An investigation of the thermal and hydraulic performance of a novel triple-helical tube heat exchanger, the THTHE, is presented. The novel design is a modified design of a DHTHE created by adding a third tube to a DHTHE tube. The third passage is expected to enhance the thermal performance of the DHTHE as a result of an increase in the temperature gradient between the hot and cold fluids. The effects of the coil radius, inner annulus spacing, water inlet temperature, direction of flow arrangement, and Dean number were explored. Five test samples with different coil radii of 150 mm, 125 mm, and 90 mm and different inner annulus spacings of 6.2 mm, 9 mm, and 12 mm were examined. The test samples were designed, fabricated, and tested to demonstrate the influence of design parameters on the thermal and hydraulic performance of the triple-helical tube heat exchanger. The experimental runs were conducted on the hot water side with the water inlet temperature T