An experimental investigation of the heat transfer and pressure drop characteristics of a circular tube fitted with rotating turbine-type swirl generators

Heat transfer enhancement and flow behaviors in horizontal circular tubes installed with five rotating turbine-type swirl generators (RTSG) are presented experimentally. This type of RTSG is an innovative design that has not been seen in the previous research. Deionized water is used as a working fluid and flows through the test section under turbulent flow conditions. A smooth, stainless steel tube 9.2 mm in ID, 0.4 mm in thickness, and 2.3 m in length is used as the test section. RTSG made from aluminum, with a twisted angle of 60 and a length of 2 cm, are located at 0.46 m equally distant along the test section. When fluid flows through the RTSG, continuously free rotations are observed, and swirl flow after RTSG is created. A DC power supply is used to supply heat load to the test section. Compared with a common, plain tube (without rotating swirl devices), the experimental results indicate that the local heat transfer coefficient of the tube with RTSG inserts is higher than that of the common, plain tube, and they increase when the working fluid flows through the RTSG. Similarly, the wall temperatures of the tube with RTSG inserts are lower than those of the common tube. However, the pressure drop of the tube fitted with RTSG is significantly greater than that of the common, plain tube. (C) 2012 Elsevier Inc. All rights reserved.