Experimental study of double pipe heat exchanger performance equipped with perforated twisted tape considering various twist ratio

One of the most common passive methods used to improve heat transfer in a circular pipe is twisted tape. Heat transfer increases when twisted tape generated secondary flow in pipe. In this paper, Nusselt number, pressure drop, effectiveness and NTU were investigated experimentally on double pipe heat exchanger with twist ratio variation on perforated twisted tape. Hot water and cold water flow rate were changed 20, 40, 60, 80 and 100 lph. The hole diameter of perforated twisted tape was 8 mm and twist ratio were 4, 6, 8, 10 and 12. The results of this research showed that at Reynolds number of 3488, the different value of Nusselt number had a maximum value of 5.73% from plain inner pipe to twist ratio of 4. When this value was compared to the condition without perforated twisted tape, the bigger pressure drop change occurred in twist ratio of 4. Twist ratio of 4 caused the average value of pressure drop greater 350% from 19.55 Pa to 87.98 Pa. Besides that, twist ratio of 4 had average different value in the effectiveness of 45.22% and NTU of 83.19% from a plain inner pipe.