In conventional air-conditioning systems, a significant portion of supplied cooling is applied to condensing moisture from the intake air and control humidity in the conditioned space. An alternate approach is to employ a desiccant dehumidification system upstream of an air cooling system, reducing electricity consumption by up to 35%. Regeneration of the diluted desiccant solution can be performed with abundant waste- or solar-heat. Existing desiccant dehumidification systems typically employ direct-contact mass-exchangers, which lead to carry-over losses of expensive and often corrosive desiccant material. In this study, an air-gap membrane distillation desiccant regeneration heat and mass exchanger is modeled analytically. With this technology, carry-over losses can be minimized since the desiccant solution does not come in direct contact with the air stream, and loud, electricity consuming air blowers are not needed. A schematic of the desiccant loop under investigation is presented in Figure 1. Some key results from this study include:
- A segmented coupled heat & mass transfer model was developed for an air-gap membrane distillation regenerator for lithium chloride solutions.
- Parametric stuides were conducted on operational and device geometry parameters. These studies were employed to develop practical engineering design guidelines.
- Rattner, A.S., Nagavarapu, A., Garimella, S., Fuller, T.F., 2011. Modeling of a flat plate membrane- distillation system for liquid desiccant regeneration in air-conditioning applications. International Journal of Heat and Mass Transfer 54 (15-16): 3650–3660. DOI: 1016/j.ijheatmasstransfer.2011.02.064.
This research was supported, in-part, by Pax Scientific, San Rafael, CA.