Methods Of Enhancing Heat Transfer Of Passive Safety System Exchanger

The passive residual heat removal heat exchanger is an important device in the passive safety system, which charged with the important task of removing core decay heat during the accident operating conditions to ensure the safety of reactor. Studying the heat transfer characteristics of heat exchanger helps us to improve safety and reliability of the entire system. In this paper, we have done some experimental research on pool boiling heat transfer characteristics of three kinds of tube bundles, including smooth tube bundle, pin-fin tube bundle and porous tube bundle, as well as condensation heat transfer characteristics of copper smooth tube bundle and low-fin tube bundle, finally, we carried out the analysis. Main contents and conclusions of this article are as follows:We designed and built the experiment bench, debugged the whole system, and completed a series of improvements to the experimental device.The pool boiling heat transfer of smooth tube bundle, pin-fin tube bundle and porous tube bundle were studied, and a large number of photographs of boiling phenomenon were taken. We compared the total heat transfer power and the boiling heat transfer coefficient of tube bundles with their single tubes respectively, the same work was done among the different tube bundles. At last, we found that the total heat transfer powers of three kinds of tube bundles are as much as ten times of their single tubes roughly. The boiling heat transfer coefficient of the smooth tube bundle and porous tube bundle are higher than their single tubes respectively, except the pin-fin tube bundle. The total heat transfer power of pin-fin tube bundle is higher than smooth tube bundle, but the heat transfer coefficient is smaller. The total heat transfer power and the heat transfer coefficient of porous tube bundle are higher than smooth tube bundle. Completed the partial immersion heat transfer experiments of porous tube bundle and we found that when the water level of the boiling water tank drops, the total heat transfer power did not immediately reduce, but when the level dropped to a certain level, the total heat transfer power began to decrease rapidly.At last, condensation heat transfer experiments of the copper smooth tube bundle and the low-fin tube bundle were finished. The results show that the condensation heat transfer coefficient of the low-fin tube bundle is much higher than the copper smooth tube bundle. The condensation heat transfer coefficient of the low-fin tube bundle rapidly decreases and then slow down, compared to smooth tube bundle, the changes in the condensation heat transfer coefficient is much smaller.