The scientific literature extensively mentions the use of a solar air heater (SAH) by utilizing solar energy for heating purposes. The poor heat-transfer rate of an SAH with a flat plate is caused by developing a laminar sub-layer near the heated base plate. The plate temperatures improve significantly, resulting in losses and a decrease in performance. The passive approach entails the placement of fins/turbulators/pouring material/ribs to the surface where the boundary layer forms to disrupt it. Artificially roughened SAH for gathering and efficiently using solar radiations for thermal purposes is extensively described in the literature. This paper includes a thorough literature overview of the history, basics, roughness evolution, forms of SAH, and recent breakthroughs in thermal performance improvement techniques for SAH compiled by several researchers. This paper uses a comparative evaluation of several roughness geometries and kinds of SAH to uncover thermohydraulic performance factors that may be considered in future research to pick the optimal configuration.

Patients with craniofacial anomalies often have appearance concerns and related social anxiety which can affect their quality of life. This study assessed the psychological impact of facial and dental appearance in patients with craniofacial anomalies in comparison to a general population control group. The study involved 102 adult patients (51% male) with congenital craniofacial anomalies and 102 controls (49% male). Both groups completed the Nepali version of Derriford Appearance Scale (DAS) and the Psychological Impact of Dental Aesthetic Questionnaire (PIDAQ) in a clinical setting to assess appearance-related distress, avoidance, and anxiety. There was a significant difference between patients and controls on both PIDAQ (mean score for patients 33.25 ± 9.45 while for controls 27.52 ± 5.67, p < 0.001) and DAS59 scores (mean score for patients 159.16 ± 31.54 while for controls 77.64 ± 6.57, p < 0.001), indicating that patients experienced greater negative psychological impact of living with their appearance (PIDAQ) and more appearance-related distress (DAS) than controls. DAS scores were not associated with gender. There was no association of the place of residence (rural vs. urban) with PIDAQ or DAS59 scores. There is a significant psychological impact of altered facial and dental appearance in patients with craniofacial anomalies compared to controls. There was no effect of locality (rural/urban) on the psychological impact of facial and dental appearance in patients.

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. Graphical Abstract

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. GRAPHICAL ABSTRACT