Coiled-Tube Gas Heaters (CTGHs) are shell-and-tube heat exchangers that incorporate small coiled tubes with a gas (supercritical CO2 or air) flowing radially through the tube bundle cooling the liquid inside the tubes. This design reduces the overall volume of the tube bundle while maximizing the heat transfer surface area, improves the effectiveness of the heater, and allows for large pressure differentials between the two heat transfer fluids. CTGHs are optimal for use as the primary heat exchanger in small modular reactors, such as SFRs and FHRs. In a previous paper, a design and optimization code, called THEEM, was developed to model CTGHs using non-dimensional heat transfer and fluid data. In order to experimentally validate this code, the Coiled-tube Air-heater Separate Effects Test (CASET) experiment was built. CASET consists of a single CTGH sub-bundle in an acrylic vessel that uses room temperature air to cool hot water in the bundle. The initial validation experiments indicate that THEEM can accurately predict the temperatures and heat exchanger effectiveness, but the pressure drop calculations may need to be reevaluated. CASET was also used to measure the distribution of the air flowing through the bundle, which could then be used to improve THEEM in the future. Finally, the Wilson plot method was used to develop heat transfer convection correlations for both the shell-side and tube-side fluids, which could have applications to other coiled tube heat exchangers.