Md. J. Nine

Is metal nanofluid reliable as heat carrier

A pre- and post experimental analysis of copper-water and silver-water nanofluids are conducted to investigate minimal changes in quality of nanofluids before and after an effective heat transfer. A single loop oscillating heat pipe (OHP) having inner diameter of 2.4mm is charged with aforementioned nanofluids at 60% filling ratio for end to end heat transfer. Post experimental analysis of both nanofluids raises questions to the physical, chemical and thermal stability of such suspension for hazardless uses in the field of heat transfer. The color, deposition, dispersibility, propensity to be oxidized, disintegration, agglomeration and thermal conductivity of metal nanofluids are found to be strictly affected by heat transfer process and vice versa. Such degradation in quality of basic properties of metal nanofluids implies its challenges in practical application even for short-term heat transfer operations at oxidative environment as nano-sized metal particles are chemically more unstable than its bulk material. The use of the solid/liquid suspension containing metal nanoparticles in any heat exchanger as heat carrier might be detrimental to the whole system.

Study on the Thermal and Flow Characteristics on the Periodically Arranged Semi-Circular Ribs in a Rectangular Channel

The article investigates turbulent flow characteristics and heat transfer enhancement on periodically arranged semicircular ribs fitted in a rectangular channel. The channel was fabricated as the aspect ratio of AR 5, rib height to hydraulic diameter ratio was 0.07, and rib height to channel height ratio was set as e/H 0.117 for various rib pitch to rib height ratios between 8 and 14. In order to predict realistic phenomena of heat transfer and flow characteristics near the wall, shear stress transport k-ω turbulence and v2-f turbulence models were chosen. The results of numerical analysis show turbulent flow characteristics, heat transfer enhancement, and the effect of friction as observed experimentally. The results shows that turbulent kinetic energy (k) is closely related to diffusion of recirculation flow, and results from v2-f turbulence model simulation are in agreement with experimental values.