Evaluation and development of heat transfer model for supercritical water flowing in 2 × 2 rod bundles with spacer grid

Abstract

Supercritical water has excellent heat transfer abilities that allows higher power density and smaller structure in power plants. However, due to the large variation of the fluid thermal-physical properties near pseudo-critical point, heat transfer to supercritical water shows abnormal behavior at certain points. Thus, an accurate prediction model of heat transfer to fluid is very important to the supercritical energy system design. The present studies performed an experiment of 2 × 2 rod bundles with spacer effect at supercritical pressure and more than 5000 data pointes were obtained. A thorough analysis and assessment of the heat transfer models was carried out, to give an insight into the characters of the present heat transfer models for the fully-developed flow and spacer grid influenced flow. The result shows that the Watts-Chou correlation can predict the so-called normal heat transfer regions without spacer grid effects. For the enhancement heat transfer region in consequence of the spacer grid, all the existing models underestimate the heat transfer abilities at supercritical condition. In addition, the enhancement factor of spacer grid design and flow conditions were evaluated. Based on these enhancement factors, a new heat transfer model for space grid effect was developed and the accuracy of heat transfer in the downstream of spacer grid was significantly improved.