Study On The Wave-Flow-Spiral Automatic Cleaning Technology And Heat Transfer Performance In Tubes

Inserting the steel spiral wire in the tube is an important means to realize the on-line cleaning the heat transfer enhancement for the heat exchangers. It has the applicable value in the energy saving field in the industry. Based on this previous work on the steel spiral wire insert, it has been proposed that using the combination of the wave flow inlet velocity and the moving steel spiral wire in the heat exchange tubes in this asticle. The wave flow drives the steel spiral wire to move reciprocately in the tube. The evenly online cleaning and the heat transfer enhancement can be improved. The main contents are as follows:(1) The feasibility of the wave flow steel spiral automatic cleaning technology and the corredsponding heat transfer enhancement is analyzed. Based on the necessary and sufficient conditions of the feasible automatic cleaning technology, the working spiral reciprocate displacement exceeds its pitch length. In the axial direction, the force from the flow is balanced with the constrained force by the relatively low elastic coeeficient spring, the softer spring. The calculation method of the entrance velocity at which the working spiral can move resiprocately is derived. The new desgined entrance instructure can provide more force to make the reciprocate displacement exceeds the sprial’s pitch reliably. Furthermore, a new valve control device is developed to change the constant flow pattern to the wave flow pattern.(2) The experiment study on the critical flow velocity at which the cleaning spiral starts vibration and the extention length for the working spiral on axial direction for fuor different parameters has been carried out, by setting up the experimental platform. The results show that different parameters cause different critical flow velocity; and the different flow velocity results in different the axial ddisplacement.It has been confirmed that the cleaning spiral can move reciprocately under the wave flow. The effective cleaning needs the flow velocity greater than the critical flow velocity. The wave amplitude is depended on the softer spring’s elastic coeeficient and the displacement distance. The lower is the softer spring’s elastic coeeficient, the smaller is the wave amplitude.(3) The Numerical simulation and analysis of the cleaning ability and the heat transfer performance of the wave flow spiral technology have been done. The results of the simulation on axial force experienced by the static spiral under a constant inlet flow velocity show that the higher is the velocity, the longer is the length of the apiral and the larger is the axial force. When the velocity increases or the length of the spiral increases, the resistance coefficient for the spiral in the flow decreases. The simulation results on the wave velocity effects on the flow in the tube and on the heat transfer show that when the wave frequence increases to a certern level, the tube outlet static pressure is greater than the inlet static pressure, and the flow backflows. The figure of the comprehensive performance evaluation factor changing with the time shows that wave flow does enhance the heat transfer. The orthogonal experiment table is built to analyze that how the three parameters of the wave flow, the initial speed, the frequncy and the wave amplitude, have influences on the cleaning ability and the heat transfer enhancement for the spiral wire automatic-cleaning technology. For enhancing the heat transfer, the importance sequence of the three parameters is the initial speed, the frequncy and the wave amplitude. When the flow speed changes in 0.1~2m/s, it can enhance the heat transfer. For cleaning ability, the sequence is the wave amplitude, the initial speed and the frequency. Coupled with the softer spring with the different elastic coefficient, the wave flow makes the spiral wire realize the evenly automatic cleaning. To qualitatively analyze the cleaning ability, that the working spiral reciprocate displacement distance exceeds the pitch length under the wave flow is set as a standard. The comprehensive performance evaluation factor is used to quantitatively to analyze the ability of the heat transfer enhancement.