Optimal Analysis of Entropy Generation and Heat Transfer in Parabolic Trough Collector Using Green-Synthesized TiO2/Water Nanofluids

This study presents an experimental nanoparticle synthesis and the numerical analysis of a parabolic trough collector (PTC) operating with olive leaf synthesized TiO2/water nanofluid. The PTC is modeled after the LS-2 collector for various operating conditions. An analysis of the heat transfer and entropy generation in the PTC is carried out based on the first and second laws of thermodynamics for various parameters of nanoparticle volumetric concentration (0 ≤ φ ≤ 8%), mass flow rate (0.1 ≤ m˙ ≤ 1.1 kg/s), and inlet temperatures (350–450 K) under turbulent flow regime. The effect of these parameters is evaluated on the Nusselt number, thermal losses, heat convection coefficient, outlet temperature, pressure drop, entropy generation rate, and Bejan number. The results show that the values of the Nusselt number decrease with higher concentrations of the nanoparticles. Also, the addition of nanoparticles increases the heat convection coefficient of the nanofluid compared to water. The thermal efficiency of the system is improved with the use of the new nanofluid by 0.27% at flow rates of 0.1 kg/s. The entropy generation study shows that increasing the concentration of nanoparticles considerably decreases the rate of entropy generation in the system. It is also observed that increasing the volumetric concentration of nanoparticles at low mass flow rates has minimal effect on the rate of entropy generation. Finally, a correlation that provides a value of mass flow rate that minimizes the entropy generation rate is also presented for each values of inlet temperature and nanoparticle volumetric concentration.

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Heat Transfer and Flow Friction Characteristics for Compact Cold Plates

Journal of Electronic Packaging ◽

10.1115/1.1536170 ◽

2003 ◽

Vol 125 (1) ◽

pp. 104-113 ◽

Cited By ~ 9

Author(s):

Chang-Yuan Liu ◽

Ying-Huei Hung

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Nusselt Number ◽

Thermal Resistance ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Average Nusselt Number ◽

Cold Plate ◽

Air Mass

Both experimental and theoretical investigations on the heat transfer and flow friction characteristics of compact cold plates have been performed. From the results, the local and average temperature rises on the cold plate surface increase with increasing chip heat flux or decreasing air mass flow rate. Besides, the effect of chip heat flux on the thermal resistance of cold plate is insignificant; while the thermal resistance of cold plate decreases with increasing air mass flow rate. Three empirical correlations of thermal resistance in terms of air mass flow rate with a power of −0.228 are presented. As for average Nusselt number, the effect of chip heat flux on the average Nusselt number is insignificant; while the average Nusselt number of the cold plate increases with increasing Reynolds number. An empirical relationship between Nu¯cp and Re can be correlated. In the flow frictional aspect, the overall pressure drop of the cold plate increases with increasing air mass flow rate; while it is insignificantly affected by chip heat flux. An empirical correlation of the overall pressure drop in terms of air mass flow rate with a power of 1.265 is presented. Finally, both heat transfer performance factor “j” and pumping power factor “f” decrease with increasing Reynolds number in a power of 0.805; while they are independent of chip heat flux. The Colburn analogy can be adequately employed in the study.

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Contribution to the Parametric Study of the Performance of A Parabolic Trough Collector

E3S Web of Conferences ◽

10.1051/e3sconf/202132102016 ◽

2021 ◽

Vol 321 ◽

pp. 02016

Author(s):

Belkacem Bouali ◽

Hanane-Maria Regue

Keyword(s):

Heat Transfer ◽

Mass Flow ◽

Flow Rate ◽

Optimal Operation ◽

Heat Transfer Fluid ◽

Parabolic Trough ◽

Parabolic Trough Collector ◽

Heat Transfer Fluids ◽

Ansys Cfx ◽

Different Seasons

This paper presents an analysis of the performance of a parabolic trough collector (PTC) according to some key operating parameters. The effects of the secondary reflector, the length and thickness of the absorber tube (receiver tube) and the flow rate of the heat transfer fluid (HTF) are investigated. The main objective is to determine an optimal operation, which improves the performance of a traditional PTC. The target variables are the temperature at the outlet of the tube, the amount of energy collected by the HTF and the efficiency of the system. The solar flux data concern the city of LAGHOUAT located in the south of Algeria. Four days in different seasons are considered. The optical analysis of the system is performed by using the open source SolTrace code. The output of this analysis is used as a boundary condition for the CFD solver. The conjugate heat transfer and the fluid flow through the absorber tube are simulated by using ANSYS-CFX solver. Water is considered as heat transfer fluids. The obtained results show that the use of a curved secondary reflector significantly improves the performance of the traditional PTC. As the thickness of the tube increases, the heat storage in the material increases, which increases the temperature at the exit of the tube and therefore the efficiency of the system. However, the length of the tube depends on the mass flow of the HTF and vice versa. To keep the efficiency constant by choosing another length, it is necessary to choose a mass flow rate proportional to the flow rate corresponding to the initial length.

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Effect of nanofluid properties and mass-flow rate on heat transfer of parabolic-trough concentrating solar system

Journal of Naval Architecture and Marine Engineering ◽

10.3329/jname.v16i1.30548 ◽

2019 ◽

Vol 16 (1) ◽

pp. 33-44 ◽

Cited By ~ 1

Author(s):

M.K. Islam ◽

Md. Hasanuzzaman ◽

N.A. Rahim ◽

A. Nahar

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Laminar Flow ◽

Turbulent Flow ◽

Transfer Coefficient ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Parabolic Trough ◽

Concentrated Solar Energy

Sustainable power generation, energy security, and global warming are the big challenges to the world today. These issues may be addressed through the increased usage of renewable energy resources and concentrated solar energy can play a vital role in this regard. The performance of a parabolic-trough collector’s receiver is here investigated analytically and experimentally using water based and therminol-VP1based CuO, ZnO, Al2O3, TiO2, Cu, Al, and SiC nanofluids. The receiver size has been optimized by a simulation program written in MATLAB. Thus, numerical results have been validated by experimental outcomes under same conditions using the same nanofluids. Increased volumetric concentrations of nanoparticle is found to enhance heat transfer, with heat transfer coefficient the maximum in W-Cu and VP1-SiC, the minimum in W-TiO2 and VP1-ZnO at 0.8 kg/s flow rate. Changing the mass flow rate also affects heat transfer coefficient. It has been observed that heat transfer coefficient reaches its maximum of 23.30% with SiC-water and 23.51% with VP1-SiC when mass-flow rate is increased in laminar flow. Heat transfer enhancement drops during transitions of flow from laminar to turbulent. The maximum heat transfer enhancements of 9.49% and 10.14% were achieved with Cu-water and VP1-SiC nanofluids during turbulent flow. The heat transfer enhancements of nanofluids seem to remain constant when compared with base fluids during either laminar flow or turbulent flow.

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Selecting the cooling water mass flow rate for a power plant under variable load with entropy generation rate minimization

Energy ◽

10.1016/j.energy.2016.04.074 ◽

2016 ◽

Vol 107 ◽

pp. 725-733 ◽

Cited By ~ 12

Author(s):

Rafał Laskowski ◽

Adam Smyk ◽

Janusz Lewandowski ◽

Artur Rusowicz ◽

Andrzej Grzebielec

Keyword(s):

Power Plant ◽

Mass Flow Rate ◽

Entropy Generation ◽

Mass Flow ◽

Flow Rate ◽

Water Mass ◽

Cooling Water ◽

Entropy Generation Rate ◽

Variable Load ◽

Water Mass Flow Rate

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Second Law Analysis for the Experimental Performances of a Cold Heat Exchanger of a Stirling Refrigeration Machine

Entropy ◽

10.3390/e22020215 ◽

2020 ◽

Vol 22 (2) ◽

pp. 215 ◽

Cited By ~ 1

Author(s):

Steve Djetel-Gothe ◽

François Lanzetta ◽

Sylvie Bégot

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Entropy Generation ◽

Mass Flow ◽

Hydraulic Diameter ◽

Entropy Generation Rate ◽

Second Law ◽

Water Mixture ◽

Fluid Friction ◽

Refrigeration Machine

The second law of thermodynamics is applied to evaluate the influence of entropy generation on the performances of a cold heat exchanger of an experimental Stirling refrigeration machine by means of three factors: the entropy generation rate N S , the irreversibility distribution ratio ϕ and the Bejan number B e | N S based on a dimensionless entropy ratio that we introduced. These factors are investigated as functions of characteristic dimensions of the heat exchanger (hydraulic diameter and length), coolant mass flow and cold gas temperature. We have demonstrated the role of these factors on the thermal and fluid friction irreversibilities. The conclusions are derived from the behavior of the entropy generation factors concerning the heat transfer and fluid friction characteristics of a double-pipe type heat exchanger crossed by a coolant liquid (55/45 by mass ethylene glycol/water mixture) in the temperature range 240 K < TC < 300 K. The mathematical model of entropy generation includes experimental measurements of pressures, temperatures and coolant mass flow, and the characteristic dimensions of the heat exchanger. A large characteristic length and small hydraulic diameter generate large entropy production, especially at a low mean temperature, because the high value of the coolant liquid viscosity increases the fluid frictions. The model and experiments showed the dominance of heat transfer over viscous friction in the cold heat exchanger and B e | N S → 1 and ϕ → 0 for mass flow rates m ˙ → 0.1 kg.s−1.

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Analytical Analysis of Heat Transfer and Entropy Generation in a Tube Filled with Double-Layer Porous Media

Entropy ◽

10.3390/e22111214 ◽

2020 ◽

Vol 22 (11) ◽

pp. 1214 ◽

Cited By ~ 1

Author(s):

Kun Yang ◽

Wei Huang ◽

Xin Li ◽

Jiabing Wang

Keyword(s):

Heat Transfer ◽

Porous Medium ◽

Porous Media ◽

Nusselt Number ◽

Double Layer ◽

Entropy Generation ◽

Single Layer ◽

Entropy Generation Rate ◽

Total Entropy ◽

Interfacial Radius

The heat transfer and entropy generation in a tube filled with double-layer porous media are analytically investigated. The wall of the tube is subjected to a constant heat flux. The Darcy-Brinkman model is utilized to describe the fluid flow, and the local thermal non-equilibrium model is employed to establish the energy equations. The solutions of the temperature and velocity distributions are analytically derived and validated in limiting case. The analytical solutions of the local and total entropy generation, as well as the Nusselt number, are further derived to analyze the performance of heat transfer and irreversibility of the tube. The influences of the Darcy number, the Biot number, the dimensionless interfacial radius, and the thermal conductivity ratio, on flow and heat transfer are discussed. The results indicate, for the first time, that the Nusselt number for the tube filled with double-layer porous media can be larger than that for the tube filled with single layer porous medium, while the total entropy generation rate for the tube filled with double-layer porous media can be less than that for the tube filled with single layer porous medium. And the dimensionless interfacial radius corresponding to the maximum value of the Nusselt number is different from that corresponding to the minimum value of the total entropy generation rate.

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First and second thermodynamic law analyses applied to a solar dish collector

Journal of Non-Equilibrium Thermodynamics ◽

10.1515/jnet-2014-0023 ◽

2014 ◽

Vol 39 (4) ◽

Cited By ~ 8

Author(s):

Vahid Madadi ◽

Touraj Tavakoli ◽

Amir Rahimi

Keyword(s):

Heat Transfer ◽

Solar Radiation ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Exergy Efficiency ◽

Exergy Destruction ◽

Flow Rates ◽

Energy And Exergy ◽

Mass Flow Rates

AbstractThe energy and exergy performance of a parabolic dish collector is investigated experimentally and theoretically. The effect of receiver type, inlet temperature and mass flow rate of heat transfer fluid (HTF), receiver temperature, receiver aspect ratio and solar radiation are investigated. To evaluate the effect of the receiver aperture area on the system performance, three aperture diameters are considered. It is deduced that the fully opened receivers have the greatest exergy and thermal efficiency. The cylindrical receiver has greater energy and exergy efficiency than the conical one due to less exergy destruction. It is found that the highest exergy destruction is due to heat transfer between the sun and the receivers and counts for 35 % to 60 % of the total wasted exergy. For three selected receiver aperture diameters, the exergy efficiency is minimum for a specified HTF mass flow rate. High solar radiation allows the system to work at higher HTF inlet temperatures. To use this system in applications that need high temperatures, in cylindrical and conical receivers, the HTF mass flow rates lower than 0.05 and 0.09 kg/s are suggested, respectively. For applications that need higher amounts of energy content, higher HTF mass flow rates than the above mentioned values are recommended.

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Modeling heat transfer of nanofluid flow in microchannels with electrokinetic and slippery effects using Buongiorno’s model

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-09-2018-0506 ◽

2019 ◽

Vol 29 (8) ◽

pp. 2566-2587 ◽

Cited By ~ 2

Author(s):

Hang Xu ◽

Huang Huang ◽

Xiao-Hang Xu ◽

Qiang Sun

Keyword(s):

Heat Transfer ◽

Entropy Generation ◽

Slip Length ◽

Generation Rate ◽

Entropy Generation Rate ◽

Lower Wall ◽

Volumetric Concentration ◽

Nanofluid Flow ◽

Cross Sectional ◽

Content Type

PurposeThis paper aims to study the heat transfer of nanofluid flow driven by the move of channel walls in a microchannel under the effects of the electrical double layer and slippery properties of channel walls. The distributions of velocity, temperature and nanoparticle volumetric concentration are analyzed under different slip-length. Also, the variation rates of flow velocity, temperature, concentration of nanoparticle, the pressure constant, the local volumetric entropy generation rate and the total cross-sectional entropy generation are analyzed.Design/methodology/approachA recently developed model is chosen which is robust and reasonable from the point of view of physics, as it does not impose nonphysical boundary conditions, for instance, the zero electrical potential in the middle plane of the channel or the artificial pressure constant. The governing equations of flow motion, energy, electrical double layer and stream potential are derived with slip boundary condition presented. The model is non-dimensionalized and solved by using the homotopy analysis method.FindingsSlip-length has significant influences on the velocity, temperature and nanoparticle volumetric concentration of the nanofluid. It also has strong effects on the pressure constant. With the increase of the slip-length, the pressure constant of the nanofluid in the horizontal microchannel decreases. Both the local volumetric entropy generation rate and total cross-sectional entropy generation rate are significantly affected by both the slip-length of the lower wall and the thermal diffusion. The local volumetric entropy generation rate at the upper wall is always higher than that around the lower wall. Also, the larger the slip-length is, the lower the total cross-sectional entropy generation rate is when the thermal diffusion is moderate.Originality/valueThe findings in this work on the heat transfer and flow phenomena of the nanofluid in microchannel are expected to make a contribution to guide the design of micro-electro-mechanical systems.

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Influence of Dimensionless Parameter on De-Ionized Water-alumina Nanofluid Based Parabolic Trough Solar Collector

Recent Patents on Nanotechnology ◽

10.2174/1872210513666190410123503 ◽

2020 ◽

Vol 13 (3) ◽

pp. 206-221

Author(s):

Vijayan Gopalsamy ◽

Karunakaran Rajasekaran ◽

Logesh Kamaraj ◽

Siva Sivasaravanan ◽

Metin Kok

Keyword(s):

Heat Transfer ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Thermal Efficiency ◽

Solar Collector ◽

Dimensionless Parameter ◽

Parabolic Trough ◽

Alumina Nanofluid ◽

Parabolic Trough Solar Collector

Background: Aqueous-alumina nanofluid was prepared using magnetic stirrer and ultrasonication process. Then, the prepared nanofluid was subjected to flow through the unshielded receiver of the parabolic trough solar collector to investigate the performance of the nanofluid and the effects of the dimensionless parameter were determined. Methods: The experimental work has been divided into two sections. First, the nanofluid was prepared and tested for its morphology, dimensions, and sedimentation using X-Ray Diffraction and Raman shift method. Then, the nanofluids of various concentrations from 0 to 4.0% are used as heat transfer fluid in unshielded type collector. Finally, the effect of the dimensionless parameter on the performance was determined. Results: For the whole test period, depending upon the bulk mean temperature, the dimensionless parameters such as Re and Nu varied from 1098 to 4552 & 19.30 to 46.40 for air and 2150 to 7551 & 11.11 to 48.54 for nanofluid. The enhancement of thermal efficiency found for 0% and 4.0% nanoparticle concentrations was 32.84% for the mass flow rate of 0.02 kg/s and 13.26% for the mass flow rate of 0.06 kg/s. Conclusion: Re and Nu of air depend on air velocity and ambient temperature. Re increased with the mass flow rate and decreased with concentration. Heat loss occurred by convection mode of heat transfer. Heat transfer coefficient and global efficiency increased with increased mass flow rate and volume fraction. The thermal efficiency of both 0% and 4.0% concentrations became equal for increased mass flow rate. It has been proven that at high mass flow rates, the time available to absorb the heat energy from the receiver is insufficient.

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