**2.1 Materials**

*Thermodynamics and Energy Engineering*

32° signifying maximum refraction [4].

**we have,**

we get

consider Snell's law of refraction and law of reflection.

and μ1 = 1.517 are refractive indices of air and glass cover [17];

And so assuming all rays are incoming perpendicular, thus,

Giving as of **Figure 1**, say we have θ1 = 32° and θ2 = 58°

**Figure 2** represents the schematic of that implementation. The angle of Glass Cover is kept at 32° following the laws of reflection and refraction, to explain that let us

**Figure 1** schematic is a focused view of glass cover in **Figure 2**, say μ2 = 1.003

Sin θ<sup>1</sup> = 1,

which is the ultimate critical angle of the glass cover, and the angle we chose is

<sup>1</sup> *× Sin* <sup>2</sup> *=* <sup>2</sup> *× Sin* <sup>1</sup> (1)

**θ<sup>2</sup> = Sin−1(μ2/ μ1) = 41.14°,** (2)

**172**

**Figure 2.**

**Figure 1.**

*Schematic of glass cover and sunrays.*

*Solar distillation still with PCM: schematic [4].*

**Figure 3** shows PCM classified according to their commonalities as per the melting point and the enthalpy of fusion. It follows that the two vital characteristics of phase change material, relating to their semantics "phase" and "change," are derivates of temperature and heat released during the phenomenon of phase change [18, 19].

In this pragmatic study, the experimental setup is similar to the one described in **Figure 1**, and the following phase change material was used:


As we can observe in **Figure 2**, both of these compounds are on the left corner of the graph with melting temperature near zero or below zero and enthalpy of fusion around 300 MJ/m3 . Hence, the comparison is rather challenging owning to the similarities between the two compounds [20].

As far as the solar distillation goes, the following **Figure 4** summarizes the various substances used for an optimized solar distillation setup. Each material novel and being researched upon [14].
