Heat Transfer and Collector Efficiency through a Direct Absorption Solar Collector with Radiative Heat Flux Effect

2015 ◽  
Vol 68 (8) ◽  
pp. 887-907 ◽  
Author(s):  
Rehena Nasrin ◽  
Salma Parvin ◽  
M. A. Alim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Solar Collector ◽  
Radiative Heat ◽  
Radiative Heat Flux ◽  
Direct Absorption ◽  
Collector Efficiency ◽  
Direct Absorption Solar Collector

Spectral Radiative Heat Transfer Analysis of the Planar SOFC

2004 ◽  
Author(s):  
David L. Damm ◽  
Andrei G. Fedorov
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fuel Cells ◽  
Solid Oxide Fuel Cells ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Solid Oxide ◽  
Radiative Properties ◽  
Radiative Heat Flux ◽  
Oxide Fuel

Thermo-mechanical failure of components in planar-type solid oxide fuel cells (SOFCs) depends strongly on the local temperature gradients at the interfaces of different materials. Therefore, it is of paramount importance to accurately predict the temperature fields within the stack, especially near the interfaces. Because of elevated operating temperatures (of the order of 1000 K or even higher), radiation heat transfer could become a dominant mode of heat transfer in the SOFCs. In this study, we extend our recent work on radiative effects in solid oxide fuel cells (Journal of Power Sources, Vol. 124, No. 2, pp. 453–458) by accounting for the spectral dependence of the radiative properties of the electrolyte material. The measurements of spectral radiative properties of the polycrystalline yttria-stabilized zirconia (YSZ) electrolyte we performed indicate that an optically thin approximation can be used for treatment of radiative heat transfer. To this end, the Schuster-Schwartzchild two-flux approximation is used to solve the radiative transfer equation (RTE) for the spectral radiative heat flux, which is then integrated over the entire spectrum using an N-band approximation to obtain the total heat flux due to thermal radiation. The divergence of the total radiative heat flux is then incorporated as a heat sink into a 3-D thermo-fluid model of a SOFC through the user-defined function utility in the commercial FLUENT CFD software. The results of sample calculations are reported and compared against the baseline cases when no radiation effects are included and when the spectrally gray approximation is used for treatment of radiative heat transfer.

Spectral Radiative Heat Transfer Analysis of the Planar SOFC

2005 ◽  
Vol 2 (4) ◽  
pp. 258-262 ◽  
Author(s):  
David L. Damm ◽  
Andrei G. Fedorov
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fuel Cells ◽  
Solid Oxide Fuel Cells ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Solid Oxide ◽  
Radiative Properties ◽  
Radiative Heat Flux ◽  
Oxide Fuel

Thermo-mechanical failure of components in planar-type solid oxide fuel cells (SOFCs) depends strongly on the local temperature gradients at the interfaces of different materials. Therefore, it is of paramount importance to accurately predict the temperature fields within the stack, especially near the interfaces. Because of elevated operating temperatures (of the order of 1000K or even higher), radiation heat transfer could become a dominant mode of heat transfer in the SOFCs. In this study, we extend our recent work on radiative effects in solid oxide fuel cells [J. Power Sources, 124, No. 2, pp. 453–458] by accounting for the spectral dependence of the radiative properties of the electrolyte material. The measurements of spectral radiative properties of the polycrystalline yttria-stabilized zirconia electrolyte we performed indicate that an optically thin approximation can be used for treatment of radiative heat transfer. To this end, the Schuster–Schwartzchild two-flux approximation is used to solve the radiative transfer equation for the spectral radiative heat flux, which is then integrated over the entire spectrum using an N-band approximation to obtain the total heat flux due to thermal radiation. The divergence of the total radiative heat flux is then incorporated as a heat sink into a three-dimensional thermo-fluid model of a SOFC through the user-defined function utility in the commercial FLUENT computational fluid dynamics software. The results of sample calculations are reported and compared against the base line cases when no radiation effects are included and when the spectrally gray approximation is used for treatment of radiative heat transfer.

Numerical Study of Radiative Heat Flux Emitted by Stainless Wire-Net Porous Media

2020 ◽  
Vol 861 ◽  
pp. 509-513
Author(s):  
Niwat Ketchat ◽  
Bundit Krittacom
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Porous Media ◽  
Radiative Heat ◽  
Solid Phase ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Radiative Heat Flux ◽  
Air Velocity ◽  
Lower Volume

Numerical model of the convective-radiative heat transfer of porous media was proposed. A stainless wire-net was used as porous media. The physical properties, consisting of porosity (φ) and optical thickness (τ0), of porous media were independent variables. The air velocity was reported in the form of Reynolds number (Re). Two equations of the conservative energy with local thermal non-equilibrium were analyzed. The gas (θf) and solid (θs) phases of conservative energy equation inside porous media were investigated. The radiative heat flux (ψ) at down-stream of solid phase emitted into outside was dealt by the P1 approximation. From the study, it was found that the level of θf and θs decreased as Re increased because the effect of convection heat transfer. Inversely, the level of ψ increased as increasing Re. The level of θf, θs and ψ were decreased as φ increased owing to a lower volume of material depended on the increasing level of φ resulting to the heat transfer rate became lower. The level of θf, θs and ψ gave increased with τ0 becaues a wider distance in absorping energy leading to a higher emission energy from the porous media was achieved.

Model Development and Performance Studies of a Concentrating Direct Absorption Solar Collector

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Ramsatish Kaluri ◽  
Sanjay Vijayaraghavan ◽  
S. Ganapathisubbu
Keyword(s):  
Numerical Model ◽  
Absorption Coefficient ◽  
Thermal Insulation ◽  
Solar Collector ◽  
Stokes Equations ◽  
Fluid Layer ◽  
Model Development ◽  
Direct Absorption ◽  
Collector Efficiency ◽  
Direct Absorption Solar Collector

A detailed three-dimensional (3D) computational fluid dynamics (CFD) model of a direct absorption solar collector (DAC) is presented. Radiative transfer equation (RTE) is coupled with Navier–Stokes equations and solved numerically to predict the collector efficiency. The spectral properties of absorbing liquids are captured using a band-averaged absorption model. This numerical model is validated with experimental data for two different types of absorbing fluids viz., gray (graphite particles in water) and nongray (copper sulfate) fluids. The validated model is used for parametric studies to determine the right design choices for an improved collector. Impact of optical concentration ratio (CR), optical density of the fluid, mass flowrate, and thermal insulation on the collector efficiency were studied. Increase in collector efficiency of up to 28% is seen due to higher optical CRs, which is attributable to good absorption characteristics of the receiver and reduced area for losses. The collector efficiency does not improve with absorption coefficient of the fluid beyond a certain value for a given thickness of the fluid layer. The range of mass flow rates considered in the study was found to have no impact on collector efficiency. Thermal insulation is found to be very effective in minimizing the overall thermal losses and enhancing the collector efficiency. The numerical model presented here may be used to identify optimum CR, absorption coefficient of liquid for a direct absorption concentrating collector.

A Numerical Study of Radiative Heat Transfer in a Cylindrical Furnace by Using Finite Volume Method

2016 ◽  
Author(s):  
Zhenhua Wang ◽  
Bengt Sunden ◽  
Shikui Dong ◽  
Zhihong He ◽  
Weihua Yang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Numerical Study ◽  
Radiative Heat Flux ◽  
Computational Time ◽  
Volume Method

In designing industrial cylindrical furnaces, it is important to predict the radiative heat flux on the wall with high accuracy. In this study, we consider CO2 and H2O which have strong absorption in the infrared range. The absorption coefficients of the gases are calculated by using the statistical narrow band (SNB) model. The spectrum is divided into 15 bands to cover all the absorption regions of the two non-gray gases. The radiative transfer equation is solved by the finite volume method (FVM) in cylindrical coordinates. To make the FVM more accurate, we discretize the solid angle into 80 directions with the S8 approximation which is found to be both efficient and less time consuming. Based on the existing species and temperature fields, which were modeled by the FLUENT commercial code, the radiative heat transfer in a cylinder combustor is simulated by an in-house code. The results show that the radiative heat flux plays a dominant part of the heat flux to the wall. Meanwhile, when the gas is considered as nongray, the computational time is very huge. Therefore, a parallel algorithm is also applied to speed up the computing process.

Improving the Efficiency of DASC by Adding CeO2/CUO Hybrid Nanoparticles in Water

2018 ◽  
Vol 24 (8) ◽  
pp. 5651-5656
Author(s):  
V. Midhun Mohan ◽  
A. M Sajeeb
Keyword(s):  
Flow Rate ◽  
Solar Collector ◽  
Cuo Nanoparticles ◽  
Hybrid Nanoparticles ◽  
Direct Absorption ◽  
Flow Rates ◽  
The Past ◽  
Hybrid Combination ◽  
Collector Efficiency ◽  
Direct Absorption Solar Collector

Solar energy is the abundantly available source of renewable energy with least impact on environment. Direct absorption solar collector (DASC) is the commonly used device to absorb heat directly from sun and make use of it for different heating applications. In the past, many experiments have been done to increase the efficiency of DASC using nanofluids. In this paper, an examination of solar collector efficiency for hybrid CeO2/CuO-water (0.1% by volume) nanofluid under various flow rates and proportions of CeO2/CUO nanoparticles is investigated. The experiments were conducted at flow rates spanning from 20 cc/min to 100 cc/min and with CeO2/CUO nanoparticles proportions of 1:0, 1:0.5, 1:1, 0.5:1, and 0:1. The efficiency increases from 16.5% to 51.6% when the flow rate is increased from 20 cc/min to 100 cc/min for hybrid CeO2/CuO(1:1)-water nanofluid. The results also showed an increase in efficiency of 13.8, 18.1, 24.3, 24.9 and 26.1% with hybrid combination of CeO2/CUO at ratios 1:0, 1:0.5, 1:1, 0.5:1, and 0:1 respectively in comparison with water at a flow rate of 100 cc/min.

Improving the Efficiency of DASC by Adding CeO2/CuO Hybrid Nanoparticles in Water

2017 ◽  
Vol 17 (01n02) ◽  
pp. 1760011 ◽  
Author(s):  
V. Midhun Mohan ◽  
A. M. Sajeeb
Keyword(s):  
Flow Rate ◽  
Solar Collector ◽  
Cuo Nanoparticles ◽  
Hybrid Nanoparticles ◽  
Direct Absorption ◽  
Flow Rates ◽  
The Past ◽  
Hybrid Combination ◽  
Collector Efficiency ◽  
Direct Absorption Solar Collector

Solar energy is the abundantly available source of renewable energy with least impact on environment. Direct absorption solar collector (DASC) is the commonly used device to absorb heat directly from sun and make use of it for different heating applications. In the past, many experiments have been done to increase the efficiency of DASC using nanofluids. In this paper, an examination of solar collector efficiency for hybrid CeO2/CuO–water (0.1% by volume) nanofluid under various flow rates and proportions of CeO2/CuO nanoparticles is investigated. The experiments were conducted at flow rates spanning from 20[Formula: see text]cc/min to 100[Formula: see text]cc/min and with CeO2/CuO nanoparticles proportions of 1:0, 1:0.5, 1:1, 0.5:1 and 0:1. The efficiency increases from 16.5% to 51.6% when the flow rate is increased from 20[Formula: see text]cc/min to 100[Formula: see text]cc/min for hybrid CeO2/CuO (1:1)–water nanofluid. The results also showed an increase in efficiency of 13.8%, 18.1%, 24.3%, 24.9% and 26.1% with hybrid combination of CeO2/CuO at ratios 1:0, 1:0.5, 1:1, 0.5:1 and 0:1, respectively, in comparison with water at a flow rate of 100[Formula: see text]cc/min.

Numerical Simulation on the Performance of Nanofluid-Based Direct Absorption Solar Collector With Parabolic Trough Concentrator

2016 ◽  
Author(s):  
Wei Chen ◽  
Guoying Xu ◽  
Sainan Zhao ◽  
Xiaosong Zhang
Keyword(s):  
Heat Transfer ◽  
Solar Collector ◽  
Numerical Study ◽  
Radiation Absorption ◽  
Transfer Model ◽  
Direct Absorption ◽  
Operating Characteristics ◽  
Parabolic Trough ◽  
Weight Concentration ◽  
Direct Absorption Solar Collector

Nanofluids obtain high stability, improved heat transfer capability and excellent optical properties, the low-temperature nanofluid-based direct absorption solar collector (NDASC) has been previously investigated. However, the detailed radiation absorption and heat transfer mechanism for a NDASC with a solar concentrator operated on medium-temperature conditions were seldom researched. Therefore, this paper presents a numerical study on the solar collection characteristics of NDASC with a parabolic trough concentrator. CuO/oil nanofluids with various weight concentration from 0.05% to 0.1% were prepared, and used as working fluids of NDASCs, respectively. Using the developed heat transfer model, operating characteristics of NDASCs were simulated. Furthermore, the influences of weight concentration of nanofluids on the heat transfer characteristics in the NDASCs were analyzed and optimum weight concentration used for the designed NDASC obtained.

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