Advanced Materials Research Vols. 984-985

Abstract: Micro channel heat exchangers (MCHX) can be broadly classified as fluidic devices that employ channels of hydraulic diameter smaller than 1 mm. The present study focused on validate the better configuration parameters of louver fin used in MCHX for apply in residential air-conditioner condenser. The study has considered for three different louver angle case, two different louver lengths for better louver angle case and finally two different louver pitches for better louver angle and louver length case. The study indicates that the pressure drop will depends upon the louver angle and pitch. The louver angle i.e. 25deg provides reasonable pressure drop and high heat transfer rate. Thus by changing the length of louver can increase the pressure drop in MCHX. The case ie., 1.2mm louver length have more heat transfer rate. But when comparing to 1mm louver length case Net Heat Transfer rate is high. So the study further continued by having the louver length 1mm and changing the louver pitch. The louver pitch 0.8 and 1.2 has only considered for the study. The length of louver can decrease the pressure drop in MCHX. The variation of net heat transfer rate to changing the louver pitch indicating the importance of number of louver present in the MCHX. Thus the present study indicates the importance of configuration parameters for MCHX. The study also indicates that the increasing the louver length and angle will increase the net heat transfer rate. While increasing the louver pitch is inversely proportional to the net heat transfer rate of MCHX.

Abstract: Study on environment friendly mixed refrigerant to replace R134a in vapour compression refrigeration (VCR) System. The mixed refrigerants investigated are propane (R290), butane (R600), isobutene (R600a) and R134a. Even though the ozone depletion potentials of R134a relative to CFC-11 are very low; the global warming potentials are extremely high and also expensive. For this reason, the production and use of R134a will be terminated in the near future. Hydrocarbons are free from ozone depletion potential and have negligible global warming potential. The results showed that, mixed refrigerant with charge of 80 g satisfy the required freezer air temperature when R134a with a charge of 110 g is used as refrigerant. The actual COP of refrigerator using mixed refrigerant was almost nearer that of the system using R134a as refrigerant. The coefficient of performance of the vapour compression refrigeration system using mixed refrigerant MR-3 [R134a/R290/ R600a/ R600 (20/35/40/5)] is having very close value with R134a and the Global warming potential of MR-3 is negligible when compared with R134a. Hence the mixed refrigerant MR-3 is chosen as an environmental friendly alternate refrigerant to R134a. The exergy analysis of the vapour compression refrigeration system using R134a and all the above mixtures are investigated. The effect of evaporator temperature on exergy efficiency and exergy destruction ratio of the system are experimentally studied. The exergy defect in the compressor, condenser, expansion device and evaporator are also obtained. Key words: R134a, Mixed refrigerant, Chlorofluorocarbons, Propane, Butane, Isobutene, REFPROP, COP, ODP, GWP, Exergy, VCR System.

Abstract: Solar powered adsorption refrigeration system is renewable source in the future energy demands and more useful for off-grid area. In this paper a mathematical model was developed to investigate the performance of a cooling cabinet of a activated carbon-ammonia adsorption refrigeration system, and a new effective method about the refrigeration studies. A brief thermodynamic study of the cooling cabinet is carried out and the effect of operating parameters such as temperature, pressure, cooling effect of the system is numerically analyzed. The impact of solar intensity on performance of the system is significant. The cooling cabinet model is completely analysied for varies capacity and it is able to calculate the cooling cabinet coil length .The designed mathematical model is analyzed by the use of coolpack software and the results are compared with ansys software. It is observed that the system operate more efficient while maximum solar intensity and the cooling effect. Key words: Solar, Adsorption Refrigeration, Mathematical model, Analysis, Solar intensity.

Abstract: Experiments have been performed to investigate the pressure drop in the microchannel heat sink by varying the cross sectional shape of the header at the inlet and at the outlet for two types of arrangement U type and Z type. The experiments are performed by using deionized water as a coolant for a mass flow rate of 50 – 120 kg/hr and Reynolds number of range 100 - 600 in an Al microchannel rectangular heat sink with 25 numbers of parallel microchannels. Experiment was carried out to find the suitable inlet and outlet header combination for both U type heat sink and Z type heat sink. The various cross sectional shapes used in this micro channel are triangular, trapezoidal and rectangular.

Abstract: Air quality indices are used for local and regional air quality management in many metro cities of the world. The present investigation was carried out to find the significance of air pollutant concentrations at commercial areas of Chennai. Suspended Particulate Matter (SPM), Respirable Suspended Particulate Matter (RSPM), Sulphur dioxide (SO2) and Oxides of nitrogen (NOX) were analyzed over two sites namely T.Nagar and Kilpauk in Chennai. Both the sampling stations selected are located in commercial areas. Several concepts and indicators exist to measure and rank the urban areas in terms of their socio-economic infrastructure and environment related parameters. In this paper an air quality index (AQI) considering the combined level of three criteria pollutants (oxides of nitrogen, sulphur dioxide, and Respirable suspended particulate matter ) is proposed.

Abstract: — The objective of the work is to compare between convergent, convergent-divergent nozzle and to analyse which has better performance in a miniature aircraft having vertical lift system. Comparison is done by having 2° and 4° attack angle at a free stream mach no 0.8 and to find the variation of pressures around, drag. CFD analysis has been performed for the miniature aircraft. Pressure forces, viscous forces, pressure coefficient and viscous coefficient are found for convergent nozzle and convergent-divergent nozzle. Also pressure variation at 2 ° and 4 ° angle of attack for Airfoil types AIG(smart fish) and NACA(Conventional) are found. It was found convergent-divergent nozzle is best suited with vertical lift having exit jet velocity 2700m/s. It is also found that airfoil produce less drag when attack angle is 4 °

Abstract: Supersonic flows associated with missiles, aircraft, missile engine intake and rocket nozzles are often steady. In this present work, the computational analysis was conducted on C-D (convergent –divergent) nozzle for understanding the flow regime with various flow properties such as velocity and various turbulent models (spalert almaras, K-ε and K-ω). The Scale down model of C-D nozzle was chosen for this study and it was modelled computationally with Gambit software package. In this integrated component model, the inlet flow is assumed a two-dimensional, steady, compressible, turbulent and supersonic. The physics based mathematical model of the considered flow consists of conservation of mass, momentum and energy equations subject to appropriate boundary conditions as defined by the physical problem stated above. The system of the governing equations with turbulent effects is solved numerically using different turbulence models to demonstrate their numerical accuracy in predicting the characteristics of turbulent gas flow in such complex geometry. Fluent software package was used for solving gas flow equations with turbulence models. The Mach number was chosen for different cases of analyses were 1.2, 1.5 and 2. For each case, different turbulence were engaged and solved and all the results were compared finally.

Abstract: The vent or opening is called nozzle. The objectives are to measure the flow rates and pressure distributions within the converging and diverging nozzle under different exit and inlet pressure ratios. Analytic results will be used to contrast the measurements for the pressure and normal shock locations. In this paper computational Fluid Dynamics (CFD) Analysis of various performance parameters like static pressure, the Mach number, intensity of turbulence, the area ratio are studied in detail for a rocket nozzle from Inlet to exit by using Ansys Fluent software. From the public literature survey the geometry co-ordinates are taken. The throat diameter and exit and diameter are same for all nozzles. After the simulation the results revealed that the divergence angle varies the mach number and other performance parameters also varies. For smaller nozzle angle the discharge coefficient increases with increasing pressure ratio until the choked condition is reached for varying the divergence angle.

Abstract: Condition monitoring of electrical equipments is indeed the earliest application of Infrared Thermography. It overcomes the disadvantages of conventional manual testing as it does not involve disassembly and reassembly of electrical equipments. Conventionally in IRT testing, hotspot is plotted across the time of testing and any abrupt deviation in the graph indicates either immediate or delayed manual. However hotspot temperature is also dependent on the environmental and operational conditions. Hence prior to plotting the hotspot temperature, it is necessary to correct the errors induced due to above factors in the measured temperature. In this paper relationship between hotspot temperature and emissivity is given as mathematical equation

Abstract: The cyborg can control robotic arm by means of the brain implant. The design of implantable node is critical because the surgically implanted node should consume very low power. In this paper, an efficient CMOS Transmitter in terms of low power is presented for Implantable Medical Devices in the MICS band. The RF front-end transmitter consists of up-conversion mixer and a power amplifier. The designs have been done using Cadence RF Spectre tools with 180 nm technology and the transmitter front-end consumes 900μW for the MICS band.