12th International Symposium on District Heating and Cooling

P-1P-4P-9P-7E-5P-14P-8The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, EstoniaFor hot water, this scheme is effective in heatexchange because the heat exchanger acts for theconsumed hot water only and can avoid extrarecirculation pipelines. But it has the drawback ofsupplying cold water or non heated water whenintermittently using hot water.3) Alternative BHWSHWRPrimary pipe lineDHWSDHWRE-1Heating water supplyHeating water returnSecondary pipe lineHWSHWR<strong>12th</strong> floor11th floor10th floor9th floor8th floor7th floor6th floor5th floor4th floor3rd floor2nd floor1st floorFig. 10 Pipeline configuration of Alternative BAlternative B is the same as Alternative A in the pointof unifying the heating water and hot water pipelines.But it is different in the point of the individual hot waterheat exchanger being installed in each home amongthe heating water pipelines. This scheme is said toresemble the pipelines installed in the apartments ofEuropean countries.HWSE-10E-11E-15E-14E-12E-13E-7E-8E-9E-6E-5E-4HWR5) Use of PEX PIPESPEX is being used in western countries as districtheating pipes for low temperature service fromrenewable resource application. For this reason PEXcan be used as secondary pipelines which normally areunder service of low temperature.VALIDATION OF SIMULATION RESULTTo validate the simulation result, the measurementvalue was compared with the prediction result by thepresent simulation method. The measured value ofDecember 2009 was used for heat loss referencevalue. As seen in Table.1 the simulation result fairlyagreed with the measured data. And the simulationmethod can be used without much modification. Formore accurate prediction it needs slightly moresupplementation in the numerical modelling of heattransfer phenomena of outer pipe surface andenvironment.Table1 Comparison of measured and predictedvalues[unit: MWh]Measurement heat Hot waterHeat loss rate9.44%loss 20.2 11.2supply 264.7 67.8Simulation heat Hot waterHeat loss rate9.90%loss 17.0 14.29supply 252.6 63.534) Alternative CHWS Heating water supplyHWR Heating water returnHWRHot water supplyHWR Hot water return<strong>12th</strong> floor11th floor10th floor9th floor8th floor7th floor6th floorHWRHWRHWSHWRSIMULATION RESULTFig. 12 shows typical heat supply and heat loss for the24 hours of 11.11.2009. The simulation result of eachscheme is shown from Fig. 13 to Fig. 17. Each graphshows similar patterns and the heat loss comparison ofeach scheme is summarized in Table 3.5th floor4th floor3rd floor2nd floorPrimary pipe lineDHWSSecondary pipe lineHWS1st floorDHWRHWRFig. 11 Pipeline configuration of Alternative CAlternative C is a variation of Alternative A to make upfor the defect of cold water supply when intermittentlysupplying hot water. In this alternative the recirculationpipelines are equipped in the buildings.Fig. 12 Hourly heat supply and heat loss of 11.11.2009109