Numerical Investigation of Gravity-Driven Granular Flow around the Vertical Plate: Effect of Pin-Fin and Oscillation on the Heat Transfer

In this paper, the heat transfer of pin-fin plate unit (PFPU) under static and oscillating conditions are numerically studied using the discrete element method (DEM). The flow and heat transfer characteristics of the PFPU with sinusoidal oscillation are investigated under the conditions of oscillating frequency of 0–10 Hz, amplitude of 0–5 mm and oscillating direction of Y and Z. The contact number, contact time, porosity and heat transfer coefficient under the above conditions are analyzed and compared with the smooth plate. The results show that the particle far away from the plate can transfer heat with the pin-fin of PFPU, and the oscillating PFPU can significantly increase the contact number and enhance the temperature diffusion and heat transfer. The heat transfer coefficient of PFPU increases with the increase of oscillating frequency and amplitude. When the PFPU oscillates along the Y direction with the amplitude of 1 mm and the frequency of 10 Hz, the heat transfer coefficient of PFPU is increased by 28% compared with that of the smooth plate. Compared with the oscillation along the Z direction, the oscillation along the Y direction has a significant enhancement on the heat transfer of PFPU.

Influence of Rectangular Ribs on Exergetic Performance in a Triangular Duct Solar Air Heater

Several artificial roughness (ribs) configurations have been used in flat plate solar air heaters (SAH) in recent years to improve their overall performance. In the present work, energy and exergy analyses of rectangular ribs in a triangular duct SAH for varying relative rib heights (e/D = 0.02–0.04), relative rib pitches (P/e = 5–15), and rib aspect ratios (e/w = 0.5–4) are evaluated and compared with smooth SAH. The analysis reveals that the entropy generated due to heat transfer is lower for the ribbed triangular duct compared to the smooth duct. It is also observed that the width of the rib plays a crucial role in minimizing heat losses to the environment. A maximum reduction of 43% and 62% in exergy losses to the environment and exergy losses due to heat transfer to the fluid is achieved, respectively, with a rib aspect ratio (e/w) of 4 compared to the smooth plate. It is found that in contrast to the smooth plate, ribs beneath the absorber plate effectively improves thermal and exergetic efficiency. Maximum enhancement of 36% and 17% is obtained in exergetic efficiency (ηex) and thermal efficiency (ηth), respectively, for e/w = 4, P/e = 10 and e/D = 0.04. Results also show the superiority of the ribbed triangular duct over the ribbed rectangular duct for an application requiring compact SAH with a higher flowrate.

Controlled self-assembly of glycoprotein complex in snail mucus from lubricating liquid to elastic fiber

Terrestrial snail could intelligently employ elastic fibers clinging itself onto the inverted smooth plate.