The effect of air velocity on the performance of the direct evaporative cooling system

Abstract

This experimental study aimed to determine the effect of airflow velocity on the performance of a direct evaporative cooling system. Rectangular-shaped honeycomb cooling pads with a length of 34 cm, a width of 25 cm, and a thickness of 3.5 cm are used as cooling media. The main parameters of the study are low air velocity (2.3 ms−1), medium (3.2 ms−1), and high velocity (3.7 ms−1). The data collected include dry bulb temperature, wet bulb temperature, output air temperature, input and output air velocity, input and output humidity, and solar radiation. These data are used to determine saturation efficiency, cooling capacity, temperature decreases, and feasibility index. The experimental results are presented in the form of tables and graphs and analysed based on existing theories. The results showed that the evaporative cooling system could produce output temperatures up to 27.5°C with input 31.4°C at low airspeed, 27.97°C with input 31.47oC at medium speed, and 27.7°C with input 31.30°C at high air speed. It was concluded that a low airflow rate would add to the cooling efficiency, and the higher the airflow rate, the lower the cooling efficiency. The results showed that evaporative cooling is achievable with a feasibility index of 19.89 ≤ F*≤ 20.67. The results also affirmed that cooling capability is higher where the feasibility indexes are comparatively low.

Modeling and optimization of integrated earth air heat exchanger and direct evaporative cooling system using ANN and RSM approaches for preserving fruits and vegetables

“…Likewise, as shown in Figure 4c, the TD increases gradually from 13.48 to 16.49°C with an increase in from 50 to 150 mm. This can be attributed to the increase in contact area and residence times between the air and water, resulting in an increased evaporation rate, air temperature drop, and heat and mass transfer rate (Hassan et al, 2022; Nada et al, 2020).…”

“…This could be attributed to the fact that at higher air flow rates, the air stream spends less time in contact with the wetted pad on the cooling surface. As a result, less water evaporates from the pad, leading to a lower increase in RH (Hassan et al, 2022; Malli et al, 2011). Figure 6b shows a gradual increment in RH rise as increases from 0.032 to 0.096 kg/s.…”

“…This could be due to the fact that at higher air velocities, the duration of contact between the air and underground pipe surface decreases, resulting in a decrease in the convective heat transfer rate (Bisoniya et al, 2014;Niu et al, 2015). Furthermore, at higher velocities, the contact time between the air and the wetted cooling pad decreases, leading to a decrease in water evaporation and a subsequent decrease in the mass transfer coefficient between the air and cooling pad (Hassan et al, 2022). Figure 4b illustrates that as m w increases from 0.032 to 0.096 kg/s, the TD increases gradually from 16.42 to 17.56 C. This can be attributed to the increase in air-to-water contact areas resulting from the higher water flow rate, which leads to greater evaporation and a rise in humidity.…”

“…This can be attributed to the increase in contact area and residence times between the air and water, resulting in an increased evaporation rate, air drop, and heat and mass transfer rate (Hassan et al, 2022;Nada et al, 2020).…”

Effect of Varieties, Solar Drying and Zeer Pot Refrigeration Lining Media on Physico – Chemical Characteristics of Chili Pepper Fruits

“…High thickness of the pericarp might be due to large air spaces between the wood shavings which increased air movement to increase evaporative cooling effect of the inner pots to conserve the fruit pericarp structures in the chili pepper fruits [49]. Thickness of pericarp of the fruits protects the fruits against insects and microbial invasions and limits water loss and gas exchange.…”