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, EstoniaTest rigThe test rig is used to determine the absolute heatlosses. The test rig has been designed in compliancewith EN 15632 and the tests are carried out accordingto ISO 8497 and EN 15632.The physical part of the Thermaflex heat lossequipment consists of three sections. The first is thewater cooled compartment in which all the tests areperformed. This compartment is kept at a constant23 °C during each measurement.Heating probes are used as a heat source. Theseheating probes are custom made by preparing a twometer Thermaflex piping segment of all availablediameters. The third part of the heat loss equipment isthe control unit. This unit powers the probes andregulates the temperature and reads out thetemperature and power values.Method of testingDifferent heating probes are used for the testing. Theprobe with the appropriate diameter is inserted in a testsample and inserted in the cooled test section.The heat loss measurement is done by measuring theenergy required to keep the probe at a constanttemperature, by measuring the current at constantvoltage in the heating coils and calculating the powerconsumption. Since the middle/testing coil is exactlyone meter in length the required energy represents theexact heat loss through one meter of piping andinsulation in W/m. For this paper the heat loss isdetermined for multiple probe temperatures.InformationFor more information concerning the test rig andmethod of testing see the paper ‗Verification of heatloss measurements‘ (J.T. van Wijnkoop et Al. [1])Blowing agent analysisAll products that are involved in this paper have beenanalyzed on quantity of blowing agent and type ofblowing agent. The following results were found:The samples of PEX/PEX I and PEX/PEX IIdid not show any amounts of hydrocarbonblowing agents;The PB/PE samples contained a quantity ofhydrocarbon blowing agent over 50 percent;The samples of ST/PUR and PEX/PURproducts contained a mixture of hydrocarbongases. These gases were analyzed. Bothproduct types contained approximately 95% ofblowing agent.Measured samplesThe table below contains all products and dimensionsof outer casing and service pipe that are treated in thispaper.Table 1: Measured productsST/PURDc/DsPEX/PURDc/DsPB/PEDc/DsPEX/PEXIIDc/DsPEX/PEXIDc/Ds-- -- 62A32 -- --90DN25 -- 90A32 90A32 90A32125DN50 -- 125A63 160A63 175A63162DN80 162A110 200A110 200A110 200A110Results of testingAll results have been extracted from measurementscarried out by the Thermaflex testing rig. The newEuropean standard EN 15632 has been used.This standard describes in Annex D a method topresent the results of testing in end-use condition. Thismeans: the product is buried in soil. According AnnexD.3 the following general values are used for thecalculation:Soil coveringo0.8 mThermal transmittance factor of earth-airo0.685 m 2 .K/WThermal conductivity of the soilo1.0 W/(m.K)The heat loss is calculated using the followingformulas:(1) Q (2) Z T flow T surroundingd 42R soil R flow H(3) Z c Z R 0 soil1(4) R soil ln2 soil4Z cd 4WmmmmKAll results are presented in W/m, measured andcalculated at a temperature difference of 60 Kelvin.This temperature difference is derived from innerservice pipe temperature minus surrounding ambientW122