Numerical analysis of a solar air heater with jet impingement - comparison of performance between jet designs

2021 ◽  
pp. 1-24
Author(s):  
Supreme Das ◽  
Agnimitra Biswas ◽  
Biplab Das
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Flow Behavior ◽  
Jet Impingement ◽  
Solar Air Heater ◽  
Circular Jets ◽  
Improved Performance

Abstract One of the ways to improve the performance of solar air heaters (SAH) is to use jet impingement on the absorber plate to cause turbulence mixing of air in contact with the plate and thereby augment the heat transfer coefficient. The objective of this work is to compare the thermohydraulic performance of a SAH with jet impingement through conical protruding jets and circular jets using finite element method based COMSOL Multi-physics software. The simulation studies were conducted for solar radiation in the range 500 – 1000 W/m2 and mass flow rate in the range 0.01 – 0.028 kg/s. The flow physics of the jet impingement process is investigated to understand the heat transfer and fluid flow behavior of the SAH with the chosen jet designs thereby obtain their performance insights. The outlet hot air temperature from the heater and its thermal efficiency are compared for different mass flow rates and solar radiations. Also the temperature distributions in the jet plate with the jet configurations are captured and their heat transfer characteristics compared to understand the thermo-fluidic behavior of the SAH. The results demonstrate improved performance of the novel conical protruded jet design that enhances the thermal efficiency up to 78.52%, which is an increase of 13.53% compared to the circular jet design. More elongated streamlines and higher turbulent kinetic energy with increased mass flow rate leading to a wide jet affected area inside the duct are the main reasons of its improved performance.

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

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.

scholarly journals Effects of Louvered Parameters on Exergetic Performance of Louvered Finned Solar Air Heater

2021 ◽  
Vol 39 (5) ◽  
pp. 1649-1658
Author(s):  
Subhash Chand ◽  
Prabha Chand
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Operating Conditions ◽  
High Mass ◽  
Solar Air Heater ◽  
Air Heater ◽  
Pitch Ratio ◽  
Exergy Performance

The aim of the present study to improve the performance of solar air heater because of low thermo-physical properties of air. In the current work, an attempt has been made to improve the performance of the heater by employing louvered fins to the absorber plate, as it not only enhances heat transfer coefficient but also improve heat transfer area. The effect of exergy performance on the geometrical parameters of louvered fin i.e., louvered angle, louvered pitch and louvered length has been studied and analyzed. The results are compared to plane solar air heater (PSAH) to evaluate the effectiveness of louvered finned solar air heater (LFSAH). The exergy efficiency of LFSAH is comparatively higher for all the operating conditions except for higher mass flow rate where it may even go below that of PSAH; possibly due to the higher pressure drop and more loss of exergy at high mass flow rate. In addition, the results conclude that for louvered parameters viz., louvered angle 20°, fin pitch to louvered pitch ratio 0.75 and louvered length to louvered pitch ratio 1.25, high exergy performance of SAH is obtained as compared to other louvered parameter values.

scholarly journals Experimental Performance of a Solar Air Collector with a Perforated Back Plate in New Zealand

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1415 ◽  
Author(s):  
Yu Wang ◽  
Mikael Boulic ◽  
Robyn Phipps ◽  
Manfred Plagmann ◽  
Chris Cunningham
Keyword(s):  
Wind Speed ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Absorber Layer ◽  
Cover Plate ◽  
Solar Air Heater ◽  
Air Mass ◽  
Back Plate

This study investigates the thermal efficiency of a solar air heater (SAH), when it was mounted on a custom-made support frame, and was operated under different air mass flow rate. This SAH is composed of a transparent polycarbonate cover plate, a felt absorber layer, a perforated aluminium back plate and an aluminium frame. The ambient inlet air of this SAH is heated as it passes through the perforated back plate and over the felt absorber layer. The heated air is blown out through the outlet. Studies of SAHs with a similar design to this SAH were not found in the literature. The experiment was carried out at Massey University, Auckland campus, NZ (36.7° S, 174.7° E). The global horizontal solar irradiance, the ambient temperature and the wind speed were recorded using an on-site weather station. Temperature and velocity of the air at the outlet were measured using a hot wire anemometer. During the experiment, the air mass flow rate was between 0.022 ± 0.001 kg/s and 0.056 ± 0.005 kg/s. Results showed that when the SAH was operated at the airflow between 0.0054 kg/s and 0.0058 kg/s, the inlet air temperature and the wind speed (between 0 and 6.0 m/s) did not impact the temperature difference between the outlet air and the inlet air. The thermal efficiency of the SAH increased from 34 ± 5% at the airflow between 0.021 kg/s and 0.023 kg/s, to 47 ± 6% at the airflow ranging from 0.032 kg/s to 0.038 kg/s, to 71 ± 4% at the airflow of 0.056 ± 0.005 kg/s. The maximum thermal efficiency of 75% was obtained at the airflow of 0.057 kg/s. The effective efficiency of the SAH was 32 ± 5% at the airflow between 0.021 kg/s and 0.023 kg/s, 42 ± 6% at the airflow ranging from 0.032 kg/s to 0.038 kg/s, and 46 ± 11% at the airflow of 0.056 ± 0.005 kg/s.

Investigation of the Thermal Performances of Flat, Finned, and v-Corrugated Plate Solar Air Heaters

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
A. E. Kabeel ◽  
A. Khalil ◽  
S. M. Shalaby ◽  
M. E. Zayed
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Convective Heat Transfer Coefficient ◽  
Operating Conditions ◽  
Experimental Results ◽  
Solar Air Heater ◽  
Outlet Temperature ◽  
Air Heater

In this research, the thermal performances of flat, finned, and v-corrugated plate solar air heaters were investigated experimentally. A solar air heater with single glass cover, single pass was designed and tested under prevailing weather conditions of Tanta city (30°43′ N, 31° E), Egypt. The solar air heater was designed to be easy to replace the absorber plate from one to another one. Comparisons between the temperature difference of air across the heater and thermal efficiencies of the flat, finned, and v-corrugated plate solar air heaters were presented. The effect of change in the mass flow rate of air on the outlet air temperature and the thermal efficiency of the heater were also studied when the mass flow rates were 0.062, 0.028, and 0.009 kg/s. The experimental results showed that the maximum value of outlet temperature of the v-corrugated plate solar air heater was 5 and 3.5 °C more than that of flat and finned plates when the mass flow rate was 0.062 kg/s, respectively. And, it increased to be 8 and 5.5 C when the mass flow rate was 0.009 kg/s. It is also indicated that the thermal efficiency of the v-corrugated solar air heater is 8–14.5% and 6–10.5% higher than that of the flat and finned plate heaters, respectively, when the mass flow rate was 0.062 kg/s under the considered configurations and operating conditions. The experimental results also indicated that the convective heat transfer coefficient of the v-corrugated heater reached up to 1.64 and 1.36 times than that of the flat and finned heaters, respectively, when the flow rate was 0.062 kg/s.

scholarly journals Transient computational fluid dynamics investigations on thermal performance of solar air heater with hollow vertical fins

2018 ◽  
Vol 22 (6 Part A) ◽  
pp. 2389-2399 ◽  
Author(s):  
Duraisamy Jagadeesh ◽  
Ramasamy Venkatachalam ◽  
Gurusamy Nallakumarasamy
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Performance ◽  
Experimental Work ◽  
Thermal Efficiency ◽  
Solar Air Heater ◽  
Outlet Temperature ◽  
Absorber Plate ◽  
Air Dryer

Evaluation of experimental thermal performance of a single pass solar air dryer is compared with a transient CFD studies is performed. Vertical hollow plates are placed below the absorber plate and compared against the flat solar absorber plate for its performance improvement. Effect of mass-flow rate, the outlet temperature of air is computationally analyzed in comparison with the experimental work, transient boundary conditions for CFD like ambient temperature, solar insolation are taken from the experimental work, and computational results are in good agreement of with experimental results with maximum error percentage of 10%. Thermal efficiency was increased with increase in mass-flow area for without fin configuration, for a specific mass-flow rate thermal efficiency had a good improvement with fin configuration than the without fin configuration.

Experimental Study on Thermal Efficiency of a Multi-Jet Anti-Icing System With Piccolo Tube

2020 ◽  
Author(s):  
Xueqin Bu ◽  
Ping Huang ◽  
Haoyang Sun ◽  
Guiping Lin
Keyword(s):  
Experimental Study ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Leading Edge ◽  
Jet Impingement ◽  
Experimental Conditions ◽  
Tube Position ◽  
Typical Model

Abstract An experimental study was conducted to investigate the jet impingement thermal efficiency of a typical model for a multijet anti-icing system under different experimental conditions such as air mass flow rate at the jet exit, piccolo tube position and circumferential angle of jet holes. The experimental results showed that jet mass flow rate, velocity at the jet exits (whether choking conditions were established at the jet exits or not) and piccolo tube-to-leading edge distance within the cavity had significant influence on thermal efficiency of the anti-icing system. The heat flux on the external surface of leading edge, diameter of jet holes and circumferential angle of jet holes had a measurable but small effect on thermal efficiency of the anti-icing system.

scholarly journals Performances of packed bed double pass solar air heater with different inclinations and transverse wire mesh with different intervals

2016 ◽  
Vol 20 (1) ◽  
pp. 175-183 ◽  
Author(s):  
Gnanadurai Sugantharaj ◽  
Kumar Vijay ◽  
Kalidasa Kulundaivel
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Packed Bed ◽  
Wire Mesh ◽  
Solar Air Heater ◽  
Double Pass ◽  
Air Heater ◽  
Collector Efficiency

Solar air heating is a technology in which the solar energy from the sun is captured by an absorbing medium and used to heat the air flowing through the heater. In this study, thermal performance of a double pass solar air heater has been investigated experimentally at different conditions. The experiments were conducted with different inclinations of the collector, with and without wire mesh vertically fixed at the second pass in transverse direction and with different mass flow rates. The effect of air mass flow rate, wire mesh pitch and collector inclination on temperature rise and thermal efficiency have been studied. Results show that efficiency increases with mass flow rate. For the same mass flow rate, the thermal efficiency increases with the decrease in the wire mesh pitch. The maximum daily average efficiency of air heater was 79.8% at 0.025 kg/s mass flow rate, 10 cm wire mesh gap and 9? collector inclination facing south. The highest collector efficiency was observed in solar air heaters with 10 cm wire mesh gap.

Effect of pre-swirl nozzle closure modes on unsteady flow and heat transfer characteristics in a pre-swirl system of aero-engine

2021 ◽  
pp. 095441002110191
Author(s):  
Gaowen Liu ◽  
Zhao Lei ◽  
Aqiang Lin ◽  
Qing Feng ◽  
Yan Chen
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Temperature Drop ◽  
Thermodynamic Characteristics ◽  
Circumferential Direction ◽  
Temperature Changes ◽  
Air Supply ◽  
Cooling Air

The pre-swirl system is of great importance for temperature drop and cooling air supply. This study aims to investigate the influencing mechanism of heat transfer, nonuniform thermodynamic characteristics, and cooling air supply sensitivity in a pre-swirl system by the application of the flow control method of the pre-swirl nozzle. A novel test rig was proposed to actively control the supplied cooling air mass flow rate by three adjustable pre-swirl nozzles. Then, the transient problem of the pre-swirl system was numerically conducted by comparison with 60°, 120°, and 180° rotating disk cavity cases, which were verified with the experiment results. Results show that the partial nozzle closure will aggravate the fluctuation of air supply mass flow rate and temperature. When three parts of nozzles are closed evenly at 120° in the circumferential direction, the maximum value of the nonuniformity coefficient of air supply mass flow rate changes to 3.1% and that of temperature changes to 0.25%. When six parts of nozzles are closed evenly at 60° in the circumferential direction, the maximum nonuniformity coefficient of air supply mass flow rate changes to 1.4% and that of temperature changes to 0.20%. However, different partial nozzle closure modes have little effect on the average air supply parameters. Closing 14.3% of the nozzle area will reduce the air supply mass flow rate by 9.9% and the average air supply temperature by about 1 K.

scholarly journals Off-Design Dynamic Performance Analysis of a Solar Aided Coal-Fired Power Plant

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2950
Author(s):  
Vinod Kumar ◽  
Liqiang Duan
Keyword(s):  
Power Plant ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Dynamic Performance ◽  
Feed Water ◽  
Saving Rate ◽  
Coal Consumption ◽  
Dynamic Performance Analysis

Coal consumption and CO2 emissions are the major concerns of the 21st century. Solar aided (coal-fired) power generation (SAPG) is paid more and more attention globally, due to the lesser coal rate and initial cost than the original coal-fired power plant and CSP technology respectively. In this paper, the off-design dynamic performance simulation model of a solar aided coal-fired power plant is established. A 330 MW subcritical coal-fired power plant is taken as a case study. On a typical day, three various collector area solar fields are integrated into the coal-fired power plant. By introducing the solar heat, the variations of system performances are analyzed at design load, 75% load, and 50% load. Analyzed parameters with the change of DNI include the thermal oil mass flow rate, the mass flow rate of feed water heated by the solar energy, steam extraction mass flow rate, coal consumption, and the plant thermal efficiency. The research results show that, as DNI increases over a day, the coal saving rate will also increase, the maximum coal saving rate reaches up to 5%, and plant thermal efficiency reaches 40%. It is analyzed that the SAPG system gives the best performance at a lower load and a large aperture area.

Heat Transfer and Flow Friction Characteristics for Compact Cold Plates

2003 ◽  
Vol 125 (1) ◽  
pp. 104-113 ◽  
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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