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The effect of variation in open area ratio (β) in a multi-V rib roughened Single-Pass Solar Air Heater (SPSAH) is analyzed in this work. Fixing values of other parameters, such as open area ratio (β) and relative roughness width (W/w), were studied with a certain range of Reynolds number (Re) ranging from 2000 to 18000. The improvement in Nusselt number ratio (Nu/Nus) and thermo-hydraulic performance (THPP) and the decline in duct friction ratio (f/fs) support the application of perforation. The empirical correlations of Nu and f are also generated with ±12% and ±7.5% accuracy. [ABSTRACT FROM AUTHOR]

A detailed study on Solar Air Heaters (SAHs) with single-pass roughening with plastic net perforated multi-V and continuous multi-V ribs was investigated and compared for its effectiveness. Improvements in the Nusselt number ratio (Nu/Nus) and the friction factor ratio (f/fs) studied with the Reynolds number (Re) ranged from 2000–18000 for a relative roughness height (e/Dh) of 0.043, a relative roughness pitch (P/e) of 10, an aspect ratio (W/H) of 12, and an angle of attack (α) of 60°, maintaining a similar flow scenario. For a syntactically roughened channel with a perforated multi-V rib, the significant enhancement was recorded in thermo-hydraulic performance with a slight decrease in pumping power. The study was extended to analyze the effect of perforation in a double pass parallel flow SAH. [ABSTRACT FROM AUTHOR]

After analyzing the effect of perforation in a single pass solar air heater in part A, an experimental comparative study was performed on a Double Pass Parallel Flow Solar Air Heater (DPPFSAH) roughened with continuous and perforated multi-V rib roughness. In DPPFSAH, for perforated rib roughness, the gain in Nu/Nus, f/fs, and Thermo-hydraulic performance parameter (THPP) for W/w = 6 are 8.33, 9.09, and 2.97, respectively. While for continuous rib for W/w = 6 the values of Nu/Nus, f/fs, and THPP are 5.93, 10.83, and 1.82, respectively, as compared to the smooth plate. The results strongly support the application of perforation in artificial roughness. [ABSTRACT FROM AUTHOR]

Present study investigates the heat transfer and friction characteristics of heat exchanger tube fitted with perforated twisted tape (PTT) insert having V cuts. A copper tube of 1 m length and 0.032 m inner diameter is used as test section to collect the experimental data by varying the twist ratio of PTT from 2 to 6 for the Reynolds number range of 2,700–23,400. V cuts are introduced in the PTT and the V-cut relative pitch ratio is varied from 1 to 2. The maximum thermo-hydraulic performance parameter is found to be 1.58. [ABSTRACT FROM AUTHOR]