## 4 Results and Discussion  
The results from the developed EC systems are obtained for the climatic conditions of Multan (Pakistan), which are presented in Figure 6. Ambient air temperature ranges from 12.3 \({}^{\circ}\)C to 42.1 \({}^{\circ}\)C. The DEC system resulted in a temperature range of 10 \({}^{\circ}\)C to 32.3 \({}^{\circ}\)C, which created a temperature gradient of 10.9 \({}^{\circ}\)C. The IEC system resulted in a temperature range of 10.8 \({}^{\circ}\)C to 35.5 \({}^{\circ}\)C, which led to a temperature gradient (i.e., difference between ambient and supply air temperature) of 7.4 \({}^{\circ}\)C. The MEC system resulted in a temperature range of 13.2 \({}^{\circ}\)C to 31.6 \({}^{\circ}\)C, which created the maximum temperature gradient of 14.4 \({}^{\circ}\)C. From these results, the MEC system performs better when compared to the DEC and IEC systems in terms of the temperature gradient. The trend of relative humidity (%) of ambient air, DEC, IEC, and MEC systems is also presented in Figure 6. The DEC, IEC, and MEC systems resulted in relative humidity ranging from 72% to 98%, 51% to 78.5%, and 66.7% to 93.6%, respectively. A maximum increase in relative humidity is observed in case of the DEC system as compared to IEC and MEC systems. Additionally, Figure 6 shows that April to June are hot and dry months whereas July to October are hot and humid months, which indicated a need for AC in both. Figure 7 shows performance of the EC systems based on wet-bulb effectiveness for DEC, IEC, and MEC systems. The DEC and MEC systems resulted in relatively higher effectiveness when compared to the IEC system. MEC system achieved maximum effectiveness of 0.98 in November. Additionally, DEC and IEC systems achieved maximum wet-bulb effectiveness of 0.96 and 0.57 in September and May, respectively. Figure 6: The annual profiles of temperature and relative humidity for ambient conditions of Multan and output conditions of the DEC, IEC, and MEC systems. Figure 8 represents the relationship of heat production (HP) and temperature-humidity index (THI) with live weight of poultry birds. HP of poultry birds increases in linear function with respect to LW. In the early stage of poultry growth, higher THI is tolerated while justifying the earlier statement about use of heaters for one-week old chicks. Heat production is at peak when poultry birds achieve harvest mass. Poultry birds ready for harvest generate the highest heat (i.e., 171 W/m\({}^{2}\)) against THI of 18.2 \({}^{\circ}\)C at 2.75-kg live weight. Figure 8: The variations of heat production and THI with respect to weight of poultry birds. Figure 7: The achieved wet-bulb effectiveness of the EC systems against the results presented in Figure 6 for climatic conditions of Multan. Figure 9 shows the relation of relative humidity and THI with reference to \(T_{db}\). Increase in humidity up to the optimal value of dry-bulb temperature works accordingly to overcome heat stress. Figure 10 represents the effect of \(T_{db}\) on THVI with respect to varying air velocity. It is noticed that, at a fixed value of \(T_{db}\), \(THVI\) decreases slightly with an increase in the velocity of air. Moreover, Figure 11 shows THI with a varying temperature and relative humidity. THI ranges from 28 \({}^{\circ}\)C to 30 \({}^{\circ}\)C, which indicates an alarming situation for the poultry birds. It turns into a dangerous situation when THI surpasses 30 \({}^{\circ}\)C. An emergency action is required if the THI value surpasses 31 \({}^{\circ}\)C. Poultry birds grow healthier at 18 \({}^{\circ}\)C to 29 \({}^{\circ}\)C and 50% RH [47]. Figure 10: The variation of THVI as a function of air velocity at different \(T_{db}\). Figure 9: The optimum thermal comfort requirements of the poultry birds of different ages. Sensible and latent HP per bird directly effects their mortality rate. It also explains the complex situation of heat stress gained by poultry birds. As the ambient temperature starts increasing, HP per bird gets increased.