## 1 Introduction  
Evaporative cooling is one of the most efficient methods for cooling agro-industrial facilities [1, 2]. The air from outside the facility is forced to enter through a constantly wet porous medium (pad). Sensible and latent heat transfer occurs when the air is in contact with the water surface. Air loses sensible heat, decreasing its temperature, while water evaporates from the surface of the pad, increasing the humidity of the air and adding latent heat. The air at the outlet of the pad has a lower temperature and a higher relative humidity than the inlet one. However, the high cost of the traditional cellulose pad makes the implementation of this technique unfeasible in small and medium agro-industrial production systems. This has prompted research on alternative materials that could be used to manufacture pads at a fraction of the cost of cellulose ones [3, 4]. Alternative materials have been selected based on the local availability, low acquisition costs and final disposal, the ones that comes as waste from other productive process, lowering their environmental impact being preferred. Tables 1 and 2 summarize the cooling efficiency (\(\eta\)) of some alternative materials that have been previously analysed, which include natural, mineral and synthetic sources; the use of natural fibres has predominated. The cooling efficiency is affected by the inlet air velocity and the pad thickness, in addition to the influence of the external thermal conditions [31]. However, conducting experimental tests to assess the influence of all factors on cooling efficiency is a time and resource consuming task. Some phenomenology mathematical models had been proposed and validated through experimental tests [32; 33] to address this issue, determining the behaviour of the pad under different environmental, operating and manufacturing conditions. This has been done exhaustively for cellulose pads, nevertheless, the main difficulty that arose for alternative materials is the computation of their convective heat and mass transfer coefficients, in addition to the computation of the air-water contact surface area. In this matter, [PERSON] et al. [13] proposed to scale the Hilper correlations [34] by the quotient between the characteristic length (\(l_{e}\)) and thickness (\(L\)) of the pad. This was validated later by [32; 35; 36] for pads manufactured with cellulose, showing good agreement between the experimental and numerical results. Moreover, few authors have reported the convective heat and mass transfer coefficients or the characteristic length [7; 13; 21; 26; 30; 33], making it difficult to develop future simulations of the same material under different conditions. \begin{table}
\begin{tabular}{c c c} \hline
**Raw Material** & **Research** & \(\eta\) **[\%]** \\ \hline Aspen fibres media & [5; 6; 7; 8] & 71.6–97.7 \\ Coconut coir fibre & [6; 7; 9; 10; 11; 12; 13; 14] & 50.8–92.86 \\ Expanded clay & [15; 16] & 42.0–83.0 \\ date palm fibre & [17] & 38.9 \\ Eucalyptus fibre & [18; 19] & 23.0–76.0 \\ Jute fibre & [17; 20; 21; 22] & 57.0–87.0 \\ Khus fibre & [7; 11; 12; 14] & 64.2–82.0 \\ Luffa fibre & [12; 17] & 55.1–73.7 \\ Palash fibres & [7] & 81.0 \\ Rice straw & [23] & 31.0–79.0 \\ Sackcloth & [24] & 69.0 \\ Slice woods & [25] & 76.0 \\ Straw fibre & [24; 25] & 71.9–90.0 \\ Wood savings & [9] & 25.0–65.8 \\ Wood wool & [9; 11; 12] & 74.2–92.2 \\ \hline \end{tabular}
\end{table} 
Table 1: Cooling efficiency (\(\eta\)) of cooling pad research studies based on organic raw materials.