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, EstoniaRESULTS AND CORRELATIONSIt is again the company´s philosophy that paves theway for innovations. One of these innovations is thedevelopment of an in-house device for testing pipesystems, directly from production, cured and degassed.This proved to be a suitable device for productioncontrol, but also for gaining more insights into productparameters.The objective of testing is to improve the knowledge ofthe produced pipe systems in order to optimize:Production methods:Machine data can be adjusted based on test results.Test results may lead to new production methods withnew equipment.Chemical and physical composition of layer material:Knowledge of various composition materials may leadto an improvement of insulating values.Cell structure and gap between insulating foam andmedium pipe:Cell size influences values, test result basedimprovements are possible. The gap is a bad insulator.The quest for a minimal gap started with testing.Improvement and minimization of this gap was anachieved challenge in the testing period.Thermaflex is a lean and mean organisation thatresponds quickly to new insights. Therefore newinsights were applied even before the complete rangeof production testing was performed.For the company, improvements of product andproduction have the highest priority. Although theproduction range is wide, the insight into specific andgeneral parameters increased considerably.The research provides the prominent variables toimprove insulation performance. Practical heat lossdetermination, in combination with analytical studies,results in a clear understanding of heat loss behaviourin single and twin flexible pipe systems during theirentire lifetime.As a result of the tests the manufacturing process isimproved in two steps.The emphasis of the first step was to diminish the cellsize of the foam. This succeeded in a decrease of cellsize by some 20%.DISCUSSION OF PARAMETERSTable 1 summarises the results of measurements andcalculations of tests on Flexalen 600 pipes directly fromproduction. Various diameters are tested andcalculated according to EN 15632 for a surfacetemperature of 10 °C and a common mediumtemperature of 70 °C (Instead of the maximum mediumtemperature of 95 °C).The table indicates the relationships between product,cross sectional area of the foam, foam density, cell sizeof the foam, remaining foaming agent, calculatedthermal conductivity and the calculated heat loss of aburied piping system.The products 50A25, 63A32, 75A40 and 90A50 arenewly developed. These products are not necessarilyDistrict Heating products. However, they are producedusing the same process and have their application inthe connection between the district heating networkand the building or house. It is also applicable in caseof low temperature differences, cooling or in-househeating or cooling.Table 1: Test results of fresh, uncured piping systemsProductFoamsection density cell size agent 50,calc Heat Loss*mm² kg/m³ (mm) % mW/m.K W/m50 A 25 1.473 50,0 0,47 52 39 15,363 A 32 2.313 34,0 0,50 52 38 15,275 A 40 3.044 38,0 0,40 46 44 17,890 A 40 5.105 42,0 0,80 64 51 17,190 A 50 4.398 39,0 0,80 62 55 23,0125 A 63 9.155 39,0 0,88 70 56 22,0160 A 75 15.688 40,3 1,20 81 54 21,0160 A 90 13.745 35,0 1,30 85 61 25,2200 A 110 21.913 45,0 1,60 81 68 27,4*) calculated heat loss of buried system at temperature difference of 60 KIn Graph 1 foam density and cell size are related to thecross sectional surface.In Table 1 the foam density varies from about 35 kg/m³to about 50 kg/m³. Graph 1 shows hardly anyrelationship with the surface of the cross section.Table 1 shows that cell size varies from 0.47 to 1.60mm. Graph 1 shows that cell size is directly related tothe cross sectional surface, however less than 1 to 1.This relationship is influenced by physical productionparameters.The latest step is altering production such that thecontent of anti-radiation agent increases. The initialresults are promising but are not yet conclusive as theanti-radiation agent is also a good heat conductor.115