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This work presents an experimental study on two different wire coils inserted in a smooth tube using both Newtonian and non-Newtonian fluids to characterize their thermohydraulic behaviour in laminar and transition flow. Dimensionless pitches of the wire coils (based on the empty tube inner diameter) were chosen as p/D= 1 and 2, whereas dimensionless wire diameter was e/D=0.09 for both wire coils. Non-Newtonian tests considered different viscosity types with concentration of 1% of CMC (Carboxyl-methyl-cellulose) solution in water at several temperatures; a wide range of flow conditions has been covered: Reynolds number from 10 to 1200 and Prandtl number from 150 to 1900. Newtonian test were carried out with propylene glycol as working fluid, covering a similar range of Prandtl and Reynolds number as the previous indicated for non-Newtonian fluids. This range of flow conditions was previously measured on the empty smooth tube, and compared with the well-known solutions. Isothermal pressure drop tests and heat transfer experiments under uniform heat flux conditions were done. At low Reynolds numbers, both wire coils behave as a smooth tube but accelerate transition to critical Reynolds numbers down to 400. Maximum augmentations of Fanning friction factor of 3.5 times and of 4.5 times of Nusselt number have been found respect to the smooth tube. AbstractThis work presents an experimental study on two dierent wire coils inserted in a smooth tube using both Newtonian and non-Newtonian uids to characterize their thermohydraulic behaviour in laminar and transitional ow. Dimensionless pitches of the wire coils were chosen as p/D= 1 and 2, whereas dimensionless wire diameter

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