2014
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Item Thermal Performances of Two-metal Micro Heat Pipes (TMMHP)(Department of Mechanical and Production Engineering (MPE),Islamic University of Technology(IUT), Board Bazar, Gazipur, Bangladesh, 2014-11-15) Iqbal, KMN SarwarElectronic machines are rapidly being developed with the increasing benefits but, getting smaller in sizes resulting in more thermal stress. In an attempt to manage this stress, a comparative study is conducted between a two-metal (Cu-Ag) micro heat pipe (TMMHP) and the presently utilized single-metal (Cu) micro heat pipe (SMMHP). Thermal effects of three TMMHPs of circular, triangular, square cross sections plus one convergent-divergent of circular cross section at steady state are experimentally investigated. The tubes have three common basic dimensions – 150 mm long hollow axial space, 3.0 ± 0.3 mm hydraulic diameter and 0.3 mm thickness. The evaporator and condenser sections are made of pure copper (k = 398 W/m-K) and pure silver (k = 429 W/m-K) having lengths of 45 mm and 60 mm respectively. The adiabatic section is made of two parts – first half is made with copper and the second half is made with silver, each part having length of 22.5 mm. All the joints were brazed with silver. Water and three low boiling point liquids – ethanol, methanol and iso-propanol – are used as working liquids. In consideration of the usage of the actual equipment, tests are conducted by placing the heat pipe at three different orientations – horizontal, vertical and at 45o inclination. To provide heat flux, SGW36 (Ni-Cr) electric heater-coil is coiled around the evaporator simulating the heat-generation of an actual device, and simultaneously the condenser section is directly cooled by water in an annular space. Internal fluid-flow is considered one dimensional. Ten calibrated K-type thermocouples are installed at different locations – five of them are to measure the temperatures of internal fluid and five are used to measure the surface temperatures of the tube at different axial locations. Temperatures are recorded by digital electronic thermometers. Unlike in the SMMHP, it is found that the boiling and super heat effects in the evaporator of TMMHP transforms the two-phase flow into a single phase superheated vapor flow, which increases TMMHP‘s heat transfer capability to three and half times the capacity of SMMHP. Such an enhanced heat transfer coefficient may be initiated from the improved convection which is developed from the different heat conductivity of metals that enables the TMMHP to reject heat at higher rate through its condenser than the rate it can take heat in through its evaporator.Item Study of Hybrid Photovoltaic Solar Thermal systems during summer months in Bangladesh(Department of Mechanical and Production Engineering (MPE),Islamic University of Technology(IUT), Board Bazar, Gazipur, Bangladesh, 2014-11-15) Miah, SohelA hybrid photovoltaic (PVT) solar system combines a simultaneous conversion of the absorbed solar radiation into electricity and heat. In this study the design of an experimental PVT/dual system, both air & water circulation with modifications in the air channel is presented. First modification is to place a thin flat metallic sheet (TMS) inside the air channel & second one is to use painted Black ribbed surfaces at the bottom of the air channel. To observe the variations of heat transmittance with change of the shape of the ribs four experimental setups with a Trapezoidal, a Saw tooth forward, a Saw tooth backward ribbed surfaces and a flat plate have been used Natural convection is applied instead of forced convection to increase the system net electrical output & thereby the overall system efficiency. All setups of the same capacity, projected area, and water heat extraction method and average depth. Performance study is carried out during the months of February to June, 2012 at IUT campus, Gazipur, Bangladesh. Significant performance has been observed with the above stated modifications. In an intense sunny day of March, the maximum temperature of water is found to be 45ºC for Trapezoidal, 44º C for Saw tooth forward, 43ºC for Saw tooth backward and 41ºC for flat plate setup. Maximum temperature of air inside the air channel is found to be 39ºC for Trapezoidal, 38ºC for Saw tooth forward, 37ºC for Saw tooth backward ribbed surfaces and 36ºC for flat plateȠ in an intense sunny day of march 2012 with an ambient temperature of 34ºC. The average efficiency from all calculated values is found to be 64% for Trapezoidal, 62% for Saw tooth forward, 61% for Saw tooth backward & 58% for flat plate setup.Item Study of Product Design Perspectives for Manufacturing Refrigerators in Bangladesh using Analytic Hierarchy Process (AHP)(Department of Mechanical and Production Engineering (MPE),Islamic University of Technology(IUT), Board Bazar, Gazipur, Bangladesh, 2014-11-15) Ahmed, FarhadProduct design is a new engineering practice in Bangladesh. Now-a-days different companies are showing willingness on manufacturing engineering products in Bangladesh, where product designing is playing very important role. Product design in R&D level can play vital role in a country on creativity, renovation &/or innovation in engineering field. Because, engineering field cannot flourish without product designing practice. However, engineers or designers may design products from different views along with their individual style spontaneously in their fields. But, a systematic approach is always prolific. There is a scope of studying & classifying product designing methodologies. Besides, there is also scope for systematic analysis on different product designing methodologies. A systematic approach on product designing methodology selection could be an effective strategy to provide business success. Different product designing methodologies could aim on specific goals for improving or aligning with productivity, manufacturability, aesthetics etc. depending on market situation, durability, cost etc. Analytical Hierarchy Process (AHP) is a multi-criteria decision making process, which could be very effective tool on these analysis.Item Investigation and Optimization of the Effects of Application of Ultrasonic Sound Frequencies during Turning Operation of Steel on Machinability Responses(Department of Mechanical and Production Engineering (MPE),Islamic University of Technology(IUT), Board Bazar, Gazipur, Bangladesh, 2014-11-15) Chowdhury, Mohammad Shariful IslamTurning is one of the most common and popular process in industry for manufacturing metallic products. The two single most important output parameters that define the product quality are surface roughness and tool wear. So it is of primary concern to reduce tool wear and surface roughness of the product in any machining process. Different studies have been carried out to determine the tool wear and surface roughness of the product and their subsequent improvements. Different techniques have been adopted to replace the traditional turning process in an attempt to minimize the tool wear and the surface roughness of the finished product. In this research, a new novel technique has been proposed and adopted with an aim to reduce tool wear and surface roughness of the product. External ultrasonic sound waves were applied during the turning process of mild steel in an attempt to reduce the cutting tool vibration thereby leading to improvements in both surface quality and tool life. Detailed experimentations were carried out to study the effect of external ultrasonic sound wave on tool life of inserts, surface roughness and cutting tool vibration. Experiments were carried out under different ultrasonic frequencies to determine the effective frequency range which optimizes the above parameters to the best degree possible. The goal was to achieve improved machinability and analyze the extent of improvement obtained in the above mentioned machinability factors and the interrelation among them by the application of ultrasonic sound wave. The experimental results showed improvements in all the above machinability factors. In addition to these, the effect of orientation of the application of the ultrasonic sound waves and the amplitude of the waves were studied in detail. Cutting tool vibration and chip morphology were also studied to support the theory suggested.