Experiments and simulations on flow and heat transfer behavior of Therminol-55 liquid phase heat transfer fluid have been conducted in a ribbed tube with the outer diameter and inner diameter 25.0 and 20.0 mm, pitch and rib height of 4.5 and 1.0 mm. respectively. Experimental results show that the heat transfer and thermal performance of Therminol-55 liquid phase heat transfer fluid in the ribbed tube are considerably improved compared to those of the smooth tube. The Nusselt number increase with the increase of Reynolds number. The increase in heat transfer rate of the ribbed tube has a mean value of 2.24 times. Also, the pressure drop results reveal that the average friction factor of the ribbed tube is in a range of 2.4 and 2.8 times over the smooth tube. Numerical simulations of three-dimensional flow behavior of Therminol-55 liquid phase heat transfer fluid are carried out using three different turbulence models in the ribbed tube. The numerical results show that the heat transfer of ribbed tube is improved because vortices are generated behind ribs, which produce some disruptions to fluid flow and enhance heat transfer compared with smooth tube. The numerical results prove that the ribbed tube can improve heat transfer and fluid flow performances of Therminol liquid phase heat transfer fluid. (C) 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.