An Air-Based Cavity-Receiver for Solar Trough Concentrators

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Roman Bader ◽  
Maurizio Barbato ◽  
Andrea Pedretti ◽  
Aldo Steinfeld
Keyword(s):  
Heat Transfer ◽  
Solar Power ◽  
Power Input ◽  
Absorption Efficiency ◽  
Conservation Equation ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Transfer Model ◽  
Pumping Power ◽  
Power Requirement

A cylindrical cavity-receiver containing a tubular absorber that uses air as the heat transfer fluid is proposed for a novel solar trough concentrator design. A numerical heat transfer model is developed to determine the receiver’s absorption efficiency and pumping power requirement. The 2D steady-state energy conservation equation coupling radiation, convection, and conduction heat transfer is formulated and solved numerically by finite volume techniques. The Monte Carlo ray-tracing and radiosity methods are applied to establish the solar radiation distribution and radiative exchange within the receiver. Simulations were conducted for a 50 m-long and 9.5 m-wide collector section with 120°C air inlet temperature, and air mass flows in the range 0.1–1.2 kg/s. Outlet air temperatures ranged from 260°C to 601°C, and corresponding absorption efficiencies varied between 60% and 18%. Main heat losses integrated over the receiver length were due to reflection and spillage at the receiver’s windowed aperture, amounting to 13% and 9% of the solar power input, respectively. The pressure drop along the 50 m module was in the range 0.23–11.84 mbars, resulting in isentropic pumping power requirements of 6.45×10−4−0.395% of the solar power input.

An Air-Based Cavity-Receiver for Solar Trough Concentrators

2010 ◽  
Author(s):  
Roman Bader ◽  
Maurizio Barbato ◽  
Andrea Pedretti ◽  
Aldo Steinfeld
Keyword(s):  
Heat Transfer ◽  
Solar Power ◽  
Power Input ◽  
Absorption Efficiency ◽  
Conservation Equation ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Transfer Model ◽  
Pumping Power ◽  
Power Requirement

A cylindrical cavity-receiver containing a tubular absorber that uses air as the heat transfer fluid is proposed for a novel solar trough concentrator design. A numerical heat transfer model is developed to determine the receiver’s absorption efficiency and pumping power requirement. The 2D steady-state energy conservation equation coupling radiation, convection and conduction heat transfer is formulated and solved numerically by finite-difference techniques. The Monte Carlo ray-tracing and radiosity methods are applied to establish the solar radiation distribution and radiative exchange within the receiver. Simulations were conducted for a 50 m-long and 9.5 m-wide collector section with 120°C air inlet temperature, and air mass flows in the range 0.1–1.2 kg/s. Outlet air temperatures ranged from 260 to 601 °C, and corresponding absorption efficiencies varied between 60 and 18%. Main heat losses integrated over the receiver length were due to reflection and spillage at the receiver’s windowed aperture, amounting to 13% and 9% of the solar power input, respectively. The pressure drop along the 50 m module was in the range 0.23 to 11.84 mbar, resulting in isentropic pumping power requirements of 6.45·10−4%–0.395% of the solar power input.

Experimental and Numerical Heat Transfer Analysis of an Air-Based Cavity-Receiver for Solar Trough Concentrators

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
R. Bader ◽  
A. Pedretti ◽  
A. Steinfeld
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Solar Power ◽  
Power Input ◽  
Heat Transfer Analysis ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Transfer Model ◽  
Outlet Temperature ◽  
Solar Receiver

We report on the field testing of a 42 m-long full-scale solar receiver prototype installed on a 9 m-aperture solar trough concentrator. The solar receiver consists of a cylindrical cavity containing a tubular absorber with air as the heat transfer fluid (HTF). Experimental results are used to validate a heat transfer model based on Monte Carlo ray-tracing and finite-volume techniques. Performance predictions obtained with the validated model yield the following results for the receiver. At summer solstice solar noon, with HTF inlet temperature of 120 °C and HTF outlet temperature in the range 250–450 °C, the receiver efficiency ranges from 45% to 29% for a solar power input of 280 kW. One third of the solar radiation incident on the receiver is lost by spillage at the aperture and reflection inside the cavity. Other heat losses are due to natural convection (9.9–9.7% of solar power input) and re-radiation (6.1–17.6%) through the cavity aperture and by natural convection from the cavity insulation (5.6–9.1%). The energy penalty associated with the HTF pumping work represents 0.6–24.4% of the power generated.

scholarly journals Comparative Modeling of a Parabolic Trough Collectors Solar Power Plant with MARS Models

Energies ◽  
2017 ◽  
Vol 11 (1) ◽  
pp. 37 ◽  
Author(s):  
Jose Rogada ◽  
Lourdes Barcia ◽  
Juan Martinez ◽  
Mario Menendez ◽  
Francisco de Cos Juez
Keyword(s):  
Heat Transfer ◽  
Water Vapor ◽  
Power Plant ◽  
Solar Radiation ◽  
Thermal Energy ◽  
Power Plants ◽  
Solar Power ◽  
Rankine Cycle ◽  
Heat Transfer Fluid ◽  
Solar Field

Power plants producing energy through solar fields use a heat transfer fluid that lends itself to be influenced and changed by different variables. In solar power plants, a heat transfer fluid (HTF) is used to transfer the thermal energy of solar radiation through parabolic collectors to a water vapor Rankine cycle. In this way, a turbine is driven that produces electricity when coupled to an electric generator. These plants have a heat transfer system that converts the solar radiation into heat through a HTF, and transfers that thermal energy to the water vapor heat exchangers. The best possible performance in the Rankine cycle, and therefore in the thermal plant, is obtained when the HTF reaches its maximum temperature when leaving the solar field (SF). In addition, it is necessary that the HTF does not exceed its own maximum operating temperature, above which it degrades. The optimum temperature of the HTF is difficult to obtain, since the working conditions of the plant can change abruptly from moment to moment. Guaranteeing that this HTF operates at its optimal temperature to produce electricity through a Rankine cycle is a priority. The oil flowing through the solar field has the disadvantage of having a thermal limit. Therefore, this research focuses on trying to make sure that this fluid comes out of the solar field with the highest possible temperature. Modeling using data mining is revealed as an important tool for forecasting the performance of this kind of power plant. The purpose of this document is to provide a model that can be used to optimize the temperature control of the fluid without interfering with the normal operation of the plant. The results obtained with this model should be necessarily contrasted with those obtained in a real plant. Initially, we compare the PID (proportional–integral–derivative) models used in previous studies for the optimization of this type of plant with modeling using the multivariate adaptive regression splines (MARS) model.

An Evaluation of the Application of Nanofluids in Intercooled Cycle Marine Gas Turbine Intercooler

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Ningbo Zhao ◽  
Xueyou Wen ◽  
Shuying Li
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Gas Turbine ◽  
Heat Transfer Performance ◽  
Volume Concentration ◽  
Inlet Temperature ◽  
Transfer Performance ◽  
Pumping Power ◽  
Flow And Heat Transfer ◽  
Overall Performance

Coolant is one of the important factors affecting the overall performance of the intercooler for the intercooled (IC) cycle marine gas turbine. Conventional coolants, such as water and ethylene glycol, have lower thermal conductivity which can hinder the development of highly effective compact intercooler. Nanofluids that consist of nanoparticles and base fluids have superior properties like extensively higher thermal conductivity and heat transfer performance compared to those of base fluids. This paper focuses on the application of two different water-based nanofluids containing aluminum oxide (Al2O3) and copper (Cu) nanoparticles in IC cycle marine gas turbine intercooler. The effectiveness-number of transfer unit method is used to evaluate the flow and heat transfer performance of intercooler, and the thermophysical properties of nanofluids are obtained from literature. Then, the effects of some important parameters, such as nanoparticle volume concentration, coolant Reynolds number, coolant inlet temperature, and gas side operating parameters on the flow and heat transfer performance of intercooler, are discussed in detail. The results demonstrate that nanofluids have excellent heat transfer performance and need lower pumping power in comparison with base fluids under different gas turbine operating conditions. Under the same heat transfer, Cu–water nanofluids can reduce more pumping power than Al2O3–water nanofluids. It is also concluded that the overall performance of intercooler can be enhanced when increasing the nanoparticle volume concentration and coolant Reynolds number and decreasing the coolant inlet temperature.

Performance Analysis of Single-Phase Space Thermal Radiators and Optimization through Taguchi-Neuro-Genetic Approach

2021 ◽  
pp. 1-18
Author(s):  
P B Chiranjeevi ◽  
Ashok V ◽  
K. Srinivasan ◽  
Thirumalachari Sundararajan
Keyword(s):  
Heat Transfer ◽  
Performance Analysis ◽  
Conjugate Heat Transfer ◽  
Computational Time ◽  
Maximum Diameter ◽  
Genetic Approach ◽  
Pumping Power ◽  
Power Requirement ◽  
Space Applications ◽  
Heat Rejection

Abstract In the thermal management of spacecraft, space thermal radiators play a vital role as heat sinks. A serial radiator with proven advantages in ground applications is proposed and analyzed for space applications. From the performance analysis, specific heat rejection of serial radiator is found to be higher than parallel radiator by 80% for maximum diameter of tube, 47% for maximum thickness of fin, and 75% for maximum pitch of tubes under consideration. Also, serial radiator requires four times higher pumping power than parallel radiator with geometric parameters and a maximum mass flow rate under consideration. In serial radiators, the cross conduction between the fins has a significant effect on its thermal performance. Thus, conjugate heat transfer simulations and optimization operations are to be performed iteratively to optimize the serial radiator, which is computationally costly. To reduce the computational time, Artificial Neural Network is trained using conjugate heat transfer simulations data and combined with the genetic algorithm to perform optimization. Taguchi's orthogonal arrays provided the partial fraction of conjugate heat transfer simulations set to train the ANN. Taguchi-Neuro-Genetic approach, a process that combines the features of three powerful techniques in different optimization phases, is used to optimize both parallel and serial radiators. The optimization aims to obtain a configuration that provides the lowest mass and lowest pumping power requirement for given heat rejection. Optimization results show that the conventional parallel radiator is about 20% heavier and requires about 35% more pumping power than the proposed serial radiator.

Optimizing an Active Solar still for Sea Water Desalination

2014 ◽  
Vol 1051 ◽  
pp. 985-991
Author(s):  
Osman Ali Hamadou ◽  
Khamlichi Abdellatif
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Sea Water ◽  
Saline Water ◽  
Phase Changes ◽  
Water Desalination ◽  
Heat Transfer Fluid ◽  
Water Yield ◽  
Inlet Temperature ◽  
Glass Cover

Sea water desalination through solar radiation distillation process can achieve low cost and sustainable fresh water for remote dry areas. In conventional passive solar stills, the solar radiation passes through the transparent cover and supplies heat to sea water with limited back reflection. The evaporative heat transfer between the water surface and the glass cover produces the distillate by means of film type condensation at the inner surface of the glass cover. In order to enhance evaporation/condensation phase changes, active solar stills were introduced. In these last, saline water is circulated and put in contact with a heat source which supplies heat to the saline water. With this extra energy, the distillate productivity is increased. In this work, heat supply is assumed to be controlled such that the temperature at the inlet of the still can be adjusted through regulation of the circulating heat transfer fluid rate. Using a modelling based on uniform temperature in each still component, a set of ordinary differential equations was derived. The input variables comprised heat transfer fluid rate, inlet temperature as well as sea water rate and basin depth. Extensive parametric studies were performed after that and optimization of the distilled water yield and rate was discussed.

Thermodynamic Analysis of Freezing and Melting Processes in a Bed of Spherical PCM Capsules

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
David MacPhee ◽  
Ibrahim Dincer
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Flow Rate ◽  
Present Model ◽  
Spherical Geometry ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Main Mode ◽  
Solidification Temperature ◽  
Flow Phenomena

The solidification and melting processes in a spherical geometry are investigated in this study. The capsules considered are filled with de-ionized water, so that a network of spheres can be thought of as being the storage medium for an encapsulated ice storage module. ANSYS GAMBIT and FLUENT 6.0 packages are used to employ the present model for heat transfer fluid (HTF) past a row of such capsules, while varying the HTF inlet temperature and flow rate, as well as the reference temperatures. The present model agrees well with experimental data taken from literature and was also put through rigorous time and grid independence tests. Sufficient flow parameters are studied so that the resulting solidification and melting times, exergy and energy efficiencies, and exergy destruction could be calculated. All energy efficiencies are found to be over 99%, though viscous dissipation was included. Using exergy analysis, the exergetic efficiencies are determined to be about 75% to over 92%, depending on the HTF scenario. When the HTF flow rate is increased, all efficiencies decrease, due mainly to increasing heat losses and exergy dissipation. The HTF temperatures, which stray farther from the solidification temperature of water, are found to be most optimal exergetically, but least optimal energetically. The main reason for this, as well as the main mode of loss exergetically, is due to entropy generation accompanying heat transfer, which is responsible for over 99.5% of exergy destroyed in all cases. The results indicate that viewing the heat transfer and fluid flow phenomena in a bed of encapsulated spheres, it is of utmost importance to assess the major modes of entropy generation; in this case from heat transfer accompanying phase change.

Numerical Investigation of Flow and Heat Transfer Performance of Nano-Encapsulated Phase Change Material Slurry in Microchannels

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Sarada Kuravi ◽  
Krishna M. Kota ◽  
Jianhua Du ◽  
Louis C. Chow
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Numerical Investigation ◽  
Phase Change Material ◽  
Temperature Fields ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Bulk Fluid ◽  
Encapsulated Phase Change Material ◽  
Change Material

Microchannels are used in applications where large amount of heat is produced. Phase change material (PCM) slurries can be used as a heat transfer fluid in microchannels as they provide increased heat capacity during the melting of phase change material. For the present numerical investigation, performance of a nano-encapsulated phase change material slurry in a manifold microchannel heat sink was analyzed. The slurry was modeled as a bulk fluid with varying specific heat. The temperature field inside the channel wall is solved three dimensionally and is coupled with the three dimensional velocity and temperature fields of the fluid. The model includes the microchannel fin or wall effect, axial conduction along the length of the channel, developing flow of the fluid and not all these features were included in previous numerical investigations. Influence of parameters such as particle concentration, inlet temperature, melting range of the PCM, and heat flux is investigated, and the results are compared with the pure single phase fluid.

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