* Mechanical Engg. Deptt., Mechanical Engg. Deptt., Medi Caps Institute of Technology & Management, Indore, India.
#Mechanical Engg. Deptt., Institute of Engg. & Technology, DAVV, Indore, India.
1 Corresponding author Address: 122, Anand Nagar, Chitawad Road, Indore, MP, 452 001, India.
Nomenclaturem
Mass of cast iron (kg)
CpSpecific heat of cast iron (J/kg K)
ρDensity of cast iron (kg/m3)
VVolume of CI block (m3)
NNumber of glass cover
TpMean temperature of plate surface (K)
TaAmbient air temperature (K)
TcMean temperature of inner surface of the cover (K)
SAbsorbed radiation by the CI (W/m2)
RaRayleigh number
NuNusselt Number
hConvective coefficient between plate and cover
UtTop losses W/m2K)
UsSide losses (W/m2K)
UbBottom losses (W/m2K)
UoOverall losses (W/m2K)
QlHeat loss (Watts)
QaHeat stored (Watts)
QarStored energy (Joules)
αAbsorbtivity of absorber surface
α'Thermal diffusivity (m2/s)
gAcceleration due to gravity (m/s2)
V'Velocity of air (m/s)
νKinematic viscosity (m2/s)
β'Volumetric coefficient of expansion of Air (K−1)
ρStefans Boltzmann constant (W/m2K4)
єpEmissivity of plate
єgEmissivity of glass cover
hwThickness of glass cover (m) Convection coefficient for air (W/m2K)
L1Length of top surface (m)
L2Width of top surface (m)
L3Total height of the system from the bottom (m)
LiThickness of insulation (m)
lSpacing between cover and plate (m)
KConductivity of cast iron (W/mK)
KiConductivity of insulation (W/mK)
KgConductivity of glass cover (W/mK)
AcArea of the absorber plate (m2)
ταTransmitivity absortivity product for absorber
LgThickness of glass cover (m).
GbAverage daily beam irradiation (W/m2)
GdAverage daily diffuse irradiation (W/m2)
nRefractive index of the glass
The performance of a salinity gradient solar pond depends on its capability to convert the input radiation in to desirable output, that is, heat storage. At a given latitude and longitude the average insolation incident on the flat surface is constant and therefore the factors which are barrier in the path of incident radiation eventually governs the performance of the pond. The effect of these factors can be reduced by replacing the various zones of the solar pond with alternative medium, restoring their functionality, so that maximum portion of the radiation can be stored. In the proposed modified pond upper convective, non convective and lower convective zones of the conventional salt gradient pond are replaced by glass cover, air and cast iron respectively. The performance of this proposed modified pond and associated heat loss is evaluated on the average day of every month for Indore city in mid western India. It has been observed that the proposed method not only improves overall performance but also simplifies the other inherent functional and operational difficulties. The results revealed that average overall efficiency is of the order of 60% whereas the losses during the night time are of the order of 15%.
Lower convective zone, non convective zone, solar pond, storage efficiency and upper convective zone
