Numerical Analysis of Heat Transfer Enhancement in a Parabolic Trough Collector Based on Geometry Modifications and Working Fluid Usage

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Eric C. Okonkwo ◽  
Muhammad Abid ◽  
Tahir A. H. Ratlamwala
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer Coefficient ◽  
Working Fluid ◽  
Al2o3 Nanoparticles ◽  
Parabolic Trough ◽  
Pressurized Water ◽  
Parabolic Trough Collector ◽  
Factors Affecting

The parabolic trough collector (PTC) is one of the most widely deployed concentrating solar power technology in the world. This study aims at improving the operational efficiency of the commercially available LS-2 solar collector by increasing the convective heat transfer coefficient inside the receiver tube. The two main factors affecting this parameter are the properties of the working fluid and the inner geometry of the receiver tube. An investigation was carried out on six different working fluids: pressurized water, supercritical CO2, Therminol VP-1, and the addition of CuO, Fe3O4, and Al2O3 nanoparticles to Therminol VP-1. Furthermore, the influence of a converging-diverging tube with sine geometry is investigated because this geometry increases the heat transfer surface and enhances turbulent flow within the receiver. The results showed that of all the fluids investigated, the Al2O3/Oil nanofluid provides the best improvement of 0.22% to thermal efficiency, while the modified geometry accounted for a 1.13% increase in efficiency. Other parameters investigated include the exergy efficiency, heat transfer coefficient, outlet temperatures, and pressure drop. The analysis and modeling of a parabolic trough receiver are implemented in engineering equation solver (EES).

Computer Simulation of Mixed Convection of Alumina-Deionized Water Nanofluid Over Four In-Line Electronic Chips Embedded in One Wall of a Vertical Rectangular Channel

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
Nalla Ramu ◽  
P. S. Ghoshdastidar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Mixed Convection ◽  
Transfer Coefficient ◽  
Base Fluid ◽  
Rectangular Channel ◽  
Working Fluid ◽  
Al2o3 Nanoparticles ◽  
Enhancement Factors

Abstract This paper presents a computational study of mixed convection cooling of four in-line electronic chips by alumina-deionized (DI) water nanofluid. The chips are flush-mounted in the substrate of one wall of a vertical rectangular channel. The working fluid enters from the bottom with uniform velocity and temperature and exits from the top after becoming fully developed. The nanofluid properties are obtained from the past experimental studies. The nanofluid performance is estimated by computing the enhancement factor which is the ratio of chips averaged heat transfer coefficient in nanofluid to that in base fluid. An exhaustive parametric study is performed to evaluate the dependence of nanoparticle volume fraction, diameter of Al2O3 nanoparticles in the range of 13–87.5 nm, Reynolds number, inlet velocity, chip heat flux, and mass flowrate on enhancement in heat transfer coefficient. It is found that nanofluids with smaller particle diameters have higher enhancement factors. It is also observed that enhancement factors are higher when the nanofluid Reynolds number is kept equal to that of the base fluid as compared with the cases of equal inlet velocities and equal mass flowrates. The linear variation in mean pressure along the channel is observed and is higher for smaller nanoparticle diameters.

Numerical investigation of flow boiling of refrigerant-based nanofluids and proposing correlations for heat transfer

2020 ◽  
Vol 234 (4) ◽  
pp. 386-393
Author(s):  
Ehsan Abedini ◽  
Arash Mohammadi Karachi ◽  
Reza Hamidi Jahromi ◽  
Kianoush DolatiAsl
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Convective Heat Transfer Coefficient ◽  
Numerical Results ◽  
Turbulent Dispersion ◽  
Working Fluid ◽  
Dispersion Force ◽  
The Heat Transfer Coefficient

The numerical simulation of subcooled flow boiling of R-113 working fluid has been done for two different nanofluids (R-113/Al2O3, R-113/TiO2) under different volume concentrations (0.5%, 1%, and 3%). The numerical results were compared with experimental results obtained by previous researchers, and the comparison shows that the numerical results are in good accordance. Nucleation site density, bubble departure frequency, and bubble departure diameter, which are three key parameters, are investigated in this study. The results express that these three parameters have the highest variation at low Reynolds numbers. The influence of different nanoparticles concentrations on the variation of the heat transfer coefficient is studied. The results indicate there is an insignificant difference between the effect of 1% and 3% concentrations on the heat transfer coefficient that means an increase of nanoparticles more than 1% concentration cannot improve heat transfer. The effect of different non-drag forces such as lubrication force, turbulent dispersion force, and lift force is also studied. Two correlations are proposed for predicting the convective heat transfer coefficient.

Heat Transfer Enhancement in Split and Recombine Flow Configurations: A Numerical and Experimental Study

2016 ◽  
Author(s):  
Mojtaba Jarrahi ◽  
Jean-Pierre Thermeau ◽  
Hassan Peerhossaini
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Working Fluid ◽  
Transfer Enhancement

Heat transfer enhancement in laminar regime by split and recombine (SAR) mechanism, based on the baker’s transformation, is investigated. Two different heat exchangers, called SAR1 and SAR2, are studied. Their geometries are inspired from the previous studies reported in the literature. The working fluid on both, shell and tube side, is water and the temperature on the shell side is kept constant. Experiments are carried out for the Reynolds number range 100<Re<3000 when the Prandtl number is between 4.5 and 7.5. The results show that the convective heat transfer coefficient in the first element of heat exchanger SAR1 is higher than that in the second one, i.e. SAR2. However, the variation in the convective heat transfer coefficient from the first to the third element along the heat exchanger SAR2 is less significant than that observed for SAR1. Moreover, SAR2 causes a higher pressure drop, especially when Re>1000, and provides a less uniform temperature field at the outlet.

Thermodynamic analysis of an α-type Stirling engine with variable phase angle

2007 ◽  
Vol 221 (8) ◽  
pp. 949-954 ◽  
Author(s):  
C Çinar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Phase Angle ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Stirling Engine ◽  
Working Fluid ◽  
Variable Phase

In this study, a variable phase angle, α-type Stirling engine was described and analysed from kinematic and thermodynamics point of view. Kinematic relations were described for the calculation of hot and cold cylinder volumes. The instantaneous temperature distribution of the working fluid, through the heating—cooling passages and regenerator, was calculated by preparing a nodal analysis in FORTRAN. Effect of phase angle variation on work generation was examined. By using three different convective heat transfer coefficient, which were 200, 300, and 400 W/m2 K, variation of work generation with working fluid mass was examined. For the same values of convective heat transfer coefficient, variation of engine power versus the engine speed was examined.

scholarly journals Application of Nanofluids in Thermal Performance Enhancement of Parabolic Trough Solar Collector: State-of-the-Art

2019 ◽  
Vol 9 (3) ◽  
pp. 463 ◽  
Author(s):  
Hamed Olia ◽  
Mohammadamin Torabi ◽  
Mehdi Bahiraei ◽  
Mohammad Hossein Ahmadi ◽  
Marjan Goodarzi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Entropy Generation ◽  
Thermal Efficiency ◽  
Performance Enhancement ◽  
Volume Fraction ◽  
Working Fluid ◽  
Parabolic Trough

The present review paper aims to document the latest developments on the applications of nanofluids as working fluid in parabolic trough collectors (PTCs). The influence of many factors such as nanoparticles and base fluid type as well as volume fraction and size of nanoparticles on the performance of PTCs has been investigated. The reviewed studies were mainly categorized into three different types of experimental, modeling (semi-analytical), and computational fluid dynamics (CFD). The main focus was to evaluate the effect of nanofluids on thermal efficiency, entropy generation, heat transfer coefficient enhancement, as well as pressure drop in PTCs. It was revealed that nanofluids not only enhance (in most of the cases) the thermal efficiency, convection heat transfer coefficient, and exergy efficiency of the system but also can decrease the entropy generation of the system. The only drawback in application of nanofluids in PTCs was found to be pressure drop increase that can be controlled by optimization in nanoparticles volume fraction and mass flow rate.

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