In addition to humans’ thermal comfort, air-conditioning (AC) could be required for various nonhuman applications, for example, animals’ AC, greenhouse AC, food storage and transportation, industrial processes, and so on. In this regard, optimum conditions of air temperature and humidity are explored and compared on psychrometric charts. Thermodynamic limitations of existing AC systems are discussed from the subject point of view. Consequently, four kinds of low-cost energy-efficient AC systems, namely: (i) direct evaporative cooling (DEC), (ii) indirect evaporative cooling (IEC), (iii) Maisotsenko cycle (M-Cycle) evaporative cooling (MEC), and (iv) desiccant AC (DAC), are investigated for climatic conditions of two cities, that is, Multan (Pakistan) and Fukuoka (Japan). In addition, systems’ fundamentals and principles are explained by means of schematic diagrams and basic heat/mass transfer relationships. According to the results, performance of all systems is influenced by ambient air conditions; therefore, a particular AC system cannot provide optimum AC for all nonhuman applications. However, one or other AC system can successfully provide desired conditions of temperature and relative humidity. It has been concluded that evaporative cooling systems provide low-cost AC for dry climates, whereas DAC system is found energy efficient and viable for humid climates.
Part of the book: Refrigeration
Productivity of livestock animals particularly sheep, goats, dairy, and beef cattle are usually affected due to high thermal/heat (sensible and latent) stresses, particularly in the developing countries. Different types of heating, ventilation, and air-conditioning (HVAC) systems are used worldwide depending upon the ambient air conditions to achieve the animals’ thermal comfort. In this chapter, few low-cost options for the air-conditioning system and for farm building designs are discussed. Desiccant-based two air-conditioning systems are considered i.e., standalone desiccant air-conditioning (D-AC) and M-cycle assisted D-AC (M-DAC) system. The feasibility of both systems is thermodynamically checked for climatic conditions of Multan, Pakistan. Daily- basis data of ambient and processed air from both systems are analyzed for the thermal comfort of Holstein Friesian cows. Temperature humidity index (THI) is calculated to investigate the thermal heat stress conditions. Results showed that the D-AC system can be used efficiently in the humid climatic conditions with relatively moderate-to-low temperatures. On the other hand, the M-DAC system can be used in humid climatic conditions with relatively high-temperature conditions. It is important to mention that the typical direct evaporative cooling systems can be obviously low-cost options in case of dry climatic conditions.
Part of the book: Low-temperature Technologies
Temperature and humidity control are crucial in next generation greenhouses. Plants require optimum temperature/humidity and vapor pressure deficit conditions inside the greenhouse for optimum yield. In this regard, an air-conditioning system could provide the required conditions in harsh climatic regions. In this study, the authors have summarized their published work on different desiccant and evaporative cooling options for greenhouse air-conditioning. The direct, indirect, and Maisotsenko cycle evaporative cooling systems, and multi-stage evaporative cooling systems have been summarized in this study. Different desiccant materials i.e., silica-gels, activated carbons (powder and fiber), polymer sorbents, and metal organic frameworks have also been summarized in this study along with different desiccant air-conditioning options. However, different high-performance zeolites and molecular sieves are extensively studied in literature. The authors conclude that solar operated desiccant based evaporative cooling systems could be an alternate option for next generation greenhouse air-conditioning.
Part of the book: Next-Generation Greenhouses for Food Security