A study of the thermal field surrounding buried district heating pipes.

Title: A study of the thermal field surrounding buried district heating pipes.
Authors: Reeve, Helen E.
Date: 1995
Abstract: Traditional deep buried water and sewer services in northern communities can be prohibitively expensive due to deep frost penetration. Alternative municipal systems can also be uneconomic owing to cost-intensive freeze protection schemes. The integration of district heating (DH) systems with domestic services allows shallow burial of all services in a common trench by using the waste heat from the DH pipes as freeze protection for the nearby municipal lines, thus providing an economically attractive solution. A steady-state 2-dimensional numerical model, based on finite volume principles, was developed as a tool for the design of integrated services systems. The model can predict the thermal field surrounding any number of pipes in any configuration and under a wide variety of ground conditions. Insulation boards can be modeled in any configuration in the soil surrounding the pipes. The main grid system is a rectangular coordinate system with local embedded sub-grids in cylindrical coordinates inserted around each pipe to reflect the radial flow of heat in the vicinity of the pipes. This numerical model was tested and proved to be self-consistent. Predicted temperatures were compared with temperatures taken around experimental pipe loops. Two systems of pipe loops with different diameters were tested, each system having an insulation board placed directly above the pipes. The predicted temperatures agreed well with the experimental temperatures. Anomalies found were explained by settling of the sand and deficiencies in backfilling in the region of the pipes due to the proximity of the insulation board to the pipes. These effects were modeled by inserting a thin air gap around the pipes, resulting in closer agreement between predicted and experimental temperatures. The model was determined to be a valid tool for the design of integrated services systems.
URL: http://hdl.handle.net/10393/10358
CollectionTh├Ęses, 1910 - 2010 // Theses, 1910 - 2010
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