Temperature variations in DH networks. Study performed with respect to networks in Denmark, Finland, Germany, the Netherlands and Sweden

摘要

In directly buried networks for district heating, the forces that result from temperature variations - operational or at special events - have great influence on the life length of the networks. An important question with respect to mechanical designs is the interpretation of recorded variations of temperature into a basis for this design. In this study, statistics and estimations from a great number of networks in five countries have been collected and investigated. In addition to this, recordings from four networks have been used for calculation of the equivalent number of full cycles with the so called Rain flow cycle count method. Our conclusion is that, under normal circumstances, the equivalent number of full cycles of the range of 100-120 deg C may be described as ''less than 10 due to operational variations'' ''less than 100 due to special events'' over a period of 30 years. The actual drop of temperature that a part of a network is subjected to when taken out of operation because of repair work seems to vary considerably from one company to the other