12th International Symposium on District Heating and Cooling

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The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, EstoniaREFERENCES[1] Z. Shelby and C. Bormann, 6LoWPAN: TheWireless Embedded Internet, November 2009.[2] J. Gustafsson, J. Delsing, and J. van Deventer,―Improved district heating substation efficiency witha new control strategy,‖ Applied Energy, vol. 87,no. 6, pp. 1996–2004, 2010. [Online]. Available:http://www.sciencedirect.com/science/article/-B6V1T-4Y648K9-1/2/-14e2e71a60c1335c8def21f6328bb9a0[3] P. Lauenburg, ―Improved supply of district heat tohydronic space heating systems,‖ Ph.D.dissertation, Dept. och Energy Sciences, LundUniversity, P.O Box 118, SE-22100, Lund,December 2009.[4] K. Yliniemi, Fault detection in district heatingsubstations. Licentiate thesis, Div. of EISLAB, Dep.of Computer Science and Electrical Engineering,Luleå University of Technology, 971 87 Luleå,Sweden: Luleå University of Technology, 2005.[5] K. Yliniemi, ―Individuell mätning av varmvattenförbrukning,‖http://www.svenskfjarrvarme.se/download/4774/Kimmo Yliniemi.pdf, 2007.[6] F. Wernstedt, P. Davidsson, and C. Johansson,―Demand side management in district heatingsystems,‖ in AAMAS ‘07: Proceedings of the 6thinternational joint conference on Autonomousagents and multiagent systems. New York, NY,USA: ACM, 2007, pp. 1–7.[7] J. Kurose and K. Ross, Computer Networking aTop-Down Approach featuring the Internet, 2nd ed.Pearson Education <strong>International</strong>, 2003.[8] G. Mulligan and 6lowPAN Working Group, ―The6lowpan architecture,‖ in Proceedings of the 4thworkshop on Embedded networked sensors, June2007.[9] ―IEEE 802.15.4-2006 standard‖,http://standards.ieee.org/getieee802/802.15.html,April 2010.[10] ―Embedded internet system technology botnia AB,‖http://www.eistec.se/, March 2010.[11] ―Crossbow technology,‖ http://www.xbow.com,March 2010.[12] ―AVR raven,‖ http://www.atmel.com, April 2010.[13] Sensinode,‖ http://www.sensinode.com, April 2010.[14] ―Contiki,‖ http://www.sics.se/contiki/, March 2010.[15] ―Tinyos,‖ http://www.tinyos.net, March 2010.11
The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, EstoniaABSTRACTON THE RADIAL CONTACT PRESSUREOF PARALLEL BURIED PIPES FOR DISTRICT HEATINGI. Weidlich 1 , M. Achmus 21 AGFW, German Heat and Power Association, Research & Development,Stresemannallee 28, 60596 Frankfurt am Main, i.weidlich@agfw.de2 Institute of Soil Mechanics, Foundation Engineering and Waterpower Engineering,Leibniz University of Hannover, Appelstr. 9A, 30167 Hannover, achmus@igbe.uni-hannover.deFor the design and calculation of buried district heatingpipe systems the magnitude of radial contact pressuresacting on the pipes is of importance, since thesepressures affect the friction forces which may bemobilized. For parallel buried pipes, the stressdistribution is generally expected to be different fromthe case of a single pipe. The present investigationcompares radial stresses according to current designdirectives for buried single pipes with numericallycalculated stresses for parallel buried pipes. Thecalculations show a deviation of the radial stressdistributions in particular for the springline area. Theresults are compared with former theoretical investigations,which predicted a reduction of radial contactpressures between the two pipes. This is verified forsmall-diameter pipes. With larger pipe diameters astress increase was identified between the pipes.However, with regard to the average radial pressureonly slight differences between single pipes andparallel buried pipes were found.INTRODUCTIONAs a part of the underground infrastructure of modernsettlements, district heating pipe networks are animportant medium of economic heat transportation. Hotwater is pumped in a flow pipe from the supply stationto the consumer at a high temperature and under highpressure, and the used water is pumped back to thesupply station in a return pipe.For buried district heating pipes the earth pressure onthe pipe, respectively the radial contact pressure, is animportant value for the design, since it affects thefriction forces which may be mobilized. The frictionforces determine the axial deflections of the pipe andthe distribution of normal stresses, which are inducedby the temperature loading of the pipe. According tothe European Standard EN 13941, the normal stresson the pipe coating is calculated for single pipe trenchconditions dependent on the overburden weight of thesoil, the diameter, the pipe weight and an earthpressure coefficient [1]. However, in practice flow andreturn district heating supply pipes are buried side byside in the same trench. Fig. 1 shows a typical situationfor buried district heating pipes according to Floss [2].Fig. 1. Typical trench condition for DH-pipes afterFLOSS [2]The distance between the two pipes depends on therequirements of the laying technique and procedure.For small distances between the two pipes aninteraction between the two pipes is to be expected.PREVIOUS WORKPrevious theoretical investigations were based on thecalculation method developed by Leonhardt, taking intoconsideration the deformation behaviour of pipe andsoil and their influence on each other [3]. Leonhardtintroduced the ―shear resistant beam on elasticbedding‖ theory, in which the backfill above the pipe isconsidered to be a shear resistant beam, which is ableto transfer shear loads, but no bending moments.Using this model it is possible to determine the shearforces activated by the deformation of the ―shearresistant beam‖ caused by different stiffnesses of thepipe and the surrounding soil, which leads to aredistribution of stresses in the soil with correspondingconcentration factors .For practical application in Germany regulationATV A 127 was published employing Leonhardt‘stheory for buried pipes [4]. This regulation can beapplied analogously to all kinds of buried pipes. Thespecial application of regulation ATV A 127 for buriedpreinsulated district heating pipes was first investigatedby Beilke [5].12
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the street the more shallow the sha
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P-1P-4P-9P-7E-5P-14P-8The 1
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to heating costs of 14,5 ct/kWh. Th
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academic access is facilitated as t
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1. CHP system operation in A2. Ther
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is covered by operating HOB. In oth
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produce heat and electricity. Fluct
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To assure that the temperatures mea
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production and provide for marginal
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In addition, it can also be observe
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owner is normally only interested i
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Stockholm district heating system a
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The values presented do of course l
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12th International Symposium on District Heating and Cooling

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