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.

A Review on Experimental and Numerical Investigations on Using Nanofluid in Volumetric Solar Energy Collectors

2014 ◽  
Author(s):  
Siamak Mirmasoumi ◽  
Mohammad Pourgol-Mohammad
Keyword(s):  
Heat Transfer ◽  
Power Plants ◽  
Radiant Energy ◽  
Solar Thermal ◽  
Working Fluid ◽  
Steam Generation ◽  
Solar Thermal Energy ◽  
Solar Absorption ◽  
Advantages And Disadvantages ◽  
Solar Power Plants

By a simple research in the scholarly articles, it can be realized that the tendency to using solar thermal energy has risen in the recent years due to its many reasonable advantages. In conventional solar thermal systems, HTFs (Heat Transfer Fluids) are pumped through the piping of a solar collector and after absorbing the solar radiant energy conveys it to water to make steam. No need to say that this method contains some losses via all methods of heat transfer. To solve this problem, researchers have shown that with direct steam generation, in which working fluid directly absorbs solar thermal and becomes vapor, solar power plants have the potential to be more productive. However, the aforesaid conventional HTFs don’t have efficient enough thermal properties and need to be improved. For this reason using nanofluid has become to some extent popular in heat transfer facilities like solar thermal collectors. In the present study, we are going to identify the advantages and disadvantages of using nanoparticles in direct solar absorption systems (DSASs). To achieve this, a general review on the experimental and numerical studies in this field is done. Additionally some of the most effective particles for such a special case, in which particles should have good radiative characteristics, are introduced. Finally, after discussion about the highlighted challenges of using nanofluids in DSASs, some helpful suggestions to overcome these problems will be presented.

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.

Experimental Study of Inclination on Non-Boiling Regime Spray Cooling

2008 ◽  
Author(s):  
Yongxian Guo ◽  
Jianyuan Jia ◽  
Weidong Wang ◽  
Shaorong Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heated Surface ◽  
Spray Cooling ◽  
Copper Surface ◽  
Experimental Results ◽  
Working Fluid ◽  
Distilled Water ◽  
Optimal Heat ◽  
Inclination Angles

Based on the maximum CHF (critical heat flux) criterion, an optimal heat transfer criterion, which is called H criterion, was proposed. Experimental apparatuses were conducted. Distilled water was used as the working fluid. Three different DANFOSS nozzles with cone angles being 54°, 50° and 54° respectively were used. A 30×30mm2 square copper surface was used as the heated surface. Experimental results indicated that the volumetric fluxes were proportioned to P0.5, where P is the pressure drop across the nozzles. The optimal distance between the nozzles and the heated surface were derived. The results indicated that the optimal heat transfer appeared while the outside of the impellent thin spray film inscribed in the square heated surface. Based on the H criterion aforementioned, two DANFOSS nozzles of the three, with cone angles being 54° and 50° respectively, were used to study the temperature distribution of the heated surface while there were spray inclination angles during spray cooling experiments. Distilled water was also used impacting on the 30×30mm2 square copper surface aforementioned and a circular heated copper surface with diameters being 30mm respectively. The heat flux of the surface was kept in constant (about 26–35W/cm2). The inclination angles were 0°, 10°, 20°, 30°, 40° and 50° respectively. Three thermocouples imbedded in the heated surface were used to predict the grads of the temperature of the surface. Experimental results indicated that the temperature and the grads of the temperature of the surface increases first and then decreases with the increase of the inclination angle.

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.

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