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, EstoniaCOMPARISON OF COMPETITIVE (SEMI) FLEXIBLE PIPING SYSTEMS BY MEANSOF HEAT LOSS MEASUREMENTI.M. Smits 1 , J. Korsman 1 , J.T. van Wijnkoop 1 and E.J.H.M. van der Ven 21Liandon B.V.2 Thermaflex <strong>International</strong> Holding B.V.ABSTRACTDifferent types of pre-insulated pipes are tested ontheir heat loss values. Three flexible pipes and a rigidpipe are tested. The different heat loss values arecompared not only on absolute heat loss, but also ontheir performance relative to the insulation surface. Theheat loss values are measured according to EN 15632and published as ―declared values‖. The declaredvalues are calculated according to EN 15632 AnnexD1-D3.The flexible pre-insulated systems, with PE and PE-Xfoams, show a variance of up to 5 W/m in the heat lossvalues. These absolute differences in the system arecaused by the outer casing dimensions of the preinsulatedpipes. Recalculation to the same outer casingdiameters shows a slight advantage for the PE systemin service pipes of 32 and 63 millimetresThe flexible piping system with the PUR insulationfoam on the other hand performs better compared toequally dimensioned flexible PE and PE-X insulationfoams.Flexible pre-insulated pipes have a higher heat losscompared to rigid pre-insulated pipes. Recalculation tothe same transport capacity [kg/s] and the same outercasing diameter also shows that rigid pre-insulatedpipes perform better. However the fact that smallerdiameters show a smaller heat loss difference betweenrigid and flexible pre-insulated pipes is interesting.INTRODUCTION & OBJECTIVEThe objective of this research is to compare differenttypes of competitive (flexible and rigid) pre-insulatedpipes on their differences in heat loss values. Thecomparison is based on an overall heat lossmeasurement under similar conditions. Overall heatloss is determined for different samples of pre-insulatedpipes, by using newly developed heat loss testingequipment as described in ‗Verification of heat lossmeasurements‘ by J.T. van Wijnkoop et al. [1]. Theheat loss data of these flexible pipes will be comparedwith practical measurement on a rigid pre-insulatedpipe.119Notice that this study does not compare entire districtheating systems. For system comparisons see „Heatloss analysis and optimization of a flexible pipingsystem‟ by J. Korsman et al. [2].NOVELTY AND MAIN CONTRIBUTIONWhere most studies only focus on one product thisstudy compares different types of flexible pre-insulatedpipes on their practical heat loss values and gives anexplanation of the practical heat loss values. It alsocompares flexible pipes with rigid pre-insulated pipeson an equal basis.BRIEF METHOD DESCRIPTIONFirst a brief description of different types of flexible preinsulatedpipes and a rigid pre-insulated pipe is given.This chapter highlights the differences and similarities.The different types of foam for plastic pre-insulatedpipes are described in a separate paragraph.Secondly, the method of testing is briefly addressed.Thirdly, the different types of flexible pre-insulatedpipes are tested on their absolute heat loss just afterproduction.Since heat loss of pre-insulated pipes can increaseover time due to degassing of the insulation foam, agas analysis is performed on all test samples.In the second paragraph the absolute heat loss valuesof the different types of flexible pre-insulated pipes arecompared on the basis of service pipe dimensions. Thethird paragraph defines a comparison on the basis ofinsulation surface and service pipe dimension.In the fourth paragraph the comparison of flexiblepre-insulated pipes versus a rigid pre-insulated pipe isdescribed. The comparison in the third and fourthparagraph is based on ―declared values‖. The definedconditions are: (1) thermal conductivity of soil: 1.0W/m.K, (2) thermal transmittance factor of earth toambient air: 0.0685 m 2 .k/W and (3) soil covering:0.8 m.In the first paragraph absolute heat loss values arecompared on the basis of corresponding service pipedimensions. The second paragraph gives a comparisonbased on equal transport capacity for flexible and rigid