Environmental Engineering Reference
In-Depth Information
q out = m out Cp Δ T =m out Cp (T out - T feed )
(3)
where T out is the temperature of water at the outlet.
The second member of equation (1) makes use of the different heat flux densities which
occur in the behavior of the cell. Two of these heat flux densities do not vary much during the
operation of the distillation cell:
q loss is a heat flux density lost through different parts of the cell which can be in a
major part controlled by an efficient thermal insulation.
q cv is the heat flux density exchanged by pure convection. In reference [14], it has
been shown that this heat flux density remains lows compared to the other concerned
heat flux densities.
The two other heat flux densities are directly related to the quantity of produced pure
water and can be varied by means of the operating parameters of the cell. Special care
concerns these heat flux densities.
Influence of the Heat Flux Density
Equation (1) describes the energy balance at the level of the liquid film through
evaporation: the first member q f representing the heat flux density applied to the wall which
supports the film, appears as a parameter which acts a deciding role in the energy balance. It
represents the source of energy occurring in the system.
In figure 3 a, the variations of the densities for the latent heat flux density q l and sensitive
q out heat flux density with respect to the heat flux density provided to the heated wall q f .
a
Figure 3. Continued on next page.
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