of different components of solar air heater is obtained using a MATLAB 8.1. Triple-pass solar air heater with fins exhibits better thermal performance, whereas double-pass solar air heater with fins is economically viable within the opted conditions. The results of the analytical models are in good agreement with experimental findings of earlier researchers.

R. Kalaivanan

Papers

Energy and Exergy Analysis of Solar Air Heaters with Varied Geometries

Energy and Exergy Analysis of Multi-Pass Flat Plate Solar Air Heater—An Analytical Approach

Energy and exergy analysis in double-pass solar air heater

Thermal Performance Studies on Multi-pass Flat-plate Solar Air Heater with Longitudinal Fins: An Analytical Approach