Ashvini Kumar

Simple multiple wick solar still: Analysis and performance

Abstract This paper presents the design, analysis and performance of a multiple wick solar still, in which blackened wet jute cloth forms the liquid surface which can be oriented to intercept maximum solar radiation and attain high temperatures on account of low thermal capacity. The wet surface consists of a series of jute cloth pieces of increasing length separated by thin black polythene sheets, resting on foam insulation supported by a net of nylon ribbon; these pieces are arranged along an incline and their upper edges are dipped in a saline water tank. Suction by the cailliary action of the cloth fibre provides a thin sheet of liquid on the cloth; the arrangement ensures that all the surface, irradiated by the sun is wet at all times. The results of an analysis based on Dunkles relation[16] are in excellent agreement with the observed performance of the still. On a typical cold sunny day in Delhi (viz. 6 February 1980) the distillate output was 2.5 l/m2 day, corresponding to an overall efficiency of 34 per cent (as compared to a maximum of 30 per cent for basin type still). The still costs less than half of the cost of a basin type still of same area and provides a higher yield of distillate.

Double basin solar still

Abstract This paper presents a periodic analysis and observed performance of a double basin solar still, mounted on a stand. Observations on this type of still are in fair agreement with the results of analysis. The daily distillate production of such a still is on the average 36% higher than that of a single basin still. Some aspects of the operation, design and performance have also been discussed.

Evaluation of an earth—air tunnel system for cooling/heating of a hospital complex

Abstract A large earth-air tunnel system meant to provide thermal comfort inside the whole building complex at one of the hospitals in India, has been evaluated. A simple theoretical model is developed to validate the experimental measurements. An 80-m length of the tunnel with a cross-sectional area 0.528m 2 and with an air velocity of 4.89 m s −1 is found to have a cooling capacity of approx. 512 kWh and a heating capacity of 269 kWh. The heating capacity was found to be inadequate for providing the necessary comfort conditions.

Effects of dye on the performance of a solar still

Experiments on the effects of dye on the output of a solar still were carried out during June, 1979. Black and violet dyes were found to be more effective than other dyes, and the performance with a dye present was found to improve, the deeper the still.

A review—Cooling by water evaporation over roof

Abstract This communication presents a review of reduction of heat flux through the roof of a building by open evaporation of water over the roof. A comparative study of (i) roof pond, (ii) spray cooling/gunny bags and (iii) moving water over the roof system is presented. Analysis of the moving water system has been given from which results for the roof pond and water spray can be obtained as special cases. Numerical results, discussion and conclusions have also been presented.

Simulation studies on a multi-stage stacked tray solar still

Abstract In this paper, a computer simulation model is presented for studying the steady-state performance of a multi-stage stacked tray solar still. The model is validated by the results of simulated experiments on a three-stage unit having an immersion type electric heater as the heating source. The results obtained from the model using the modified heat and mass transfer relationships proposed in previous study are in good agreement with the experiments. Numerical results are also presented in the paper to appreciate the relative performance of the proposed multi-stage, stacked tray solar still with a diffusion type, multi-stage solar still.

Utilization of waste hot water for distillation

Abstract The yield of a solar still can be increased by introducing hot feed water available from power and chemical plants into a still; even in the absence of sun appreciable yields are obtained. In this paper the performance of a solar still has been studied in two modes of waste water utilization: (i) Flowing waste hot water from thermal power plants at constant rate through the solar still. (ii) Feeding waste hot water obtained from thermal power plants once a day. Dependence of the distillate output on various operating parameters has also been investigated.

Thermal performance of a solar pressure cooker based on evacuated tube solar collector

This paper presents the thermal performance of a community type solar pressure cooker based on evacuated tube solar collector. The developed design of solar pressure cooker has separate parts for energy collection and cooking unit and both are coupled by heat exchanger. The paper has presented the performance results of experimental study conducted on solar pressure cooker and a simulation model has been developed for predicting the cooker performance under a variety of operating and climatic conditions. The theoretical model is validated against the experimental results. The obtained results have suggested a possibility of several batches of solar cooking on a clear sunny day under typical conditions of Delhi.

Periodic theory of an open roof pond

This paper describes an analysis of the reduction of the heat flux coming into a room through a roof with an open water pond. A periodic analysis of the system, based on the linearisation of Dunkles6 expressions for convective, radiative and evaporative losses, is presented. Numerical computation for the heat flux has been carried out for a typical hot day, the 19th of June, 1979, in New Delhi. These results were compared with those for a water-sprayed system. It was found that, for typical parameters, there are reductions in the maximum heat flux entering the room of 48% and 41% for the roof pond and water-sprayed systems, respectively (for a relative humidity of 0·8). The corresponding reductions in daily heat input into the room are 20% and 35%, respectively. Load levelling is, of course, much better in the case of the open roof pond.

Transient analysis of solar still

Abstract This paper presents an analysis of the transient performance of a basin type mounted still; explicit expressions for hourly variation of temperature of glass cover and water in the basin and distillate output have been obtained. The results of the analysis are in good agreement with experiments.