Category: SOLAR ENERGY 3

Dimensionless numbers and momentum and heat transfer correlations

Before there were computers we let nature be the computer. This was performed by using dimensionless numbers and developing correlations between them, particularly when designing complicated flow or heat transfer processes. The essence of the procedure was to take the differ­ential equation applicable to the process at hand and make it dimension­less. The variables were […]

Physical properties

Fig. B.1 Various properties of liquid water including: viscosity (д, •), density (p, o), heat capacity (Cp, ■), thermal conductivity (k, □), a group of parameters used in the calculation of the Rayleigh number (Ra = [gxp2Cp/kp]ATL3 = CRaATL3, see the text for the definition of the parameters used to determine CRa, *) and the […]

The effect of an envelope

When a cover was placed on a flat plate solar energy collector it was found that the device became more thermally efficient despite the fact that the cover admitted less insolation. The gauge of the insolation reaching and absorbed by the absorber plate was || or ||, which is a com­plicated calculation requiring detailed knowledge […]

The basic process

The basic parabolic trough STEGE process has a large area of parabolic reflectors that concentrate insolation to absorber pipes through which a heat transfer fluid (typically) flows to receive the energy. The pipes have a selective surface and are surrounded by a clear glass concentric tube to minimize heat transfer to the surroundings, similar to […]

The Rankine cycle

The Rankine cycle is the cycle of choice to produce electricity and is shown in Fig. 9.1 in a pressure (P)-enthalpy (H) diagram. Water is the usual working fluid in the cycle. Although there are more details to the cycle than shown, such as a reheat component, this will be ignored here so the reader […]