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, Estoniaradiators in the building is running at 60/45ºC at DOT(represented by narrow black lines in Fig. 8 troughFig. 13).The radiator types tested were: Panel radiator, see Fig. 5 Column radiator, see Fig. 6.* Calculated for new radiators of the same dimensionsmanufactured by Lenhovda radiator factory [3]The radiators are located in traditional officeenvironment in a building built in 1960.Data acquisitionMeasured parameters in the test were: secondarysupply and return temperature (T ss and T sr ), indoortemperature (T i ) and outdoor temperature (T out ).The impact on return temperature for a given supplytemperature was then calculated.In Fig. 7, a screenshot from the logger software isshown. The return temperature is decreased by 5°Cwhen the fan is switched on. This results in anincreased heat output by more than 60 %.fanT sr,0 =39 T sr,Fan =34Fig. 5 Add-on-fan blower mounted on a panel radiator.T ss (ºC)T sr (ºC)T i (ºC)T out (ºC)U fan (V)Fig. 7 Log file from field study.New reduced temperature program will be derived innext section.MODIFYING SPACE HEATING TEMPERATUREPROGRAMFig. 6 Add-on-fan blower mounted on a column radiator.For each radiator the fans have been run at twodifferent rotation speeds. The net electric powerconsumption (P fan ) has been measured. See Table 1 forP fan and the design heat energy output at DOT. Notethat the electric power to the add-on-fan blower isconstant and not dependent on the relative heat output.Table 1 Radiator and add-on-fan blower design.RadiatortypePanelColumnP fan(el)2.7 W1.9 W3.0 W2.2 WQ @ DOT, 60/45ºC(Heat)360 W*430 W*MethodWhen the add-on-fan blower is switched on, the T pr isdecreasing, causing an additional heat output since m sis kept constant. See Fig. 8.Temperature [C]6055504540353025T ssT sr,0T sr,FanOriginal cooling in radiatorAdditional cooling withadd-on-fan-operation200 0.2 0.4 0.6 0.8 1Relative heatloadFig. 8 Increased cooling of secondary system.25