Thermal Engineering

An analytical solution to the problem of an MHD oscillatory boundary layer flow past a porous horizontal plate with periodic suction is presented. The fluid in the boundary layer rotates about an axis normal to the plate with a uniform angular velocity. A magnetic field of uniform strength is assumed to be applied normal to the plate. The equations governing the flow and heat transfer are solved by regular perturbation technique assuming the solution to be consist of a mean part and a perturbed part. The expressions for the temperature fields, skin friction at the plate due to primary and secondary velocity fields and the rate of heat transfer from the plate to the fluid in terms of Nusselt number are obtained in non dimensional form. The dimensionless expressions for the amplitude and phases of the fluctuating parts of the skin friction, Nusselt number at the plate are also derived. The skin friction due to primary velocity and skin friction due to secondary velocity at the plate, the amplitude and phase of the fluctuating part of , the rate of heat transfer from the plate to the fluid in terms of Nusselt number and amplitudes and phases of the fluctuating parts of it are demonstrated graphically and the effects of the parameters M (Hartmann number), (rotation parameter)and A (suction parameter)on these fields are discussed.It is seen that M, ,A have significant effect on the flow and heat transfer characteristics.2000 Mathematics subject classification: 76W05

The Americium-Beryllium neutron irradiation facility at the National Nuclear Research Institute (NNRI), Ghana, was re-designed with a 20 Curie source using MCNP5 to investigate the maximum amount of flux that is produced by the source. The main objective was to enable us harness the maximum amount of flux for optimization of neutron activation analysis. The design was compared with the values recorded in the existing Am-Be source design. The thermal neutron flux ranges from (1.80 ± 0.0008) × 106 n/cm2.s to (2.28 ± 0.0008) × 105 n/cm2.s. The epithermal neutron flux ranges from (8.20 ± 0.0008) × 105 n/cm2.s to (3.73 ± 0.0008) × 104 n/cm2.s and that of the fast neutron flux ranges from (4.20 ± 0.0008) × 105 n/cm2.s to (1.72 ± 0.0008) × 104 n/cm2.s. The keff of the Am-Be source design was obtained as 0.00115 ± 0.0008.

Experimental and numerical investigation of the thermal conductivity in particulate filler filled (wood dust) epoxy composites have been studied in the present work. The thermal conductivity of particulate filled polymer composite is calculated experimentally using guarded heat flow meter method in accordance with ASTM-E 1530 standard. This study shows that the incorporation of wood dust results in reduction of conductivity of epoxy resin and there by improves its thermal insulation capability. Further the thermal conductivity of particle filled composites has been calculated numerically using the microstructure images by identifying each pixel with a finite difference equation and accompanying appropriate image processing. It has been observed that numerical results, experimental values and all other models are close to each other at low particulate content. On comparison, it has been found that the errors associated with the numerical values with respect to experimental ones lie in the range of 3.4 to 14.8%, the same results from Rules-of- mixture and Maxwell’s correlations lie in the ranges of 3.4 to 29.2% and 4.2 to 46.7% respectively. The incorporation of glass fibre in wood dust filled epoxy resin reduces the thermal conductivity further. With addition of 6.5vol%, 11.3vol%, 26.8vol% and35.9vol%of wood dust and 9.6vol% glass fibre the thermal conductivity of epoxy resin dropped by about 43.6%, 47.5%, 60.3% and 62.8% respectively.

The effects of ethanol addition to the intake air manifold (ethanol fumigation) with percentage 10% and 20% on CO, HC, smoke and soot emissions of a single cylinder diesel engine have been investigated experimentally and compared with each other and with the original diesel engine (100 % diesel fuel). The results show that the optimum percentage for ethanol fumigation is 20%. This percentage produces an increase in CO emissions, HC emissions and reduction in engine smoke and soot mass concentration.

Heat pipe technology becomes popular in waste heat recovery applications and in heating, ventilation and air conditioning (HVAC) systems in recent years, especially in increasing the dehumidification efficiency and cooling capacity of the cooling coil especially in warm-climate countries. An experimental study was carried out on air-to-air thermosyphon heat pipe heat exchanger (THPHE) filled with R134a as the working fluid and a fill ratio of 60% of the evaporator volume. Two configurations were tested; plain and grooved (rifled) inner surface THPHE. For each THPHE module, the lengths of the evaporator and condenser sections were 300 mm and the central adiabatic section was 100 mm. There were 6 rows of 48 copper tubes with 12 mm outside diameter. Aluminum wavy plate fins were fixed between the tubes to increase the heat transfer area. A test rig was set up to study the thermal performance of the THPHE, different sets of experiments were carried out by varying the heat load as well as the mass flow rate inlet to evaporator section of the heat exchanger; the two THPHEs were examined under low temperature (30-60?C) operating conditions. Four evaporator section air face velocities namely, 1, 1.5, 2, and 2.5 m/s were tested while ambient air flowed through condenser section with air face velocity controlled at 1.5 m/s. The results shows that the THPHE effectiveness values are shown to vary with the evaporator inlet temperature and mass flow rates. Also, the inner grooved THPHE showed a significant effect on increasing the thermal performance of the heat exchanger as compared with the plain inner surface THPHE

Exhaust of simple, reheat and inter-cooling cycle of gas turbine cycle posses a lot of energy. Sometime this energy is so much that it can run another cycle or it can be used to heat the compressed air from the compressor to the combustion charmer that results to increase the overall efficiency of the plant. Air Bottoming Cycle (ABC) was proposed as an alternative for the conventional steam bottoming cycle. In spite of the cost of reducing hardware installations it could achieve a thermal efficiency of 80%. This paper is the parametric analysis of regenerative ABC Combine Cycle. The variables are compression ratio of topping cycle, peak temperature of the combustion chamber and mass flow rate of bottoming cycle. The result shows the gain in net work output as well as efficiency of combined cycle is 14% to 33%.

The use of a latent heat storage system using Phase Change Materials (PCM) is an effective way of storing thermal energy (solar energy, off-peak electricity, industrial waste heat) and has the advantages of high storage density and the isothermal nature of the storage process. In the present era the utilizations of electricity and other conventional modes are quite in effective to the present demand and in other hand the role of alternative energy resources which compensates the present energy demands of the world will be not enough for the future. Meanwhile by the year 2020 the renewable energy resources are depleting so that it will become in need of very high energy demand due to over population in India comparing to the world resources and their populations. Now it clearly shows that trapping the solar energy and storing the heat by means of suitable PCMs will give other hand support to solve the energy crisis will help to bring out a new milestone in energy storage revolutions. It has been demonstrated that, for the development of a latent heat storage system, choice of the PCM plays an important role in addition to heat transfer mechanism. The information on the latent heat storage materials and systems is enormous and published widely in the literatures. In this paper, an attempt has been made to provide information from the previous works on PCMs and latent heat storage systems. This review may have been planned to be useful to the scientists and researchers to investigate more on PCMs.

In this study effect of exhaust gas recirculation (EGR) on performance, emission and combustion of a single cylinder, four stroke spark ignition are investigated. EGR is one of the most effective means of reducing NOx emissions from IC engines and is widely used in order to meet the emission standards. In the present work, experimental investigation has been carried out to study the performance, emission and combustion characteristics by exhaust gas recirculation in a SI engine using various catalytic coatings and different EGR flow rate. Experimental results show that NOx emissions were reduced when the engine was operated with cooled EGR. The maximum NOx reduction for copper coated engine with 10% EGR is about 45 % lower than standard engine. The other catalytic coatings like chromium and nickel shown the NOx reduction of 7 % and 4 % lower than standard engine.

This paper presents a framework of thermodynamic, energy and exergy, analyses of industrial Wood fired thermic fluid heater. Mass, energy, and exergy analysis were used to develop a methodology for evaluating thermodynamic properties, energy and exergy input and output resources in industrial wood fired thermic fluid heater. Determined methods make available an analytic procedure for the physical and chemical exergetic analysis of wood fired thermic fluid heater for appropriate applications. The energy and exergy ef?ciencies obtained for the entire fluid heater was 60.62% and 27.69% at standard reference state temperature of 25 oC. Chemical exergy of the material streams was considered to offer a more comprehensive detail on energy and exergy resource allocation and losses of the processes in a thermic fluid heater

In Indian textile industry, the number of factors affects on energy consumption. A detailed study was conducted for small the scale textile industry in depth for the various processes involved, chemicals required, operating parameters, mass to liquor ratio(MLR), energy requirements during processes including different losses etc. and to study effect of MLR on dyeing process in order to achieve acceptable good quality of cotton coloured products. The process temperature and time, water inlet temperature and liquor ratio were found to be the main parameters that affect energy destruction rates. In addition, some technical information’s has been included with schematics processes used for production as also machineries.