12th International Symposium on District Heating and Cooling

E-2P-1P-2P-4E-1P-6P-3P-9E-3The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, Estoniainstalled underground between buildings andsubstation as well as in the buildings themselves in theapartment complex. The simulation was performeddaily in view of calculation time.VARIOUS SCHEMES FOR SIMULATION1) Present Scheme<strong>12th</strong> floor11th floor(1)(2)HWSHWRHWRHWRHeating water supplyHeating water returnHot water supplyHot water return10th floor9th floor8th floor7th floor6th floor5th floorHWSHWRHWRHWR(3)Primary pipe lineSecondary pipe line4th floor3rd floor2nd floorDHWSDHWRHWSHWRHWRHWR1st floorfluid temperature, °Cambient temperature, °Cconvection heat transfer coefficient,radiation heat transfer coefficient,internal heat transfer coefficient,insulation thermal conductivity,pipe thermal conductivity,external pipe diameter,external insulation diameter,internal pipe diameter,For accurate simulation, individual flow rate was usedrespectively and differently based on total measuredflow rate and read amount of individual flow meter of518 homes throughout the year. By doing this, the flowrate in the individual pipelines can be determinedaccording to the usage amount of heating water andhot water. This similarly leads to actual flow rate in thepipelines. From this complicated process, the numberof individual flow rate of hot water and heating watercomes to 378,140. Macro which was combined withExcel and Flowmaster was used for a 365 dayanalysis. This process requires 32 hours for 8 buildingsfor only one case.Fig. 8 Pipeline configuration of present schemeThe present scheme is composed of 4 pipelines, two ofwhich are for heating water supply and return and theother two of which are for hot water supply and return.Heating water is supplied to each home and returnedfrom each home and resultantly the flowrate of supplyand return are equal. On the other hand hot water hasa certain amount of recirculation in order to keepsupply water hot. Hence the same amount ofconsumed hot water in each individual home should besupplied to the hot water heat exchanger to guaranteeinstant hot water supply.2) Alternative AAlternative A is a scheme which removes the hot waterpipelines and combines with the heating waterpipelines. Thus there are only two pipelines of supplyand return from substation to each building. Thesesupply and return pipelines have two functions ofheating and hot water supply and return. By reducingfrom 4 to 2 pipelines the heat transfer surface area canbe decreased. However, this scheme hasdisadvantages in summer when the heating watersupply has been closed. If the pipelines should be usedfor the supply of hot water, the resultant water speed inthe pipelines would be very small.HWSHWRHWRHWRHeating water supplyHeating water returnHot water supplyHot water return<strong>12th</strong> floor11th floor10th floor9th floor8th floor7th floor6th floorHWRHWSHWR5th floor4th floor3rd floorPrimary pipe lineDHWSSecondary pipe lineHWS2nd floor1st floorDHWRHWRFig. 9 Pipeline configuration of Alternative A108