Abstract
In this paper, a membrane heat pump is proposed and analyzed. Fundamentally, the proposed heat pump consists of an aqueous CaCl2 solution flow separated from a water flow by a vapor-permeable membrane. The low activity of the solution results in a net flux of water vapor across the membrane, which heats the solution stream and cools the water stream. This mechanism upgrades water-side low-temperature heat to solution-side high-temperature heat, creating a "temperature lift." The modeling results show that using two membranes and an air gap instead of a single membrane increases the temperature lift by 185%. The model predicts temperature lifts for the air-gap design of 24, 16, and 6 °C for inlet temperatures of 55, 35, and 15 °C, respectively. Membranes with lower thermal conductivities and higher porosities improve the performance of single-membrane designs while thinner membranes improve the performance of air-gap designs. This device can be used with a solar heating system which already uses concentrated salt solutions for liquid-desiccant cooling.
Original language | American English |
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Pages (from-to) | 113-124 |
Number of pages | 12 |
Journal | Journal of Membrane Science |
Volume | 337 |
Issue number | 1-2 |
DOIs | |
State | Published - 2009 |
NREL Publication Number
- NREL/JA-550-46281
Keywords
- Desiccant
- Energy storage
- Heat and mass transfer modeling
- Heat pump
- Membrane distillation