Experimental Investigation On Single Phase Flowcharacteristics Of Upward Flow In Narrow Annulus Of Concentric Tube Heat Exchanger

Abstract

Abstract : This research was carried out to investigate the single phase flow characteristics of upward flow with/without heat exchange in narrow annulus of concentric tube heat exchanger. In this experiment, direction of flow was upward flow. Hydraulic diameter of the narrow annulus was 4.77 mm. Flows in the inner tube and in narrow annulus were in opposite directions. Working fluid used in this research was water. From this research, it was shown that the flow characteristics of water through the narrow annulus were different from those in conventional pipes. For the flow without heat exchange in narrow annulus, the flow transition from laminar to turbulent flow was initiated earlier than that in normal pipes at a Reynolds number range from 1,533 to 1,880. The flow transition with heat exchange occurred for a Reynolds number in the range of 1,545 to 1,846. Flow friction factor of the upward flow with heat exchange was larger than that without heat exchange at the Reynolds number was lower than 600. The flow friction characteristics in narrow annulus had relations to the water temperature difference at the inlet and outlet of the annulus. Their influences on the flow friction were concentrated in the laminar flow area.

Keywords : Friction factor, Narrow annulus, Reynolds number