# Review of Dew Point Evaporative Cooling Technology for Air Conditioning Applications
## 4 Dew Point Evaporative Coolers Research  
### Experimental Studies of DPICE Performance  
Indirect evaporative coolers consume electricity and water for the production of cooling energy. Their effectiveness depends on the device geometry and quality of water distribution in wet channels. It should be emphasized that dew point devices achieve EER values of 40, which is an advantage compared to typical compressor systems. Nevertheless, scientists are striving to reduce electricity consumption by modifying the geometry of evaporative exchangers. Regarding the method of supplying water to evaporative exchangers,  
Figure 3: Indirect evaporative coolers [(8)]: (**a**) Counter-flow indirect evaporative cooling (IEC). (**b**) Dew point cross-flow IEC. (**c**) Regenerative dew point IEC. (**d**) Cross flow IEC. water distribution systems in the exchangers are developed and improved through the use of special hydrophobic coatings or porous materials, allowing for capillary distribution of water in the cooler. There are some studies focusing on the pressure drop reduction in indirect evaporative coolers. [PERSON] [9] analyzed the performance of different IEC geometry and flow arrangement (counter and parallel water). They examined how different plates' protrusion and pitch affects IEC wet bulb effectiveness and pressure drop. It was found that plates geometry influences both surface wettability and heat transfer rate. The parallel water distribution and flow arrangement causes higher wet bulb effectiveness and lower pressure drop, compared to the counter flow configuration. Some authors focused on the coolers' improvements by modifying water distribution. [PERSON] et al. [10] experimentally investigated a novel dew point cooler equipped with a super-performance hydrophilic material layer, complex structure of the heat exchanger and intermittent water supply system. The device performance was compared to a typical commercial dew point air cooler (M30) under five different climatic conditions in the laboratory. The results show that for the same inlet airflow parameters, the new prototype obtains the lower product air temperature, higher coefficient of performance (COP) values and higher wet-bulb and dew-point effectiveness. [PERSON] et al. [11] conducted an experimental study on a cross-flow indirect evaporative cooler in conditions of condensation of water vapor from the product air. They investigated the device performance for different inlet airflow parameters. During the experiment, parameters like the outlet, primary air temperature, wet bulb-effectiveness, water consumption rate, heat transfer rate, and condensation rate were reported. They found three different cases of condensation in the exchanger: non-condensation, partial condensation, and total condensation (see Figure 3). Different water spray configurations in indirect evaporative coolers were studied by [PERSON] et al. [12]. They proposed a water spraying method which allowed IEC performance improvement to be obtained. [PERSON] et al. [13] analyzed the impact of two different wet surface materials on the DPIEC thermal performance. They compared the exchanger made of polystyrene and nylon fiber with the DPIEC made of aluminum foil. It was found out that nylon fiber filling allows achieving better device performance. There are some older studies about indirect evaporative coolers materials which are worth mentioning. [PERSON] et al. [14] proposed the most suitable material for forming the channels (metals, fibers, ceramics, zeolite, and carbon) of indirect evaporative coolers. They established that material thermal properties have low influence on the heat and mass transfer rates. The possibility of shape formation and its holding ability, compatibility with water-proof coating, contamination risk, and cost are more important in terms of material selection. The obtained results showed that the wick and attained metals are the most adequate structure/material compared to the others.