Thermal Engineering

Performance of a domestic split type air conditioner was evaluated by using two different refrigerants, i.e., R22 and R290. This paper presents the outcomes of this comparative study. The experimental investigation was conducted by using a 1 hp air conditioning unit. Power consumptions by the complete system including the evaporator as well the by the compressor alone were measured by clamp meter. Temperature was also measured at different locations by digital fluke thermometer whereas digital multimeter was used to measure the current supplied to the system. The air conditioner was run for six hours each time by setting three different set point temperatures, i.e., the cold air temperature coming out from the evaporator. From the measured information, coefficient of performance (COP), and energy efficiency ratio (ERR) were calculated for each refrigerant. The results revealed that R290 refrigerant has better COP and EER compared to R22 refrigerant. The usage of R290 refrigerant can reduce energy consumption up to 11 %. In addition to that, at the same air conditioning unit, the amount of R290 refrigerant required is relatively half of that required by R22 refrigerant.

Double-diffusive natural convection in a square cavity is numerically analyzed using velocity-vorticity form of Navier-Stokes equations. The governing equations consist of vorticity transport equation, velocity Poisson equations, energy and solutal concentration equations. Galerkin’s weighted residual finite element method is employed to solve the coupled governing equations through isoparametric formulation. Numerical predictions of vorticity, velocities, temperature and solutal concentration are computed using an iterative algorithm in order to resolve the coupling between the governing equations. The capability of the velocity-vorticity formulation is demonstrated by a detailed study on the variation of Nusselt and Sherwood numbers for a wide range of the characteristic parameters.  Our simulation results show that at high Lewis number, the average Nusselt number decreases and the average Sherwood number increases with increase in buoyancy ratio. 

Diurnal fluctuations cannot penetrate at certain depth of ground. Ground at this depth gives stable thermal environment. Utilizing the soil for heat dissipation purpose, ETHE (Earth Tube Heat Exchanger) system was designed and developed for a typical space in closed loop mode for storage of high value seeds maintaining RH in addition to cooling the air. Seed storage structure based on ETHE of 54 m3 was constructed as per design calculations. ETHE was made of PVC pipe 0.16 m outer diameter and 42 m in length, buried 2.7 m deep below soil surface in loop mode. Different seeds were stored in storage structure. Seed storage studies under ETHE indicated higher germination compared to ambient condition storage. However, there was no appreciable change in vigor index. The average relative humidity inside was relatively stable and temperature was considerably different as compared to ambient over the entire year. The work of ETHE was in heating mode from mid July to November and in cooling mode from November to mid July.

The aim of this paper, is to use a more realistic model which incorporates the effects of Brownian motion and the thermophoresis of nanoparticles for studying the effect of some control parameters on the onset of convective instability in a rotating Hele-Shaw cell filled of a Newtonian nanofluid layer and heated from below, this layer is assumed to have a low concentration of nanoparticles. The linear study which was achieved in this investigation shows that the thermal stability of Newtonian nanofluids depends of the Coriolis force generated by the rotation of the system, the Hele-Shaw cell parameter, the Brownian motion, the thermophoresis of nanoparticles, the buoyancy forces and other thermo-physical properties of nanoparticles. The studied problem will be solved analytically by converting our boundary value problem to an initial value problem, after this step we will approach numerically the searched solutions by polynomials of high degree to obtain a fifth-order-accurate solution.

The fission product isotopic inventories have been estimated for a 90.2% highly enriched uranium (HEU) fuel core of the Ghana Research Reactor-1 (GHARR-1) using the ORIGEN2 code. The results indicate a gradual decrease in the ¹³⁵Xe inventory, and a build up in the ²³⁹U and ²³⁹Np inventory. The results will assist in assessing the bounding radiological consequences of a release of actinides from fuel material. It will also assist in the design of a nuclear spent fuel storage cask for GHARR-1 using local material (Serpentine).

Subcooled nucleate flow boiling is a very efficient heat transfer mechanism and therefore applied in many technical applications. A numerical simulation was conducted to predict the bubble lift-off size in a BWR-scaled vertical upward annular channel, which had been compared with some experimental results. A force balance analysis of a growing bubble was performed to predict the bubble lift-off size.

Thermophoresis and radiative heat transfer on the unsteady boundary layer flow of a Casson fluid past an exponentially porous stretching sheet under the influence of a magnetic field in the presence of heat source/sink and chemical reaction is analysed. The governing partial differential equations of the flow are transformed into non-linear ordinary differential equations using similarity variables which are then solved numerically employing shooting technique along with Runge-Kutta iterative scheme. The graphical results reveal that the suction and magnetic field decelerate the velocity while the Casson parameter shows an opposite trend. The thermal boundary layer thickness is increased by the Casson parameter and heat source parameter. The rate of heat transfer is enhanced by thermal radiation parameter. The thermophoresis parameter along with Schmidt number is found to reduce the concentration predominantly.

This Paper presents the parametric study for a four stroke single cylinder SI Engine using a dual fuel Gasoline and LPG as an alternative fuel for investigating the performance and emissions of SI Engine. The performance parameters brake power, torque, Bsfc, Bmep were examined with using AVL BOOST Software. In addition the exhaust emissions like NOX, CO & HC were also measured.SI engine fuelled by LPG has slightly decreased on power output as compared to Gasoline. However, engine fuelled by LPG reduce on specific fuel consumption (SFC). This study investigates the effect of dual fuel LPG with gasoline in a four-stroke spark ignited single cylinder SI Engine. The study was carried out at varying load for constant engine speed. The main objective of the parametric study is to investigate the effects of replacing individual petrol and LPG with their optimum mixture of dual fuel in a spark ignition engine, and to prove reduction in emissions.

In India Green Buildings have got good results and benefits. The benefits include reduction in power consumption of 20-40% and 30-40% reduction in the consumption of portable water. The Indian Green Building Council (IGBC) has validated the benefits. IGBC has totally wiped the notion that Green Buildings are costlier. Green Buildings has got the benefits like high productivity of the occupants, safety of occupants and also best operating practices fro day one. Green Buildings can be constructed with an incremental cost of 1-7%. Many Green Buildings have been monitored for the past 5 years on the view of energy savings. The new technologies , various methods and issues faced during the implementation and solving them were discussed.

Heat pipe is a device which absorbs heat from hot junction and transfer heat to other junction. If space available is more than straight heat pipes are used but when space availability is problem in electronic circuits or cards bend heat pipes are used. According to investigation it is found that bend heat pipes of angle 90 and 120 degree are most suitable in electronic systems. Experimental analysis of bend copper heat pipes for different orientations which are suitable in electronic circuits mostly are taken for study and effect of bend Angle and heat transfer rate is calculated on a test rig by using methanol as a working fluid . Study is done on bend copper Heat pipe having 8 mm diameter and length 180 mm long and find out most suitable bend heat pipe and maximum heat transfer rate.