A thermal vacuum chamber is used to perform the thermal vacuum tests of a satellite system and its components. A cryogenic blower is a core component of the gaseous nitrogen (GN2) closed loop thermal control system for thermal vacuum chambers. The goal of this research is to predict and verify the performance of a cryogenic blower. Design requirements of a blower are a flow rate of 150 CFM, a differential pressure of more than 50 kPa, and an ability to withstand hot and cryogenic temperatures. If the test conditions are considerably different from design conditions with a large Reynolds number difference, the prediction of performance using fan’s law is no longer valid. A CFD simulation and Reynolds number correction method should be considered to predict the performance. This paper describes a cryogenic blower performance test, a CFD analysis and a comparison of results such as between a performance test on a closed loop thermal control system and a CFD simulation, with Reynolds number similarity and Reynolds number correction, to verify the Reynolds number difference.
The performance test of a cryogenic blower at ambient and operating conditions was executed. The performance prediction at operating conditions using the similarity conversion, a CFD simulation and Reynolds number correction was conducted to compare and verify the performance of a cryogenic blower. The summary of this study is as follows :
The cryogenic blower performance of the design conditions can be predicted by fan law from the performance test results under standard atmospheric conditions. However, predicted results cannot be valid in case of large Reynolds number differences between test and design conditions. The large relative error is generated mainly because the general similarity equation is not considered by the characteristics of the fluid, such as a friction loss. Therefore, when predicting cryogenic blower performance, the similarity of Reynolds number must be ensured.
The Reynolds number correction method of PTC 10 is the way to predict the performance of the design conditions. Since the relative error in the operational range is below 3%, it is possible to obtain valid results. However, the Reynolds number correction method should be applied to the allowable range, such as specific ratio and magnitude of mechanical Reynolds number. When predicting the turbo machinery performance such as a cryogenic blower and a compressor, the Reynolds number difference between the test condition and the design condition should be considered.
According to the CFD simulation results for the cryogenic blower, the predicted performance in a hot and cryogenic temperature is satisfied the required differential pressure. The CFD model was validated, compared with the test results of the ambient condition and operating conditions in the closed loop thermal control system. It will be used to predict the performance of a variety of shapes for a cryogenic blower.