Thermal performance assessment of a trapezoidal salinity gradient solar pond with different sidewall inclination angles: a numerical investigation

In this research, analysis of entropy generation for mixed convection fluid flow in a trapezoidal enclosure is numerically investigated. To achieve this goal, the influences of Grashof number, Reynolds number and inclination angle of enclosure side walls on the distributions of the velocity and temperature fields and the values of entropy generation and Bejan numbers are examined with full details. The Boussinesq approximation is used to calculate the buoyancy force. Also, the entropy generation numbers are calculated according to the second law of thermodynamics. In addition, the modified blocked region method is applied to accurately simulate the diagonal walls of the trapezoidal enclosure. The results of numerical solution show that the maximum values of the flow irreversibility in the whole computational domain of the enclosure are related to the case with the highest values of Grashof number, Reynolds number and inclination angle of side walls.

A numerical study to predict the energy and exergy performances of a salinity gradient solar pond with thermal extraction

Solar ponds collect solar radiation and store it in the form of thermal energy over a period of time. The performance of a solar pond depends upon the performance of the heat exchange process. In this study, a laboratory model solar pond was fabricated and provided with an in-pond heat exchanger. To perform the computational study the lower convective zone (LCZ) of the solar pond alone was modelled using ANSYS Design Modeler. The analysis was carried out on the plain tube in-pond heat exchanger of the solar pond for different heights of LCZ for two different flow rates of heat transfer fluid. The performance parameters such as outlet water temperature, rate of heat transfer, effectiveness of heat exchanger, and pressure drop were analysed. The rate of heat transfer, pressure drop, Nusselt number and effectiveness of heat exchanger are evaluated by changing the velocity vectors of the fluid flow at the entrance of the in-pond heat exchanger. The rate of heat transfer is found to be higher for turbulent flow than laminar flow for different temperatures of LCZ.

The exergy performance of solar pond with porous media added in the lower convective zone (LCZ) has been experimentally and theoretically studied. The effect is investigated under three cases, which are solar pond without adding any porous media (case A), with cinder (case B) and with multi-type porous media of cinder and cobblestones (case C), respectively. The results show case C gains the highest LCZ temperature and exergy efficiency, and case A has the lowest temperature and efficiency; and the maximum transient exergy efficiencies of the three cases are found to be 19.23%, 19.83% and 21.61%, respectively. The daily mean exergy efficiency of case C is 2.66% higher than case A, and 1.87% higher than case B. The results indicate that adding porous media, i.e., cinder or the mixture of cinder and cobblestones increases the LCZ temperature of solar pond, and it also improves the exergy performance of solar pond.

Heat extraction from Non-Convective and Lower Convective Zones of the solar pond: A transient study

Key factors impacting performance of a salinity gradient solar pond exposed to Mediterranean climate

Renewable energy is becoming a significant source of energy due to the intensification in crude oil prices and the upsurge in greenhouse effects due to burning of fossil fuels. With only finite source of fossil fuel and exponential increase in the demand of power because of increase in human population, power generation from renewable energy promises a sustainable future for the mankind. Solar energy can be harnessed to meet our energy needs for a sustainable future. After the remarkable hike in oil prices numerous countries began to do an extensive research and development to utilize solar energy. There are many methods to trap solar energy, but an effective one was by using solar pond. Solar pond is an unnaturally constructed pond in which large temperature can be maintained in the lower convective zone by the way of higher salt concentration and by preventing natural convection so these ponds are termed as salt gradient solar pond. In this current research a salt gradient solar pond is designed and developed. Further the Thermal Analysis and Performance of the same model has been done in Vizag Climatic Condition. The same model can be utilized for generating sensible and latent heat for room heating and industrial heating applications. Moreover, electrical power can be generated by using suitable heat exchanger and working medium of low boiling point values such as ammonia.

Salinity gradient solar pond: Validation and simulation model

The trapezium is often a better approximation for the FinFET cross-section shape, rather than the design-intended rectangle. The frequent width variations along the vertical direction, caused by the etching process that is used for fin definition, may imply in inclined sidewalls and the inclination angles can vary in a significant range. These geometric variations may cause some important changes in the device electrical characteristics. This work analyzes the influence of the FinFET sidewall inclination angle on some relevant parameters for analog design, such as threshold voltage, output conductance, transconductance, intrinsic voltage gain (AV), gate capacitance and unit-gain frequency, through 3D numeric simulation. The intrinsic gain is affected by alterations in transconductance and output conductance. The results show that both parameters depend on the shape, but in different ways. Transconductance depends mainly on the sidewall inclination angle and the fixed average fin width, whereas the output conductance depends mainly on the average fin width and is weakly dependent on the sidewall inclination angle. The simulation results also show that higher voltage gains are obtained for smaller average fin widths with inclination angles that correspond to inverted trapeziums, i.e. for shapes where the channel width is larger at the top than at the transistor base because of the higher attained transconductance. When the channel top is thinner than the base, the transconductance degradation affects the intrinsic voltage gain. The total gate capacitances also present behavior dependent on the sidewall angle, with higher values for inverted trapezium shapes and, as a consequence, lower unit-gain frequencies.

Effects of porous media on thermal and salt diffusion of solar pond

Experiment and simulation study of a trapezoidal salt gradient solar pond

Transient study of a solar pond under heat extraction from non-convective and lower convective zones considering finite effectiveness of exchangers

A one-dimensional mathematical model which simulates the dynamic performance of stratified solar brine ponds is described. The model simulates the upper convective zone, the middle nonconvective zone, and the lower convective zone. In addition to the energy flux, the model simulates the varying brine densities as a function of temperature and salt concentration, and thus is able to examine various pond stability criteria. On the basis of model operational studies, the following results are presented: (i) a study of overall pond efficiency in terms of the upper convective layer; (ii) an optimization study of the thickness of the nonconvective zone in terms of net energy transmission to the lower convective zone; (iii) an investigation of the heat storage efficiency and of the overall pond efficiency as a function of pond loading rate for a particular depth of storage zone.

This paper presents a mathematical model of the performance of the salt gradient solar pond. A lumped parameter model of the upper convective zone, non-convective zone and lower convective zone is used. This model enables the temperatures of the upper-convective zone and the lower convective zone of the solar pond to be predicted. The experimental results agree well with theoretically predicted values. The major error in the theoretical results is due to the difference between the theoretical value of the solar radiation inside the water and that observed experimentally. It is found that the experimental value of the solar radiation at a depth of 90 cm is approximately 26 per cent of the total solar radiation falling on the solar pond surface, whereas the corresponding theoretical value is found to be 33 per cent. The results conclude that the lumped parameter model can be used as a simple model to predict the performance of the solar pond.

A study on exergetic performance of using porous media in the salt gradient solar pond