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, Estonia1200(1) ST.PUR.PE Ref (2) PB as measured std eng.1000Pipe Length [m]800600400200Fig. 12, Pressure drop steel network with increasedservice pipe flowThere is not a lot of difference between both graphs inFig. 10 and Fig. 12. The reason for this is that thedesign maximum fluid velocity is rather low for steel.This may prove different for the PB network, which isdesigned with smaller diameters in the periphery. SeeFig. 13, which can be compared to Fig. 11.The graph in Fig. 13 indeed shows an increasedpressure drop in the service pipes connecting thehouses, when the flow in those pipes is artificiallyincreased to 100% of the installed power. However, thetotal pressure drop stays within the same limits as doesthe steel network under similar conditions (Fig. 12).016 20 25 32 40 50 63 75 90 110Nominal diameter [mm]Fig. 14, Pipe length histogram Steel and PBAs a result of the use of smaller diameters with PB, thedistribution of pipe lengths generally shifts to the left inthe pipe histogram. As heat loss increases withdiameter (see Fig. 8) this should have a positive effecton the total distribution system heat loss.This shift to the left may be taken one step further,since the wall thickness of the smallest PB mediumpipes currently is chosen a bit larger than the strengthclass (SDR11) requires. This is done for ease ofinstallation. If the thickness of these pipes is chosen nolarger than SDR11, there is a slight additional shift tothe left, see Fig. 15.(1) ST.PUR.PE Ref (2) PB as measured std eng.(3) PB impr. Fresh all SDR1112001000Pipe Length [m]800600400200Fig. 13, Pressure drop PB network with increased servicepipe flowThe result of both design calculations is plotted inFig. 14, steel in red and PB in green.016 20 25 32 40 50 63 75 90 110Nominal diameter [mm]Fig. 15, Pipe length histogram steel, PB and PB SDR11networks315