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, EstoniaTable 2, Results heat loss equipment for the competitiveproductsHeat loss of competitive products in W/m tested onthe Thermaflex heat loss equipmentSample 40 °C 50 °C 60 °C 70 °C 80 °CSample 1 2.5 4.5 6.4 8.4 10.3Sample 2 6.5 8.8 11.2 13.5 15.9made of metal. Furthermore no heat guards are used.This means the outer ends of the piping system areinsulated and the heat loss is corrected with acalculated value. In the paragraph ―European standardmethod description‖ a more detailed description isgiven. As can be seen in Fig 4 the heat distribution inthis case is not uniform along the test specimen,proving the need for the van Rinsum correction.Sample 320Heat loss results thermaflex heat loss equipmentHeat loss [W/m]15105040 50 60 70 80Temp erature inner service pipe [°C]Competitive samp le 1Competitive samp le 2Fig 4, Thermal image of the sample at institute oneIn contradiction to the Thermaflex test rig, no integratedcomputer controlled power supply system is used. Thepower for the heating probe is first theoreticallycalculated and manually set to this value. For thetemperature measurement thermocouples and a datalogger with computer link are used.Graph 3, Results heat loss equipment for the competitiveproductsTEST INSTITUTE ONEThis institute is specialized in measuring heat loss indifferent types of insulation. The test facility used forthe Flexalen 600 system is specially designed formeasuring the heat loss of (pre-) insulated pipingsystems. This means the facility is designed tomeasure all different types and diameters.Measurement principle institute oneThe measurements are all based on the calculated endapparatus, using the van Rinsum theory as correction,as described in the paragraph European standard [1]method description of this paper.Physical test facilityThe physical part of the test facility is similar to theThermaflex test rig and also consists out of the threeelements: A temperature controlled compartmentwhere the tests are carried out at a constanttemperature of 23 °C. FIW also uses heating probes asa heat source but, since it is not specially designed forthe Flexalen 600 system, they are made to fit allsystems. To ensure the fit of the probes in all differentsystems the diameters are smaller, and for durability254Method of testingThe heating probe is positioned in the centre of the testpipe with positioning foam in three sections of the pipe.On these foam blocks four thermocouples are placed in0, 90, 180 and 270 degrees on the inner surface of theservice pipe. For the outcome of the pipe innertemperature the mean of the four values is used. Tomeasure the temperature on the outside casing of theinsulation, five groups of four thermocouples are usedin the same configuration as the inner pipe. Thedifference being that the thermocouples are placedboth on and in between the corrugations of the casing.The test sample, with the heating probe, is placed inthe conditioned container thereafter the test can bestarted. The power supply of the heater is turned on bysetting the voltage and current of the power unit to afixed value so the electrical power equals thecalculated heat loss.Depending on the diameter of the test sample and thetest temperature the waiting time for the heating of thesample is five to eight hours due to the low, fixed powerinput. After a constant temperature of the outer casingis achieved the actual test cycles start. Each test cycleconsists of a measurement of 30 min in which the outercasing temperature is to be constant. If not the cyclehas to be restarted. In total ten cycles will be performedon each sample. After the test the values are corrected