Study on Dehumidification Performance of a Multi-Stage Internal Cooling Solid Desiccant Adsorption Packed Bed
Abstract
:1. Introduction
2. System Description
3. Construction of the Testing Rig
3.1. Testing Rig
3.2. Test Methods and Conditions
4. Analysis and Discussion
4.1. Dehumidification Capacity
4.2. Dehumidification Efficiency
4.3. Water Content
4.3.1. Water Content of the Whole Dehumidification Device
4.3.2. Water Content of Each Stage
4.4. Moisture Ratio
4.4.1. Moisture Ratio of the Whole Dehumidification Device
4.4.2. The Moisture Ratio of Each Stage
4.5. The Temperature of Solid Desiccant
4.5.1. The Average Temperature of the Whole Dehumidification Device
4.5.2. The Average Temperature of Each Stage
4.6. Temperature Difference between the Inlet and Outlet Air
5. Dehumidification Calculation Model
5.1. Mass Balance
- The water content of the desiccant in the axial gradient can be neglected.
- The solid desiccant and the exit air of the dehumidification module are mass equilibrium.
- Isothermal adsorption is achieved in the dehumidification process.
- The average volume of air is used to simulate the mass transfer process.
5.2. Energy Balance
6. Conclusions
- The internal cooling adsorption bed could improve the dehumidification efficiency effectively. It was more obvious in low temperature and low humidity conditions than in hot and humid. It could also be obtained with the use of free-cooling [25], refrigerators with new thermoacoustic technology [26], or the use of “Smart-windows” [27], for reducing the thermal required load.
- Water temperature has a great influence on the dehumidification effect. The lower the temperature of water, the more the dehumidification efficiency improves. For the ICSPB operating under the inlet air temperature of 20 °C and relative humidity of 55%, the dehumidification efficiency could be improved by 59.69% and 39.32% with cold water of 14 °C and 18 °C supplying to the heat exchangers respectively, for this purpose, geothermal heat pumps [28] could be used.
- Under the condition of low temperature and humidity, the utilization ratio of the solid desiccant with internal cooling was 1.2–1.5 times that of non-internal cooling test conditions in the effective dehumidification time.
- The outlet air temperature could be reduced by 14 °C maximally compared with that without internal cooling when the ICSPB operated at the inlet air temperature of 34 °C, relative humidity of 68% and water temperature of 28 °C. So that the sensible heat load could be reduced, and special heat recovery units [29] could be used.
- In the multi-stage dehumidification bed, the first stage adsorption bed played the most important role.
Author Contributions
Funding
Conflicts of Interest
Nomenclature
A | cross-sectional area, m2; |
C | perimeter of air flow passage, m; |
c | specific heat, kJ/kg K; |
d | humidity ratio, g water/kg dry air; |
G | mass flux, kg/m2 s; |
K1 | regression constant depending on the inlet air temperature; |
K2 | regression constant depending on the inlet air temperature; |
h | heat transfer coefficient, kW/m2 K; |
hm | mass transfer coefficient, kg/m2 s; |
HA | adsorption heat, kJ/kg; |
L | thickness of solid desiccant, m; |
m | mass of the desiccant, kg; |
MR | moisture ratio; |
Re | Reynolds number; |
T | temperature, °C; |
u | velocity of the air, m/s; |
w | water content ratio, kg water/kg dry silica; |
τ | time, h; |
ρ | density, kg/m3; |
η | dehumidification efficiency, %; |
ε | fractional void volume; |
β | constant; |
Subscript | |
0 | initial condition; |
a | air; |
e | final condition; |
in | inlet; |
out | outlet; |
s | solid desiccant; |
w | water |
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Name | Type | Main Parameters |
---|---|---|
Environmental cabinet | TEMI1000 | Temperature range: −20–90 °C; accuracy: ±0.01 °C; relative humidity range: 0–85%; accuracy: ±0.1% |
Multi-channel temperature and humidity monitor | PC-2WS | Accuracy: ±2% in humidity, ±0.2 °C in temperature |
Multi-channel temperature logger | AT4364 | Sensor: K-type; accuracy: ± (value × 0.5% + 1) °C |
Water chiller | - | Refrigerating capacity: 3 HP; power: 2250 W; accuracy: ±2 °C |
Rotameter | LZS-15 | Range: 100 to 1000 L/h; accuracy: ±5% |
Booster pump | CRS25-10 | Volume Flowrate: 80 L/h; lift: 10 m; power: 200 W |
Self-priming pump | 1.5ZDK-20 | Volume Flowrate: 15 m3/h; lift: 20 m; suction: 8 m; power: 750 W |
Fan | ASB20-4-1M | Mass flow rate: 486 m3/h; power: 190 W |
Anemometer | TESTO 405-V1 | Range: 0 to 10 m/s; accuracy: 0.01 m/s |
Electronic balance | JCS-A/C | Range: 0 to 3 kg; accuracy: 0.01 g |
Electronic scale | TCS-01 | Range: 75 kg; accuracy: 2 g |
Drying oven | DHG-9145A | Temperature range: 10–300 °C; accuracy: ±1.0 °C |
Test No. | Water Temperature (°C) | Inlet Air Temperature (°C) | Inlet Air Humidity (%) | Humidity Capacity (g/kg) | Volume Flow of the Cold Water (L/h) | Wind Speed (m/s) |
---|---|---|---|---|---|---|
1 | no water | 20 | 55 | 8.00 | — | 0.35 |
2 | 14 | 20 | 55 | 8.00 | 800 | 0.35 |
3 | 18 | 20 | 55 | 8.00 | 800 | 0.35 |
4 | 18 | 20 | 80 | 11.70 | 800 | 0.35 |
5 | no water | 34 | 68 | 23.04 | — | 0.35 |
6 | 28 | 34 | 68 | 23.04 | 800 | 0.35 |
7 | 32 | 34 | 68 | 23.04 | 800 | 0.35 |
8 | 32 | 34 | 80 | 27.28 | 800 | 0.35 |
Test No. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
---|---|---|---|---|---|---|---|---|
Water content ratio (kg/kg) | 0.140 | 0.295 | 0.224 | 0.316 | 0.258 | 0.305 | 0.270 | 0.307 |
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Share and Cite
Yang, W.; Ren, J.; Lin, Z.; Wang, Z.; Zhao, X. Study on Dehumidification Performance of a Multi-Stage Internal Cooling Solid Desiccant Adsorption Packed Bed. Energies 2018, 11, 3038. https://doi.org/10.3390/en11113038
Yang W, Ren J, Lin Z, Wang Z, Zhao X. Study on Dehumidification Performance of a Multi-Stage Internal Cooling Solid Desiccant Adsorption Packed Bed. Energies. 2018; 11(11):3038. https://doi.org/10.3390/en11113038
Chicago/Turabian StyleYang, Wansheng, Jiayun Ren, Zhongqi Lin, Zhangyuan Wang, and Xudong Zhao. 2018. "Study on Dehumidification Performance of a Multi-Stage Internal Cooling Solid Desiccant Adsorption Packed Bed" Energies 11, no. 11: 3038. https://doi.org/10.3390/en11113038