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정준철 ( Joon-cheol Jeong ),김우철 ( Woo-cheol Kim ),김경민 ( Kyung Min Kim ),손홍균 ( Hong-kyun Sohn ),김정구 ( Jung-gu Kim ),이수열 ( Soo-yeol Lee ),김희산 ( Heesan Kim ) 한국부식방식학회 2020 Corrosion Science and Technology Vol.19 No.6
Failure analysis on the welded type 304 pipe used for cooling water piping in the district heating primary side was conducted. Inorganic elements and bacteria in the cooling water and in corrosion products were analyzed, and the weldment was inspected by microscopy and a sensitization test. Corrosion damages were observed in the heat-affected zone, on weld defects such as incomplete fusion or excessive penetration caused by improper welding, or/and at the 6 o'clock position along the pipe axial direction. However, the level of concentration of chloride in the cooling water as low as 80 ppm has been reported to be not enough for even a sensitized type 304 steel, meaning that the additional corrosive factor was required for these corrosion damages. The factor leading to these corrosion damages was drawn to be the metabolisms of the types of bacteria, which is proved by the detection of proton, sulfur containing species, biofilms, and both bacteria and corrosion product analyses.
저온 열공급이 지역난방용 열수송관의 수명에 끼치는 영향 연구
김주용(Jooyong Kim),김연수(Yeon Soo Kim),한홍열(Hongyeol Han),정준철(Joon Cheol Jeong) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
District heating is an efficient system that provides heating in large residential areas such as apartments by transporting heat over long distances using District Heating Pipes from heat remaining in the process of generating power from plants or heat produced from dedicated boilers. Currently, domestic district heating systems operate at high temperatures of up to 120 degrees. However, the supply of low temperature heat is gradually increasing overseas due to the interest in energy efficiency and environmental issues is increasing and the supply of unused and renewable energy is increasing. Reduction of supply temperature level is a favorable condition for maintaining long-term-term thermal performance of the insulation and minimizing thermal loads applied to district heating networks, but The large variation in supply temperature due to the use of various heat sources may adversely affect the life of low-cycle fatigue in the district heating networks. In this study, the effects of low temperature heat supply on the district heating networks were analyzed by analyzing the life of the insulation based on the Arrhenius equation and the life of the steel pipe according to the low-cycle fatigue theory.