## 1 Introduction  
Air-conditioning (AC) is the process of controlling temperature and humidity of ambient air to achieve thermal comfort for a range of occupants [1; 2]. It involves various processes to condition the ambient air, which includes cooling, heating, humidification, dehumidification, and ventilation [3]. Applications of the AC are not only limited to humans' thermal comfort but also to agricultural products' storage and livestock applications [4]. Livestock sector as a part of agriculture sector is of prime importance for any growing economy [5]. It includes animal farming for meat and milk production as well as poultry farming for meat and egg production [6]. According to Pakistan Statistical Yearbook [7], the poultry sector under the agriculture sector contributed 1.4% in overall gross domestic product (GDP) of the country during economical year 2017-2018 [7]. Out of total meat production (i.e., 4.3 million tons), 1.47 million tons poultry meat is produced in the country, which highlighted the significance of the poultry sector in the economy [7].  
In a poultry farm, cooling and ventilation of surrounding air are necessary for optimum growth of poultry birds [8]. These birds are highly susceptible to slight fluctuation in temperature and humidity of the surrounding air [8]. The poultry birds require an optimum temperature-humidity index (THI) throughout their growth up to the meat harvest stage. To achieve the required _THI_ for the poultry birds, ambient air is conditioned. Several types of cooling systems are being used to attain thermal comfort of the poultry birds [3]. In Pakistan, pad type direct evaporative cooling (DEC) system is commonly preferred for cooling of air in poultry farms [9].  
Typical hot and dry conditions of the country move to hot and humid conditions in the monsoon (i.e., heavy rainfall) season, which result in higher relative humidity in ambient air. This, therefore, limits the performance of a standalone DEC system [10]. Consequently, advanced evaporative cooling (EC) systems, namely the indirect evaporative cooling (IEC) system and the Maisotsenko-cycle based cooling (MEC) system, can be a better option for poultry farming in Pakistan [11]. EC systems are power-efficient when compared to conventional vapor compression air-conditioning systems in hot and dry climatic conditions [1; 12]. The EC systems are simple in design (structure), energy efficient, and environmentally-friendly as compared to traditional vapor compression air-conditioning (VCAC) systems. The AC systems being traditionally used across the world consume a major share of primary energy and exhaust hydrochlorofluocarbon-carbons (HCFCs)/hydro-fluorocarbons (HFCs)/chlorofluocarbons (CFCs) [13; 14; 15; 16]. Alternatively, HCFC, HFC, and CFC free refrigerants and desiccant unit based AC systems are also being studied [17; 18]. Whereas, the EC systems have a very low carbon footprint when compared to the VCAC systems [19; 20]. Objectives of this study include performance evaluation of three types of EC systems for the climatic conditions of Multan (Pakistan) and feasibility analysis of these EC systems for thermal comfort based on THI of poultry birds in poultry houses across Multan.