An investigational examination was conducted to examine the effect of V-down aligned gap with staggered rib roughness on the heat dissipation rate and frictional behaviour of airflow in a rectangular solar air heater (SAH) duct. The roughness geometry comprised both variable and fixed geometrical parameters: the variable parameters included the relative rib pitch (p/e) from 6 to 14, staggering ratio (p’/p) from 0.2 to 0.8, and relative size of staggered rib (r/g) from 0.25 to 2. Meanwhile, the fixed parameter included a relative gap breadth (g/e) of 4, number of gaps (Ng) of 3, and relative height of rib (e/Dh) of 0.0433. Span of Reynolds number (Re) varies from 4000 to 15,000 throughout this study. The geometrical parameters were analysed and optimized to evaluate the overall impact of roughness configuration on SAH performance. Results indicates that the maximum Nusselt number and friction factor were increased by up to 2.16 and 2.74 times, respectively compared to a smooth surface particularly at optimal configuration of p/e of 10, p’/p of 0.4, r/g of 1, e/Dh of 0.043, g/e of 4, and Ng of 3. The thermal-hydraulic performance (THP) parameter of the proposed V-rib geometry was compared with existing V-rib geometries to validate the overall behaviour of the present rib roughness. Furthermore, correlations in terms of the heat transfer function R (e+), and the roughness function G (e+) were developed to predict the performance of the present V-rib roughness.
BhattiMSShahRK. Turbulent and transition flow convective heat transfer. In: KakacSShahRKAungW (eds). Handbook of single-phase convective heat transfer. New York, NY: John Wiley and Sons Inc, 1987. Chapter 4.
2.
SainiJS. Use of artificial roughness for enhancing performance of solar air heater. Proceedings of XVII national and VI ISHME/ASME heat and mass transfer conference, January 05-07, 2004, Kalpakkam (India), pp. 103–112.
3.
SinghJLanjewarA. Effect of physiognomic behaviour of symmetrical arc rib roughness having gaps and staggered rib on the thermal performance of solar air heater. Energy Sources, Part A Recovery, Util Environ Eff2023; 45(1): 1030–1047.
4.
SinghJLanjewarA. Thermal performance of solar air heater having discrete symmetrical arc rib with staggered rib roughness. Proc IME C J Mech Eng Sci2024; 238(2): 598–617.
5.
PrasadKMullickSC. Heat transfer characteristics of a solar air heater used for drying purposes. Appl Energy1983; 13(2): 83–93.
6.
VermaSKPrasadBN. Investigation for the optimal thermo-hydraulic performance of artificially roughened solar air heaters. Renew Energy2000; 20(1): 19–36.
7.
SahuMMBhagoriaJL. Augmentation of heat transfer coefficient by using 90 broken transverse ribs on absorber plate of solar air heater. Renew Energy2005; 30: 2057–2073.
8.
SharmaSKKalamkarVR. Experimental and numerical investigation of forced convective heat transfer in solar air heater with thin ribs. Sol Energy2017; 147: 277–291.
9.
GuptaDSolankiSCSainiJS. Thermo-hydraulic performance of solar air heaters with roughened absorber plates. Sol Energy1997; 61: 33–42.
10.
AharwalKRGandhiBKSainiJS. Experimental investigation on heat-transfer enhancement due to a gap in an inclined continuous rib arrangement in a rectangular duct of solar air heater. Renew Energy2008; 33: 585–596.
11.
AharwalKRGandhiBKSainiJS. Heat transfer and friction characteristics of solar air heater ducts having integral inclined discrete ribs on absorber plate. Int J Heat Mass Tran2009; 52: 5970–5977.
12.
KumarTSMittalVThakurNS, et al.Second law analysis of a solar air heater having 60 inclined discrete rib roughness on absorber plate. Afr J Environ Sci Technol2010; 4(13): 913–929.
13.
SainiSKSainiRP. Development of correlations for Nusselt number and friction factor for solar air heater with roughened duct having arc-shaped wire as artificial roughness. Sol Energy2008; 82(12): 1118–1130.
14.
HansVSGillRSSinghS. Heat transfer and friction factor correlations for a solar air heater duct roughened artificially with broken arc ribs. Exp Therm Fluid Sci2017; 80: 77–89.
15.
GillRSHansVSSinghS. Investigations on thermo-hydraulic performance of broken arc rib in a rectangular duct of solar air heater. Int Commun Heat Mass Tran2017; 88: 20–27.
16.
SinghJLanjewarA. Experimental investigation and performance prediction of SAH using different arc rib roughness geometries–A comparative study. Arch Therm2024; 45: 33–44.
17.
SinghAPVarunSSiddhartha. Effect of artificial roughness on heat transfer and friction characteristics having multiple arc shaped roughness element on the absorber plate. Sol Energy2014; 105: 479–493.
18.
PandeyNKBajpaiVKVarun. Experimental investigation of heat transfer augmentation using multiple arcs with gap on absorber plate of solar air heater. Sol Energy2016; 134: 314–326.
19.
Ebrahim MominAMSainiJSSolankiSC. Heat transfer and friction in solar air heater duct with V-shaped rib roughness on absorber plate. Int J Heat Mass Tran2002; 45(16): 3383–3396.
20.
MuluworkKBSainiJSSolankiSC. Studies on discrete rib roughened solar air heaters. Proceedings of national solar energy convention, Roorkee, 1998, pp. 75–84.
21.
SinghSChanderSSainiJS. Heat transfer and friction factor correlations of solar air heater ducts artificially roughened with discrete V-down ribs. Energy2011; 36: 5053–5064.
22.
PatilAKSainiJSKumarK. Heat transfer and friction characteristics of solar air heater duct roughened by broken V-shape ribs combined with staggered rib piece. J Renew Sustain Energy2012; 4: 013115.
23.
KarwaR. Experimental studies of augmented heat transfer and friction in asymmetrically heated rectangular ducts with ribs on the heated wall in transverse, inclined, V-continuous and V-discrete pattern. Int Commun Heat Mass Tran2003; 30: 241–250.
24.
KarwaRBairwaRDJainBP, et al.Experimental study of the effects of rib angle and discretization on heat transfer and friction in an asymmetrically heated rectangular duct. J Enhanc Heat Transf2005; 12(4): 343–355.
25.
GiovanniT. Heat transfer in rectangular channels with transverse and V-shaped broken ribs. Int J Heat Mass Tran2004; 47: 229–243.
26.
MaithaniRSainiJS. Heat transfer and friction factor correlations for a solar air heater duct roughened artificially with V-ribs with symmetrical gaps. Exp Therm Fluid Sci2016; 70: 220–227.
27.
MaithaniRSainiJS. Performance evaluation of solar air heater having V-ribs with symmetrical gaps in a rectangular duct of solar air heater. Int J Ambient Energy2017; 38(4): 400–410.
28.
DeoNSChanderSSainiJS. Performance analysis of solar air heater duct roughened with multigap V-down ribs combined with staggered ribs. Renew Energy2016; 91: 484–500.
29.
JainPKLanjewarA. Overview of V-RIB geometries in solar air heater and performance evaluation of a new V-RIB geometry. Renew Energy2019; 133: 77–90.
30.
JainPKLanjewarA. Effect of staggered rib length on performance of solar air heater using v-rib with symmetrical gap and staggered rib. ARPN journal of Engineering and applied science2017; 22: 6291–6300.
31.
LanjewarAMBhagoriaJLAgrawalMK. Review of development of artificial roughness in solar air heater and performance evaluation of different orientations for double arc rib roughness. Renew Sustain Energy Rev2015; 43: 1214–1223.
32.
LanjewarABhagoriaJLSarviyaRM. Experimental study of augmented heat transfer and friction in solar air heater with different orientations of W-Rib roughness. Exp Therm Fluid Sci2011; 35: 986–995.
33.
KumarABhagoriaJLSarviyaRM. Heat transfer and friction correlations for artificially roughened solar air heater duct with discrete W-shaped ribs. Energy Convers Manag2009; 50(8): 2106–2117.
34.
ThakurSThakurNS. Investigational analysis of roughened solar air heater channel having W-shaped ribs with symmetrical gaps along with staggered ribs. Energy Sources, Part A Recovery, Util Environ Eff2019; 45: 7389–7404.
35.
HansVSSainiRPSainiJS. Heat transfer and friction factor correlations for a solar air heater duct roughened artificially with multiple v-ribs. Sol Energy2010; 84(6): 898–911.
36.
KumarASainiRPSainiJS. Experimental investigation on heat transfer and fluid flow characteristics of air flow in a rectangular duct with Multi v-shaped rib with gap roughness on the heated plate. Sol Energy2012; 86(6): 1733–1749.
37.
RaviRKSainiRP. Nusselt number and friction factor correlations for forced convective type counter flow solar air heater having discrete multi V shaped and staggered rib roughness on both sides of the absorber plate. Appl Therm Eng2018; 129: 735–746.
38.
JainPKLanjewarARanaKB, et al.Effect of fabricated V-rib roughness experimentally investigated in a rectangular channel of solar air heater: a comprehensive review. Environ Sci Pollut Res2020; 28: 4019–4055.
39.
PachoriHChoudharyTSheoreyT, et al.A novel energy, exergy and sustainability analysis of a decentralized solar air heater integrated with V-shaped artificial roughness for solar thermal application. Sustain Energy Technol Assessments2024; 66: 103816.
40.
HegdeAKPaiRKaranthKV. Influence of solar insolation on energy and exergy efficiency of a rectangular duct solar air heater with various types of V rib roughness: an analytical approach. Int Commun Heat Mass Tran2024; 153: 107397.
41.
KumarDLayekAKumarA. Enhancement of thermal efficiency and development of Nusselt number correlation for the solar air heater collector roughened with artificial ribs for thermal applications. Environ Sci Pollut Res Int2024; 31(53): 62427–62441.
42.
ChaurasiaSDwivediASethiM, et al.Experimental investigation on heat transfer and friction factor characteristics for novel hybrid roughness used in solar air heater. Exp Heat Transf2024; 38: 271–287.
43.
AlamT. Development of correlations of Nusselt number and friction factor of solar thermal collector equipped with hybrid rib roughness. Sol Energy Mater Sol Cell2024; 272: 112887.
44.
KantRAlamTSinghD, et al.Performance improvement of solar air heater duct-employing rib roughness on absorber: an experimental study. Exp Heat Transf2024; 37(7): 1139–1154.
45.
VarunSRPSainiRPSingalS. Investigation of thermal performance of solar air heater having roughness elements as a combination of inclined and transverse ribs on the absorber plate. Renew Energy2008; 33(6): 1398–1405.
46.
JaurkerARSainiJSGandhiBK. Heat transfer and friction characteristics of rectangular solar air heater duct using rib-grooved artificial roughness. Sol Energy2006; 80(8): 895–907.
47.
PaniraniPNGhanbariJ. Design and optimization of bio-inspired thin-walled structures for energy absorption applications. Int J Crashworthiness2022; 28(1): 1–12.
48.
DivyasharadaNSKumarVJoshiGN. Computational study on effect of free-stream turbulence on bio-inspired corrugated airfoil at different sections at low Reynolds number. AS2025; 8: 219–235.
49.
XingJHanSHuoT, et al.Flow and heat transfer characteristics of bio-inspired rhombus-patterned ribs: performance optimization using response surface methodology. Int J Therm Sci2024; 199: 108928.
50.
DeyPSahaSK. Fluid flow and heat transfer in microchannel with porous bio-inspired roughness. Int J Therm Sci2021; 161: 106729.
51.
ZhuSLiLQiT, et al.The effect of swallow-shaped bionic ribs on the thermal-hydraulic performance of heat exchanger tubes. Therm Sci Eng Prog2023; 46: 102180.
52.
ASHRAE Standard 93. Method of testing to determine the thermal performance of solar collectors, American Society of heating. Refrigeration and Air Conditioning Engineers, Atlanta, GA2003.
53.
KlineSJMcClintockFA. Describing uncertainties in single sample experiments. J Mech Eng1953; 75: 3–8.
54.
RosenhowWand HartnettJP. Hand book of heat transfer. New York, NY: Mc Graw Hill, 1973, pp. 7–122.
55.
WebbRLEckertERGoldsteinR. Heat transfer and friction in tubes with repeated-rib roughness. Int J Heat Mass Tran1971; 14: 601–617.
56.
NikuradseJ. Laws of flow in rough pipes. Washington: National Advisory Committee for Aeronautics, 1950.
57.
DippreyDFSaberskyRH. Heat and momentum transfer in smooth and rough tubes at various Prandtl numbers. Int J Heat Mass Tran1963; 6(5): 329–353.
58.
SinghJAmbadeJLanjewarA. Thermal–hydraulic evaluation of solar air heaters with symmetrical gap arc rib roughness. J Therm Anal Calorim. 2025. doi:10.1007/s10973-025-14277-7.
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