Sharif Digital Repository

This paper developed a new mathematical model to investigate the heat transfer as well as wick's thickness of a heat pipe. The model was established by conservative equations of continuity, momentum, and energy in the thermal boundary layer. Using a similarity variable, the governing equations were changed to a set of ordinary differential equations and were solved numerically by the forth-order Runge-Kutta method. The flow variables, such as velocity components, wick's thickness, and Nusselt number, were obtained. The results show that the Nusselt number is proportional to the square root of the Darcy-modified Rayleigh number and to the distance from the edge of the condenser surface.... 

In present paper the theory of the micropolar fluid based on a Cosserat continuum model has been applied for analysis of Couette flow and turbulent flow through rough pipes. The obtained results for the velocity field have been compared with known results from experiments done by Reichardt at Max Plank institute for fluids in Gottingen [1,2] and analytical solution of the problem from Gradient theory by alizadeh[3] for couette problem and with known results from experiments done by Nikuradse (1932).the boundary condition used here was the no slip one and Trostel's slip boundary condition[4].a good agreement between experimental results and the results of the problem for Reynolds near 18000... 

In this research, the developing turbulent swirling flow in the entrance region of a pipe is investigated analytically by using the boundary layer integral method. The governing equations are integrated through the boundary layer and obtained differential equations are solved with forth-order Adams predictor-corrector method. The general tangential velocity is applied at the inlet region to consider both free and forced vortex velocity profiles. The comparison between present model and available experimental data demonstrates the capability of the model in predicting boundary layer parameters (e.g. boundary layer growth, shear rate and swirl intensity decay rate). Analytical results showed... 

Microscale fluid dynamics has received intensive interest due to the emergence of microelectromechanical systems (MEMS) technology. Fluid flow in microdevices has some characteristics which one of them is rarefaction effect related with gas flow. In this work, the steady state laminar rarefied gas flow in the entrance region of parallel plate microchannels is investigated by the integral method with slip flow conditions at solid surface. The effects of Knudsen number on friction factor and Nusselt number are presented in graphical form as well as analytical form. Also the effect of Knudsen number on hydrodynamic entry length is presented. The results show that as Knudsen number increases the... 

In this study, effect of desiccant wheel, heat exchanger and cooling coil will be evaluated on decreasing the wet bulb temperature of entering air to cooling tower and decreasing the outlet cold water temperature. For this purpose, change effect of desiccant wheel parameters will be investigated on wet bulb temperature of outlet air from heat exchanger. After that, optimum parameters and minimum wet bulb temperature will be selected. Then, outlet cold water temperature will be achieved for various cooling coil surface temperature with definition of by pass factor and also by using optimum desiccant wheel parameters and entrance air wet bulb temperature to tower related to cooling coil... 

The pipe-spool fabrication process is a critical operational section in the piping projects that usually used to accelerate and discipline the installation process, especially, when we have a particular deadline for the project. For this reason, the fast and optimal scheduling of the fabrication activities with considering the real conditions and using manual or traditional methods is a significant problem for the decision-makers. In this paper, we use a novel linear programming model to schedule the spool fabrication activities based on the flexible job shop scheduling problem (FJSP). Because FJSP is a challengeable NP-hard problem, we solve the proposed mathematical model with a heuristic... 

Advanced Encryption Standard (AES) is the most popular symmetric encryption method, which encrypts streams of data by using symmetric keys. The current preferable AES architectures employ effective methods to achieve two important goals: protection against power analysis attacks and high-throughput. Based on a different architectural point of view, we implement a particular parallel architecture for the latter goal, which is capable of implementing a more efficient pipelining in field-programmable gate array (FPGA). In this regard, all intermediate registers which have a role for unrolling the main loop will be removed. Also, instead of unrolling the main loop of AES algorithm, we implement... 

In order to study the heat transfer mechanism and predict the heat transfer capability of a pulsating heat pipe (PHP), a numerical model was used to simulate the oscillating behavior of liquid slug considering liquid film thickness in the evaporator and reduction of liquid film thickness due to evaporation. In this article, thermal performance of an open loop closed end PHP of copper with a diameter of 1 mm and various working fluids including water (DW) and ethanol was investigated. The governing equations of mass, momentum, and energy equations were solved for liquid slug and vapor plugs. The results showed that by considering liquid film thickness behind the liquid slug, for both the...