# Analytical Investigation of a Novel System for Combined Dew Point Cooling and Water Recovery
## 2 Materials and Methods
The standard DPC-WR module consists of two dew point coolers that are coupled in two stages (1 st and 2 nd stage). Each dew point cooler is a counter-flow regenerative exchanger, made of alternating series of the primary and secondary channels. The air enters the DPC-WR system in the 1 st stage (1\(i\) in Figure 1). Flowing through the primary channels, the air is cooled without increasing its moisture content. Cooled air that leaves the primary channels (1\(o\) in Figure 1) is divided into two parts. One part is delivered to the secondary channels in the 1 st stage (1\(o\) = 2\(i\) in Figure 1), while the second part is directed to the secondary channels in the 2 nd stage (1\(o\) = 3\(i\) in Figure 1). The water (salt water, wastewater, or any other medium from which water can be recovered) is delivered to the secondary channels in the 1 st stage. Due to the dew point cooling principles, there is a water vapor transfer from the water into the air that flows through the secondary channels in the 1 st stage. The mineral compounds or other contaminants do not evaporate and so they can be removed from the module (discharge liquid). The air that enters the secondary channels in the 2 nd stage (3\(i\) in Figure 1) has a low temperature due to the pre-cooling in the 1 st stage. On the other hand, the air that enters the adjacent primary channels (2\(o\) in Figure 1) is highly humidified due to water evaporation in the 1 st stage. This humidified air contacts with the plate surface of low temperature, which results in water vapor condensation. This condensate will be of similar quality to distilled water, so it can be collected and further processed as needed. In addition to the condensation process, standard dew point cooling is realized in the 2 nd stage, resulting in the cooling of the air that flows through the primary channels. The air that leaves the secondary channels (4\(o\) in Figure 1) is significantly cooled and slightly more humid that the ambient air that enters the DPC-WR system (1\(i\) in Figure 1). In order to realize the dew point cooling in the 2 nd stage, water has to be supplied to the secondary channels. This can be the same water as that supplied to the 1 st stage, or it is possible to further concentrate the discharge liquid from the 1 st stage. To make this happen, the discharge liquid from the 1 st stage would be returned to the secondary channels in the 2 nd stage, where the remaining water will evaporate. In such a case, an additional highly concentrated discharge liquid would be obtained after passing the 2 nd stage, which could be used, e.g., in the recovery of valuable elements or other materials contained therein. The proposed DPC-WR system does not use an external heat source for water evaporation but instead uses the renewable psychometric energy related to the latent heat of water evaporation. The energy is delivered to the DPC-WR system with ambient air, and electric energy is used to transport the air through the following stages. The system can operate with ambient air so that no additional heat source is needed; nevertheless, any kind of low-grade heat with temperatures (32-60 \({}^{\circ}\)C) is expected to enhance the system performance. This type of low-parameter heat can be obtained by using, for example, solar collectors or hybrid photovoltaic-solar systems. As it can be seen, the DPC-WR system allows both air cooling and water recovery. The cooled air is suitable for a variety of applications including air conditioning appliances. The DCP-WR system allows for the recovery of water from seawater or wastewater, among others. The water fed to the system should only be free of solid particles that could clog the channels, so to prevent this, it should be filtered beforehand. The system can also be used to concentrate various types of leachate, e.g., leachate after a membrane process. In such cases, in addition to the cooled air, both recovered water (of similar quality to distilled water) and a concentrated discharge liquid are produced.