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, EstoniaThe rigid system in this paper; ST/PUR.Method of testingAll heat loss tests are performed on a test rig that hasbeen designed in compliance with EN 15632. Thetests are carried out according to ISO 8497 andEN 15632.Blowing agent analysisAll measured products are checked on type of gas andgas content. The ST/PUR and PEX/PUR productscontain approximately 95 percent of blowing agent.The PB/PE product range has a quantity over 50% ofblowing agent.In the products of PEX/PEX II and PEX/PEX I noHydrocarbon gases were detected.Comparison of flexible pre-insulated pipesA fair comparison is difficult because of differences inouter casing and other dimensions. These conclusionsare therefore only valid for the products that have beentested for this paper.In a buried condition the PB/PE pre-insulated pipeshows for equally dimensioned pipes 90A32 and200A110 the lowest absolute heat loss values for allpre-insulated pipes based on PE or PE-x foam.As mentioned before, the absolute differences in thesystem are caused by the dimensions of the preinsulatedpipes. Recalculation of the same outer casingdiameter shows also an advantage for thePB/PE system in service pipes of 32, 63 and 110 mm.See Graph 5.Heat Loss [W/m]PB/PE PEX/PEX I PEX/PEX II PEX/PUR ST/PUR40.035.030.025.020.015.010.05.00.090/DN25-PB32 160/DN50-PB63Diameter service pipe [mm]200/DN80-PB110Graph 5 Relative Heat Loss 32, 63 and 110 mm servicepipe, all with an equal outer casing and transport capacity(dT = 60 K)The flexible piping system with the PUR insulationfoam on the other hand performs better compared toflexible PE and PE-X insulation foams with equaldimensions.Comparison of flexible piping system versus therigid pre-insulated pipesFlexible pre-insulated pipes have a higher absoluteheat loss compared to rigid pre-insulated pipes.Recalculation to the same transport capacity [kg/s] andthe same outer casing diameter shows that rigid preinsulatedpipes perform better.However the fact that smaller diameters show a smallerheat loss difference between rigid and flexible preinsulatedpipes is interesting.To be comparable in heat loss some dimensions of theflexible piping systems range need to be optimized.However, other advantages of flexible pipe systems, forinstance the potential decrease of service metersbecause of a curved layout-design, can partlycompensate the higher heat loss compared to the rigidsystem (see ‗Heat loss analysis and optimization of aflexible piping system‘ by J. Korsman et al. [2]).ADDENDUMSignificant product improvement of the PB/PE/PE pipesystem has led to a decrease in heat loss [4]. Graph 5is updated with these improvements resulting in thecomparison displayed in Graph 6. The new samplesare displayed under the name of PB/PE II.Heat Loss [W/m]40.035.030.025.020.015.010.0PB/PE PB/PE II PEX/PEX I PEX/PEX IIPEX/PUR5.00.0ST/PUR90/DN25-PB32 160/DN50-PB63Diameter service pipe [mm]200/DN80-PB110Graph 6 Relative Heat Loss 32, 63 and 110 mm servicepipe, all with an equal outer casing and transport capacity(dT = 60 K)126