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Abstract
Packed liquid desiccant dehumidification systems are regarded as energy-saving and environmentally friendly technologies compared with conventional dehumidification technologies. The packing type plays a significant role in the system performance, but comparative studies of the different types are limited. First, this article investigates the dehumidification performance of liquid desiccant dehumidification with three packing types: corrugated structured, S-shaped polyvinyl chloride, and globular-shaped polypropylene. Then, the operation performance of solar-assisted liquid desiccant air-conditioning systems with different packings is simulated. A commercial building in Hong Kong was chosen as the case study. Results show that each specific packing surface area and structure determines the dehumidification performance by significantly influencing the liquid/air contact area and time. The enthalpy and moisture effectiveness of the corrugated structured packing were found to be 1.69 and 1.60 times those of S-shaped polyvinyl chloride packing, and 1.97 and 1.87 times those of globular-shaped polypropylene packing. The main reason is that the corrugated structured packing has a denser structure with a smaller volume of individual modules, which could provide a large specific surface area, but the dehumidification performance did not increase proportionally with the specific surface area. When the specific surface area increased from 81.8 to 537.3 m2/m3, the enthalpy and moisture effectiveness increased from 0.35 to 0.6 and from 0.38 to 0.61, respectively. Furthermore, the simulation results showed that for the commercial building, the maximum electricity savings percentage for globular-shaped polypropylene packing liquid desiccant air-conditioning systems, S-shaped polyvinyl chloride packing liquid desiccant air-conditioning systems, and corrugated structured packing liquid desiccant air-conditioning systems was 11, 21, and 42%, respectively. For globular-shaped polypropylene packing liquid desiccant air-conditioning systems, a minimum solar collector area of 219m2 was required to avoid consuming more electricity. The authors also found that the dehumidification performance could be enhanced with an increase of desiccant/air mass flow rate ratio and inlet air temperature. This article will help researchers and engineers optimize the design of liquid desiccant air-conditioning systems with different packing types.
Nomenclature
| e | = | void ratio (-) |
| h | = | enthalpy (kJ/kg) |
| I | = | solar irradiance (W/m2) |
| L | = | actual flow length (m) |
| m | = | mass flow rate (kg/s) |
| n | = | number of data (-) |
| S | = | surface area (m2) |
| T | = | temperature (°C) |
| t | = | contact time |
| V | = | volume (m3) |
| v | = | velocity (m/s) |
| ω | = | moisture content (g/kg) |
| ϵma | = | moisture effectiveness (-) |
| ϵha | = | enthalpy effectiveness (-) |
| η | = | specific surface area (m2/m3) |
| ξ | = | desiccant concentration (-) |
Subscripts
| a | = | air |
| amb | = | ambient |
| s | = | solution |
| in | = | inlet |
| out | = | outlet |
| removal | = | moisture removal rate |
Funding
The work described in this article was financially supported by The Hong Kong Polytechnic University through Projects G-YBAM and 1-ZVBK. The authors appreciate the partial financial supports of the Project “Investigation on the dynamic film waves and its effect on the heat and mass transfer of falling film liquid desiccant air-conditioning system” supported by the National Natural Science Foundation of China (Grant No. 51406172).