Tube and shell side coupled thermal analysis of an HTGR helical tube once through steam generator using porous media method

• 2D code of a helical tube OTSG using porous media method was developed.
• The code considers thermal mixing in tube bundles and the coupled heat transfer effects of OTSG.
• This makes the analysis of thermal non-uniformity in large steam generator possible.
• The values of temperature deviations caused by geometrical and thermal–hydraulic deviations are given.

To ensure the safety and efficiency of high temperature gas-cooled reactors, it is critical to understand the temperature non-uniformity of their once through steam generators. Large temperature non-uniformity can cause overheating of the tubes and may require a reduction in output. In order to correctly predict the thermal distribution in the tube bundles of the steam generators, the effect of thermal mixing and coupled heat transfer between the primary and secondary sides should be considered. A two-dimensional computer code based on the porous media method, coupling the tube and shell side of the steam generator was developed. This code was used to predict the thermal performance of the once through steam generator under normal operating conditions. The temperature non-uniformities caused by geometric and thermal–hydraulic deviations were also analyzed. It was found that a 1% change in the flow rate for a given tube line resulted in a temperature variation of 5 °C while shifting a tube line by 1 mm caused a temperature variance of 7 °C. It was also found that a plugged tube caused a large increase in temperature for the remaining tubes in the tube line. Finally, the influence of Peclet number on temperature was analyzed.