Effect of Substrate Conductivity on the Transient Thermal Transport of Hygroscopic Droplets during Vapor Absorption
In all kinds of liquid desiccant dehumidification systems, the temperature increase of the desiccant solution due to the effect of absorptive heating is one of the main reasons of performance deterioration. In this study, we look into the thermal effects during vapor absorption into single hygroscop...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2020-02-01
|
| Series: | Micromachines |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2072-666X/11/2/193 |
| _version_ | 1818542874010058752 |
|---|---|
| author | Zhenying Wang Daniel Orejon Khellil Sefiane Yasuyuki Takata |
| author_facet | Zhenying Wang Daniel Orejon Khellil Sefiane Yasuyuki Takata |
| author_sort | Zhenying Wang |
| collection | DOAJ |
| description | In all kinds of liquid desiccant dehumidification systems, the temperature increase of the desiccant solution due to the effect of absorptive heating is one of the main reasons of performance deterioration. In this study, we look into the thermal effects during vapor absorption into single hygroscopic liquid desiccant droplets. Specifically, the effect of substrate conductivity on the transient heat and mass transfer process is analyzed in detail. The relative strength of the thermal effect and the solutal effect on the rate of vapor absorption is investigated and compared to the thermal effect by evaporative cooling taking place in pure water droplets. In the case of liquid desiccants, results indicate that the high thermal conductivity of copper substrates ensures more efficient heat removal, and the temperature at the droplet surface decreases more rapidly than that on Polytetrafluoroethylene (PTFE) substrates. As a result, the initial rate of vapor absorption on copper substrates slightly outweighs that on PTFE substrates. Further analysis by decomposing the vapor pressure difference indicates that the variation of vapor pressure caused by the temperature change during vapor absorption is much weaker than that induced by the concentration change. The conclusions demonstrate that a simplified isothermal model can be applied to capture the main mechanisms during vapor absorption into hygroscopic droplets even though it is evidenced to be unreliable for droplet evaporation. |
| first_indexed | 2024-12-11T22:27:52Z |
| format | Article |
| id | doaj.art-c01c079d009a47c98d2249a271fd0c15 |
| institution | Directory Open Access Journal |
| issn | 2072-666X |
| language | English |
| last_indexed | 2024-12-11T22:27:52Z |
| publishDate | 2020-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Micromachines |
| spelling | doaj.art-c01c079d009a47c98d2249a271fd0c152022-12-22T00:48:13ZengMDPI AGMicromachines2072-666X2020-02-0111219310.3390/mi11020193mi11020193Effect of Substrate Conductivity on the Transient Thermal Transport of Hygroscopic Droplets during Vapor AbsorptionZhenying Wang0Daniel Orejon1Khellil Sefiane2Yasuyuki Takata3International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, JapanInternational Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, JapanInternational Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, JapanInternational Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, JapanIn all kinds of liquid desiccant dehumidification systems, the temperature increase of the desiccant solution due to the effect of absorptive heating is one of the main reasons of performance deterioration. In this study, we look into the thermal effects during vapor absorption into single hygroscopic liquid desiccant droplets. Specifically, the effect of substrate conductivity on the transient heat and mass transfer process is analyzed in detail. The relative strength of the thermal effect and the solutal effect on the rate of vapor absorption is investigated and compared to the thermal effect by evaporative cooling taking place in pure water droplets. In the case of liquid desiccants, results indicate that the high thermal conductivity of copper substrates ensures more efficient heat removal, and the temperature at the droplet surface decreases more rapidly than that on Polytetrafluoroethylene (PTFE) substrates. As a result, the initial rate of vapor absorption on copper substrates slightly outweighs that on PTFE substrates. Further analysis by decomposing the vapor pressure difference indicates that the variation of vapor pressure caused by the temperature change during vapor absorption is much weaker than that induced by the concentration change. The conclusions demonstrate that a simplified isothermal model can be applied to capture the main mechanisms during vapor absorption into hygroscopic droplets even though it is evidenced to be unreliable for droplet evaporation.https://www.mdpi.com/2072-666X/11/2/193thermal effectssubstrate conductivityabsorptive heatingevaporative coolingvapor pressure difference |
| spellingShingle | Zhenying Wang Daniel Orejon Khellil Sefiane Yasuyuki Takata Effect of Substrate Conductivity on the Transient Thermal Transport of Hygroscopic Droplets during Vapor Absorption Micromachines thermal effects substrate conductivity absorptive heating evaporative cooling vapor pressure difference |
| title | Effect of Substrate Conductivity on the Transient Thermal Transport of Hygroscopic Droplets during Vapor Absorption |
| title_full | Effect of Substrate Conductivity on the Transient Thermal Transport of Hygroscopic Droplets during Vapor Absorption |
| title_fullStr | Effect of Substrate Conductivity on the Transient Thermal Transport of Hygroscopic Droplets during Vapor Absorption |
| title_full_unstemmed | Effect of Substrate Conductivity on the Transient Thermal Transport of Hygroscopic Droplets during Vapor Absorption |
| title_short | Effect of Substrate Conductivity on the Transient Thermal Transport of Hygroscopic Droplets during Vapor Absorption |
| title_sort | effect of substrate conductivity on the transient thermal transport of hygroscopic droplets during vapor absorption |
| topic | thermal effects substrate conductivity absorptive heating evaporative cooling vapor pressure difference |
| url | https://www.mdpi.com/2072-666X/11/2/193 |
| work_keys_str_mv | AT zhenyingwang effectofsubstrateconductivityonthetransientthermaltransportofhygroscopicdropletsduringvaporabsorption AT danielorejon effectofsubstrateconductivityonthetransientthermaltransportofhygroscopicdropletsduringvaporabsorption AT khellilsefiane effectofsubstrateconductivityonthetransientthermaltransportofhygroscopicdropletsduringvaporabsorption AT yasuyukitakata effectofsubstrateconductivityonthetransientthermaltransportofhygroscopicdropletsduringvaporabsorption |