Applied Mechanics and Materials Vols. 592-594

Abstract: In internal combustion engines, only a part of the fuel energy flow is transformed into power available at the crankshaft, while the most part of the fuel energy flow is lost as coolant, exhaust gases and other waste heat flows.The focus of this study is to evaluate the performance of three-fluid re-circulating type heat exchanger to recover energy from exhaust gas The cold fluid is re-circulated to enhance the recovery of heat from the exhaust gases. Finite element model of the heat exchanger is developed based on the detailed geometry and the specific working conditions and the effectiveness of the heat exchanger is computed. Non-Dimensional parameters are introduced which makes the analysis more versatile. The effectiveness is computed for different values of NTU, Heat capacity ratios, Overall heat transfer coefficient ratio between fluid channels and the inlet temperature.

Abstract: In thisstudy, the heat transfer analysis of internal combustion engine of motorbike is performed with the various fin geometries. Generally rectangular fins are used for motorbike but still this fin geometry could be modified to increase the heat transfer rate.A numerical investigation is carried out for two geometries such as annular and wavy, of finned engine cylinder using CFD and the results are compared. Various experimental methods are presented in literature to see the effect of wind velocity, fin geometry and the ambient temperature on heat transfer rate. In the present paper an effort is made to study the effect of wind velocities and fins geometries on the heat transfer rate and simulation of the heat transfer using CFD. The models are generated in CATIA V5 and simulated in FLUENT software. The results show that the heat transfer rate and effectiveness of the wavy fins is better than for the annular fins.

Abstract: This experimental study finds the effect of condensation on the thermal performance of heat pipe. Condensation heat transfer rate, heat transfer coefficient and variation of temperature over the heat pipe are measured at vertical and horizontal position of HP, by varying the steam-to-surface temperature difference. It is found that the condensation heat transfer rate for vertical position of heat pipe with CuO nanofluid is 2.07 times higher than the horizontal position, whereas the increase in heat transfer coefficient is 1.94 times. Using CuO nanofluid instead of deionized water in the heat pipe enhances the heat transfer rate and heat transfer coefficient by 1.25 and 1.42 times respectively for the vertical orientation.

Abstract: The article deals with visualization of heatlines and isotherms during cooling of a hot moving steel plate numerically. The cooling of the plate is assumed using single spray-water jet. The visualization process is carried out by forming and discretizing the governing energy equation based on finite volume method. The linear algebraic equations are solved by tri-diagonal matrix algorithm (TDMA). Accordingly, a numerical code is developed on FORTRAN platform. In the computational domain, a suitable heat transfer region for cooling is identified analyzing the heatline distribution in the domain and depends on the process parameters. Accordingly a parametric study is performed and reveals that effective heat transfer region increases with increasing jet velocity and cooling methods, and decreases with increasing plate velocity.

Abstract: Early investigation on utilization of Jatropha methyl ester (JME) tyre pyrolysis oil (TPO) blends in a single cylinder, constant speed, direct injection diesel engine revealed that a blend of 80% JME and 20% TPO referred to as JMETPO20 blend give a better performance and lower emissions compared to other Jatropha methyl ester tyre pyrolysis oil (JMETPO) blends. In this study, for further improvement on performance and emission characteristics, and also to find optimum injection timing for blend, experiments have been carried out with varying the injection timing. Tests have been conducted under two advanced and two reratarded injection timings in addition to the original injection timing of 23 °CA bTDC. The experimental test results showed that for the JMETPO20 blend at advanced injection timing of 24.5 °CA the brake thermal efficiency increased by about 2.21%, compared to the result of original injection timing at full load. For the JMETPO20 blend at advanced injection timing of 24.5 °CA the nitric oxide and carbon dioxide emission increased by about 4.56% and 11.91% respectively at full load, and the carbon monoxide emission decreased by about 11.21%, compared to that of original injection timing.

Abstract: Nerium methyl ester, an esterified biofuel, has an excellent cetane number and a reasonable calorific value. It closely resembles the behaviour of diesel. However, being a fuel of different origin, the standard design limits of a diesel engine is not suitable for Nerium methyl ester (NME). Therefore, in this work, a set of design and operational parameters are studied to find out the optimum performance of Nerium methyl ester run diesel engine. This work targets at finding the effects of the engine design parameter viz. fuel injection pressure (IP) on the performance with regard to specific fuel consumption (SFC), brake thermal efficiency (BTHE) and emissions of CO, CO₂, HC, NO_x with N20 as fuel. Comparison of performance and emission was done for different values of injection pressure to find best possible condition for operating engine with NME. For small sized direct injection constant speed engines used for agricultural applications, the optimum injection pressure was found as 240bar.Methyl esters from Nerium, with properties close to diesel; show better performance and emission characteristics. Hence Nerium (N20) blend can be used in existing diesel engines without compromising the engine performance. Diesel (25%) thus saved will greatly help the interests of railways in meeting the demand for fuel,as diesel trains are operated at maximum load condition.

Abstract: The principal objective of the paper is to modify the conventional vapor compression refrigeration system by connecting heat exchangers thereby heating and cooling of water is done simultaneously. The vapor refrigerant is supplied to the hermetic sealed compressor where the refrigerant gets compressed to a temperature of 100-120^◦ C. The compressor is connected to a counter flow heat exchanger. Experimentation is carried out to design and manufacture a modified vapor compression refrigeration system. The main parameters considered during the design are connection of a compressor to a hermetically sealed compressor, keeping polyurethane foam as insulating material, adjusting the capillary tube and finned evaporators. The operations carried during the fabrication of equipment are bending, brazing and arc welding process. After the experimental setup has been fabricated the system is checked for the performance by using refrigerants R-22 and R-407.The results are plotted between heating temperatures, cooling temperatures with respect to time in minutes.

Abstract: The study of evaporation of water droplets over horizontal heated surfaces is an intense area of research because of its wide application in various fields of heat transfer. The characterization of the behavior of water droplets is important in studying the cooling effects produced over impinging surfaces. The present study focuses on analyzing the shape and size of the droplets by applying image processing techniques. In the present work, a fixed volume of single water droplet is made to impinge on a horizontal Aluminium surface using a designed microcontroller based syringe pump. The formation and the dynamics of bubbles are recorded using a high speed camera. Image processing technique is used to determine the droplet parameters such as contact angle, spreading radius and to study the shape of the droplet. The surface temperature is measured using a Thermocouple connected to an online Data acquisition system. The effect of the characteristics of droplet on the decrease in surface temperature can be seen from the temperature – time graph and the processed photographs taken using high speed camera. The decrease in base plate temperature is found to be depending on the behavior and the properties of the droplet.

Abstract: Now a day biodiesel becomes best alternative for diesel fuel. Thermogravimetry technique has great acceptance in the field of fossil fuel. The thermal and kinetics properties of diesel and Jatropha biodiesel are analyzed by using popular technique of thermogravimetry. The aim is to study the behavior of diesel, biodiesel and their blends in Nitrogen gas atmosphere at the heating rate of 5K/min, 10K/min and 15K/min from 30°C to 600°C. From study it is found that as heating rate increases peak is shifting toward higher value which shows that there is less uniform heating. The study clearly shows biodiesel is more stable than diesel indicating that transesterification make sample less stable. The Arrehenius Kinetic model is applied to study the activation energy. As percentage of biodiesel increases, stability of sample increases and hence increases in activation energy

Abstract: A Finite volume based numerical study on lid driven cavity flow having partially heated bottom wall with constant heat flux is presented. Effect of Rayleigh number between 10³-10⁶, Richardson number ranging between 0.5 to 8 and length of heating zone (0.2, 0.5 and 0.8) has been studied. Rayleigh number represents the extent of thermal input and its rise leads to strengthening of convection effect. Formation of secondary vortices in cavity slows down due to combined effect of thermal heating and top wall movement. Temperature distribution gets increasingly nonlinear with rise in Richardson number and peak shifts towards the centre. Any increase in lid velocity causes drop in Ri and centre of the vortex shifts towards right part of the cavity. The peak velocity is observed in right half of the cavity due to top wall movement in that direction.