Author details

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

• Evaporative cooling systems provide low-cost AC, which can be utilized for various nonhuman applications. However, the cooling potential is the function of ðTinÞdb � ðTinÞwb or ðTinÞdb � ðTinÞdp and, therefore, can be only employed for dry climatic conditions. Due to simple designing and operation, these systems should be considered on top priority for AC

• Instead, desiccant AC systems are found to be an energy-efficient and viable solution for humid climatic conditions and can be operated on low-grade waste heat, biomass, and/or solar thermal energy. As DAC performance is directly related to regeneration temperature, they can provide various supply air conditions, which are required by many non-

• Additionally, hybrid systems based on evaporative cooling and/or desiccant AC can also

this study.

112 Refrigeration

wherever applicable.

human AC applications.

AC Air-conditioning

h Enthalpy [kJ/kg]

HCFCs Hydrochlorofluoro-carbons HFCs Hydro-fluorocarbons

CFCs Chlorofluoro-carbons

COP Coefficient of performance [–] DAC Desiccant air-conditioning DBT Dry-bulb temperature [�C] DEC Direct evaporative cooling GWP Global warming potential

Nomenclature

be established for efficient and sustainable AC.

ASHRAE American society of heating, refrigeration, and AC engineers

Muhammad Sultan<sup>1</sup> \* and Takahiko Miyazaki<sup>2</sup>

\*Address all correspondence to: muhammadsultan@bzu.edu.pk

