The capability to validate integral transient response models is of critical importance for licensing new reactor designs. The Kairos Power testing program has developed a methodology to design scaled experiments that predict the thermal fluid behavior of the Kairos Power Fluoride Salt–Cooled High-Temperature Reactor (KP-FHR). Such experiments will be used as part of the assessment base of evaluation models supporting KP-FHR safety analysis. The Hierarchical Two-Tiered Scaling (H2TS) methodology was selected for Kairos Power scaling efforts that will be applied to integral effects tests (IETs) for system-level testing. In this paper, the scaling methodology is presented for thermal fluid IETs that will model the KP-FHR primary heat transport system under normal operations and transient conditions involving transition to natural circulation. This paper provides a basis for using surrogate fluids for testing that requires the thermal fluid performance of the KP-FHR primary coolant lithium fluoride–beryllium fluoride [2LiF/BeF2 (Flibe)] to be replicated. Kairos Power intends to use heat transfer oil as a surrogate fluid for Flibe in thermal fluid IETs. This paper demonstrates that this class of surrogate fluids is an acceptable substitute for Flibe salt for some types of scaled IETs and that the principal thermal fluid properties can be properly scaled with minor distortions over the range of conditions expected for both normal and off-normal operating conditions of the KP-FHR.