Temperature and velocity sophisticated measurement techniques have been integrated in a novel way for plenum-to-plenum natural circulation thermal hydraulics investigations in a separate-effects dual-channel facility designed with a representative geometry of prismatic modular reactor core. Time-and-frequency domain analysis has been conducted for the time series data obtained to determine the appropriate sampling time and frequency needed to collect data that statistically represents the time-averaged mean value. Preliminary tests have been conducted to examine the validity of implementing these techniques as well to investigate if flow fields inside prismatic core heated channels are affected by other different temperatures core channels. It is worth mentioning that the velocity measurements (i.e., obtained by using hot wire anemometry) were corrected to account for temperature differences between calibration and experimental conditions. Preliminary results reveal that the top section of the heated channel is significantly affected by cooled channel. This implies that naturally-driven flow has a delicate nature and flow fields inside core heated channels are influenced by temperature gradients exist within the prismatic reactor core after loss of flow accidents.