A numerical model that predicts the helium mass required for propellant tank pressurization during propellant outflow was developed. The model has the feature of including the effects of the internal hardware of the propellant tank such as baffles, pressurant storage tanks, and other instrumentation. It used a finite volume method that divides the ullage and tank wall one-dimensionally along the propellant tank axis. A series of cryogenic propellant drainage tests were carried out to verify the developed numerical model. The required amount of helium mass predicted by the model showed very good agreement with test data within an accuracy of 2:27% under the operating conditions. The developed model was applied to the pressurization system of Korea Sounding Rocket-III, and the results were compared with the flight-test data. The comparison results showed that the developed model was satisfactory for the prediction of the required helium mass during flight. Additionally, a parametric study was performed to test the sensitivity of the developed model, and the results showed that the heat transfer coefficient between the ullage and the tank wall was the key factor in the accuracy of the model.

The temperature of cryogenic propellant in the propellant tank increases during flight due to heat input from surroundings. The propellant which temperature rises up over the required condition of turbo-pump remains as unusable propellant at the end of flight. In this paper the estimation method of the heat transfer coefficient at the upper layer of cryogenic propellant was presented. The heat transfer mode at the propellant upper layer was considered as conduction. Temperature distributions near propellant surface obtained from heat transfer coefficient were compared with test data to show the possibility of this method.초 록 추진제탱크 내의 극저온 추진제는 발사체의 비행 과정동안 주변으로부터 에너지를 흡수하여 온도가 상승한다. 비행 종료 시점에 있어 터보펌프 입구 요구조건 이상으로 온도가 상승된 추진제는 사용할 수 없는 잔류추진제로 남게 된다. 본 논문에서는 극저온 추진제 상층부의 온도변화를 살펴보기 위하여 추진제 표면 근처에서의 열전달계수를 구해보고자 하였다. 추진제 상층부의 열전달을 전도로 단순화하 여 열전달계수를 예측하는 방법을 제시하였다. 이를 통해 얻어진 추진제 상층부의 온도를 시험데이터 와 비교하여 열전달계수 예측 방법의 적용 가능성을 확인하였다.

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