# Analysis of Hydrogen Filling of 175 Liter Tank for Large-Sized Hydrogen Vehicle
## 4 Conclusions  
In this study, CGH\({}_{2}\) behavior in a hydrogen tank was investigated numerically during its filling. To validate the numerical approach, numerical models for the adaptation of gas and turbulence models were investigated. Numerical parametric studies of hydrogen filling behavior were conducted to estimate the CGH\({}_{2}\) behavior in a hydrogen tank under different ambient temperatures and initial state of charge (SOC) pressure conditions during filling for the 175 L tank. The main conclusions of this study are as follows:  
* From a numerical validation study for the comparison of experimental results of Zheng et al. [6] with a Type III hydrogen tank, gas model and turbulence model were validated. The Redlich-Kwong gas model and realizable k-epsilon and RSM models was found to be a suitable gas model and turbulence model, respectively. However, the realizable k-epsilon model was found to be a suitable turbulence model considering the accuracy, convergence, and computational cost for the calculation of the CGH\({}_{2}\) filling phenomenon.
* The average times to charge hydrogen up to 70 MPa were 600, 495, 191, and 148 s for 5, 10, 20, and 35 MPa, respectively, indicating that the average charging time of hydrogen was from 600 s to 148 s for 7% to 50% SOC for the 175 L tank. The time when the pressure reached 70 MPa was influenced by the ambient temperature and SOC condition. For the 5 MPa SOC condition, the time to fully charge up to 70 MPa had a time difference of 29 s between ambient temperature conditions of 313 K and 243 K. Less time difference (17 s) was observed to fully charge hydrogen for a large SOC condition of 35 MPa compared with the 5 MPa case.
* With the different SOC conditions, the maximum temperature rise of the hydrogen tank when the pressure reached 70 MPa decreased as the initial SOC pressure increased because the temperature rise occurred rapidly for the relatively smaller SOC condition. The temperature rises of hydrogen reached 313-353 K at an ambient temperature of 243-313 K for the 5 MPa SOC condition. However, at 35 MPa of SOC, the temperature of hydrogen reached 298-349 K at an ambient temperature of 243-313 K.
* A relationship between the initial SOC pressure condition and the maximum temperature rise of hydrogen gas showed that the maximum temperature rise increased with decreasing ambient temperature, and the rise increased with decreasing SOC.
* The numerical approach for the applications presented in this paper could also be widely applied to design hydrogen facilities and systems. The present model will be compared with a three-dimensional model in a future study.  
Conceptualization: M.-S.K. and S.-W.C.; Methodology: H.-K.J. and J.-H.R.; Validation: M.-S.K. and S.-W.C.; Investigation: K.-W.L. and J.-H.R.; Data Curation: M.-S.K. and S.-W.C.; Writing, Review and Editing--Original Draft Preparation: M.-S.K.; Supervision, M.-S.K. All authors have read and agreed to the published version of the manuscript.  
This research is funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea) for the Materials/Parts Technology Development Program (20017575, Development of Applicability Evaluation Technology for Cryogenic Insulation Material and Storage Vessel considering Operating Condition of Hydrogen Commercial Vehicle).  
Not applicable.  
This work was supported in part by the Materials/Parts Technology Development Program (20017575, Development of Applicability Evaluation Technology for Cryogenic Insulation Material and Storage Vessel considering Operating Condition of Hydrogen Commercial Vehicle) funded By the Ministry of Trade, Industry & Energy (MOTIE, Korea), and in part by the Railroad Technology Research Program through the Ministry of Land, Infrastructure and Transport of Korean Government under Grant 22 RTRP-C146008-05.  
The authors declare no conflict of interest.