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Showing 2 results for Slip Condition
Behrooz Behroozi, Majid Ghasemi,
Volume 17, Issue 4 (6-2017)
Abstract
With the development of micro-mechanical systems, human became interested in concentrating on the small-scale impact on the flow and heat transfer in micro-channels. A micro-channel is required for a gas sensor to guide the gas flow. Reducing the size of channel has lead the scientist to concentrate on micro-sensor. Metal oxide gas micro-sensors are used to detect gases such as O3, SO2, CO2, NO, NH3, CH4 and etc. Metal oxide gas micro-sensors are small in size, low cost in fabrication and consume little power. The purpose of the current study is to numerically investigate the micro-channel wall thickness and diameter on gas inlet temperature under the influence of thermal creeping. The governing nonlinear differential equations, mass, momentum, energy, and species, are coupled and solved by a commercial code. The channel is assumed to be two dimensional. Since the Knudsen number is between 0.01 and 0.1, the slip boundary condition, Maxwell equation, is utilized. The result shows that as wall thickness increases the gas inlet temperature increases and temperature difference between gas inlet and outlet decreases. On the other hand as channel diameter decreases the gas inlet temperature increases.
M. Aligholami , A. Rostamzadeh Khosroshahi ,
Volume 19, Issue 10 (10-2019)
Abstract
The aim of this study is the modeling of the solar chimney for achieving the relation between turbine output power and geometrical parameters. In this regards, 9 different models are determined based on the variety of chimney height and diameter for investigating the effects of geometrical parameters on the turbine performance. As well as, in order to improvement of system performance, the hydrophobic surfaces were evaluated with consideration of friction reduction by verification of slip condition on walls. The k-ε turbulent model was used to modeling turbulence flow and reverse-fan model was employed for simulating the turbine. For this purpose, the extracted data from the mass flow rate and velocity changes were validated with prior studies and then were compared in different pressure jumps in order to better comprehension of the performance of the turbine. The optimization was done through the defined models and it was observed that to have a better and optimized design, the geometrical parameters should have been considered in the system design simultaneously. Meanwhile, the chimney diameter should have been paid more attention as one of the most important design parameters. Also, the precise correlation was represented to estimate the turbine output power with respect to the height and diameter of the chimney. Furthermore, based on the applying of slip condition on walls for simulating hydrophobic surfaces, shear stresses reduction was done and it was revealed that the hydrophobic surfaces could have a positive effect on the performance of SCPP up to 5 percent.
