3. The mathematical model of an active basin-type solar distillation system with enhanced water recovery condenser

This section will focus in developing the relationships of heat and mass transfer in an active solar distillation system with enhanced water recovery condenser. Then, this mathematical model will be validated by comparing its results with those from the experimental model.

An active solar distillation system with enhanced water recovery condenser has been chosen in this study for several reasons. Compared with other types of active solar stills such as solar stills coupled with flat plate or evacuated tube collectors, solar stills coupled with parabolic concentrator, solar stills coupled with heat pipe, solar stills coupled with hybrid PV/T system, multistage active solar distillation systems, multi-effect active solar distillation systems, etc., solar stills represent simple yet mature technology. This is suitable for poor and developing countries and communities like Vietnam.

The main disadvantage of a conventional passive solar still as low productivity and efficiency can be overcome by changing the principle of operation as follows:


It is often to present all solar components QT, Q<sup>0</sup>

Distillation - Modelling, Simulation and Optimization

Mb dTb

system with enhanced water recovery condenser

and (14) can be written as

from the experimental model.

and communities like Vietnam.

outputs.

effective.

34

air-vapor mixture entering the still.

lower temperature to increase condensing process.

Mg dTg

> Mw dTw

by the global solar incidence of the sloped cover, QT, which is well-known computed [9]. If τb, τw, and τ<sup>g</sup> are, respectively, defined as the proportions of solar radiation incident absorbed by the basin, water, and glass liner, formulae (12), (13),

dt <sup>¼</sup> <sup>τ</sup>bQT <sup>þ</sup> qcw <sup>þ</sup> qew <sup>þ</sup> qrw � qra <sup>þ</sup> qca

dt <sup>¼</sup> <sup>τ</sup>wQT � qcw <sup>þ</sup> qew <sup>þ</sup> qrw <sup>þ</sup> qw�<sup>b</sup>

This section will focus in developing the relationships of heat and mass transfer

An active solar distillation system with enhanced water recovery condenser has been chosen in this study for several reasons. Compared with other types of active solar stills such as solar stills coupled with flat plate or evacuated tube collectors, solar stills coupled with parabolic concentrator, solar stills coupled with heat pipe, solar stills coupled with hybrid PV/T system, multistage active solar distillation systems, multi-effect active solar distillation systems, etc., solar stills represent simple yet mature technology. This is suitable for poor and developing countries

The main disadvantage of a conventional passive solar still as low productivity and efficiency can be overcome by changing the principle of operation as follows:

• Using air as an intermediate fluid and using forced convection to increase the heat transfer in the still, leading to increase the evaporation of water.

• Replacing saturated air in the passive solar still by "drier" air to increase the potential for mass transfer in the still, resulting in increasing the distillate

condenser to increase efficiency from a lower condensing temperature. If the

• Recovering heat extracted in the condensing process and using it to preheat the

• Replacing the limited condensing area of the hot glass covers in the standard still by the external condenser with much larger heat exchange areas and much

• Circulating the air-vapor mixture from the passive still to an external

water with low temperatures such as well water or wastewater from refrigeration process is available, then this condensing process will be more

3. The mathematical model of an active basin-type solar distillation

in an active solar distillation system with enhanced water recovery condenser. Then, this mathematical model will be validated by comparing its results with those

<sup>T</sup>, and Q″

<sup>T</sup> in the above formulae

(15)

(16)

dt <sup>¼</sup> <sup>τ</sup>bQT <sup>þ</sup> qw�<sup>b</sup> � qb (17)
