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, Estoniacorresponding heat loss is calculated using the thesisof Wallentén [5], as in (5). i Where:1ln sd 2d 1 2 T probe T casing1 ln id 3d 21 ln c T probe /T casing = Probe / Casing temperature d 1 to d 4 = inner/outer diameters of servicepipe and casingd 4d 3λ s , λi, λ c = heat coefficient of service pipe,insulation and casingGraph 2 represents the comparison on the basis ofthe same outer casing.35.030.0PB/PE PEX/PEX I PEX/PEX II PEX/PUR(5)is expanded by evaluating the heat loss incorrelation to the foam area.Rigid Pre-insulated pipesThe different systems and their correspondingdimensions are represented in Table 1.The rigid pipe product that has been testedaccording to EN 15632 was the ST/PUR product.First the absolute heat loss is displayed, followed by arecalculation towards transport capacity and finally theinsulation area analysis.Absolute heat lossIn this paragraph all absolute heat loss values arecompared. The rigid DN25 pipe service pipe iscompared with a flexible PB/PE-x service pipe with anouter diameter (OD) of 32 mm. DN50 is compared withOD 63 mm and DN80 is compared with OD 110 mm.In Graph 3 the results are displayed for temperaturedifferences of 60 Kelvin.Heat Loss [W/m]25.020.015.010.05.00.090/32 160/63 200/110Diameter casing/service pipe [mm]Graph 2 Relative Heat Loss 32, 63 and 110 mm servicepipe, all with an equal outer casing (dT=60K).Result analysisThe flexible pre-insulated systems, with PE and PE-xfoams, show a variance in heat loss values. Theabsolute differences in the system are caused by thedimensions of the pre-insulated pipes and the quantityand type of blowing agent that has been used. Also therecalculation to the same outer casing diametersshows an advantage for the PE foamed system in PBservice pipes of 32, 63 and 110 millimetres.COMPARISON OF FLEXIBLE PLASTIC PRE-INSULATED PIPES VERSUS A RIGID PIPINGSYSTEMIn this chapter the flexible pre-insulated pipes arecompared with a rigid piping system. Thecomparison is based on diameter. The comparison124Heat Loss [W/m]PB/PE PEX/PEX I PEX/PEX II PEX/PUR ST/PUR35.030.025.020.015.010.05.00.0DN25-PB32 DN50-PB63 DN80-PB110Diameter service pipe [mm]Graph 3 Absolute Heat Loss DN25/PB32, DN50/PB63 andDN80/PB110 mm service pipe (dT = 60 K)).The different test samples show a wide variance in thediameter of the outer casing.The heat loss for ST/PUR 160DN80 is much lowercompared to the heat loss of the 200A100 flexiblepiping products.Even the difference with the PUR based PEX/PURsystem is high (28 percent). For the PE and PE-x foambased products the difference is even higher(42 percent)The heat loss for ST/PUR 90DN25 is more or lesscomparable with the heat loss for PB/PE type 90A32(9 percent). So it seems that for smaller sizes the