Effect of air velocity, temperature, and relative humidity on drying kinetics of rubberwood
Kiln drying of rubberwood lumbers is a complex transport phenomenon for realistic modeling and simulation. To decouple this complexity, researchers usually divide their research into two parts. The first one is single-lumber drying kinetics to describe how wood lumber responds to its surface conditi...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2020-10-01
|
| Series: | Heliyon |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2405844020319940 |
| _version_ | 1828783258873102336 |
|---|---|
| author | Malisa Chanpet Nirattisai Rakmak Nirundorn Matan Chairat Siripatana |
| author_facet | Malisa Chanpet Nirattisai Rakmak Nirundorn Matan Chairat Siripatana |
| author_sort | Malisa Chanpet |
| collection | DOAJ |
| description | Kiln drying of rubberwood lumbers is a complex transport phenomenon for realistic modeling and simulation. To decouple this complexity, researchers usually divide their research into two parts. The first one is single-lumber drying kinetics to describe how wood lumber responds to its surface conditions. Then they combine this drying kinetics with a lumped transport model or dispersion model or computational fluid dynamics. The mathematical models are then solved numerically to predict the industrial kiln drying behaviors. This work focuses on the drying kinetics of stacked rubberwood lumbers using hot air at different air velocity (0.5, 1.5, 2.5, 3.5, 4.0 m/s), relative humidity (6–67% relative humidity (RH)) and temperature (60–100 °C). The drying kinetics followed the conventional drying theory. However, the two drying periods, namely constant and falling rate (CRP and FRP), were not distinct. As the air velocity increased, the transition from CRP to FRP is faster. The middle of the transition period (at critical moisture content, CMC) moves closer to the fiber saturation point (FSP). The overall mass transfer coefficients in the falling rate period for stacked rubberwood drying were lower than those predicted by the Ananias correlation. Hence, a modified formula was proposed, representing the overall moisture transfer coefficients as a function of air velocity, temperature, relative humidity, and lumbers thickness for the range of variables under investigation satisfactorily. In general, the drying rate and the overall moisture transfer coefficient increased with increasing air velocity, drying temperature, and decreasing RH. Relative humidity directly affects the driving force of moisture transfer rate because higher RH is associated with higher equilibrium moisture content. A lumped parameter model for kiln drying was also developed. After being integrated with the estimated mass transfer coefficient, the model can predict the moisture profiles in lab-scale kiln drying satisfactory, although the model needs more validation data. These kinetic parameters and correlation for stacked rubberwood drying can be used in more complex models and process optimization in future research. |
| first_indexed | 2024-12-11T18:02:07Z |
| format | Article |
| id | doaj.art-856b4afc680b4721bdd6a1f9adc2ecc1 |
| institution | Directory Open Access Journal |
| issn | 2405-8440 |
| language | English |
| last_indexed | 2024-12-11T18:02:07Z |
| publishDate | 2020-10-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Heliyon |
| spelling | doaj.art-856b4afc680b4721bdd6a1f9adc2ecc12022-12-22T00:55:51ZengElsevierHeliyon2405-84402020-10-01610e05151Effect of air velocity, temperature, and relative humidity on drying kinetics of rubberwoodMalisa Chanpet0Nirattisai Rakmak1Nirundorn Matan2Chairat Siripatana3School of Engineering and Technology, Walailak University, 80161, Nakhon Si Thammarat, ThailandSchool of Engineering and Technology, Walailak University, 80161, Nakhon Si Thammarat, Thailand; Biomass and Oil-Palm Excellence Center, Walailak University, 80161, Nakhon Si Thammarat, ThailandSchool of Engineering and Technology, Walailak University, 80161, Nakhon Si Thammarat, ThailandSchool of Engineering and Technology, Walailak University, 80161, Nakhon Si Thammarat, Thailand; Biomass and Oil-Palm Excellence Center, Walailak University, 80161, Nakhon Si Thammarat, Thailand; Corresponding author.Kiln drying of rubberwood lumbers is a complex transport phenomenon for realistic modeling and simulation. To decouple this complexity, researchers usually divide their research into two parts. The first one is single-lumber drying kinetics to describe how wood lumber responds to its surface conditions. Then they combine this drying kinetics with a lumped transport model or dispersion model or computational fluid dynamics. The mathematical models are then solved numerically to predict the industrial kiln drying behaviors. This work focuses on the drying kinetics of stacked rubberwood lumbers using hot air at different air velocity (0.5, 1.5, 2.5, 3.5, 4.0 m/s), relative humidity (6–67% relative humidity (RH)) and temperature (60–100 °C). The drying kinetics followed the conventional drying theory. However, the two drying periods, namely constant and falling rate (CRP and FRP), were not distinct. As the air velocity increased, the transition from CRP to FRP is faster. The middle of the transition period (at critical moisture content, CMC) moves closer to the fiber saturation point (FSP). The overall mass transfer coefficients in the falling rate period for stacked rubberwood drying were lower than those predicted by the Ananias correlation. Hence, a modified formula was proposed, representing the overall moisture transfer coefficients as a function of air velocity, temperature, relative humidity, and lumbers thickness for the range of variables under investigation satisfactorily. In general, the drying rate and the overall moisture transfer coefficient increased with increasing air velocity, drying temperature, and decreasing RH. Relative humidity directly affects the driving force of moisture transfer rate because higher RH is associated with higher equilibrium moisture content. A lumped parameter model for kiln drying was also developed. After being integrated with the estimated mass transfer coefficient, the model can predict the moisture profiles in lab-scale kiln drying satisfactory, although the model needs more validation data. These kinetic parameters and correlation for stacked rubberwood drying can be used in more complex models and process optimization in future research.http://www.sciencedirect.com/science/article/pii/S2405844020319940Mechanical engineeringThermodynamicsKiln dryingDrying kineticsEnergy cost savingMass transfer coefficient |
| spellingShingle | Malisa Chanpet Nirattisai Rakmak Nirundorn Matan Chairat Siripatana Effect of air velocity, temperature, and relative humidity on drying kinetics of rubberwood Heliyon Mechanical engineering Thermodynamics Kiln drying Drying kinetics Energy cost saving Mass transfer coefficient |
| title | Effect of air velocity, temperature, and relative humidity on drying kinetics of rubberwood |
| title_full | Effect of air velocity, temperature, and relative humidity on drying kinetics of rubberwood |
| title_fullStr | Effect of air velocity, temperature, and relative humidity on drying kinetics of rubberwood |
| title_full_unstemmed | Effect of air velocity, temperature, and relative humidity on drying kinetics of rubberwood |
| title_short | Effect of air velocity, temperature, and relative humidity on drying kinetics of rubberwood |
| title_sort | effect of air velocity temperature and relative humidity on drying kinetics of rubberwood |
| topic | Mechanical engineering Thermodynamics Kiln drying Drying kinetics Energy cost saving Mass transfer coefficient |
| url | http://www.sciencedirect.com/science/article/pii/S2405844020319940 |
| work_keys_str_mv | AT malisachanpet effectofairvelocitytemperatureandrelativehumidityondryingkineticsofrubberwood AT nirattisairakmak effectofairvelocitytemperatureandrelativehumidityondryingkineticsofrubberwood AT nirundornmatan effectofairvelocitytemperatureandrelativehumidityondryingkineticsofrubberwood AT chairatsiripatana effectofairvelocitytemperatureandrelativehumidityondryingkineticsofrubberwood |