Global in-tube flow heat transfer and pressure drop measurements were conducted with Water (Pr = 4.42) and Ethylene Glycol (Pr = 80.5–135.7), in the laminar-transition-turbulent flow regime (Re = 400–39,750) in double pipe heat exchangers fabricated from doubly enhanced tubes. The internal fin height to effective diameter ratio e_f,i/d_eff varied between 0.0289 and 0.0314. The internal groove helix angles varied between 35 and 40°, while the internal fin pitch to height p/e_f,i ratios varied between 3.4 and 5.36. The external fin density was 40 fins per inch (25.4 mm). In comparison to a smooth tube, tube-side (internal) heat transfer enhancements (h_{deff,enhanced}/h_deff,smooth) of up to 6% were measured with Ethylene Glycol in the laminar regime, while tube-side enhancement of up to 34% was measured with water in the turbulent flow regime. The overall heat transfer enhancement (UA_eff)_enhanced/(UA_eff)_smooth based on the overall heat transfer coefficients was measured as 116% with water in the turbulent flow regime. Transition to fully developed rough pipe flow was detected in the enhanced tubes after a critical Reynolds number and the corresponding Prandtl number exponent was estimated to be 0.47. At constant pumping power, the maximum tube-side heat transfer enhancement was 6% with Ethylene Glycol in the laminar regime, and 18% with water in the turbulent regime. On a constant heat duty basis, the maximum reduction in pumping power was 23% with Ethylene Glycol in the laminar regime and 54% with water in the turbulent regime. Although the inner (tube-side) heat transfer enhancement is lower than that measured in conventional micro-fin tubes (inner grooves only), the overall heat transfer enhancement suggests that these tubes will be useful for designing heat exchangers deploying fluids of similar thermal conductivity in the tube and annulus. Typical applications include, but are not limited to, design of marine oil coolers, lubricating oil coolers, and sub-cooled sections of condensers.