Applied Mechanics and Materials Vols. 592-594

Abstract: Increasing of fluid pressure in phase change applications is an important area for research, as it requires high grade energy. Low grade energy (heat energy) may be employed to develop fluid pressure in selective applications with isochoric heating in a non-flow process. Pressure vessel is a common example working on isochoric heating process to develop steam pressure. Experiments are conducted in this vessel to analyze the characteristics of isochoric heating process. Some of the characteristics investigated are (i) mass of the steam leaving the vessel for a given volume ratio (mass of water contained in the vessel to volume of the vessel), ratio of time taken to release steam to heating time, ratio of enthalpy of the steam leaving the vessel to useful enthalpy rise of water and steam mixture for different volume ratio. The effect of insulating the circumference of the vessel on the above mentioned characteristics are also investigated in this paper. Further experiments using any liquid refrigerant as working medium can lead this research to attain a remarkable development of using low grade energy for refrigeration applications

Abstract: The performance of an adsorbed natural gas (ANG) storage system with natural convection heat transfer between the ANG bed and the ambient air is studied. Results are obtained for the bed without and with external fins on ambient air side. A one dimensional transient conduction model with suitable kinetic equation is formulated to simulate the performance of the bed filled with a homogeneous mixture of activated carbon and graphite. The model duly considers non-ideal behaviour of natural gas, variable specific heat of the adsorbed phase and heat of adsorption. Results are obtained for the case of constant pressure charging and constant flow discharging. The performance of the ANG bed is evaluated in terms of delivery capacity and discharge time. Results are obtained at an ambient temperature of 308 K and 35 bar for a charging time of 3.34 min. It is found that under this condition, the bed temperature increases by 70 and 45K and the storage capacity reduces by 75 and 60% without and with external fins, respectively. During discharge also, due to insufficient heat supply the bed temperature drops to very a low value thereby increasing the amount of adsorbate retained at the end of discharge process. This study clearly shows the need for improving the heat transfer rate from or to the ANG bed for higher delivery capacity.

Abstract: Combustion of fossil fuels is one of the major sources of greenhouse gas CO₂, it is therefore necessary to develop technologies that will allow us to utilize the fossil fuels while reducing the emissions of greenhouse gases. Pressure swing adsorption (PSA) is a potential technique for removing CO₂ from high-pressure fuel gas streams. Zeolites are suitable candidate sorbents for use in the PSA process. Studies of the gas adsorption of CO₂ onto zeolite 13X and zeolite 4A were conducted at a temperature of 25 °C, 35 °C, 45 °C and 60 °C up to a pressure of 1 bar. The data fitting is accomplished with the Toth and Sips adsorption models which are generally used for micro-porous adsorbents such as zeolites. Moreover, regeneration studies have been conducted in order to verify the possibility of adsorbents reutilization, to determine its CO₂ adsorption capacity within consecutive cycles of adsorption–desorption. Zeolite with higher surface area showed higher CO₂ adsorption capacity. There is no full reversibility for the two zeolites.

Abstract: The two-phase flow through porous media is an important topic which spans a broad spectrum of engineering disciplines especially in porous heat pipes. Heat pipe is a thermodynamic device that transports heat energy from one location to another with a negligible temperature drop. The aim of the present work is to investigate the phase change mechanisms, namely boiling and condensation, in the flat heat pipe system with different orientation. Governing equations used for the formulation are continuity, mixture momentum, liquid conservation and energy equations. These equations are converted into three ordinary differential equations using similarity transformation and two-phase similarity solutions are obtained for both boiling and condensing flows. In each case, a two phase zone where the liquid and vapour can coexist appears adjacent to the wall. As the heat transfer at the wall gradually enhances, the liquid saturation at the wall approaches to the limiting value, zero, for boiling and unity for condensation. The present work is an attempt to predict numerically the liquid wall saturation, non-dimensional temperature, non-dimensional temperature gradient and effect of Sherwood number during the phase change of water-steam system in the heat pipe for horizontal and vertical cases. Nomenclature

Abstract: In this paper, a two phase flow distribution in a horizontal pipe is numerically analyzed by solving one dimensional steady state momentum equation for predicting the pressure drop (∆P), quality of steam at outlet of the pipe (X), void fraction (α). The heat absorbed by the pipe (Q) and the mass flow rate (W) of water are varied over a wide range to investigate the above parameters. The locations of the two phase mixture are discussed. Pressure drop along the pipe is inconsistent for different flow rate so, the stable and unstable steady state solution is also carried out using Linear Stability analysis. The present numerical results are compared with the reported data from the literature and found that they are in good agreement. This study is used to calculate the pressure, temperature, hold up and quality within the horizontal pipe.

Abstract: The aim of study is to develop highly reliable and less time consuming steam dryness fraction measuring experimental setup. This method of dryness fraction measurement is based on throttling process which is obtained by using orifice plate. Calculation of orifice diameter was done by using ISO 5167 for given pressure drop. This paper deals with the conceptual design of orifice in a steam pipe line. The objective of the conceptual design is to obtain throttling process. Three parameters are chosen for the conceptual design: the diameter of the orifice, the aspect ratio between length and diameter and the entrance angle to the orifice. This work also deals with validation of calculated orifice diameter through CFD simulation for pressure drop in pipe line. To simulate the throttling process, the inlet condition of the orifice upstream flow is fixed at 10 bar and 180°C. The temperature and pressure is measured at the outlet of the orifice while steam is flowing through the pipe. An orifice diameter of 11.00mm is selected as the optimal value to keep throttling process. The resulting optimal orifice design will be used in steam pipe line.

Abstract: Estimation of higher heating value (HHV) is one of the basic step in performance modeling and calculations of thermal systems. The HHV of liquid fuels is determined experimentally, which is time consuming and expensive. From literature survey it is observed that the HHV of most of the liquid fuel is a function of viscosity. In this paper an equation is developed for samples of diesel fuel. The HHV calculated using equation for samples using viscosity show average difference of 0.06255% for diesel fuel. For unknown diesel samples the equation shows satisfactory agreement with the experimental results. This equation can be used to predict HHV of unknown diesel fuel by knowing its viscosity.

Abstract: Ever increasing demand and consequent rise in prices of petroleum products, stringent emission standards, the exponential depletion rate of fossil fuel reserves and escalation in the number of vehicles on the road have forced us to look for alternatives to meet the present and future demands of the energy requirements. Biodiesel production from waste oils and fats are cost effective methods which prevent the environmental pollution by proper disposal techniques. In this study, biodiesel was prepared from the waste effect chicken fat using the two stage esterification process. The present investigation deals with the cold exhaust gas recirculation (EGR) with the flow rates of 10, 20, 30% on a four stroke, single cylinder, direct injection (DI) diesel engine fueled with waste chicken fat biodiesel blends to reduce the NO_x emissions of the engine. Experimental results showed higher oxides of nitrogen emissions when fueled with waste chicken fat biodiesel without EGR and found reduced NO_x emissions about 25% when operating with B20 fuel blend with 30% EGR. The EGR level was optimized as 20% based on the significant reduction in NOx emissions, minimum possible smoke, CO, HC emissions and comparable brake thermal efficiency.

Abstract: The present study deals with the effect of inlet air cooling on performance of simple combined cycle power plant (CCPP) .During hot days the density of air decreases, which reduce the mass flow rate of air in to compressor. The power consume by the compressor increases with increase in intake air temperature, which reduce net power output of gas turbine cycle. Mechanical refrigeration system at inlet of compressor has been used to reduce the inlet temperature of air to desired level. The performance analysis of CCPP was carried out using software developed in MATLAB.

Abstract: The thermal contact resistance (TCR) between similar and dissimilar materials (copper, aluminium, brass and type 304 stainless steel) was assessed. Copper foil, aluminium foil, lead and Sn-9Zn lead free solder were selected as thermal interface materials (TIMs). The interfacial contact pressure was varied by application of load on materials in contact. The interfacial heat flux was estimated by solving the inverse heat conduction problem (IHCP). At higher load, the temporal variation of thermal contact resistance showed early occurrence of peak and lower values of TCR. The use of thermal interface materials reduced the contact resistance between the hot source and cold sink materials. Among the interface materials used, Sn-9Zn lead free solder showed the lowest contact resistance. This was attributed to the solid to liquid phase transformation at higher temperatures and the conformance of the interface material to surfaces in contact. Factorial experiments were carried out to determine the significance of experimental variables on TCR. The analysis showed that the effect of applied load on TCR was significant compared to other parameters.