To address the lack of sufficient validation for the thermodynamic design methods of intermediate fluid vaporizers (IFV) and the inadequacy of research on IFV heat transfer testing technologies, a fully structured IFV test prototype was developed. Additionally, an IFV supercritical vaporization heat transfer performance test system was established using liquid nitrogen as the working medium. Laboratory tests on IFV supercritical heat transfer and flow performance were conducted. The results show that the root mean square deviation of gas-phase temperature measurement points in the experimental system is within 1 ℃, and the deviation for liquid-phase measurement points is within 0.1 ℃, demonstrating good temperature uniformity across the measurement points. The thermal balance error of the working medium on both the hot and cold sides is within 5%, indicating that the prototype and testing system are reasonably designed. For IFV boiling heat transfer, the Cooper criterion is found to be overly optimistic under conditions of low wall superheat. Instead, the Mostinsk criterion is recommended, with an additional 10% design margin. The error between the corrected heat transfer coefficient calculations and the experimental measurements is less than 5%. Under experimental conditions, the measured average condensation heat transfer coefficient is approximately 20% lower than the calculated value based on segmented calculations. The causes of weakened condensation in the intermediate medium are analyzed, and improvement suggestions are proposed from the perspectives of structure optimization, heat transfer design and commissioning and installation. This research provides experimental and validation support for the design of IFV supercritical heat transfer systems and serve as a reference for the engineering design of IFV products.