scholarly journals Optical-thermal properties of an MWCNT/EG nanofluid intended as the working fluid in a direct absorption solar collecto

2019 ◽  
Vol 48 (1-2) ◽  
pp. 121 ◽  
Author(s):  
Jeonggyun Ham ◽  
Yunchan Shin ◽  
Honghyun Cho
Keyword(s):  
Thermal Properties ◽  
Working Fluid ◽  
Direct Absorption

OPTIMUM OPTICAL PROPERTIES OF THE WORKING FLUID IN A DIRECT ABSORPTION COLLECTOR

2011 ◽  
Vol 18 (3) ◽  
pp. 239-247 ◽  
Author(s):  
Jiafei Zhao ◽  
Mingjiang Ni ◽  
Chunhui Shou ◽  
Yanmei Zhang ◽  
Wei Wei ◽  
...  
Keyword(s):  
Optical Properties ◽  
Working Fluid ◽  
Direct Absorption

Computation of Thermodynamic Properties of Carbon Dioxide in the Range 0–750 Deg C

1970 ◽  
Vol 92 (3) ◽  
pp. 301-309 ◽  
Author(s):  
G. Angelino ◽  
E. Macchi
Keyword(s):  
Carbon Dioxide ◽  
Thermal Properties ◽  
High Temperature ◽  
Thermodynamic Properties ◽  
Thermodynamic Functions ◽  
Critical Region ◽  
Density Measurement ◽  
Working Fluid ◽  
Power Cycles ◽  
Wide Range

The computation of power cycles employing carbon dioxide as working fluid and extending down to the critical region requires the knowledge of the thermodynamic properties of CO2 within a wide range of pressures and temperatures. Available data are recognized to be insufficient or insufficiently accurate chiefly in the vicinity of the critical dome. Newly published density and specific heat measurements are employed to compute thermodynamic functions at temperatures between 0 and 50 deg C, where the need of better data is more urgent. Methods for the computation of thermal properties from density measurement in the low and in the high temperature range are presented and discussed. Results are reported of the computation of entropy and enthalpy of CO2 in the range 150–750 deg C and 40–600 atm. The probable precision of the tables is inferred from an error analysis based on the generation, by means of a computer program of a set of pseudoexperimental points which, treated as actual measurements, yield useful information about the accuracy of the calculation procedure.

Investigation of Thermal Properties in Nanofluids for Thermal Energy Storage Applications

2013 ◽  
Author(s):  
Aitor Zabalegui ◽  
Bernadette Tong ◽  
Hohyun Lee
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Energy Storage ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Working Fluid ◽  
Traditional Theory ◽  
Energy Storage Applications ◽  
Particle Addition

Phase change materials (PCMs) are promising for thermal energy storage applications, but low thermal conductivity limits their heat exchange rate with a working fluid. The nanofluid approach has been established as a method of thermal conductivity enhancement, but particle addition may have an adverse effect on specific energy storage capacity. Latent heat reduction beyond traditional theory has been observed experimentally for carbon nanotubes dispersed in paraffin wax. Nanofluid latent heat and effective thermal conductivity were analyzed to investigate the effects of particle addition on thermal properties affecting PCM energy storage performance. It is shown that particle diameter significantly impacts nanofluid latent heat, with smaller particles generating greater degrees of reduction, but has a negligible effect on thermal conductivity. A method to approximate nanofluid latent heat of fusion is presented, considering the diameter-dependent reduction observed.

Heat Transfer Augmentation in Solar Collectors Using Nanofluids: A Review

2020 ◽  
Vol 6 (2) ◽  
pp. 72-81 ◽  
Author(s):  
Morteza Anbarsooz ◽  
Maryam Amiri ◽  
Iman Rashidi ◽  
Mohammad Javadi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Process ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Optical Parameters ◽  
Solar Collectors ◽  
Direct Absorption ◽  
Heat Transfer Augmentation

Background: Enhancing the heat transfer rate in solar collectors is an essential factor for reducing the size of the system. Yet, various methods have been presented in the literature to increase the heat transfer rate from an absorber to the heat transfer fluid. The most important methods are: the use of evacuated receivers, addition of swirl generators/turbulators and use of various nanofluids as the heat transfer fluid. Objective: The current study reviews the achievements in the enhancement of solar collectors’ heat transfer process using various types of nanofluids. The review revealed that the most widely employed nanoparticles are Al2O3 and Carbon nanotubes (CNTs) and the most popular base fluid is water. Most of the investigations are performed on indirect solar collectors, while recently, the researchers focused on direct absorption methods. In the indirect absorption collectors, the thermal conductivity of the working fluid is essential, while in a direct absorption collector, the optical properties are also crucial. Optimization of the optical parameters along with the thermophysical properties of the nanofluid is suggested for the applications of solar collector.

scholarly journals A Reciprocating Solar-Heated Engine Utilizing Direct Absorption by Small Particles

1984 ◽  
Vol 106 (1) ◽  
pp. 29-34 ◽  
Author(s):  
P. G. Hull ◽  
A. J. Hunt
Keyword(s):  
Mechanical Energy ◽  
Solar Flux ◽  
Working Fluid ◽  
Thermodynamic Efficiency ◽  
Direct Absorption ◽  
Small Particles ◽  
Compression Stroke ◽  
Particle Mixture ◽  
Heat Engines ◽  
New Type

A new type of reciprocating solar engine utilizing small particles to absorb concentrated sunlight directly within the cylinders is described. The engine operates by drawing an air-particle mixture into the cylinder, compressing the mixture, opening an optical valve to allow concentrated sunlight to enter through a window in the top of the cylinder head, absorbing the solar flux with the particles, and converting the heat trapped by the air-particle mixture into mechanical energy with the downward stroke of piston. It differs from other gas driven heat engines using solar energy in three main respects. First, the radiant flux is deposited directly in the working fluid inside the cylinder; second, the heat is directed to the appropriate cylinder by controlling the solar flux by an optical system; third, the gas is heated during a significant portion of the compression stroke. The thermodynamic efficiency of the engine is calculated using an analytical model and is compared to several other engine cycles of interest.

Predicted Efficiency of a Nanofluid-Based Direct Absorption Solar Receiver

2007 ◽  
Author(s):  
Himanshu Tyagi ◽  
Patrick Phelan ◽  
Ravi Prasher
Keyword(s):  
Flat Plate ◽  
Pure Water ◽  
Incident Radiation ◽  
Operating Conditions ◽  
Heat Transfer Analysis ◽  
Working Fluid ◽  
Direct Absorption ◽  
Low Efficiency ◽  
Flat Plate Collector ◽  
Solar Receiver

Due to its renewable and non-polluting nature solar energy is often used in applications such as electricity generation, thermal heating and chemical processing. The most cost-effective solar heaters are of the “flat-plate” type, but these suffer from relatively low efficiency and outlet temperatures. The present study theoretically investigates the feasibility of using a direct absorption solar receiver (DAR) and compares its performance with that of a typical flat-plate collector. Here a nanofluid—a mixture of water and aluminum nanoparticles—is used as the absorbing medium. A two-dimensional heat transfer analysis was developed in which direct sunlight was incident on a thin flowing film of nanofluid. The effects of absorption and scattering within the nanofluid were accounted for. In order to evaluate the temperature profile and intensity distribution within the nanofluid the energy balance equation and heat transport equation were solved numerically. It was observed that the presence of nanoparticles increases the absorption of incident radiation by more than 9 times over that of pure water. According to the results obtained from this study, under similar operating conditions, the efficiency of a DAR using nanofluid as the working fluid is found to be up to 10% higher (on an absolute basis) than that of a flat-plate collector.

scholarly journals Estimation of Cement Thermal Properties through the Three-Phase Model with Application to Geothermal Wells

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2839 ◽  
Author(s):  
Adonis Ichim ◽  
Catalin Teodoriu ◽  
Gioia Falcone
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Working Fluid ◽  
Geothermal Systems ◽  
Well Performance ◽  
Three Phase ◽  
Geothermal Wells ◽  
Ancient Times ◽  
Efficient Heat Transfer ◽  
Selection Of

Geothermal energy has been used by mankind since ancient times. Given the limited geographical distribution of the most favorable resources, exploration efforts have more recently focused on unconventional geothermal systems targeting greater depths to reach sufficient temperatures. In these systems, geothermal well performance relies on efficient heat transfer between the working fluid, which is pumped from surface, and the underground rock. Most of the wells designed for such environments require that the casing strings used throughout the well construction process be cemented in place. The overall heat transfer around the wellbore may be optimized through accurate selection of cement recipes. This paper presents the application of a three-phase analytical model to estimate the cement thermal properties. The results show that cement recipes can be designed to enhance or minimize heat transfer around wellbore, extending the application of geothermal exploitation.

scholarly journals Experimental Research on the Selective Absorption of Solar Energy by Hybrid Nanofluids

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 8186
Author(s):  
Xin Jin ◽  
Guiping Lin ◽  
Haichuan Jin ◽  
Zunru Fu ◽  
Haoyang Sun
Keyword(s):  
Solar Energy ◽  
Low Cost ◽  
Clean Energy ◽  
Absorption Efficiency ◽  
Working Fluid ◽  
Hybrid Nanofluid ◽  
Selective Absorption ◽  
Solar Collectors ◽  
Direct Absorption ◽  
Hybrid Nanofluids

As low-cost, widely distributed and easily accessible renewable clean energy, solar energy has attracted more and more attention. Direct absorption solar collectors can convert solar energy into heat, but their efficiency is closely related to the absorption performance of the working fluid. In order to improve the absorption efficiency of direct absorption solar collectors, an experimental study on the selective absorption of solar energy by hybrid nanofluids was carried out. Five hybrid nanofluids were prepared and characterized, and the energy transfer advantages of hybrid nanofluid over single nanofluid were carefully studied. Experiments have found that the light-to-heat conversion properties of hybrid nanofluids show no obvious advantages or disadvantages compared with single nanofluid, and their performance is closely related to the types of nanoparticles. In addition, the hybrid nanofluid generally has two peaks, exactly the same as the single nanofluid in the mixed component, but the absorption curve is flatter than that of the single nanofluid. Further research of more types of hybrid nanofluids can provide new insights into the use of solar energy.

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