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, 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
The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, Estoniapre-insulated pipes. The third paragraph founds thesecond comparison by adding a heat loss value basedon insulation surface.Finally, both flexible and rigid pre-insulated pipes arecompared, resulting in conclusions concerning flexibilityversus heat loss behaviour.barrier (EVOH) is placed in Polyurethane (PUR)insulation foam with a corrugated outer casing of highdensity poly-ethylene (HDPE). This product shows atight connection between the service pipe, the foamand the outer casing. This product therefore cannot bere-used once it is formed.PRE-INSULATED PIPESThis paper compares different types of pre-insulatedpipes and highlights their mutual similarities anddifferences.The flexible pre-insulated pipe systems are; Two different types of Cross linked Polyethylene(PEX) service pipe with Cross linkedPolyethylene (PEX) insulation; One type of Cross linked Polyethylene (PEX)service pipe with Polyurethane (PUR) insulation;One type of Polybutene (PB) service pipe withPolyethylene (PE) insulation.The rigid pre-insulated pipe system is;One type of Steel (ST) service pipe withPolyurethane (PUR) insulation.Firstly all types of pre-insulated pipes are functionallyexplained. Secondly the different kinds of foamproduction methods are described. All types of preinsulatedpipes described are commonly availableproducts used for district heating purposes in Europe.PEX service pipe with PEX insulationA short description of the PEX/PEX systems is given.Figure 1 shows the cross section view of thePEX/PEX/PE pre-insulated pipe. A cross linked Polyethylene(PE-Xa) service pipe with anti-oxygen barrier(EVOH) is placed in a multiple layered low-densitycross linked poly-ethylene (PE-X) insulation foam witha corrugated outer casing of high density Poly-ethylene(HDPE). Because of the cross linking in both servicepipe and foam this product cannot be re-used.Fig. 2. Section view of PEX/PUR pipePB service pipe with PE insulationThe third type of pre-insulated pipe is a flexible PB/PEpipe. Figure 3 shows the cross section view of thePB/PE/PE pre-insulated pipe. A Polybutene (PB)service pipe with anti-oxygen barrier (EVOH) is placedin a low-density poly-ethylene (LDPE) insulation foamwith a corrugated outer casing of high density Polyethylene(HDPE).The PB service pipe makes it possible to use electrofusion welding with a PB coupling. This makes a strongbond. Corrosion is not an issue, because PB is inertwith water.There is no connection between the PB and foam plusouter casing. Therefore it is possible to re-use bothelements in own production. The complete product canbe re-used.Information regarding the use of this product is given in‗‘New economical connection solutions for flexiblepiping systems‘ (Engel) [7].Fig. 3. Section view of the PB/PE pipeSteel service pipe with PUR insulationFig.1. Section view of the PEX/PEX pipePEX service pipe with PUR insulationThis paragraph describes the flexible PEX/PUR preinsulatedpipe. Figure 2 shows the cross section viewof the PEX/PUR/PE pre-insulated pipe. A cross linkedpoly-ethylene (PE-Xa) service pipe with anti-oxygenThe last system described in this paper is the rigidsteel/PUR system. Figure 4 shows the cross sectionview of the ST/PUR/PE pre-insulated pipe. A steel (St)service pipe is placed in Polyurethane (PUR) insulationfoam with a smooth outer casing of high density Polyethylene(HDPE). Because of the steel service pipe,the complete system has to be mechanically welded.Also, because of the combination of steel and water,there is a potential risk of corrosion.120
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produce heat and electricity. Fluct
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production and provide for marginal
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In addition, it can also be observe
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Stockholm district heating system a
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12th International Symposium on District Heating and Cooling

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