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, Estoniatemperature (70 degrees Celsius minus 10 degreesCelsius).Table 2: Results according to EN 15632 at a temperaturedifference of 60 Kelvin.Product Type Heat LossBuriedsystemW/mΛ System(W/m.K)ST/PUR 90DN25 11.6 0.042ST/PUR 160DN80 16.0 0.033PEX/PUR 162A110 22.3 0.049PB/PE 63A32 15.2 0.038PB/PE 90A32 12.8 0.044PB/PE 125A63 22.0 0.056PB/PE 200A110 27.4 0.068PEX/PE II 90A32 16.6 0.057PEX/PE II 160A63 17.6 0.055PEX/PE II 200A110 31.1 0.073PEX/PE I 140A32 12.5 0.057PEX/PE I 175A63 17.6 0.059PEX/PE I 200A110 28.8 0.051COMPARISON OF FLEXIBLE PLASTICPRE-INSULATED PIPESThis chapter compares the flexible pre-insulated pipes.The comparison is based on three diametersrepresenting the entire diameter range for plastic preinsulatedpipes.The comparison is expanded by evaluating the heatloss in correlation to the outer casing diameter (resp.the foam area).In Table 1 the flexible plastic pre-insulated pipes aredefined. These are the products PEX/PEX, PEX/PURand PB/PE.For more information concerning the PB/PE preinsulatedpipes see „Heat loss of flexible plastic pipesystems, analysis and optimization‟ by van der Ven etal. [4].The 32, 63 and 110 millimetre service pipesFirst the absolute heat loss is displayed, followed bythe insulation area analysis.Absolute heat lossIn this paragraph all absolute heat loss values arecompared for the 32, 63 and 110 millimetre servicepipes.In Graph 1 the results are displayed for temperaturedifference of 60 Kelvin.Heat Loss [W/m]35.030.025.020.015.010.05.00.0PB/PE PEX/PEX I PEX/PEX II PEX/PUR90/32 160/63 200/110Diameter service pipe [mm]Graph 1 Absolute Heat Loss 32, 63 and 110 mm servicepipe (dT = 60 K)The products based on PE or PE-x foam show higherheat losses for the 110 mm service pipe than thesystem based on PUR foam. The difference isapproximately 20 percent.The different test samples show a wide variance in thediameter of the outer casing.Therefore, only the results for the 32 millimetre servicepipe are comparable for PB/PE 90A32 and PEX/PEX II90A32. For the 110 mm service pipe, a comparison canbe made between the PEX/PUR 200A110, PB/PE200A110, PEX/PEX II 200A110 and PEX/PEX I200A110.Another difference in this comparison is the use of aPB pipe or a PE-x pipe. PB and PE-x have differentthermal conductivities (0.19 W/m.K versus 0.40W/m.K). However, this effect is already corrected byusing the Wallentén equation [5], as shown in (1).Insulation areaTo compare the different kinds of flexible pre-insulatedpipes on their performance, all outer diameters arealtered towards 90, 160 and 200 millimetres. The123