| In the power plant, the heat-exchangers abrade in the tail flue of the boilers. The abrasion comes from ash of coal's combustion, which results in a great deal of the safety problem and the economy loss. Engineering practice witnesses that the heat-exchangers used of helix finned tubes instead of that used of smooth tubes is an effective method lightening abrasion. This research' purpose is the flow characteristic when two-phase smoke with ash pass between the fins of helix finned tube bundle, and the reason of lightening abrasion.In order to research that flow characteristics, gas-solid two-phase flow is a subject that should be studied. An single microcosmic granule's flow state is studied in this research. Between the fins a small ash gets gravitation, resistance Magnus force and Saffman force. Magnus force and Saffman force result that the granule keep away from the pins, which can reduce the opportunity of the granule and fins contact and is theory base of lightening abrasion.Besides the theory study, experiment study is an study method of gas-solid two-phase flow characteristics. This experiment' instrument is particle dynamic analyzer (PDA), which is advanced laser instrument made of Dantec company in Danmark. PDA' principle is Doppler theory, which can measure simultaneity radius, speed and concentration. PDA has good precision and space distinguish efficiency without demarcation, which is the absolute measure method without contact.In order to study the gas-solid flow characteristics between the fins, the cold smoke circulating test unit with PDA system is set up in the laboratory. The granule radius, main and tangent mean speed and granule concentration are measured on 5 representational plane between the pins.According to the analysis of data from experiment, the gist can be found in the theory analysis to explain the experiment phenomenon, this can explain theabrasion reason of helix finned tube bundle. It will be the theory base in thepractise application. |
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