**4. Discussion**

The rationale behind conducting this study was to establish a clear relationship between incident solar radiation and the amount of fresh water produced. After developing the relationship and analyzing statistical information, we concur with the results from confirming data with two different depths [28, 29]. Then PCM was introduced, we chose phenol having attributions of economic availability and versatile properties. Phenol was also varied between two heights, and data was contrasted with that of water. Underlying factors were calculated as follows related to the heat and mass transfer [15].

We know from Dunkle [30], the hourly evaporation per m<sup>2</sup> from solar still is given by:

$$\mathbf{Q}\_{w} = \mathbf{0} : \mathbf{0}1 \,\mathbf{G} h\_{cw} (P\_w - P\mathbf{g}) \tag{6}$$

*where,*

$$\mathbf{Nu} = \mathbf{h}\_{\text{cw}} \mathbf{d}/\mathbf{k} \tag{7}$$

*C and n are constants. Also, the heat produced or*

$$\mathbf{Q}\_{\text{ produced}} = m\_w \, ^\ast \mathbf{L} = \mathbf{U} \mathbf{A} \, \mathbf{\tilde{g}} \, \mathbf{T} \dots \mathbf{\tilde{g}} \, \mathbf{T} = \mathbf{T} \mathbf{a} - \mathbf{T} \mathbf{b}, \tag{8}$$

*which is approximately (***Ta** *−* **Tw)** *as basin and water temperature is almost the same, basin being assumed a black body.*

*Above gives a model to find Q and A for the required basin the fraction Q/A yields the power in kWh/m2 .*

#### **4.1 Effect of the amount of water**

For a fixed amount of water, the cumulative amount of freshwater produced had a steep rise as the sun goes higher until sunsets (**Table 5**). PCM, however, continue to heat the water even after the sunset giving the effect of evaporation a boost. We are assuming this as a unit operation under steady-state conditions because we are assuming that the feed water equals the sum of the rate of freshwater produced

#### *Thermodynamics and Energy Engineering*


**Table 5.**

*Cumulative distillate collected results.*

#### **Figure 14.** *Cumulative distillate collected at two heights.*

and the rate of hot water leaving the unit. Accordingly, the productivity of the unit decreases since the vapor pressure decreases. One also can notice (**Figure 11**) that the rate of production is significant during the day time and gets lower after sunset. The outcome of variation of height is that the amount of distillate collected reduced with the increase in the height of water in the solar still (**Figure 14**) [31, 32].
