Reviews

Heat and mass transfer in unsaturated porous media. Final report

“…In practice these resistances must be experimentally determined. Classical wind tunnel studies have shown the resistances to be of the form (Campbell, 1977):…”

“…Resistances calculated from this form of equation are adequate for forced convection situations in which wind shear is the dominant force causing fluid movement. In the free convection situations which occur when the soil surface warms above air temperature due to large radiation loads, other procedures for calculating resistance must be adopted (Campbell, 1977).…”

“…Since the vapor density at the soil surface is strongly dependent on temperature and atmospheric conditions, it is often eliminated from the flux equation by substituting the Penman transformation and the energy balance equation Ln order to obtain the Penman equation (Campbell, 1977). The resultant equation is satisfying insofar as it qualitatively shows the effects of windspeed, net radiation, temperature and atmospheric vapor density on evaporation.…”

“…. calculated temperature dependence from the equation relating water potential and relative humidity (Campbell, 1977) and obtained better but not perfect results. Although the theoretical validity of his calculations has recently been challenged (Herkelrath, 1981), it can certainly be said 20 that Sophocleous' scaling of temperature dependence with ~/T is a useful numerical approximation.…”

“…In practice, this technique is often simplified further in order to decrease requirements for collection of meteorological data. The Penman equation (Campbell, 1977) is an example of such a simplification. For situations in which the dominant component of the energy balance is radiation and water supply to the soil surface is not limiting, the Penman equation will…”