Heat Transfer Performance of a Parabolic Trough Receiver Using SWCNTs-Therminol®VP-1 Nanofluids

2017 ◽  
Author(s):  
Aggrey Mwesigye ◽  
Josua P. Meyer
Keyword(s):  
Heat Transfer ◽  
Solar Energy ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Concentration Ratio ◽  
Heat Transfer Performance ◽  
Energy System ◽  
Transfer Performance ◽  
Parabolic Trough ◽  
Flow Rates

In this paper, the potential for improved thermal performance of a high concentration ratio parabolic trough solar energy system working with high thermal conductivity single-walled carbon nanotubes (SWCNTs) and Therminol®VP-1 nanofluid is numerically investigated. In the numerical analysis, the practical heat flux profiles expected for parabolic trough receivers were obtained using Monte-Carlo ray tracing and coupled with a computational fluid dynamics tool using user defined functions to investigate the thermal performance of the parabolic trough solar energy system. A parabolic trough system with a concentration ratio of 113 was considered in this study and heat transfer fluid inlet temperatures between 400 K and 650 K were used. The volume fraction of SWCNTs in the base fluid was in the range 0% to 2.5% and the flow rates used were in the range 0.82 to 69.41 m3/h. Results show improvements in the convective heat transfer performance and receiver thermal efficiency as well as a considerable reduction of the receiver thermal losses with increasing volume fractions. The heat transfer performance increases up to 64% while the thermal efficiency increases by about 4.4%. Higher increments are observed at low flow rates and inlet temperatures. The receiver thermodynamic performance also increases significantly with the use of nanofluids. Entropy generation rates reduce by about 30% for the range of parameters considered.

Thermal Performance of a Receiver Tube for a High Concentration Ratio Parabolic Trough System and Potential for Improved Performance With Syltherm800-CuO Nanofluid

2015 ◽  
Author(s):  
Aggrey Mwesigye ◽  
Zhongjie Huan ◽  
Josua P. Meyer
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Concentration Ratio ◽  
Low Flow ◽  
Fluid Temperature ◽  
Parabolic Trough ◽  
High Concentration ◽  
Flow Rates

In this paper, the thermal performance of a high concentration ratio parabolic trough system and the potential for improved thermal performance using Syltherm800-CuO nanofluid were investigated and presented. The parabolic trough system considered in this study has a concentration ratio of 113 compared with 82 in current commercial systems. The heat transfer fluid temperature was varied between 350 K and 650 K and volume fractions of nanoparticle were in the range 1–6%. Monte-Carlo ray tracing was used to obtain the actual heat flux on the receiver’s absorber tube. The obtained heat flux profiles were subsequently coupled with a computational fluid dynamics tool to investigate the thermal performance of the receiver. From the study, the results show that with increased concentration ratios, receiver thermal performance degrades, with both the receiver heat loss and the absorber tube circumferential temperature differences increasing, especially at low flow rates. The results further show that the use of nanofluids significantly improves receiver thermal performance. The heat transfer performance increases up to 38% while the thermal efficiency increases up to 15%. Significant improvements in receiver thermal efficiency exist at high inlet temperatures and low flow rates.

Experimental Study on Thermal Efficiency of Parabolic Trough Collector (PTC) Using Al2O3/H2O Nanofluid

2015 ◽  
Vol 787 ◽  
pp. 192-196
Author(s):  
E. Siva Reddy ◽  
R. Meenakshi Reddy ◽  
K. Krishna Reddy
Keyword(s):  
Experimental Study ◽  
Solar Energy ◽  
Thermal Efficiency ◽  
Base Fluid ◽  
Concentration Ratio ◽  
Volume Fraction ◽  
Nano Particles ◽  
Parabolic Trough ◽  
Flow Rates ◽  
Parabolic Trough Collector

Dispersing small amounts of solid nano particles into base-fluid has a significant impact on the thermo-physical properties of the base-fluid. These properties are utilized for effective capture and transportation of solar energy. This paper attempts key idea for harvesting solar energy by using alumina nanofluid in concentrating parabolic trough collectors. An experimental study is carried out to investigate the performance of a parabolic trough collector using Al2O3-H2O based nanofluid. Results clearly indicate that at same ambient, inlet temperatures, flow rate, concentration ratio etc. hike in thermal efficiency is around 5-10 % compared to the conventional Parabolic Trough Collector (PTC). Further, the effect of various parameters such as concentration ratio, receiver length, fluid velocity, volume fraction of nano particles has been studied. The different flow rates employed in the experiment are 2 ml/s, 4 ml/s and 6 ml/s. Volumetric concentration of 0.02%, 0.04% and 0.06% has been studied in the experiment. Surfactants are not introduced to avoid bubble formation. Tracking mode of parabolic trough collector is manual. Results also reveal that Al2O3-H2O based nanofluid has higher efficiency at higher flow rates.

Heat Transfer Enhancement With Delta Winglets Vortex Generator for Different Arrangement in a Circular Tube

2018 ◽  
Author(s):  
Md. Islam ◽  
A. Nurizki ◽  
A. Kareem ◽  
A. Baba
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Circular Tube ◽  
Flow Behavior ◽  
Vortex Generator ◽  
Attack Angle ◽  
Transfer Performance ◽  
Pitch Ratio

Various technologies have been developed to enhance the heat transfer. Vortex generator (VG) is one of the passive techniques which can change the flow behavior and ultimately enhances the heat transfer performance. Delta winglet (DW) vortex generator can create longitudinal and horseshoe vortices which do not decay until further downstream and consequently increase heat transfer coefficient with comparatively lower pressure drop. With this vortex generator, it is expected to have higher Nusselt number with some increase of friction factor. Therefore, this study is to study the effect of pitch ratio (PR) and attack angle (B) of DW vortex generator to increase the thermal performance of heat exchanger. Four delta winglets are attached into a ring. Those rings attached with VGs will be used to investigate the influence of different parameters to heat transfer performance. In this study VGs were placed inside a circular copper tube and the heating coil was wrapped up around the outer surface of the copper tube to generate a constant heat flux condition. The experimental setup consists of a blower, orifice meter, flow straightener, calm/flow developing section and test section. The results show the friction factor, Nusselt number, and Thermal Performance Enhancement. It increases the thermal performance due to the formation of longitudinal vortex inside the circular tube. Pitch ratio and attack angle seem to have significant impact on the flow and heat transfer. The Pitch ratio of 1.6 have the highest impact on both (f/f0) and (Nu/Nuo) followed by attack angle. Smoke flow visualization technique was used to study flow behavior and flow structures.

Enhanced Flow Boiling Heat Transfer Using Radial Microchannels

2016 ◽  
Author(s):  
Alyssa Recinella ◽  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Flow Boiling ◽  
Cross Sectional Area ◽  
Working Fluid ◽  
Transfer Performance ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Flow Cross

Flow boiling has the ability to remove high heat fluxes while maintaining a low wall superheat. Various researchers have developed enhanced microchannel geometries to improve the heat transfer performance of the system. Recently, a number of new studies have used the increasing flow cross-sectional area concept to overcome flow instabilities and record high CHF. In this work, a new geometry is experimentally investigated utilizing a radial cross-section, which provides the increasing fluid flow cross-sectional area in the flow direction. The flow boiling performance is studied using radial microchannels and water as the working fluid. Four different flow rates ranging from 120–400 mL/min are studied for this new geometry. Heat transfer performance (boiling curve and heat transfer coefficient) and pressure drop characteristics are discussed for all flow rates. Furthermore, the work is supported by high speed visualization of the bubble dynamics. The boiling performance obtained is compared to the existing data in the literature.

Convective Heat Transfer Performance of Water and FC-72 in an One Side Heated Rectangular Channel Having Pin-Fins

2008 ◽  
Author(s):  
Liang-Han Chien ◽  
S.-Y. Pei ◽  
T.-Y. Wu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Rectangular Channel ◽  
Transfer Performance ◽  
Flow Rates ◽  
Finned Surface

This study investigates the convective heat transfer performance of two fluids (water and FC-72) in a one side heated rectangular channel of 20mm in width and 2mm in height. The heated side has either a smooth surface or a pin-finned surface. The inlet fluid temperature was maintained at 30°C. The total length of the test channel was 113 mm, with a heated length of 25mm. The flow rate varied between 80 and 960 ml/min, and the heat flux was between 18 and 98 W/cm2. Single phase convection was the dominant heat transfer mechanism in the present water tests, and the performance was mainly controlled by flow rate. Contrarily, the heat flux was the major factor for the heat transfer performance in FC-72 as a result of the dominant boiling effect. At a fixed flow rate, the pin-finned surface yielded up to 30% higher heat transfer coefficient and greater critical heat flux than those of a smooth surface. The convective heat transfer coefficient of FC-72 was greater than water at low flow rates (80∼160 ml/min) and heat fluxes between 18 and 35 W/cm2. However, the heat transfer performance of water was superior to FC-72 at high flow rates.

Optimization of Single Row Jet Impingement Array by Varying Flow Rates

2013 ◽  
Author(s):  
Nicholas Miller ◽  
Sin Chien Siw ◽  
Minking K. Chyu ◽  
Mary Anne Alvin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Jet Impingement ◽  
Upstream Region ◽  
Channel Height ◽  
Transfer Performance ◽  
Mean Velocity ◽  
Flow Rates ◽  
Downstream Region ◽  
High Heat Transfer

The current detailed experimental study focuses on the optimization of heat transfer performance through jet impingement by varying the coolant flow rate to each individual jet. The test section consists of an array of five jets, which is individually fed and metered separately, and expels air through one exit. The jet diameter D, channel height to jet diameter H/D, and jet spacing to diameter S/D, are all held constant at 9.53 mm (0.375 in), 2 and 4 respectively. The Reynolds number, which is based on jet diameter and bulk mean velocity at each jet, ranges from 50,000 to 80,000. A transient liquid crystal technique is employed in this study to determine the local and overall-average heat transfer coefficient distribution on the target plate. Commercially available CFD software, ANSYS CFX, is used to qualitatively correlate the experimental results and to provide detailed insights of the flow field created by the array of jets. The results revealed higher heat transfer coefficients in the impingement area, while decreasing in the radial direction. The upstream region exhibited high heat transfer performance, which is ultimately driven by the jet impingement from the first jet to the third jet. Heat transfer performance decreases at the downstream region with the development of cross-flow. By varying the jet flow rates at approximately ±2%, local heat transfer at the downstream region is elevated and the total heat transfer enhancement on the target surface is enhanced up to 35% compared to the baseline case.

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