5. Conclusions

presented in Figure 9(b) are based on constant εdp, they may not be exactly similar to real experiments. In this regard, lots of studies have reported experimental results along with numerical models for MEC which can be found from references [50–52]. In addition, a recent study [6] provides basic correlation for performance evaluation of MEC, which can be represented by

where win, Tin, and Tout represent inlet humidity ratio [g/kgDA], inlet, and outlet air temperatures [�C], respectively. The values of constant A1, B1, and C<sup>1</sup> are 6.70, 0.26, and 0.53, respectively.

It can be noticed from Sections 4.1–4.3 that cooling potential of evaporative cooling techniques is function of ðTinÞdb � ðTinÞwb or ðTinÞdb � ðTinÞdp; therefore, it can be only applied in dry regions/climates. In contrary, desiccant AC (DAC) could be an energy-efficient and viable solution for humid climates [1]. The DAC possesses ability to deal sensible and latent load of AC distinctly and can be operated on low-grade waste heat, biogas, and/or solar energy. The ability of desiccant material to adsorb water vapors from ambient air makes DAC system a suitable choice for AC in high humidity regions [3]. A typical DAC system based on solid desiccant rotor is shown in Figure 10(a). First, ambient air (1) is passed through the desiccant dehumidifier where it is dehumidified due to water vapor pressure difference between air and desiccant (process 1–2). This process will be isenthalpic in case of ideal situation, that is, neglecting sorption heat. Thus, the temperature of dehumidified air (2) is increased due to heat of water vapor condensation. Second, the dehumidified air (2) is sensibly cooled initially by heat exchanger (process 2–3) followed by low-cost cooling processes (process 3–4), for example, IEC. On the other hand, desiccant will be saturated with water vapor adsorption after some time. Therefore, regeneration/hot air (6) is passed through the desiccant (process 6–7) which removes the adsorbed water vapors for cyclic usage of desiccant. Referring to Figure 10(a), inlet and outlet air conditions of DAC can be simply expressed by Eqs. (18)–(25), while detailed

ðToutÞdb ¼ A<sup>1</sup> þ B1ðTinÞdb þ C1ðwinÞ ð17Þ

ðT2Þwb ¼ ðT1Þwb ð18Þ

ðT6Þdb ¼ fðw1, RH2Þ ð22Þ

RH<sup>6</sup> ≤ RH<sup>2</sup> ð23Þ

w<sup>4</sup> ¼ w<sup>3</sup> ¼ w<sup>2</sup> ð24Þ

ð19Þ

ð20Þ

ð21Þ

Eq. (17). The correction is valid for the range of Tin = 20–45�C and win = 10–25 g/kgDA.

4.4. Desiccant AC (DAC)

110 Refrigeration

DAC models can be found from references [4, 53].

ðT3Þdb ¼ ðT2Þdb � εHX

ðT4Þdb ¼ ðT3Þdb � εIEC

ðT5Þdb ¼ ðT1Þdb þ εHX

ðT2Þdb � ðT1Þdb

ðT3Þdb � ðT1Þwb

ðT2Þdb � ðT1Þdb

The chapter discusses the fundamentals of various nonhuman air-conditioning (AC) applications from the viewpoint of low-cost and energy-efficient AC. In this regard, optimum conditions are explored and compared on psychrometric charts for numerous nonhuman AC applications. Most of them require dissimilar conditions as compared to conventional humans' thermal comfort. Conventional vapor compression based AC systems are found thermodynamically inefficient and expensive; therefore, it has been realized that low-cost energy-efficient AC is direly needed. Thus, study proposes four kinds of low-cost energy-efficient AC systems which are based on evaporative cooling and thermally driven conceptions. Fundamentals and principle of each system is explained by means of basic heat/mass transfer relationships. Moreover, system performance is evaluated for climatic conditions of two cities, that is, Multan and Fukuoka. According to the results, performance of all systems is highly influenced by ambient air conditions, and, therefore, a particular AC system cannot provide optimum AC for all applications. However, one or other AC system can successfully provide desired conditions of temperature and relative humidity. In general, following conclusions have been made for this study.

