Thermal Analysis of a Helical Tube Once Through Steam Generator of HTGR

Steam Generator (SG) is one of the most important pieces of equipment in High Temperature Gas-cooled Reactor (HTGR). It requires high reliability in a very critical working condition. The thermal analysis of HTGR SG and its uncertainty becomes very important. Large thermal non-uniformity and the resulting high temperature will damage the structure. The SG of HTGR is very different from the boilers of conventional thermal power plant. The heat transfer almost all contributes to convection (counter flow pattern) but not radiation. One dimensional (1D) and two dimensional (2D) codes were developed for the thermal analysis of the SG of HTGR. The 1D code is able to calculate the overall performance. It solves the one dimensional equations for both the shell and tube side. The 2D code is designed to analyze the temperature non-uniformity in the SG. Two dimensional Reynolds-Averaged Navier Stokes equations are solved for the shell side, one dimensional equations are solved for the tube side. The thermal mixing effect in the shell side tube bundle can be included. The thermal deviations caused by secondary side flow rate uncertainty and manufacturing tolerance of tube helical diameter are analyzed. The results show that radiation only contributes to about 0.6 percent of the total thermal power. Secondary flow rate fluctuation of 1% causes an outlet steam temperature variation of 3 °C. Heat transfer tube helical diameter tolerance of 1mm causes an outlet steam temperature deviation of 4 °C.