CFD Numerical Investigation of a New Solar Flat Air-Collector Having Different Obstacles with Various Configurations and Arrangements

This work deals with a numerical parametric optimization study of a new Solar Flat Air Collector (SFAC) configuration. The CFD numerical parametric study investigates various SFAC structures inside the air cavity without obstacles and with spherical, cubic, cylindrical, and pyramidal obstacles. The study optimizes the most convenient configuration and arrangement that allow for the increase of the heat-transfer surface and to make the flow homogeneous in order to generate turbulence zones inside the SFAC air cavity. The result shows that the thermal performances of the cubic form are close to those of the spherical obstacles. Another set of simulations was performed to evaluate the performances of the cubic shape baffles for three orientation angles equal to 0°, 22.5°, and 45°, respectively. Each configuration has three forms of arrangement with a relative roughness pitch (b/a) varying between 2, 4, and 6. The results of the simulation study showed that the relative roughness pitch, the Reynolds number, as well as the angle of orientation influence the performance and the operation of the SFAC. The results of the simulations showed that the combination of an orientation of 45° with a roughness pitch of b/a = 2 increases the SFAC thermal performances, which can reach 85%.

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Numerical Research of Roughness Effects on Flow and Heat Transfer Characteristics in Flat Microchannels

ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer, Volume 3 ◽

10.1115/mnhmt2009-18412 ◽

2009 ◽

Author(s):

Heming Yun ◽

Baoming Chen ◽

Binjian Chen

Keyword(s):

Heat Transfer ◽

Surface Roughness ◽

Reynolds Number ◽

Conjugate Heat Transfer ◽

Entrance Length ◽

Heat Transfer Characteristics ◽

Roughness Effects ◽

Relative Roughness ◽

Flow And Heat Transfer ◽

Numerical Research

Roughness effects on flow and heat transfer in flat microchannels has been numerically simulated by using CFD with fluid-solid conjugate heat transfer techniques, the surface roughness has been modeled through a series triangular toothed roughness cells. In this paper, the influence for roughness on the entrance length of flow and heat transfer has been emphasized, the influence for relative roughness on transitional Reynolds number has been also analyzed at the same time.

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Effects of interfacial heat transfer, surface tension and contact angle on the formation of plasma-sprayed droplets through simulation study

Surface and Coatings Technology ◽

10.1016/j.surfcoat.2016.09.066 ◽

2016 ◽

Vol 307 ◽

pp. 807-816 ◽

Cited By ~ 15

Author(s):

Yongang Zhang ◽

Steven Matthews ◽

A.T.T. Tran ◽

Margaret Hyland

Keyword(s):

Heat Transfer ◽

Surface Tension ◽

Contact Angle ◽

Simulation Study ◽

Heat Transfer Surface ◽

Interfacial Heat Transfer ◽

Plasma Sprayed

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Development of a low Reynolds number enhanced heat transfer surface using flow visualization techniques

International Journal of Heat and Fluid Flow ◽

10.1016/s0142-727x(01)00140-0 ◽

2002 ◽

Vol 23 (4) ◽

pp. 444-454 ◽

Cited By ~ 10

Author(s):

J.-H Ko ◽

M.E Ewing ◽

Y.G Guezennec ◽

R.N Christensen

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Flow Visualization ◽

Low Reynolds Number ◽

Heat Transfer Surface ◽

Enhanced Heat Transfer ◽

Low Reynolds ◽

Visualization Techniques

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An Experimental Investigation on Flow Behavior and Heat Transfer Affected by Roughness in the Circular Micro-Channels

Volume 2: Micro/Nano-Thermal Manufacturing and Materials Processing; Boiling, Quenching and Condensation Heat Transfer on Engineered Surfaces; Computational Methods in Micro/Nanoscale Transport; Heat and Mass Transfer in Small Scale; Micro/Miniature Multi-Phase Devices; Biomedical Applications of Micro/Nanoscale Transport; Measurement Techniques and Thermophysical Properties in Micro/Nanoscale; Posters ◽

10.1115/mnhmt2016-6612 ◽

2016 ◽

Author(s):

Yitu Tian ◽

Haiwang Li

Keyword(s):

Heat Transfer ◽

Surface Roughness ◽

Reynolds Number ◽

Flow Behavior ◽

Relative Roughness ◽

Flow And Heat Transfer ◽

Spark Erosion ◽

Circular Microchannel ◽

Poiseuille Number ◽

Circular Microchannels

Surface roughness is one of the most important factors to determine the flow and heat transfer characteristics of the microchannel. This paper experimentally and theoretically investigated the effects of surface roughness for the flow and heat transfer behavior within the circular microchannel. The stainless steel circular microchannels were fabricated by electrical spark-erosion perforating and drilling separately to control the relative roughness of the surface which is 1% for drilling method and 1.5% for electrical spark-erosion perforating method. Each test piece includes 44 identical circular microchannels in parallel with diameter of 0.4 mm. In the experiments, the air flowed through the circular microchannels with Reynolds number changing from 200 to 2600. The results showed that the surface roughness in microchannels has a remarkable effect on the performance of flow behavior and heat transfer within the circular microchannel. The values of Poiseuille number and Nusselt number are higher when the surface relative roughness is larger. At the same time, the flow behavior is inconsistent with the behavior within the macrochannel. For the flow behavior, Poiseuille number increases monotonously with the increase of Reynolds number, and is higher than the constant theoretical value. The Reynolds number for the transition from laminar to turbulent flow is between 1400 and 1600. For the heat transfer property, Nusselt number also increases as the increase of the Reynolds number.

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Computational fluid dynamics based study for analyzing heat transfer and friction factor in semi-circular rib-roughened equilateral triangular duct

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

10.1108/hff-10-2015-0438 ◽

2017 ◽

Vol 27 (4) ◽

pp. 941-957 ◽

Cited By ~ 19

Author(s):

Rajneesh Kumar ◽

Anoop Kumar ◽

Varun Varun

Keyword(s):

Heat Transfer ◽

Fluid Dynamics ◽

Reynolds Number ◽

Nusselt Number ◽

Friction Factor ◽

Absorber Plate ◽

Ansys Fluent ◽

Content Type ◽

Relative Roughness ◽

Rib Roughened

Purpose The purpose of this computational fluid dynamics (CFD)-based study on semicircular rib-roughened equilateral triangular duct is to investigate heat transfer, friction factor and thermohydraulic performance parameter. The analysis is carried out by simulating problem in ANSYS (Fluent). The Reynolds number in the study varies from 4,000 to 24,000. Nusselt number is calculated for different Reynolds number using various turbulent models available in ANSYS (Fluent) for a smooth duct and compared the results with the Dittus–Boelter correlation. Design/methodology/approach The analysis has been done by solving basic fluid governing equations (continuity, momentum and energy) by using finite volume method (FVM). The semicircular ribs were fabricated on the absorber plate. The constant amount of heat flux is applied on the absorber plate, whereas other two walls are made adiabatic. The semi-implicit method for pressure linked equations (SIMPLE) algorithm is used with pressure–velocity-coupled disretization to estimate the results. The selection of turbulent model has been done on the basis of Nusselt number prediction in the smooth duct. Findings The renormalization-group k − ε model predicts the Nusselt number more accurately as compared to standard k − ε model, standard k − ω model, shear stress transport (SST) k − ω and realizable k − ε model in the Reynolds number ranges from 4,000 to 24,000 with a ± 5.5% deviation from Dittus–Boelter equation for smooth duct. The maximum thermo-hydraulic performance is observed of the order of 1.7 for arrangement which has a relative roughness height of 0.067 and relative roughness pitch of 7.5 at higher Reynolds Number of 24,000. Originality/value Although, many experimental studies are available in the area of rib-roughened ducts, the present study is based on CFD analysis of semicircular rib-roughened equilateral triangular duct and the results are predicted in terms of Nusselt number, friction factor and thermohydraulic performance parameter. Moreover, the predicted result of Nusselt number and friction factor is validated by comparing with Dittus–Boelter correlation and modified Blasius equation, respectively. This advantage made Fluent a powerful tool for analyzing the internal fluid flow through roughened ducts.

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Heat transfer measurement in a rectangular channel of solar air heater with Winglet type ribs using liquid crystal thermography

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4051692 ◽

2021 ◽

pp. 1-9

Author(s):

Amit Kumar ◽

Apurba Layek

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Liquid Crystal ◽

Rectangular Channel ◽

Angle Of Attack ◽

Solar Air Heater ◽

Air Heater ◽

Liquid Crystal Thermography ◽

Relative Roughness ◽

Absorber Surface

Abstract This paper deals with the study of heat transfer in solar air heater consisting of Winglet shaped roughness on the absorber plate using liquid crystal thermography technique. The winglet type roughness element was placed on the absorber surface of a rectangular channel solar air heater having an aspect ratio of 4. The absorber surface was heated uniformly by a constant heat flux of 800 W/m2. The non-dimensional roughness parameter considered as relative roughness pitch i.e., P/e, and its values range between 5-12 with Reynolds number (Re) range between 6500 - 22000. The value of angle of attack i.e., alpha and relative roughness width i.e. (W/w) were kept constant, and the relative roughness pitch was varied to measure the heat transfer coefficient. The enhancement in heat transfer has been compared and it is observed that at P/e of 8 for the angle of attack (α) of 60 degrees resulting it's optimum value. The enhancement of heat transfer with the increase in Reynolds number is also noted.

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