Rheological Properties of Heat Transfer Liquids for Solar Thermal Systems

2016 ◽  
Vol 74 (1) ◽  
pp. 207-212
Author(s):  
M. Frk ◽  
J. Hylsky ◽  
D. Strachala
Keyword(s):  
Heat Transfer ◽  
Rheological Properties ◽  
Solar Thermal ◽  
Thermal Systems

Heat Transfer Fluids for Optimal Year-Round Operation of Solar Thermal Systems in Central Europe

2014 ◽  
Vol 63 (1) ◽  
pp. 183-190
Author(s):  
J. Hylsky ◽  
L. imonova ◽  
M. Frk ◽  
J. ubarda ◽  
M. Kadlec
Keyword(s):  
Heat Transfer ◽  
Central Europe ◽  
Solar Thermal ◽  
Thermal Systems ◽  
Heat Transfer Fluids

Heat Loss Characteristics of a Roof Integrated Solar Micro-Concentrating Collector

2011 ◽  
Author(s):  
Tanzeen Sultana ◽  
Graham L. Morrison ◽  
Siddarth Bhardwaj ◽  
Gary Rosengarten
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Large Scale ◽  
Radiation Heat Transfer ◽  
Industrial Process ◽  
Hot Water ◽  
Solar Thermal ◽  
Convection Heat ◽  
Thermal Systems ◽  
Optical Efficiency

Concentrating solar thermal systems offer a promising method for large scale solar energy collection. It is feasible to use concentrating solar thermal systems for rooftop applications such as domestic hot water, industrial process heat and solar air conditioning for commercial, industrial and institutional buildings. This paper describes the thermal performance of a new low-cost solar thermal micro-concentrating collector (MCT), which uses linear Fresnel reflector technology and is designed to operate at temperatures up to 220°C. The modules of this collector system are approximately 3 meters long by 1 meter wide and 0.3 meters high. The objective of the study is to optimize the design to maximise the overall thermal efficiency. The absorber is contained in a sealed enclosure to minimise convective losses. The main heat losses are due to natural convection inside the enclosure and radiation heat transfer from the absorber tube. In this paper we present the results of a computational investigation of radiation and convection heat transfer in order to understand the heat loss mechanisms. A computational model for the prototype collector has been developed using ANSYS-CFX, a commercial computational fluid dynamics software package. Radiation and convection heat loss has been investigated as a function of absorber temperature. Preliminary ray trace simulation has been performed using SolTRACE and optical efficiency has been evaluated. Finally, the MCT collector efficiency is also evaluated.

Suitability of various heat transfer fluids for high temperature solar thermal systems

2019 ◽  
Vol 159 ◽  
pp. 113973 ◽  
Author(s):  
Ravindra Vutukuru ◽  
A. Saikiran Pegallapati ◽  
Ramgopal Maddali
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Solar Thermal ◽  
Thermal Systems ◽  
Heat Transfer Fluids

scholarly journals Heat Transfer of Nanomaterial over an Infinite Disk with Marangoni Convection: A Modified Fourier’s Heat Flux Model for Solar Thermal System Applications

2021 ◽  
Vol 11 (24) ◽  
pp. 11609
Author(s):  
Mahanthesh Basavarajappa ◽  
Giulio Lorenzini ◽  
Srikantha Narasimhamurthy ◽  
Ashwag Albakri ◽  
Taseer Muhammad
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Thermal Energy ◽  
Fossil Fuels ◽  
Marangoni Convection ◽  
Solar Thermal ◽  
Solar Collectors ◽  
Thermal Systems ◽  
Flux Model ◽  
Heat Flux Model

The demand for energy due to the population boom, together with the harmful consequences of fossil fuels, makes it essential to explore renewable thermal energy. Solar Thermal Systems (STS’s) are important alternatives to conventional fossil fuels, owing to their ability to convert solar thermal energy into heat and electricity. However, improving the efficiency of solar thermal systems is the biggest challenge for researchers. Nanomaterial is an effective technique for improving the efficiency of STS’s by using nanomaterials as working fluids. Therefore, the present theoretical study aims to explore the thermal energy characteristics of the flow of nanomaterials generated by the surface gradient (Marangoni convection) on a disk surface subjected to two different thermal energy modulations. Instead of the conventional Fourier heat flux law to examine heat transfer characteristics, the Cattaneo–Christov heat flux (Fourier’s heat flux model) law is accounted for. The inhomogeneous nanomaterial model is used in mathematical modeling. The exponential form of thermal energy modulations is incorporated. The finite-difference technique along with Richardson extrapolation is used to treat the governing problem. The effects of the key parameters on flow distributions were analyzed in detail. Numerical calculations were performed to obtain correlations giving the reduced Nusselt number and the reduced Sherwood number in terms of relevant key parameters. The heat transfer rate of solar collectors increases due to the Marangoni convection. The thermophoresis phenomenon and chaotic movement of nanoparticles in a working fluid of solar collectors enhance the temperature distribution of the system. Furthermore, the thermal field is enhanced due to the thermal energy modulations. The results find applications in solar thermal exchanger manufacturing processes.

Potential Heat Transfer Fluids (Nanofluids) for Direct Volumetric Absorption-Based Solar Thermal Systems

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Vikrant Khullar ◽  
Vishal Bhalla ◽  
Himanshu Tyagi
Keyword(s):  
Heat Transfer ◽  
Optical Properties ◽  
Amorphous Carbon ◽  
Solar Thermal ◽  
Solar Irradiation ◽  
Working Fluid ◽  
Distilled Water ◽  
Thermal Systems ◽  
Nanoparticle Dispersions ◽  
Carbon Based

Nanoparticle dispersions or more popularly “nanofluids” have been extensively researched for their candidature as working fluid in direct-volumetric-absorption solar thermal systems. Flexibility in carving out desired thermophysical and optical properties has lend the nanofluids to be engineered for solar thermal and photovoltaic applications. The key feature which delineates nanofluid-based direct absorption volumetric systems from their surface absorption counterparts is that here the working fluid actively (directly) interacts with the solar irradiation and hence enhances the overall heat transfer of the system. In this work, a host of nanoparticle materials have been evaluated for their solar-weighted absorptivity and heat transfer enhancements relative to the basefluid. It has been found that solar-weighted absorptivity is the key feature that makes nanoparticle dispersions suitable for solar thermal applications (maximum enhancement being for the case of amorphous carbon nanoparticles). Subsequently, thermal conductivity measurements reveal that enhancements on the order of 1–5% could only be achieved through addition of nanoparticles into the basefluid. Furthermore, dynamic light scattering (DLS) and optical measurements (carried out for as prepared, 5 h old and 24 h old samples) reveal that nanoclustering and hence soft agglomeration does happen but it does not have significant impact on optical properties of the nanoparticles. Finally, as a proof-of-concept experiment, a parabolic trough collector employing the amorphous carbon-based nanofluid and distilled water has been tested under the sun. These experiments have been carried out at no flow condition so that appreciable temperatures could be reached in less time. It was found that for the same exposure time, increase in the temperature of amorphous carbon based nanofluid is approximately three times higher as compared to that in the case of distilled water.

scholarly journals Performance Evaluation of Elimination of Stagnation of Solar Thermal Systems

Processes ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 621 ◽  
Author(s):  
Miroslav Rimar ◽  
Marcel Fedak ◽  
Jakub Vahovsky ◽  
Andrii Kulikov ◽  
Peter Oravec ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Thermal Systems ◽  
Heat Transfer Medium ◽  
Limit Values ◽  
Fully Automatic ◽  
Thermal Saturation ◽  
Solar Thermal System ◽  
The Ideal

The study deals with the possibility of elimination of stagnation of thermal systems. The state of stagnation of thermal systems leads to overheating and evaporation of the heat transfer medium, which increases pressure and can lead to damage to the solar thermal system. Stagnation can occur due to a fault and stopping of the circulation pump, which causes the circulation of the heat transfer medium to stop. Another possibility is to achieve thermal saturation in the system, which can be affected by low heat consumption from the system. Elimination of stagnation is possible by various construction designs of collectors or by using other technical means. This study describes an experiment verifying the usability of a thermal collector’s tilting system to eliminate thermal stagnation of the system. The system is fully automatic, and when recording the limit values, ensures that the panel is rotated out of the ideal position, thus reducing the amount of received energy. In this way, the temperature of the medium in the system can be reduced by up to 10% in one hour. In the case of thermal saturation of the system, the solution is the automatic circulation of heat-transfer fluid through the system during the night and the release of thermal energy to the outside. These results suggest that the methods used actively eliminate stagnation of thermal systems.

scholarly journals Carbon-based Nanofluid Applications in Solar Thermal Energy

2019 ◽  
Vol 111 ◽  
pp. 01056
Author(s):  
Nur Çobanoğlu ◽  
Ziya Haktan Karadeniz ◽  
Alpaslan Turgut
Keyword(s):  
Heat Transfer ◽  
Renewable Energy ◽  
Solar Energy ◽  
Renewable Energy Sources ◽  
Energy Systems ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Energy Sources ◽  
Solar Thermal Energy ◽  
Thermal Systems

Renewable energy sources such as solar, wind and geothermal are proposed as an alternative to fossil fuels whose excessive use causes global warming. The most popular one of the renewable energy sources is considered as solar energy due to the fact that required energy is provided by the sun entire year around the world. Solar energy systems convert the solar radiation to the useful heat or electricity. In order to achieve better performance in solar thermal systems many studies have been conducted. Some of these studies suggest that heat transfer fluid could be changed with the nanofluids which can be defined as new generation heat transfer fluid. Nanofluids are suspensions of nano-sized particles such as metals, metal-oxides, and Carbon-allotropes (C), in the conventional base-fluids (water, ethylene glycol and oil). Using nanofluid enhances the efficiency and thermal performance of solar systems due to their better thermophysical and optical properties. Recently, C-based nanofluids are getting attention due to their enhanced thermal conductivity and absorptivity at even low concentrations. The results show that C-based nanofluids have a potential to use in solar energy systems: solar collectors, solar stills, photovoltaic/thermal systems.

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