Mapping of Heat Distribution Networks at Sawmills and Modeling of their Heat Losses and Pressure Drops

Abstract

Through years of research and new investments in boilers and dryers at sawmills, the heat distribution networks (HDNs) have been neglected. Very little literature on HDNs at sawmills is available. More extensive research has been performed on district heating networks. Due to its similarities to an HDN, some of the performed research is of relevance, but a more thorough analysis of HDNs is required. Through interviews with employees at sawmills, the current situation of Swedish sawmills has been mapped. The sawmills are different in some ways, but they also have important similarities. In particular, both investigated sawmills lack of proper documentation of their HDNs. There is also evidence of outdated sections of the pipe systems, which indicates potential for improvements in performance of the HDN. A mathematical model has been developed with available information from the interviews and analysis of relevant literature as a background. The model is used to illustrate improvement potential for an HDN by comparing current heat losses and pressure drops of an actual HDN with estimates using Matlab as a simulation tool. The Matlab programme is flexible with many user defined parameters and is capable of handling many variations in the investigated HDN. The simulation results show a theoretical potential for the investigated sawmill at Mörlunda to decrease their heat losses from circa 970kW to 91kW. The model is very sensitive and requires detailed input data to make accurate estimates. However, the simulations illustrate several useful trends for factors affecting the performance of an HDN at a sawmill.