Basin Liner Research Articles

Thermal performance of a single basin solar still with PCM as a storage medium

Transient mathematical models are presented for a single slope-single basin solar still with and without phase change material (PCM) under the basin liner of the still. Analytical expressions for temperatures of the still elements and the PCM have been obtained. The still performance has been investigated by computer simulation. Numerical calculations have been carried out, using stearic acid as a PCM, on typical summer and winter days in Jeddah (lat. 21° 42′ N, long. 39° 11′ E), Saudi Arabia. Effect of mass of the PCM ( m pcm ) on the daylight P dl , overnight P on and daily productivity P d and efficiency η d of the still for different masses of basin water m w has been investigated. It is found that P dl decreases as m pcm increases; but P on and P d increase significantly with an increase of m pcm due to the increased amount of the heat stored within the PCM. During discharging of the PCM, the convective heat transfer coefficient from the basin liner to basin water is doubled; thus, the evaporative heat transfer coefficient is increased by 27% on using 3.3 cm of stearic acid beneath the basin liner. Therefore, on a summer day, a value of P d of 9.005 (kg/m 2 day) with a daily efficiency of 85.3% has been obtained compared to 4.998 (kg/m 2 day) when the still is used without the PCM. The PCM is more effective for lower masses of basin water on winter season.

Experimental study of the enhancement parameters on a single slope solar still productivity

The performance of a single slope solar still using different operational parameters was studied experimentally. The still productivity increased up to 51% when combined enhancers such as asphalt basin liner and sprinkler have been applied to the still. Also the ambient conditions were found to have direct effect on the productivity of the still. The night production in the absence of solar radiation contributed to 16% of the daily output due to the differences in temperature between the cover and water, and the decrease of heat capacity. The study also showed that the daily production of still can be increased by reducing the depth of the water in the basin.

Effect of inclination of external flat plate reflector of basin type still in winter

This paper presents a theoretical analysis of a basin type solar still with an internal reflector (two sides and back walls) and an inclined flat plate external reflector on a winter solstice day at 30° N latitude. We are proposing a new geometrical method for calculating the solar radiation reflected by the inclined external reflector and then absorbed on the basin liner. Using this method, we performed a numerical analysis of heat and mass transfer in the still in order to determine the effectiveness of the inclination of the external reflector. We found that the benefit of a vertical external reflector would be smaller or even negligible for a still with a larger value for the glass cover angle, while an inclined external reflector can increase the distillate productivity of the still at any glass cover angle, and the external reflector angle should be set at about 15° from vertical on a winter solstice day. The daily amount of distillate of the still with the inclined external reflector would be about 16% greater than that with the vertical external reflector, and about 2.3 times as large as that of the still with neither the internal nor the external reflector on a winter solstice day.

Theoretical analysis of a basin type solar still with internal and external reflectors

This paper presents a theoretical analysis of a basin type still with internal and external reflectors. We propose a geometrical method to calculate the solar radiation reflected by the internal and the external reflectors and then absorbed on the basin liner. We also performed numerical analysis of heat and mass transfer in the still, and found that the internal and the external reflectors can remarkably increase the distillate productivity throughout the year except for the summer season, and the increase in the daily amounts of distillate by adding the internal and the external reflectors to the single-slope basin type still for the entire year would be averaged as 48%.

Construction and performance of an assisted solar distiller

The design and construction of a new type of assisted solar distiller is presented. The device consists of a basin-type distiller, with the peculiarity that the basin liner is extended as an integrated solar collector accumulator with quite simple characteristics, recently developed at the National University of San Luis (Argentina). The covering is easy to remove for cleansing, and an improvement of the design for future tasks is being considered. The new distiller was compared with a common basin-type distiller and a commonplace basin-type distiller coupled with a flat solar collector. Daytime, nocturnal, weekly and hourly measurements showed that the daily production of the new assisted solar distiller always surpassed that of the basin-type distiller by approximately 70%, and that of the basin-type distiller coupled with a flat solar collector by approximately 20%. Results of 2 years of measuring are presented.

Parametric studies of passive/active solar stills by using modified convective mass transfer relations

SYNOPSIS In the present work, the effects of design parameters—namely water depth, absorptivity of basin liner and water mass, bottom insulation thickness and collector area for passive and active solar still—have been studied by using two sets of values of the constants C and n, by using inner and outer glass cover temperatures of the solar stills for a typical day under Delhi climatic conditions. The studies have been based on the basic energy balance equations of different components of passive and active solar stills taking into account modified values of C and n for convective mass transfer for both the systems. The results obtained in the present case are in accordance with the results reported earlier.

Monthly performance of passive and active solar stills for different Indian climatic conditions

The monthly performance of passive and active solar stills for different Indian climatic conditions was evaluated. Numerical computations were carried out for hourly variations of average insolation at the Chennai, Jodhpur, Kolkata, Mumbai and New Delhi stations. The analysis was based on the quasi-steady-state condition. Analytical expressions for water temperature, glass cover temperature and yield as a function of climatic parameters — namely solar intensity, ambient air temperature and design parameters (water depth, absorptivity of basin liner, wind velocity, bottom insulation and cover inclinations) — were also derived. On the basis of numerical computations, it was inferred that: (1) the annual yield significantly depends on water depth, inclination of condensing cover and collector as expected for both passive and active solar stills; and (2) the annual yield for a given water depth increases linearly with the collector area for an active solar still.

04/01408 Experimental comparative study of the performances of single and double basin solar-stills: Al-Karaghouli, A. A. and Alnaser, W. E. Applied Energy, 2004, 77, (3), 317–325

A transient analysis of a double-basin solar still coupled to a flat plate solar collector is presented. The analysis has been carried out for both the natural (thermosiphon) and forced circulation of water between the collector and the still. Explicit expressions for the temperatures of water mass, glass cover, and basin liner of the proposed system have been developed. Effect of water depth on the distillate output and efficiency of the proposed system has been studied in detail. For appreciation of the analytical results, numerical calculations have been made for a typical day under Delhi climatic conditions. Performance of the proposed system has also been compared with that of the uncoupled double-basin solar still.

Computer modelling of passive solar still by evaluating absorptivity of basin liner

SYNOPSIS Based on energy balance equations, the expressions for effective absorptance and transmittance product (ατ)eff water and glass temperatures, yield and instantaneous efficiency of a passive solar still have been derived. A computer model has been developed to predict the performance of a solar still using the inner glass temperature. The present model uses values of constants Cinner and ninner obtained from using experimental data from 16, 17, 18, 19 and 20 June 2001, in the climatic conditions of Delhi. It is inferred that there is reasonable agreement between the experimental and predicted theoretical results.

Experimental study of basin-type, multiple-effect, diffusion-coupled solar still

Basin-type, multiple-effect, diffusion-coupled solar stills consisting of a tilted double glass cover, a horizontal basin liner and a number of closely spaced vertical partitions in contact with saline-soaked wicks were constructed and then examined in an outdoor experiment in fall and winter at Okinawa, Japan. This new type of still is greatly improved by narrowing diffusion gaps between the partitions, increasing the number of partitions, sandwiching small spacers between partitions and insulating the frame of the glass cover. The daily performances of the improved still are in good agreement with predictions calculated from the theoretical model developed by Tanaka et al. [1]. The still with 5-mm diffusion gaps between 11 partitions produces 14.8–18.7 kg/d distillate per unit effective area of the glass cover at 20.9–22.4 MJ m −2 d −1 solar radiations incident on the glass cover and 19–30°C ambient air temperatures and is highly productive in comparison with the 7-effect diffusion-type still with 8-mm gaps developed by Okamura et al. [2] and the 3-effect diffusion-type still with 19-mm gaps of Cooper and Appleyard [3].

Parametric investigation of a basin-type-multiple-effect coupled solar still

Parametric analysis was performed for the basin-type multiple-effect coupled solar still with a triangle cross-section consisting of a horizontal basin liner and a number of vertical parallel partitions in contact with saline-soaked wicks with narrow gaps between the partitions, under dry weather conditions at 26.1 °N latitude. The productivity of the still increased in winter with an increase in the angle between the glass cover and the basin and decreased in summer. In the spring and autumn seasons productivity had a gentle peak between a 40° and 45° angle. Increasing supply rates of saline water to the wicks and increasing initial mass of the basin water decreased productivity. With a decrease in diffusion gaps between partitions, productivity exponentially increased, and it also showed exponential increases with an increase in the number of distillation cells between the partitions. The productivity of the still of 13 partitions with 5-mm gaps and a 40° angle of the glass cover was four times more than the basin-type stills, and the still was more productive than the conventional multiple-effect stills by about 40% or more.

A highly productive basin-type-multiple-effect coupled solar still

A newly designed multiple-effect solar still with a triangle cross-section consisting of a horizontal basin liner, a tilted double glass cover and the vertical parallel partitions in contact with saline-soaked wicks is presented and theoretically analyzed. Solar radiation is absorbed in the basin and in the first partition, and the partition section recycles the energy from the basin as well as solar energy, which is directly absorbed by the first partition. A single distillation cell with a 5-mm diffusion gap between vertical partitions has been experimentally explored. No contamination of distillate with saline water was experimentally detected in the single distillation cell, and the experimental observation of the wick and the measurements of the temperature drop through the cell with the 5-mm gap showed that dry patches hardly appear on the wick. The proposed still with 5-mm diffusion gaps is theoretically predicted to produce distillate of 15.4kg −2 m −2d −1 on a sunny day of G ti =22.4 MJ/m −2d −1 solar radiation, and its efficiency is about 3.5 times larger than the average experimental value for the conventional basin type stills by Cooper [20] and 1.2-1.6 times larger than the experimental maximum values of the conventional multiple-effect stills [3,9].

Performance evaluation of distillation-cum-greenhouse for a warm and humid climate

This paper describes the performance evaluation of distillation-cum-greenhouse for a warm and humid climatic condition. Numerical computations have been carried out for a typical day in January for Chennai, India. Various temperatures, namely plant and water, as a function of climatic and design parameters, were obtained by solving coupled single-order differential equations using the Runge-Kutta method. Room air, transparent cover, basin liner temperature and distillate output were also worked out by using the value of plant and water temperature. Analysis showed that there is a significant effect in the plant, water temperatures and distillate output due to a change in the fraction of the solar radiation incident on the north wall ( F n ), depth of water, α b and the inclination of the roof whereas the heat capacity of the plant has a marginal effect on these temperatures and distillate output. The study revealed that vegetables can be grown in a warm and humid climate in a coastal region by the construction of a distillation-cum-greenhouse unit.

Thermal modelling of a double condensing chamber solar still: an experimental validation

In this communication, a thermal model of a double condensing chamber solar still (DCS) has been presented. The thermal model is based on energy balance equations for the different components of a double condensing chamber solar still (DCS), namely the water mass, the first and second condensing covers and the basin liner, including the reflecting mirror. Experiments were conducted for both the single slope conventional solar still (CSS) and double condensing chamber solar still (DCS) on an hourly basis for comparison of their performance. Numerical computations for evaluating the hourly temperatures and yield have been performed for Delhi climatic conditions. The obtained results have been compared with the experimental observations. It is observed that there is a fair agreement between the theoretical and experimental observations.

THERMAL MODELLING OF CONCENTRATOR ASSISTED SOLAR DISTILLATION WITH WATER FLOW OVER THE GLASS COVER

We present the thermal modelling of a concentrator assisted solar distillation system by incorporating the effect of water flow over the glass cover. Based on energy balance equation for each component of the system namely the flowing water, the glass cover, the water mass and the basin liner, an analytical expression for the temperature of the flowing water, the glass cover, the water mass and the yield have been derived. Further an expression for an instantaneous thermal efficiency as a function of climatic and design parameters have also been given. On the basis of numerical computation, it is inferred that there is significant improvement in the performance of a solar still due to water flow over the glass cover. The results have also been experimentally validated.

Improved design of a double effect solar still

A simple transient analysis of a solar still is presented incorporating the effect of water flowing over the glass cover. An idea of utilizing the evaporated mass of the water flowing over the glass cover has been suggested and investigated. The effects of other system parameters, like addition of dye, basin water mass and basin liner absorptivity, have also been studied. It is observed that the flow of water over the glass cover enhances the still productivity remarkably and also flowing water at a very low rate and collection of condensed vapour is always advisable to obtain comparably much more distillate output.

Analytical expression for thermal efficiency of a passive solar still

Using energy balance equations for the different components of a passive solar still (namely, glass cover, water mass and basin liner), the effect on its thermal efficiency of water flowing over the glass cover with uniform velocity has been studied analytically. The efficiency is found to increase due to the water flow at higher depths of water in the basin. The result is validated by the experimental results of other authors.

Parametric investigations on a basin type solar still

A thermal analytical study of a basin type solar still, based on the transient approach, has been presented. Explicit expressions for the glass cover temperature, water temperature, basin liner temperature, distillate output and the efficiency of the still have been developed. The effect of several parameters, e.g. water mass in the basin, initial water temperature, absorptivity of the basin liner, on the performance of the proposed system, has been a subject of detailed investigations in this communication. For quantitative assessment of the analytical results, numerical calculations have also been carried out, and the results have been presented graphically.

Transient analytical investigations on a single basin solar still with water flow in the basin

Investigations on the performance of a single basin solar still with water flow in the basin are presented following a transient analytical approach. An explicit expression for the temperature of the flowing water in the basin has been developed as a function of time and the space coordinate. Apart from this, explicit expressions for the glass cover temperature, basin liner temperature, distillate output and efficiency of the proposed system have also been presented. The results of the investigations are depicted graphically.

Transient analysis of double-basin solar still integrated with collector

A transient analysis of a double-basin solar still coupled to a flat plate solar collector is presented. The analysis has been carried out for both the natural (thermosiphon) and forced circulation of water between the collector and the still. Explicit expressions for the temperatures of water mass, glass cover, and basin liner of the proposed system have been developed. Effect of water depth on the distillate output and efficiency of the proposed system has been studied in detail. For appreciation of the analytical results, numerical calculations have been made for a typical day under Delhi climatic conditions. Performance of the proposed system has also been compared with that of the uncoupled double-basin solar still.