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

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.

Effect of Gap Position in Broken V-rib Roughness Combined with Staggered Rib on Thermohydraulic Performance of Solar Air Heater

Green ◽  
2011 ◽  
Vol 1 (4) ◽  
Author(s):  
Anil K. Patil ◽  
J. S. Saini ◽  
K. Kumar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Hydraulic Performance ◽  
Solar Air Heater ◽  
Artificial Roughness ◽  
Effective Technique ◽  
Air Heater ◽  
Flow Through ◽  
Absorber Surface

AbstractApplication of artificial roughness on underside of absorber surface has been found to be effective technique to improve thermo hydraulic performance of solar air heaters. In progression to the previous researches, the present study discloses the effect of broken V-rib roughness combined with staggered ribs on heat transfer and friction in a flow through artificially roughened solar air heater duct. The experimentations were performed to collect the data on heat transfer and friction by varying the Reynolds number (Re) between 3000 and 17,000, relative gap position (

scholarly journals THERMOHYDRAULIC PERFORMANCE OF AN EQUILATERAL TRIANGULAR DUCT WITH ARTIFICIAL ROUGHNESS USED IN SOLAR AIR HEATER

2013 ◽  
pp. 46-51
Author(s):  
GAURAV BHARADWAJ ◽  
VARUN VARUN ◽  
AVDHESH SHARMA
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Angle Of Attack ◽  
Roughness Height ◽  
Solar Air Heater ◽  
Artificial Roughness ◽  
Absorber Plate ◽  
Air Heater ◽  
Relative Roughness

The thermohydraulic performance of artificially roughened equilateral triangular solar air heater duct has been investigated and the comparision of the same has been presented with that of a conventional smooth solar air heater duct. The range of relative roughness height (e/Dh) is from 0.021 to 0.043, value of angle of attack (α) and relative roughness pitch (p/e) has been 30° and 8 respectively. The range of Reynolds number is from 5600 to 28000 and aspect ratio of the duct is 1.15. It has been found that the thermohydraulic performance of artificially roughened triangular solar air heater duct is always more than that of the smooth absorber plate in the range of Reynolds number investigated.

scholarly journals Computational fluid dynamics analysis of a V-rib with gap roughened solar air heater

2018 ◽  
Vol 22 (2) ◽  
pp. 963-972 ◽  
Author(s):  
Jitesh Rana ◽  
Anshuman Silori ◽  
Rajesh Maithani ◽  
Sunil Chamoli
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Friction Factor ◽  
Angle Of Attack ◽  
Solar Air Heater ◽  
Computational Domain ◽  
Cfd Analysis ◽  
Air Heater ◽  
Relative Roughness ◽  
Computational Fluid Dynamics Analysis

A CFD analysis of a solar air heater has been carried out using V-shaped ribs as artificial roughness on the absorber plate. The relative roughness pitch, P/e = 6-12, Reynolds number of 3800-18000, relative roughness height, e/D = = 0.042, and angle of attack, ? = 30?-75?, have been selected as design variables of V-shaped rib for analysis. The ANSYS FLUENT 15.0 with renormalization group k-? turbulence model is selected for the analysis of computational domain of solar air heater. The enhancement of Nusselt number and friction factor with Reynolds number for different values of a relative roughness pitch are presented and discussed by CFD analysis. The effect of angle of attack and Reynolds number on enhancement of Nusselt number and friction factor is also presented. The optimum value of rib configuration based on constant pumping power requirement has been derived using thermohydraulic performance parameter and has been found maximum at angle of attack of 60? and P/e = 10.

Experimental Investigation of Heat Transfer and Friction Characteristics of Arc-Shaped Roughness Elements Having Central Gaps on the Absorber Plate of Solar Air Heater

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Navneet Kumar Pandey ◽  
Vijay Kumar Bajpai
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Friction Factor ◽  
Angle Of Attack ◽  
Solar Air Heater ◽  
Maximum Enhancement ◽  
Friction Characteristics ◽  
Air Heater ◽  
Circular Arcs

Thermal performance of solar air heater does not take into account the energy loss due to friction for propelling air through the duct. In this work, an experimental investigation has been carried out to study the effect of heat transfer and friction characteristics of turbulent flow of air passing through rectangular duct which is roughened by circular arcs having gaps of 2 mm in between arranged in angular fashion, and the roughened wall is uniformly heated. The thermal and friction characteristics are governed by duct aspect ratio (W/H), hydraulic diameter (D), and relative roughness pitch (P/e), angle of attack of angular arc (α), and Reynolds number (Re). Experiments encompassed the Reynolds number ranges from 3600 to 15,100, P/e ranges from 6 to 20, and angle of attack of angular arc of flow over the protrusions ranges from 15 deg to 75 deg. The results have also been compared to W-shaped roughness inclined at 45 deg. The maximum enhancement in heat transfer and friction factor is 3.15 and 3.93 times as compared with smooth duct. Arc with gaps have also been observed to be better than their W-shaped counterparts. These experimental results have been used to study their influence on Nusselt number and friction factor, and empirical relations have been derived using regression analysis.

scholarly journals Thermal Performance of Three Sided Artificially Roughened Double Duct Parallel Flow Solar Air Heater

2018 ◽  
Vol 7 (1) ◽  
pp. 5-15
Author(s):  
Chander Kant ◽  
Prashant Kumar ◽  
Ankur Gill ◽  
Dhiraj Parkash Dhiman
Keyword(s):  
Heat Transfer ◽  
Reynold Number ◽  
Parallel Flow ◽  
Working Fluid ◽  
Solar Air Heater ◽  
Absorber Plate ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Air Heater ◽  
Relative Roughness

A solar air heater is basically a heat exchanger, which intercepts the incident solar radiation, converts it into heat and finally transfers this heat to a working fluid for an end use system. The mode of air flowing in the ducts of a solar air heater is one of the most significant aspects concerned with solar air heater which dominantly affect. A double duct parallel flow artificially roughened solar air heater with three sides of the absorber plate is investigated in the current study. Unlike the conventional model of solar air heater with only one sided roughened absorber plate, a novel solar air heater with three artificially roughened absorber plate is used so that the surface area of the absorber plate is increased which ultimately increases the rate of heat transfer. Additionally, a double duct parallel flow arrangement through inner and outer duct of solar air heater is considered order to enhance the heat transfer rate. A numerical investigation of the heat transfer and friction factor characteristics of a double duct parallel flow three sided artificially roughened solar air heater has been carried out. A commercial finite volume CFD code ANSYS FLUENT is used to simulate turbulent air flow through artificial roughened solar air heater. Governing equations of the fluid flow and heat transfer i.e. Navier-Stokes equation and energy equation are solved with RNG k-ε turbulence model. Nine different configuration of square rib are studied with relative roughness pitch (P/e = 5-10) and relative roughness height (e/D = 0.03-0.06). The Reynold number of the flow is varied from 2500 to 16000.

Heat Transfer and Friction Factor Correlations for Solar Air Heater With Gap in V-Rib With Symmetrical Gap and Staggered Ribs

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Sumer Singh Patel ◽  
Atul Lanjewar
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Smooth Surface ◽  
Heat Transfer Analysis ◽  
Operating Parameters ◽  
Solar Air Heater ◽  
Gap Size ◽  
Maximum Enhancement ◽  
Air Heater ◽  
Relative Roughness

Abstract The present experimental study is concerned with heat transfer analysis of air flowing in solar air heater duct with a gap in V-rib with symmetrical gap and staggered ribs geometry. The investigated parameters are Reynolds number (Re) of 4000–14,000, relative roughness pitch (p/e) of 12, relative roughness height (e/Dh) of 0.043, angle of attack (α) of 60 deg, relative staggered rib pitch (p′/p) of 0.65, relative gap size (g/e) of 4, relative staggered rib size (r/e) of 4, relative gap position of additional gap in each symmetrical rib elements (d/w) of 0.65, relative gap size of additional gap in each symmetrical rib elements (g′/e) of 1, number of main gaps (Ng) of 1, 2, 3, 4, and number of additional gap (ng) varying from 1 to 5. Fourteen roughened absorber plates were tested. The maximum enhancement in Nusselt number (Nu) and friction factor (f) was 2.34 and 2.79 times that of smooth surface corresponding to the number of main gaps (Ng) of 4 with the number of additional gaps (ng) of 4. The performance of the gap in V-rib with symmetrical gap and staggered rib geometry has been compared with the existing latest V-rib geometry and smooth surface. The proposed gap in V-rib with symmetrical gap and staggered ribs geometry has a better performance than the existing latest V-rib geometry. The following correlations have been developed for heat transfer and friction factor in terms of roughness and operating parameters. Heat transfer:Nur=0.0073(Re)0.9788(Ng)0.2790(ng)0.0184exp[−0.1678(ln(Ng))2]exp[−0.0129(ln(ng))2] Friction factor:fr=0.0477(Re)−0.0678(Ng)0.5919(ng)−0.0562exp[−0.4922(ln(Ng))2]exp[−0.0487(ln(ng))2]

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