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.

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"Solar air heater (SAH) has vast applications in agriculture, crop drying and other field. In solar air heater, air temperature increases at the exit section. Research has worked extensively in SAH field, experimentally and numerically to observe the performance of SAH. In the present work, a 3D model of SAH is created in Design Modeler of ANSYS and simulation is run in ANSYS Fluent for the Reynolds number range between 2000-18000. Main objective of the study is to calculate the Nusselt number (dimensionless number) and friction factor influenced by pressure drop inside the duct. Numerical results are validated with the experimental results and compared with the Modified Dittus-Boelter equation and Modified Blasius equation. Mean percentage absolute error in simulation results are within range of 10%.

Wire cut Electrical-Discharge Machining (WEDM) is a machining process which utilizes a thin wire (around 0.18mm) for material removal. In modern machining of complex object, it plays an important role. Process parameters have great in-fluence on WEDM. MRR, SR and WT are varying process parameters. In this article surface roughness (SR) in WEDM process was analysed using Taguchi method. To validate the results analytical and experimental results were investigated. In experiments it was observed, when peak current value was increased, SR value also increases and in resultant a rough surface was produced. Peak current was observed as most influential parameter with contribution of 82.12%.

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