2.1. Animals' thermal comfort

cooling and humidification is required in summer season of Multan (Pakistan), whereas heating and humidification is required in dry winters of Fukuoka (Japan) [3]. Certainly, there could be numerous AC applications which may require specific conditions of Ta and RH, for example, animals' AC [4], greenhouse AC [2, 5], agricultural products' storage and preservation [6, 7], and so on. The requirements of Ta and RH vary dynamically with respect to time and may even vary from species to species [4]. On the other hand, the AC term is mostly associated with humans' thermal comfort as far as conventional literature and primary objectives are concerned [8, 9]. Therefore, lots of AC technologies have been established for humans' thermal comfort and are under practice in order to obtain typical conditions of Ta and RH, particularly for summer and winter seasons [1, 10]. Out of them, most popular and highly efficient systems are based on electric-driven compressors. Although compressor-based AC systems achieve desired Ta and RH conditions efficiently, these are thermodynamically inefficient and consume huge amount of primary energy [1, 10]. Moreover, these systems are based on environmentally harmful technologies and consume hydro-fluorocarbons (HFCs)/chlorofluoro-carbons (CFCs)/hydrochlorofluoro-carbons (HCFCs). Consequently, the conventional vapor compression–based AC (VAC) systems possess certain global warming potential (GWP) and ozone layer depletion potential (ODP). Thermodynamic limitations as

well as merits/demerits of typical VAC system are highlighted in Section 3.

application.

98 Refrigeration

In the twenty-first century, lots of energy-efficient and low-cost AC systems have been studied, designed, developed and are under practice for various AC applications, for example, data center [11–13], museums [14–16], hospitals [17], automobiles [18, 19], wet markets [20], marine ships [21], greenhouses [22], agricultural products storage [7], animals' thermal comfort [6], industrial processes [23], electronic cooling [24], turbine inlet air cooling [25], and so on. Most of these systems are either thermally driven or based on evaporative cooling conception. These systems are not involved in the use of any kind of refrigerants, thus enabling zero GWP and ODP. As heat is the input energy source for thermally driven AC systems, these systems can be employed for efficient utilization of low-grade waste heat, solar thermal energy, and biogas or biomass, and so on. On the other hand, evaporative cooling-based AC systems are always handy (wherever applicable), because they only require water with small energy to run the fan. However, evaporative cooling or thermally driven AC systems are highly influenced by ambient air conditions; therefore, systems optimization will be required for each and every AC

From the above perspective, this chapter discusses sensible and latent load of AC required for various nonhuman AC applications. Ideal temperature and humidity zones are represented and compared on psychrometric charts. Consequently, various low-cost energy-efficient AC systems are proposed and discussed for the subjected applications. In addition, thermody-

Apart from humans' thermal comfort, ideal temperature and humidity could be required in many situations as discussed in the introduction section. The intensity of the required AC is

namic limitation of VAC system and scope of proposed systems is also highlighted.

2. Nonhuman air-conditioning (AC)

In general, designing of animals' housing according to the required temperature and humidity is usually complicated due to the environmental factors which affect the well-being and production of animals [26]. Similarly, designing of animals' AC system is directly affected by the economic factor; therefore, animals' AC is not very popular especially in developing countries, for example, Asia and Africa regions. However, lots of low-cost techniques are adopted in these regions in order to achieve the desired conditions that may not be sufficient in many cases. It is worth mentioning that the air-flow/ventilation rate is an important parameter for animals' AC similar to temperature and humidity. Therefore, designing of sensible and latent load of AC is provided after finalizing the optimum air-flow rates. Air-flow rate is a dynamic parameter in case of animals' AC, and it varies from season to season as well as from species to species. American society of heating, refrigeration, and airconditioning engineers (ASHRAE) provides basic guidelines for animals' AC which can be found from references [26–29]. For example, according to ASHRAE, ventilation rate of 17–22 L/s is required for cows (weight 500 kg each) in winter season, whereas it is 67–90 L/s and 110–220 L/s for spring and summer seasons, respectively. Similarly, growing pigs (weight 34–68 kg) require 3–35 L/s flow, whereas finishing pigs (weight 68–100 kg) require 5–60 L/s. Figure 1(a) shows typical constraints while selecting the optimum ventilation rate for livestock buildings [30, 26]. It can be observed that there are many factors which need to be addressed for selecting optimum ventilation rate. In addition, supplied air temperature and humidity from the AC unit is directly associated with the air-flow rates [3]. Consequently, the ideal temperature and humidity required for various animals is shown in Figure 1(b) [4, 26]. It can be noticed that the animals require higher relative humidity in general as compared to human beings [3]. On the other hand, animals are relatively less sensitive to temperature but require distinctive conditions for each breed. Moreover, potential of livestock industry can also be determined from Figure 1(b) simply by plotting the ambient air conditions of different cities and/or regions.
