Distillation - Modelling, Simulation and Optimization

It is often to present all solar components QT, Q<sup>0</sup> <sup>T</sup>, and Q″ <sup>T</sup> in the above formulae 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), and (14) can be written as

$$M\_{\rm g} \frac{dT\_{\rm g}}{dt} = \tau\_b Q\_T + q\_{cw} + q\_{cw} + q\_{rw} - \left(q\_{ra} + q\_{ca}\right) \tag{15}$$

$$M\_w \frac{dT\_w}{dt} = \tau\_w Q\_T - \left(q\_{cw} + q\_{ew} + q\_{rw} + q\_{w-b}\right) \tag{16}$$

$$M\_b \frac{dT\_b}{dt} = \tau\_b Q\_T + q\_{w-b} - q\_b \tag{17}$$

3.1 Developing of the relationships of heat and mass transfer in an active solar

enhanced water recovery condenser. The airflow entering the solar still with a temperature of Tfin and moisture content win is heated up. After absorbing the vapor from the basin water, the airflow exits the solar still at a temperature of Tfout and moisture content wout. Then the hot air-vapor mixture passes through the dehumidifying coil, acting as a condenser. The dehumidifying coil with cooling water running inside will cool the hot air-vapor mixture down and condense the vapor from the mixture to produce the distillate. The air after passing the condenser has Tc-out and wc-out. The airflow continues passing through the preheater before going back to the still; hence, part of its heat will be extracted to recover in the

The Mathematical Model of Basin-Type Solar Distillation Systems

DOI: http://dx.doi.org/10.5772/intechopen.83228

Figure 2 presents a schematic diagram of an active solar distillation system with

The heat and mass transfer relationships in this still can be seen in Figure 3. The heat and mass transfer is mainly similar to that of the conventional solar still, except the energy reflecting from the basin water through convection qcw and evaporation qew will go into the flowing air first (defined as qcwf and qew) instead of going directly to glass as in the conventional case. Then, the flowing air (the flow) will release part of its energy to the glass through convection qcfg. The gained energy of the flow, mainly from the basin water, will increase both latent heat (hout – hin) and

From Figure 3, the energy and mass balances for the glass, for the flow in the

dTg

dt (18)

qcfg <sup>þ</sup> qrw <sup>þ</sup> <sup>α</sup>gQT <sup>¼</sup> qra <sup>þ</sup> qca <sup>þ</sup> Mg

Schematic diagram of a forced circulation solar still with enhanced water recovery.

distillation system

preheater.

sensible heat Mf

Figure 2.

35

dTf

dt of the flow.

still, for the basin water, and for the basin are
