Investigation of V-down staggered rib roughness for improved solar air heater efficiency: An experimental analysis Piyush Kumar Jain, Jitendra Singh, Atul Lanjewar, Anoop Pratap Singh Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy, 2025 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/D h ) 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/D h 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.
Heat transfer efficiency and economic evaluation of solar air heaters featuring symmetrical gap arc rib and staggered segment as a turbulence generator Jitendra Singh, Jaigopal Ambade, Atul Lanjewar International Journal of Ambient Energy, 2025 This study examines the fluid flow behaviour beneath the absorber plate within a solar air heater duct, focusing on the application of artificial roughness in improving the heat transfer coefficient between the flowing fluid and the absorber plate. Enhancement in heat transfer is primarily attributed to the disruption of the boundary sub-laminar layer that develops underneath of absorber plate. This study reveals the effect of the number of gaps on the half-arc and relative gap size on the SAH duct’s performance using symmetrical gap arc-rib combined with staggered segment. The proposed roughness geometry is obtained by dividing the arc segment into equal numbers along the absorber plate’s width, preventing the reformation of the boundary layer along the arc length. To measure the usefulness of the proposed roughness geometry, experimental results were compared with those obtained from a smooth duct and the existing best arc roughened geometry. Several design factors were considered as constant during roughness fabrication. Numeral of gaps and ratio of gap size to rib height varied between 2–5 across Reynolds numbers of 4000–14,000. Results show that enrichment in Nusselt number is 2.31 times with respect to flat duct, and enrichment in the friction factor is 3.86 and 3.61 for specific configurations. Maximum thermohydraulic parameter obtained is 1.60.
Experimental investigation and performance prediction of SAH using different arc rib roughness geometries - A comparative study Jitendra Singh, Atul Lanjewar Archives of Thermodynamics, 2024 This study aims to investigate and compare the thermal performance of a solar air heater using a passive technique to enhance heat transfer between the absorber plate and the flowing fluid. The technique involves generating turbulence near the heat transferring surface through the use of artificial rib roughness. The study focuses on two different novel roughness geome-tries: full symmetrical arc rib roughness and half symmetrical arc rib roughness. By introducing additional gaps and varying the number of gaps in the roughness geometries, the study examines their effects on the solar air heaters thermal performance. The artificially roughened surface creates different turbulent zones, which are essential to the development of different types of turbulence in the vicinity of the heat transferring surface. The study finds that an optimal escalation in Nusselt number and friction factor by 2.36 and 3.45 times, respectively, occurs at certain gap numbers as 6 and ng as 5 for full symmetrical arc rib roughness. The maximum thermal-hydraulic performance parameter of 1.66 is attained at a Reynolds number of 6 000. The study also conducts correlation, mathematical modeling, and performance prediction under different operating circumstances.
Thermal performance of solar air heater having discrete symmetrical arc rib with staggered rib roughness Jitendra Singh, Atul Lanjewar Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science, 2024 This paper investigates physics of forced flow underneath the absorber plate in solar air heater (SAH) integrated with new arc geometry namely discrete symmetrical arc rib with staggered rib roughness. This article signifies the impact of roughness pitch relative to rib height (p/e) on the thermal performance of rectangular roughened SAH duct having discrete symmetrical arc rib with staggered rib (present study). Novel arc rib geometry (present study) is achieved by providing an additional gap in a significantly long continuous arc segment of existing best arc rib geometry to break the boundary layer reformation along it. Range of parameters considered for experimental run for new geometry were Reynolds number (Re) as 3000–15,000, roughness pitch relative to rib height (p/e) of 6–14, flow attack angle (α) of 30°, staggered rib pitch relative to roughness pitch (p′/p) of 0.4, number of symmetrical gap over full arc (Ng) as 6, number of additional gap in symmetrical arc elements (ng) as 5, gap width relative to rib height (g/e) as 3, rib height relative to hydraulic diameter (e/Dh) as 0.043, relative gap position (d/w) and additional gap width relative to rib height (g′/e) as 0.65 and 1 respectively. Five different roughened test plate with the variation of p/e as 6, 8, 10, 12, and 14 were tested. Optimum augmentation is perceived in Nu at p/e as 10 and for f at p/e as 8. Maximum thermo-hydraulic performance parameter (THPP) is achieved at p/e as 10 that corresponds to Re as 6000. Correlation, mathematical model, performance prediction and economic evaluation have also been done under different operation conditions.
Effect of physiognomic behaviour of symmetrical arc rib roughness having gaps and staggered rib on the thermal performance of solar air heater Jitendra Singh, Atul Lanjewar Energy Sources Part A Recovery Utilization and Environmental Effects, 2023 This article pertains to physiognomic behavior of flowing air underneath the absorber plate using artificial roughness to enrich heat transfer coefficient (h) between the absorber plate and the flowing fluid by penetrating the boundary sub-laminar layer developed underside of the SAH duct absorber plate. This article reveals the effect of relative gap width (g/e) on thermal performance of roughened SAH duct using symmetrical arc rib roughness having gaps and staggered rib. The present novel arc rib geometry is obtained by providing additional gap in considerably long continuous arc segment of existing best arc rib geometry so as to break the boundary layer reformation along it. To determine the improvement in the proposed work, experimental results are compared with smooth SAH duct. The investigating parameters for proposed geometry are Re as 3000–16000, p/e as 10, α of 30°, p’/p of 0.4, Ng as 4, ng as 4, g/e as 2–5, e/Dh as 0.043, d/w as 0.65, g’/e as 1 and g/e as 2–5. Optimal escalation is perceived in Nu and f at g/e as 4 and 3, respectively. Maximum THPP is attained at g/e as 4. Under different operating circumstances, correlation development and economic evaluation have been conducted.
V-shaped roughened geometries and their effect on heat transfer and friction factor in solar air heater Sustaining Tomorrow Via Innovative Engineering, 2021
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 Sciences, 2017
