Experimental Investigation of Heat Transfer Enhancement Mechanism for Self-rotating Cleaning Twisted-tape Tube

摘要

The turbulent characteristics of the flow in a tube with self-rotating cleaning plastic twisted tape have been investigated experimentally by using Laser Doppler Velocimeter. The results show the flow in the tube is spiral motion following the self-rotating plastic twisted tape. Axial velocity is higher in the annular area near the tube wall than that of the central area of the tube, and the axial turbulence is stronger than that of the smooth tube; the tangential velocity increases as the radius increase, and the tangential turbulence is very high. According to the turbulent characteristics of the flow, convective heat transfer enhancement mechanism is analyzed initially for the self-rotating twisted-tape tube. It is found that the spiral motion of the fluid formed by forced eddy and parallel axial flow and the increase of axial velocity in the annular area near the wall tube will enhance the vibration of boundary and the mixture between the boundary fluid flow and central fluid flow, also make the boundary's thickness thin. The results will provide experimental base for the further theory research of heat transfer enhancement mechanism inside the tube with self-rotating cleaning plastic twisted tape.