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, EstoniaVERIFICATION OF HEAT LOSS MEASUREMENTSJ.T. van Wijnkoop 1 , E. van der Ven 21Liandon B.V, 2 Thermaflex <strong>International</strong> Holding B.V.ABSTRACTHeat loss tests are performed on different samples ofthe Thermaflex Flexalen 600 series and oneST-PUR-PE sample at the Thermaflex heatlossequipment and two German test facilities. At thesefacilities two different testing methods are used. Thesemethods are both described in the European standard[1] but show significant differences in the results. In thispaper the different methods of testing are described.Furthermore the Thermaflex heat loss equipment isverified with the test institute that uses the same testingmethod.INTRODUCTIONLast year Liandon developed a test-rig for Thermaflexto measure heat loss of insulated plastic pipingsystems. With this test-rig it is possible for Thermaflexto test the in house produced pre-insulated, semiflexible pipes in various diameters.To verify the test results, the results of the Thermaflexheat loss equipment are compared with the test resultsof two acknowledged institutions. For this paper twoGerman institutions are chosen, since they bothmeasure in compliance with the European standard EN15632 [1], however with different methods described inthis paper. In order to give an appropriate comparison,knowledge of the testing methods of both systems isrequired. In this paper the testing methods of all threesystems is covered, together with the comparison ofthe test-results. Since the testing facilities use twodifferent methods described in the standard, thecomparison refers to the test methods and the testresults.The objective of this paper is to compare the testmethods and test results of the two different testinstitutes with the Thermaflex heat loss equipment andverify the outcome. As in “Heat loss of flexible plasticpipe systems analysis and optimization”(E. Van der Ven et Al.) [4] and “Performance of preinsulated pipes” (I. Smits et Al.) [6] these results areused to compare different sizes of the Flexalen 600series and competitive products.conditions, as defined by the European standard [1].The ability to conduct equally based heat lossmeasurement result in an objective comparison ofdifferent types of (semi) flexible piping systems,providing the opportunity to highlight strengths andweaknesses of (competitive) piping systems.Furthermore, in contradiction to most heat loss tests,the test time in the Thermaflex test-rig is only a fewhours so the test can be performed during production.This provides the opportunity to optimize the productionprocess real-time and measure the heat loss of theproduct several times during a production run. Thisguarantees the quality of the produced batch.In addition the handling of the equipment is made easy,so no specially trained staff is needed for testing,making it possibly for operators to carry out the tests.EUROPEAN STANDARD METHOD DESCRIPTIONThe European standard EN 15632 [1] allows twodifferent methods of heat loss or thermal conductiontesting. These methods both state the same on internalheating of the service pipe but vary on the method ofcompensation for heat loss in axial direction.The first method, the guarded end method, states noaxial heat transfer is permitted. This should beaccomplished by the use of end guards, an extra pairof heating elements at both ends of the service pipe asshown in Fig 1. By heating the ends separately to thesame temperature as the middle test section no heattransfer will take place to the ends of the service pipe.In this case a theoretical compensation is not requiredsince the test section only has losses in radial direction.This method is used in the Thermaflex heat lossequipment and at one of the institutes.NOVELTY AND MAIN CONTRIBUTIONThe Thermaflex test-rig is newly developed for theresearch of heat loss of pre-insulated pipes. Thenovelty of this system is its ability to measure theoverall heat loss of different samples under similar250Fig 1, Longitudinal section guarded end heating probeThe second method described for compensating foraxial heat loss is the calibrated or calculated endmethod. The calibrated end method will not be coveredin this paper since it is not used in our comparisons.