The book covers brief introduction and concepts about the conventional air conditioning and evaporative cooling technologies. It presents the thermodynamic performance and relevant characteristics of direct evaporative cooling system to gain knowledge about the effects of inlet velocity of air, outdoor air temperature, cooling pad thickness and their configurations. It also explains about a developed thermodynamic model by using Logarithmic Mean Temperature Difference (LMTD) approach to predict the performance of the cooling pads. The nano-refrigerant is used in the Vapor Compression Refrigeration System (VCRS), and also in evaporative cooling combined with VCRS, then both the systems are compared. This book also helps in improving the feasibility and applicability of the developed system by decreasing the size of "evaporative cooling combined with vapour compression based air conditioning system". In this book, conventional air conditioner coupled with honeycomb cooling pads forproviding better thermal comfort at a minimum operating cost in hot & dry weather is theoretically investigated.