TABLE OF CONTENTS Pages Symposium 1 - the National Sea ...

carried out for both the 50 m 3 and the 100 m 3 tanks (air volumes of 85 m 3 and 200 m 3 ,
respectively).
Extended energy budget Model (EM)
The EM consists of three energy balance equations, corresponding to the three
components of the system (tank water, inside air and cover, see Figure 1), and one
mass balance equation of water vapor in the air.
1. energy balance of the water: αwSi–Li–Hw–λEw–Hr–Hm=ρwdCwdT/dt
2. energy balance of the air: Hw–Hc–Hv+λEw–λEc–λEv=0
3. energy balance for the greenhouse cover : So–Si+Li–Lo+Hc+λEc–Ho=0
4. mass balance of water vapor: Ew–Ec–Ev=0
Hc
Ho
λEc
Hw λEw
Figure 1: Energy fluxes in the covered tank system.
The explicit expressions for the various fluxes utilized conductive, convective
and radiative transfer coefficients, which were adapted from experiments and from the
greenhouse literature (Kittas, 1985; Papadakis et al., 1992; Seginer et al.,1988). The
meteorological and control variables were taken from the experiments.
Radiation Model (RM)
An analysis of the results obtained with the EM (to be described briefly in the
Results and Discussion section) indicated that the convective fluxes were relatively
unimportant when the structure over the tank was not ventilated (as in winter). For
such conditions a simplified model, RM, with emphasis on the radiative fluxes was
developed (after Seginer et al.; 1988).
The EM consists of only two energy balance equations, one for the tank water
and one for the cover.
5. Energy balance for the water : αwτcG–(Fw–Fc)–β(Fc–Fs)–Hr = 0
6. Energy balance for the cover : αcG+(1–γ)(Fw–Fc)+(β–η)(Fc–Fs) = 0
where Fi is a shorthand notation for σTi 4
Lo
Li
Si
So
2
λEv
Hv
Hr
Hm