Influence of the number of stages on the heat source temperature of desiccant wheel dehumidification systems using exergy analysis

• Heat sources temperature (ths) of desiccant wheel systems doesn't always decrease with the increase of SN (stage number).
• The influence of SN on ths is analyzed using exergy destruction and unmatched coefficient.
• For water driven systems, the cases of (mccpw)/(macpa) around 4 and SN being 2–4 are preferred, with ths around 55 °C.
• For refrigerant driven systems, higher SN leads to lower ths, and 4-stage system with COP round 4.5 is preferred.

The influence of the number of stages on the heat source temperature (ths) of desiccant wheel dehumidification systems that adopt water or refrigerant as cooling/heating media is examined in this paper. Under the same working conditions, when the exergy provided by the hot water (Eh) or the power input of the compressor (P) are reduced, ths can also be reduced. To reduce Eh and P, the exergy destruction of the desiccant wheels and heat exchangers should be reduced. The influence of stage number on the exergy destruction of the desiccant wheels is not significant when Ar and Fr are equal to 1. However, stage number has a significant influence on the exergy destruction of the heat exchangers. For water-driven systems, as stage number increases, ths (inlet temperature of the hot water) does not always decrease. The optimal stage number varies according to the water's total mass flow rate. A (mccpw)/(macpa) value of around 4 and the number of stages being 2–4 are preferable, with ths being around 55 °C and tcs being higher than 18 °C. When refrigerant is used, as the number of stage increases, ths (condensing temperature) decreases. In this scenario, a 4-stage system with COP around 4.5 is preferable.