Study of an argon–hydrogen RF inductive thermal plasma torch used for silicon deposition by optical emission spectroscopy

The hydrogenation of silicon deposited on a substrate for photovoltaic applications has been obtained by a plasma torch. This method shows a great advantage and leads to the improvement of the electronic properties of the material. The hydrogenation of silicon allows the crystallographic defects elimination (dislocations, dangling bonds) which leads to an increase of the diffusion length.In order to understand silicon hydrogenation by RF inductive thermal plasma spraying, a study of the discharge by optical emission spectroscopy (OES) has been undertaken. This study has been compared with the hydrogen content measured by the exodiffusion technique.The detection of highly excited species of atomic and molecular hydrogen proves the specificity of the inductive plasma. Hydrogen emission lines have been used to calculate the electronic density on the plasma axis. Furthermore, the ArI lines were used to calculate the electronic temperature in the plasma. With this information, the deviation from the local thermodynamic equilibrium (LTE) of the plasma has also been estimated.     

Analysis of a novel metal hydride cycle for simultaneous heating and cooling

Out of the many promising applications of metal hydrides, refrigeration, heat pumping and heat transformation are important. In order to achieve improved performance, a novel three-alloy cycle is proposed in which, for heat input at an intermediate temperature, heat outputs at high temperature and also at warm temperature are obtained in addition to refrigeration. The performance of this cycle using the alloys LaNi_4.6Sn_0.4, LaNi_4.7Al_0.3 and MmNi_4.5Al_0.5 is studied based on thermodynamics and reaction kinetics. Coefficients of performance, half-cycle times and specific alloy outputs are evaluated.     

Autothermal sorption-enhanced steam reforming of bio-oil/biogas mixture and energy generation by fuel cells: Concept analysis and process simulation

A concept of sorption-enhanced steam reforming of bio-oil/biogas for electricity and heat generation by phosphoric acid fuel cells is investigated. The process is modeled using SIMSCI Pro II process simulator. Sorptive removal of the carbon dioxide from the reaction site results in low CO and _CO2${\mathrm{CO}}_2$ concentrations (<1%$<1\%$) in the reformate, as a result it can be used in the phosphoric acid fuel cell without any further fuel cleanup. High hydrogen concentration and calorific value of the reformate enable the operation of the fuel cell at a high-efficiency mode despite of the high carbon/hydrogen ratio of the bio-fuel. Addition of biogas to the reformer enables autothermal operation of the reformer, as well as significantly improves the efficiency of the process. The simulation shows that the overall efficiency of the proposed system is compatible with the efficiency of the system using “classical” steam reforming of the fuel. The process exhibits 6% lower electrical efficiency compared to the system utilizing natural gas, and 4.6% higher efficiency compared to a system using bio-oil as a fuel.     

First and second law analyses of a typical solar air dryer system: a case study

This communication presents an experimental study based on energy and exergy analyses of a typical solar air dryer. On the basis of the experimental results, the first and the second law efficiencies are calculated with respect to the available solar radiation. It is found that the second law efficiency is much less than the first law efficiency irrespective of the mass flow rate of the circulating fluid. It is also found that both efficiencies are an increasing function with respect to the mass flow rate of the working fluid. For a particular day, it is also found that first and second law efficiencies fluctuate according to radiation. The results obtained in this article are found to be consistent with those obtained by earlier authors as given in the literature.     

Thermodynamic analysis and parametric study of an intercooled–reheat closed-cycle gas turbine on the basis of a new isentropic exponent

The thermodynamic analysis and parametric study of an intercooled–reheat closed-cycle gas turbine is presented in this paper, on the basis of a new (harmonic mean) isentropic exponent. An analytical expression is derived for the optimum pressure ratio and maximum non-dimensional net work output. It is found that the optimum pressure ratio and the maximum non-dimensional net work are high when the ratio of extreme temperatures of cycle (i.e. T _max and T _min) and isentropic efficiencies of compressor and turbine (i.e. η_c and η_t) are high. The theoretical results are also compared with the practical conditions of power plant.     

Heat transfer from an immersed vertical tube to a gas fluidized bed

Fluidization and heat transfer experiments have been conducted in gas fluidized beds of two different sizes, viz., 305 × 305 mm² and 305 × 152.5 mm² and with particles of silica sands ($\text{d}\text{?}{}_{\mathrm{p}}\text{= 167, 488, 504, and 745 μ}\text{m}$), glass beads (d_p = 427 μm) and millet seeds (d_p = 2064 μm) with immersed smooth vertical heated tubes of diameter 12.7, 28.6, and 50.8 mm. Important conclusions are drawn concerning the dependence of heat transfer coefficient on fluidization velocity, bed particle diameter, tube diameter and nature of bed fluidization. The heat transfer data are employed to assess the available literature correlations for heat transfer coefficient and for its maximum value.     

A novel photogalvanic cell using anthraquinone-2-sulfonate

A photoelectrochemical cell based on the photochemistry of anthraquinone-2-sulfonate (D) has been set up. In the presence of formate at pH 11.0, D on illumination produces D^? or D^2?. In the absence of oxygen, at the platinum electrode the anodic reaction is D^? → D + e, or D^2? → D + 2e, and at the dark electrode the cathodic reaction is O₂ + 2H₂O + 4e → 4OH^?. The open circuit potential of the cell is 500 mV. The short circuit current is 180 μA. The cell has been recycled at least eight times. The efficiency increases with platinized platinum electrode in the dark chamber. The steady current under illumination is 65 μA with the same open circuit voltage of 500 mV. The short circuit current is 250 μA. With a CdS electrode in the illuminated chamber the efficiency is even better. The open circuit voltage is 560 mV. After charging by illumination for 8 h a steady current of 120 μA can be drawn from the cell, with illumination off, for 40 h. The short circuit current is 450 μA. The maximum power output is 4.2 × 10^?6W The cell can be recycled at least four times without any loss in efficiency. Grey deposition on the CdS electrode possibly indicates electrode decomposition.     

Passive solar heating of a non-airconditioned building with movable insulation over the roof pond

This paper presents a simple mathematical model for solar space heating in a non-airconditioned building with movable insulation over the roof pond. The building room considered is of rectangular shape (6 m × 5 m × 4 m) based on the ground. The effects of heat conduction to the ground, heat transfers to furnishings and heat losses due to air ventilation/infiltration have been taken into account in the general heat transfer analysis. The day-to-night change of insulation over the roof pond has been represented by a rectangular step function variation of the heat transfer coefficient at the pond's surface. An increase of 3 to 4°C in the room air temperature is achieved by means of movable insulation over the roof pond on a mild winter's day (17th February, 1982) in New Delhi.     

Thermoelectric cold-chain chests for storing/transporting vaccines in remote regions

The cold chain is one of the key elements of the preventive health-care delivery system. Vaccines have to be carried long distances, stored in remote places and during this period the temperature has to be maintained within certain specified values. Realizing the needs of such requirements, the Department of Science & Technology, New Delhi (Govt. of India) assigned a project to the R&D Division of MECON, Ranchi for development of Thermoelectric Cold-Chain Chest operated by 12 V DC vehicular battery. The resulting portable thermoelectric (i.e. Peltier effect) Cold-Chain Chest (TCC) operated successfully even in an ambient environment of 45 °C, mainly for preserving and transporting life-saving medicines for urban as well as rural areas.