Experimental Investigation of Solar-Driven Hollow Fiber Membrane Liquid Dehumidification System
2. Experimental Set-Up
2.1. Hollow Fiber Membrane Liquid Dehumidification System
2.2. Solar Water Heating System
2.3. Cooling Water System
2.4. Experimental Procedure
- Prepare a 35% LiCl solution with LiCl powder and deionized water;
- Fill the solution tank with 35% LiCl solution to the operating level;
- Turn on the solar collector, adjust the hot water flow rate and run for a period of time, until the hot water temperature meets the regeneration temperature;
- Turn on the air-cooled chiller and set the flow rate and temperature, until the chilled water temperature reaches a predefined value;
- Turn on the dehumidification and regeneration fans and adjust the air flow rate;
- Turn on the solution pump and adjust the solution flow rate to send the desiccant liquid from the solution tank to the dehumidifier;
- The system starts to run, and the experiment can be performed after the system parameters meet the requirements and stability.
3. Data Processing
3.1. Data Recording
3.2. Performance Indices
3.3. Uncertainty Analysis
4. Results and Discussion
4.1. Daily and Hourly Variations in Solar Radiation and Solar Collector Performance
4.2. Hourly Variation in Dehumidification Efficiency and Cooling Capacity
4.3. Hourly Variation in Hot Water Temperature and Regeneration Capacity
4.4. Hourly Variation in the COP of the Dehumidification System and Solar Collector
- The higher/lower hot water temperatures usually correspond to the greater/lower solar radiation. From July to September 2020 in Guilin, China, the maximum daily solar radiation was mainly in the range of 400 W/m2–1000 W/m2, while the maximum daily water temperature was between 50 °C and 80 °C. This means that the solar collectors provide sufficient energy to meet the regeneration demands of the dehumidification system and maintain the system operating continuously.
- The dehumidification capacity, dehumidification efficiency and cooling capacity had the maximal values of 0.23 g/s, 71.3%, and 0.63 kW at 17:30, respectively. The regeneration capacity between 12:00 and 16:00 was larger than the dehumidification capacity, while the desiccant solution concentration in the system kept increasing. Therefore, the dehumidification and cooling capacity increased accordingly. This provides for the performance of the dehumidification system when the solar radiation was lower (15:30–17:50).
- The hot water in the solar collector supplied energy for solution regeneration. The hot water temperature had a maximum value of 55.5 °C at 15:00, which lagged by about 1.5–3.5 h compared to the maximum solar radiation. The maximum regeneration capacity was 0.36 g/s, which was 0.13 g/s larger than the dehumidification capacity. The water temperature was above 48 °C after 12:00. The regeneration capacity was larger than the dehumidification capacity, which means that the regenerator performance met the system circulation demand. However, the regeneration capacity before 10:30 was less than the dehumidification capacity, which means that the dilute solution needed to be auxiliary-heated to maintain the steady operation of the system.
- Because the heat absorption performance of solar collectors was limited, the heat not absorbed dissipated into the ambient, which decreased the COP of solar collectors with the increase in solar radiation. Further, the COP of the dehumidification system and solar collector had the opposite trend to solar radiation. Further, they showed a trend of decrease first, then stabilization for some time and then increased, in which the COP of solar collectors changed more significantly.
- It is efficient and economical to supply regenerative energy to hollow fiber membrane liquid dehumidification systems by solar energy. The heat provided by the solar collectors can satisfy the system regeneration demands and ensure the stable operation of the system. However, the auxiliary heating of the regeneration solution is needed to provide regeneration heat when the solar radiation is lower, such as on cloudy and rainy days. In addition, the solar-driven hollow fiber membrane liquid dehumidification system performs better in regions with larger solar radiation.
Institutional Review Board Statement
Data Availability Statement
Conflicts of Interest
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|Geometry Structures||Values||Unit||Membrane Properties||Values||Unit|
|Module length||280||mm||Outer diameter||1.7||mm|
|Module width||150||mm||Inner diameter||1.5||mm|
|Module height||100||mm||Water contact angle||72 (outer)||°|
|Tube pitch||3.5||mm||Pore size||0.10||μm|
|Packing Fraction||0.251||-||Diffusivity||9 × 10−7||m2/s|
|Number of total fibers||1660||-||Thermal conductivity||0.17||W/(m·K)|
|Dehumidifier Module||Values||Unit||Regenerator Module||Values||Unit|
|Air flow rate||60||m3/h||Air flow rate||60||m3/h|
|Inlet air temperature||26.8–33.7||°C||Inlet air temperature||24.8–28.9||°C|
|Inlet air humidity ratio||19.2–21.5||g/kg||Inlet air humidity ratio||12.8–14.3||g/kg|
|Cooling water flow rate||120||L/h||Hot water flow rate||120||L/h|
|Cooling water temperature||22||°C||Solution flow rate||120||L/h|
|Air velocity||Testo 425||±0.03 m/s||0–20 m/s|
|Water flow rate||LZB-10||±4 L/h||16–160 L/h|
|Solution temperature||PT-100||±0.15 °C||−20–250 °C|
|Air temperature||Siemens QFM 2160||±3.00%||0–100%|
|Relative humidity||Siemens QFM 2160||±1 °C||−35–50 °C|
|Data acquisition||Agilent 34970A||±0.15%||-|
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Liang, C.-H.; Hu, J.-L.; Li, N.-F.; He, Z.-P.; Mo, C.; Zeng, S. Experimental Investigation of Solar-Driven Hollow Fiber Membrane Liquid Dehumidification System. Membranes 2023, 13, 383. https://doi.org/10.3390/membranes13040383
Liang C-H, Hu J-L, Li N-F, He Z-P, Mo C, Zeng S. Experimental Investigation of Solar-Driven Hollow Fiber Membrane Liquid Dehumidification System. Membranes. 2023; 13(4):383. https://doi.org/10.3390/membranes13040383Chicago/Turabian Style
Liang, Cai-Hang, Jia-Li Hu, Nan-Feng Li, Zhi-Peng He, Chou Mo, and Si Zeng. 2023. "Experimental Investigation of Solar-Driven Hollow Fiber Membrane Liquid Dehumidification System" Membranes 13, no. 4: 383. https://doi.org/10.3390/membranes13040383