Thermal Engineering

Numerous industrial components or spare parts require a hard resistant surface, known as the case and relativity soft, tough and shock resistant inside called the core. This paper therefore runs through all the processes that are necessary in heat treating steels and alloys and finally case hardening which is required for structures of parts needed in the industries. It is the application of this heat treatment known as case hardening that we can obtain a structural member that is hard and soft, i.e. strong and tough. Hardness refers to the ability to resist wear while toughness is the ability to resist tear. Therefore a steel or alloy piece that contains these amazing qualities has its special applications in gears and cams, etc. A combination of the ability to withstand shock and serration makes this topic case hardening attractive for heat treatment of steels and alloys.

Energy input for technological, industrial, social and economical development of a nation. Gasification means the transformation of solid fuels into combustible gases in presence of an oxygen carrier (air, O2, H2O, CO2) at high temperatures. The gasification process occurs at temperatures between 600-1000 °C and decomposes the complex hydrocarbons of wood. The gasification process, with high temperature, produces ash and char, tars, methane, charcoal and other hydrocarbons. Well-designed updraft gasifier is simplest type of gasifier. A biomass up draft gasifier was specially developed to meet the heat requirements of Indian kitchens as well as industrial applications. The physical properties and proximate analysis of maize cob and biomass briquettes was determined. The combustion zone temperature is vary in between 955 to 974.00 and 731 to 820,40 °C at four fuel consumption rate i.e. 4,6,8 and 10 kg/h using maize cob and biomass briquettes as a fuel in the system respectively. The up draft biomass gasifier efficiency is vary in between 68.06 to 75.63 per cent and 65.38 to 72.65 per cent at four fuel, consumption rate i.e. 4,6,8 and 10 kg/h using maize cob and biomass briquettes as a fuel in the system respectively.

The mathematical model CFD, presented in this study, which was designed to evaluate the performance and characteristics of STPP in Baghdad city (Iraq) with the compound parabolic concentrator (CPC) as a variant of the solar collector. For the purpose of performance analysis and simulations, many expensive and complex programs are usually used, but these tools are directed to perform initial assessments of performance efficiency and feasibility of the project in terms of the output temperature of the solar field and output power generation. To study the solar stations properly, accurate information about the weather, climate and work environment should be available, as well as extensive data on the solar radiation values of the geographical area on which the project will be set up.

In this study, the effects of seven nanofilm types on organoleptic properties have been investigated and microbial counts of packed volume bread have been studied. Packed of volume bread has been evaluated due to 21 days at three temperatures. Microbial counting was done in 5°C, 20°C and 35°C in fourteenth day. The results analysis indicated that the main factors such as film type, storage temperature and duration had significant effect on the bread staling rate. The lowest and highest staling rate was observed at SC3 film and control regular respectively. With the increasing nanosilver percentage, the total number of microbes declined. In three temperatures greatest number of total germs and mold was related to the control regular. Lowest and the most number of total molds and microbes was found in 5°C and 35°C respectively. Therefore, the SC3 hybrid nanofilm, has been recognized as the best film for keeping bread more fresh.

This study examines the problem of MHD mixed convection flow between a horizontal parallel flat wall and a long wavy wall in the presence of thermal radiation, Dufour effect and first order chemical reaction embedded with slip boundary condition. The governing equations include the continuity, linear momentum, energy and mass transfer equations which are solved analytically by using exact solution method. The results of this parametric study on the velocity, temperature and concentration distributions are shown graphically and the physical aspects of the problem are highlighted and discussed. The effect of shear stress, rate of heat and mass transfer coefficients at the channel walls are displayed in tables.

Energy and exergy efficiencies of a of a combined gas and steam power plant under different ambient conditions have been studied in this paper. Irreversibility rate of the plant and its major components were examined at different weather conditions. The effect of condenser pressure variation was considered in the energy and exergy analysis to present a better approach close to the actual condition. It was found that as ambient temperature decreases, exergy efficiency decreases while the energy efficiency remains almost constant. Also the exergy analyses show that the most irreversibility occurs in combustion engine following by gas turbine and compressor. The analyses also show that the condenser pressure is an important parameter that affects the output power, thermal and exergy efficiency of the cycle. Results of this research may help optimization of energy consumption and decreasing the pollution of the environment.

The most significant energy consumers in energy related industries are boilers and other gas-fired systems. Combustion efficiency term commonly used for boilers and other fired systems and the information on either carbon dioxide (CO2) or oxygen (O2) in the exhaust gas can be used. Efficiency increase and pollutant emission control are the most significant projects of the world. In this paper the incomplete combustion process has solved and the effect of excess air to boiler pollution has considered. The concept of equilibrium constant and molar balanceused to find unknown coefficient in combustion products. The conclusion shows there is an optimum for excess air to reduce boiler pollution and increase boiler efficiency. The conclusion also shows to reduce mole fraction of NO, CO2 and CO in a gas fired boiler, the excess must be about 10 percent.

The concept of the low heat rejection (LHR) is to suppress the heat rejection to the coolant and recovering this heat energy into useful work. The main objective of this work is to increase the performance of the engine and improve the fuel economy by coating piston face using metal matrix composite materials (MMCM). The neem kernel oil is selected as fuel, which has high viscosity, low volatility and low cetane number. In the present study, neem kernel oil (NKO) is converted into neem kernel oil methyl esters (NKOME) by transesterification process. The tests are conducted with NKO, NKOME and diesel on the coated and uncoated engines for different loads at rated speed. The combustion, emission and performance characteristics are determined and compared.

This paper proposes a new nanofluid thermal conductivity analytical model based on the combination of static and modified Brownian motion mechanism. This is applicable for spherical nanoparticles, the particle volume fraction of 0.005, and critical size nanoparticles. This model is compared with Al2O3/water and CuO /water based nanofluid using existing thermal conductivity models and the experimental results in the open literature. This model deviates 2-5% with the existing Brownian motion theoretical model and experimental results. It is found that the Brownian motion contribution is significant only when the particle size is less that that of critical size and nominal particle volume fraction. It concludes that higher the particle volume fraction leads to lowering the Brownian motion velocity of particles in base fluids resulting degrading the nanoconvection.

Fluid flow in a backward – facing step (BFS) geometry is one of the most important bench mark problems used in computational fluid dynamics (CFD). It consists of an out flow boundary condition. In the present work, the laminar, incompressible flow over backward facing step is being calculated using computational fluid dynamics. The Reynolds number taken for the simulation is 800. For Re = 800, the momentum and energy solutions at various downstream locations are compared with the bench mark results and found to be in good agreement with bench mark results.