Sharif Digital Repository

Microstructural characteristics and mechanical properties of a friction stir welded cast aluminum bronze (Cu-9Al-1Fe), produced by a sand casting method, have been investigated at tool rotation of 850-1500 rpm and traverse speed of 50-100 mm/min. Refinement of the primary coarse cast microstructure in the base metal was seen after friction stir welding. Microstructure of the stir zone was characterized in four distinct areas of non-isometric fine grains while a significant grain growth was noticed in some of the areas. Conditions of grain growth are defined with high heat input intensity and low heat transfer capability. The grain size was observed to decrease after FSW, resulting in a... 

In the present research an experimental investigation is performed to explore the effects of working fluid, heat input, ferrofluid concentration, magnets location, and inclination angle on the thermal performance of an Open Loop Pulsating Heat Pipe (OLPHP). Obtained results show that using ferrofluid can improve the thermal performance and applying a magnetic field on the water based ferrofluid decreases the thermal resistance. It shows that at an inclination angle of the OLPHP to be zero, the thermal performance of the present OLPHP reduces. Best heat transfer capability was achieved at 67.5 degree relative to horizontal axis for all of working fluids. Variation of the magnets location... 

Nanotechnology is widely used in heat transfer devices to improve thermal performance. Nanofluids can be applied in heat pipes to decrease thermal resistance and achieve a higher heat transfer capability. In the present article, a comprehensive literature review is performed on the nanofluids’ applications in heat pipes. Based on reviewed studies, nanofluids have a high capacity to boost the thermal behavior of various types of heat pipes such as conventional heat pipes, pulsating heat pipes, and thermosyphons. Besides, it is observed that there must be a selected amount of concentration for the high-performance utilization of nanoparticles; high concentration of nanoparticles causes a... 

The perspectives of utilization of a screen mesh heat pipe (HP) for low to medium operating temperature applications are studied in this study. A two-dimensional mathematical model for heat and mass transfer of HPs is presented to define its performances under steady state operations. The model couples heat conduction in the wall with both liquid flow in the wick and vapor flow in the core. Experimental analysis is developed to evaluate the influence of operating parameters (the orientation and the cooling temperature) as well as the evaporator section length on the performance of the HP. Furthermore, a modeling approach to optimize the HP performance from a thermal point of view is... 

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...