12th International Symposium on District Heating and Cooling

The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, EstoniaHEAT LOSS OF FLEXIBLE PLASTIC PIPE SYSTEMS,ANALYSIS AND OPTIMIZATIONEJ.H.M. van der Ven 1 , R.J. van Arendonk 21Thermaflex <strong>International</strong> Holding B.V2 Liandon B.V.ABSTRACTA newly developed, in-house, test rig for measuringheat loss of pipe systems allows the user to analysevarious systems in a short timeframe. This allows quickinsights into heat loss variables and mathematicalanalyses. The effect of alternative compositions ofinsulation and other layers can be evaluated within ashort time span.This already led to improvements of the productionprocess and of the insulating foam.INTRODUCTIONLiandon developed a heat loss testing rig forThermaflex to test their produced flexible pipe systems.Within a short time the pipe system, undergoing a heatloss test, tends towards the controlled temperature inthe sections of the sample, the added power reachesequilibrium and the test results can be collected.Due to the short time required for testing, the results ofalternative production methods are easily available.Due to the short response time the test is a great helpin the search for product and production improvements.The objective of this paper is to present the results ofthe research to the overall heat loss performance of aflexible plastic pipe product, Flexalen 600.The objective of the research is:1 Find correlations between heat loss and otherparameters of the pipe system such as outerdiameter, inner diameter, foam surface and foamstructure. These correlations are determined by themathematical analysis of practical heat lossmeasurements.2 Find possibilities for the improvement of the pipeparameters by analysing the heat loss correlations.NOVELTY AND MAIN CONTRIBUTIONThe actual heat loss of pre-insulated pipe products isdetermined under controlled, similar conditions for anentire diameter range. This range comprises variousouter diameters, various inner diameters and variouscompositions in materials and pipe systems. The timerequired for one single test run varies from half an hourfor a small-sized pipe to about eight hours for thelargest sized diameter.The novelty of the test rig is described in the paper‗Verification of heat loss measurements conducted on(semi) flexible pipe systems‘ [3].The novelty for product improvement is that due to thereduced time required for a test run the effect ofalternative systems can be mathematically analysedand evaluated in a short time. In this way the analysesof alternative production methods has a shortfeedback. Optimization of the product can be effectedin a short time.In the near future the test rig will be used for qualitycontrol of the production process. This test will partlyreplace other currently applied standard tests, such asdensity and cell size measurements.METHOD DESCRIPTIONIn the Flexalen 600 pre-insulated pipe a PB mediumpipe is encapsulated in insulating foam, which isprotected against wear and tear in a corrugated hardcover pipe. The pipe product has a solid bondingbetween the insulation and cover and no bondingbetween the insulation and the medium pipe.According to EN 15632, the European Standard forpre-insulated flexible pipe systems, this pipe system isclassified part 3: Non bonded system with plasticservice pipes. The Flexalen 600 plastic pipe systemdiffers in some areas significantly from most othersystems in this class:1 Physical bonding between foam and outer casing,2 One layer of foam, filling the complete spacebetween service pipe and cover,3 Next to other connection methods the service pipescan also be connected by welding.Annex D of part 1: Classification, general requirementsand test methods give rules for calculation of the heatflow to ambient (heat loss) from measured values,making the heat flow of various parameterscomparable.The heat loss calculations of annex D are based on thethesis of Wallentén as published in Steady-state heat112