A new method on fluid-to-fluid scaling for heat transfer in tubes at supercritical pressures

Supercritical fluid heat transfer has great significance for the thermal-hydraulic design and safety performance of the SCWR (Super-Critical Water-cooled Reactor). Experimental studies on heat transfer at prototypical conditions of SCWRs would suffer a huge cost on safety and economy, which strongly limits the research of supercritical water heat transfer. One solution is to adopt model fluid technique which has been applied in thermal and fluids engineering widely. Therefore, finding the equivalent relationship between the experimental data in model fluid and those in prototype fluid becomes a key issue. It means a fluid-to-fluid scaling method is necessary for converting experimental data obtained by using model fluid into the prototype fluid. In the present study, from the perspective of thermo-physical properties similarity and conservation equations similarity, considering the comprehensive influence of the experimental conditions and fluid types, a theoretical study on fluid-to-fluid scaling is performed and most importantly, a new scaling method is proposed. The new scaling method adopts a modification on thermo-physical properties. Several dimensionless numbers are obtained according to the dimensionless momentum and energy governing equations. A new dimensionless number En is derived to present the comprehensive influence of experimental conditions and fluid types. According to the theoretical analysis, an entire set of scaling laws applied for supercritical fluid heat transfer in circular tubes was obtained. Based on the heat transfer data of supercritical R134a, the new scaling method was validated, indicating the feasibility and accuracy of the proposed new scaling method.