A method to restrain natural convection in ground flow field test of spacecraft
- Paper number
IAC-06-A2.4.04
- Author
Mr. Jun Jiang, Beijing Institute of Spacecraft System Engineering, China
- Coauthor
Mr. Qiang Liu, China Academy of Space Technology (CAST), China
- Year
2006
- Abstract
Natural convection in sealed module of manned spacecraft navigating in space can be ignored in micro-gravity environment. To avoid centralization of carbon dioxide exhaled by cosmonauts and control thermal environment of devices within the spacecraft, a forced convection system must be set up in addition to the other conventional thermal control methods. Thermal design engineer needs to know the characteristics of heat and mass transfer in micro-gravity environment by ground tests. However, in ground test, the devices such as wind fan will release the disperse heat, and hence lead to natural convection. Specially, in many areas of sealed module the air flow rate is lower, therefore the influences of natural convection on the flow field should not be ignored, otherwise, the flow field can not be simulated precisely. Generally, cooled packages covering the surface of whole module are often used to restrain natural convection in ground test, and a complicated temperature control system is installed to assure air temperature uniformity within the module. This method was used in the flow test of the Alpha space station, in which four modules were combined and modeled by a 1:1 model. To restrain natural, many thermal control equipments were used to assure air temperature uniformity, but the systems are quite complex and need a considerable investment. In this paper, a local temperature control method is introduced to improve temperature uniformity by controlling temperature level of high heat sources. Theoretical analysis reveals that the method can restrain natural convection effectively. When air temperature difference meets the condition of Gr/(Re*Re)<0.1, the influences of natural convection on the flow field can be ignored. In addition, a simplified model is presented to analyze the errors resulted from omitting the influences of natural convection. The anlytic results show that the errors of the flow field are less than 0.18% and errors of heat transfer coefficient are less than 0.4% when the local temperature difference is limited within 2.3K. These are verified by a detailed numerical simulation. The method and model presented in this paper are simple and feasible to restrain and analyze the influence of natural convection in the ground test of spacecraft.
Keywords: restrain natural convection ground flow field test manned spacecraft error analysis
- Abstract document
- Manuscript document
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