Applied Mechanics and Materials Vols. 813-814

Abstract: This paper investigates the performance and characteristics of saw tooth shape micro channel in the theoretical level. If the conduct area of the nano fluid increases the heat transfer also increases. The performance curve has drawn Reynolds number against nusselt number, heat transfer co efficient. Pressure drop plays an important role in this device. If pressure drop is high the heat transfer increases. The result in this experiment shows clearly that the heat transfer is optimized.

Abstract: One of the essential needs of a living thing on earth is the pure water and nowadays this valuable natural resource is facing severe scarcity problems. Solar distillation is a better choice to minimize this problem by harvesting solar radiation in solar still and thereby producing pure water from hard water or brine. In this work, an attempt was made to enhance the productivity of still by flat plate collector, sponge, the combination. Finally, the productivity of the simple still was compared with that of a flat-plate collector, sponge, the combination. Use of flat plate collector and sponge increases the overall temperature of the still water and enhance the evaporation respectively thereby this will improve the condensate production of the solar still. It was observed that productivity increased by 14% in case of still with a collector, 10% for still with a sponge and 17% for still with collector sponge combination when compared with simple still.

Abstract: The rising demand for environmentally acceptable lubricant has led researchers to look to vegetable oils as an alternative to petroleum based lubricants. Vegetable oils have radically distinctive properties owing to their unique chemical structure which have greater ability to lubricate and have higher biodegradability. In spite of advantages, they are limited to inadequate thermo-oxidative stability and poor low-temperature properties which hinder their utilization. In the present study in order to produce a bio lubricant with good thermo-oxidative stability, rapeseed oil was subjected to two different chemical modification techniques viz., epoxidation method and successive transesterification method. The thermo-oxidative stability of formulated oil was analysed using Thermo Gravimetric Analysis (TGA). TGA analysis divulges that the thermo-oxidative stability of rapeseed oil was greatly improved with the epoxidation method in comparison with the successive transesterification method.

Abstract: The PV/T hybrid system is a combined system consisting of PV panel behind which heat exchanger with fins are embedded. The PV/T system consists of PV panels with a battery bank, inverter etc., and the thermal system consists of a hot water storage tank, pump and differential thermostats. In the present work, the modeling and simulation of a Solar Photovoltaic/Thermal (PV/T) hybrid system is carried out for 5 kWp using TRNSYS for electrical energy and thermal energy for domestic hot water applications. The prominent parameters used for determining the electrical efficiency, thermal efficiency, overall thermal efficiency, electrical thermal efficiency and exergy efficiency are the solar radiation, voltage, current, ambient temperature, mass flow rate of water, area of the PV module etc. The simulated results of the Solar PV/T hybrid system are analyzed for the optimum water flow rate of 25 kg/hr. The electrical efficiency, thermal efficiency, overall thermal efficiency, equivalent thermal efficiency, exergy efficiency are found to be 10%, 34%, 60%, 35% and 13% respectively. The average tank temperature is found to be 50°C.

Abstract: The present numerical study deals with the natural convection heat transfer on the surface of a vertical cylinder with external longitudinal fins. The aim of the study was to determine the effects of geometric parameters like fin height, fin number and fin shape on the heat transfer and thus obtain the optimum parameters that will maximize the rate of heat transfer have been discussed. The numerical investigation consists of an aluminium cylinder of length 1m and diameter 0.07m with air as the working fluid. It has been seen from the numerical investigation that the heat transfer increases with fin height. It is also observed that there exists optimum fin number for maximum heat transfer. Keeping the fin number, fin height and volume fixed, it was found that the heat transfer is maximum for rectangular shaped fin.

Abstract: In most of the engineering applications unnecessary heat is produced. Fins are extended surface which are used to enhance heat transfer rate from a surface by increasing the area exposed to convection. The addition of fin increases the surface area and this forms an economical solution for increasing the efficiency and the performance of the device. In the present study a comparative analysis is made between an array of hollow pin fins in upward facing and sideward facing arrangement under natural convection. The model is numerically investigated using commercial CFD code ANSYS FLUENT©. The fin outer diameter (12mm) and fin height (50mm) are kept constant. The parameters varied are the internal diameter of the fins and the heat laod. The results show that the sideward fins have lower base plate temperature as expected due to buoyancy effects. However hot spots are identified in the case of sideward facing fins which will affect the heat transfer characteristics when compared to upward facing hollow cylindrical pin fins.

Abstract: A gas-solid multiphase flow is simulated using CFD to investigate the fluid dynamics of a fluidized bed reactor. The simulation is based on Euler-Euler two fluid model where Kinetic Theory of Granular Flow is used for predicting the solid phase transport properties. The simulation procedure is validated by reproducing and comparing hydrodynamic parameters with those available in the literature. The effect of different turbulence models on bed fluid dynamics is analyzed and k-ε RNG per-phase model is found to have better prediction accuracy compared to other models. The minimum fluidization velocity, granular temperature, bed expansion, particle velocity and volume fraction are determined by the model.

Abstract: Conservation equations of mass, momentum and energy have been solved using Fluent 14 to compute the Nusselt number and wall temperature of a finned rectangular Micro-channel for a laminar flow for water and nanofluids under mixed flow condition. Alumina based water is considered as nano fluid for the present investigation. It has been found from the numerical investigation that as the percentage of alumina is increased in the base fluid (water) the heat transfer rate is increased. It has been found that the wall temperature decreases with increase in fin number. The heat transfer is found to be more in rectangular shaped fin compared to any other shape both for the water and nanofluid. In addition to thermal characteristics, the variation of pressure drop for different fin number has also been investigated.

Abstract: Abstract-Flow over two offset square cylinders in a confined channel is simulated for different Reynoldsnumber to reveal the forced convection heat transfer from the heated square cylinders to the ambientfluid. The bottom of the cylinder is maintained at constant temperature. The distance between thecylinder in normal direction as well as transverse direction are fixed as 2d and the blockage ratio is fixedas 0.167. Heat transfer from the cylinders to the ambient fluid as well as conducted within solid wallthrough conjugate interface boundary investigated in connection with Reynolds number are reportedfor both steady and periodic flow. Simulation is carried out for Reynolds number varies from 10 to100 for the fluid as air with Prandtl number as 0.71. The isotherm contours, local Nusselt number andaverage Nusselt number are reported for various Reynolds number. The stagnation zone results higherNusselt number than remaining walls and rear wall results lowest Nusselt number. The downstreamcylinder results higher Nusselt number than the upstream cylinder. The top and bottom surfaceNusselt number from upstream and downstream cylinder are not analogous to single cylinder placed ina channel.

Abstract: In the present numerical investigation, the flow field of confined slot air jet in a rectangular computational domain is reported. In the present work the flow field parameters like reattachment length, vortex center and horizontal velocity profiles for various Reynolds numbers and for various aspect ratios are presented .The present study reveals that the vortex centers are moving in a downstream direction with increase in Reynolds number. The reattachment length is directly dependent on the Reynolds numbers. In case of vortex dynamics, the vortex size is indirectly dependent on the inlet jet width. In the present investigation, SIMPLE algorithm is used to solve the governing equations. It is concluded that the aspect ratio and the Reynolds number are playing dominant roles in flow field of the present computational domain.