نشریه مهندسی مکانیک و ارتعاشات
سال هفتم شماره 1 (پیاپی 22، بهار 1395)

Thermoelectrics are solid-state devices. They are semiconductors that produce electricity using based on the Seebeck and Peltier effect as semiconductor cooler. Thermoelectric has interesting features compared to conventional cooler and electrical appliances. The absence of moving parts result in increasing reliability, reducing maintenance, and increasing the system life. Lack of fluid reduces environmental pollution as well as being quiet which is a great advantage. With rapid development of technology in the field of semiconductor materials, thermoelectric has attracted a lot of attention these days. In this paper the thermoelectric technology, materials, application in the field of cooling has briefly reviewed.

In this study First, The heat recovery unit as an appropriate solution The energy savings will be introduced. Went on to study heat recovery from the hot exhaust gas compression facilities Qazvin And the waste of energy, The evacuation of hot gases through the exhaust flue gas turbines on the environment has been determined For this work, according to data compression station Qazvin Aspen software with the help of the flow of energy in the hot gas exhaust flue Haysys first in both the max Simulation results show that for a unit of 50 MW to 90 MW of energy waste is near imum and minimum simulated turbine and heat removal capacity in both Grdyd extraction. Dark The heat removal capacity is largely dependent on the flow rate and temperature of the exhaust gas Then, according to the existing proposals and as an example, heat generated from the hot exhaust gases from the chimney at a power plant generating steam used as the maximum speed turbine and turbine output parameters such as pressure and pump inlet temperature of heat recovery exchanger examined Placed.

Study on the type of flow, to design and improve the mechanical systems necessary fluids. May in the new speed measurement tools, such as hot wire flowmeter Hot wire Anemometry, laser dog vane ( Laser Doppler Anemometry ) and the image of the particle image velocimetry poll particles more application of this study was trying to operating theory, applications, benefits and drawbacks. The three methods paid attention to the study conducted HWA method in places where it is appropriate to less heat and lower accuracy is concerned, as well as in places where there is less mobility (due to take pictures of successive) and cost less launch is considered the best method, PIV method is sensitive places and accurate and also of fluids and gases that have a high speed, the best way to assess could LDA that maintain speed.

In this study, a hybrid cooling system, including ground-to-air heat exchanger and a cylindrical roof is studied. In the proposed system, the ground-to-air heat exchanger cooling system passive system and cylindrical roof as natural ventilation, to achieve thermal comfort conditions and also supplies the required cooling load of the building in the city of Semnan have been used.The outside air is then passed over the roof, increasing speed and reducing pressure leads to indoor air is evacuated where the relative vacuum in the room leads to cool air in underground channels conducted into the building. Simulation of three-dimensional air flow in the heat exchanger surface-to-air, cylindrical roof and the room was solved by Fluent software. For this building and the heat exchanger in a channel with dimensions 120 × 40 × 40 meters have been placed as computing space. The data, ground-to-air outlet temperature of the heat exchanger was calculated numerically with MATLAB computer code and finally the temperature was brought to the room. The results show that the system with 2 tube dr = 0.082 for the space Lr = 7.14 can be abstain comfort condition in Semnan. Also according to the results, opening for the roof span is Ar = 0.082. In this study, the effect of different factors such as wind speed, average room temperature, the aperture diameter of roof, diameter, length and number of tubes ground-to-air heat exchanger was investigated.

One of the common methods of structural damage detections and identification of location and severity of the damage in structures is investigation of changes in modal parameters before and after damage. These methods which are mostly based on optimization techniques use an objective function based on natural frequencies and mode shapes. This paper reviews previous researches in damage detection techniques based on modal parameters and common objective functions used in the optimization stage in the damage detection process. To this end, damage detection methods based on natural frequency, mode shape, curvature mode shape and both of mode shape and natural frequency are reviewed. In the following, due to high importance of objective function in the damage detection process, objective functions based on modal assurance criterion, flexibility matrix and natural frequency and mode shapes are compared

In this study entropy generation inside horizontal concentric annulus for Cu Nano-fluid (water) under the constant-temperature conditions has been investigated. The fluid flow inside the cylinder is laminar and the outer cylinder is rotating. The temperature of the outer cylinder is higher and the temperature difference of the two cylinders is always constant. (Result show) Adding nanoparticles to the base fluid at constant boundary conditions has very little effect on the temperature distribution. As the Brinkman number increases, the entropy generation increases where using nanoparticles in the base fluid decreases entropy generation. Friction and heat transfer effects on the total entropy has been studied. It has been shown viscous dissipation is more effective in entropy generation. Extracted results shows that as the Reynolds number increase, the amount of entropy generation increases, and adding nanoparticles lead to the increase of Nusselt number up to 30 percent.

In this study, Numerical investigation of energy absorption of conical grooved tubes under dynamic axial load by LS DYNA was considered. In order to achieve axisymmetric collapse mode inner and outer grooves were created around the surface of conical tubes. The purpose of this study was consideration of the effects of number of grooves and grooves deeps on energy absorption and crush force efficiency. The results indicate that with the increase in number of grooves the collapse modes would not change. In addition to this, with the increase in number of grooves maximum crush load and collapse modes decrease but the force-displacement curves would be smoother