The <str<strong>on</strong>g>12th</str<strong>on</strong>g> <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>Symposium</str<strong>on</strong>g> <strong>on</strong> <strong>District</strong> <strong>Heating</strong> <strong>and</strong> <strong>Cooling</strong>,September 5 th to September 7 th , 2010, Tallinn, Est<strong>on</strong>iaTab. 3 Main technical parameters for design the systemMax cooling dem<strong>and</strong>19,2 MWAmbient temp. calc.27 o CSimultaneous factor 0,85<strong>Cooling</strong> stati<strong>on</strong> capacity18 MWAnnual average cooling c<strong>on</strong>sumpti<strong>on</strong> 21600 MWhSupply water temp6 o CReturn water temp (max c<strong>on</strong>sumpti<strong>on</strong>) 16 o CReturn water temp (min c<strong>on</strong>sumpti<strong>on</strong>) 13 o Ccase sea water temperature is below 5 o C. Maximalpressure drop in both circuits is selected 0,85 bar. Heatexchanger parameters are indicated in Table 5.Tab. 5 Free-cooling heat exchanger parametersHeat exchangers capacitySea water (SW) supply temp.SW return temp.SW flow<strong>District</strong> cooling supply temp.<strong>District</strong> cooling return temp.5x3600 kW4,5 o C10 o C130 l/s6 o C16 o CWater chiller coolingCentralized cooling plant c<strong>on</strong>tains up to 4 water chillersto gain flexibility of the system. Also it is possible toc<strong>on</strong>struct the cooling plant step by step according toc<strong>on</strong>sumers‘ interest <strong>and</strong> cooling energy dem<strong>and</strong>.System c<strong>on</strong>tains four 4500 kW water chillers withcentrifugal compressors. It is possible to adjust thecooling power of the unit between 300–4500 kW whichmakes the system more energy (el) efficient during thepartial load period. The c<strong>on</strong>denser has to be producedfrom titan or similar resistant material due to fact that itis being cooled with sea water. In the following Table 4are indicated technical parameters for water chillers.<strong>District</strong> cooling flowMax pressure dropTab. 6 Coolant parametersSea water (SW)SW tempMax pressure<strong>District</strong> cooling liquidTemperatureMax pressure72 l/s0,85 bar1,5-18 o C6 bar10-18 o C10 barTab. 4 Water chiller parameters<strong>Cooling</strong> powerRefrigerantC<strong>on</strong>denser temp.Seawater (SW) supply temp.SW return temp.SW flow (each unit)4x4500 kWR-134a28 o C18 o C24 o C215 l/sSea water coolingThe sea water is supplied through insulated 800mmpipes to pumping stati<strong>on</strong> using sea water gravity. Threepumps (max 1080 m3/h) with frequency c<strong>on</strong>verters areinstalled using parallel scheme to sucti<strong>on</strong> pipe. Seawater pressure is ca 1,5 m <strong>and</strong> pumps will add 2 barsto overcome self-cleaning filters, heat exchangers <strong>and</strong>c<strong>on</strong>densers pressure drop. Frequency c<strong>on</strong>verters areused to lower energy c<strong>on</strong>sumpti<strong>on</strong> during partial load.Evaporator temp.COP full load 73 o CCOP partial load 12<strong>District</strong> cooling supply temp.<strong>District</strong> cooling return temp.<strong>District</strong> cooling flow (each unit)Free-cooling6 o C16 o C115 l/sWhen sea water temperature is lower than returntemperature from the network free-cooling through heatexchangers can be used. Optimum logarithmictemperature difference shall be app. 1,5 o C. Five heatexchangers with capacity of 3600 kW are selected,which assure whole cooling plant capacity (18 MW) in<strong>Cooling</strong> plant operati<strong>on</strong> modes<strong>Cooling</strong> plants are designed to have three differentoperati<strong>on</strong> modes: SW temperature < 5 o C. Completely free-cooling; SW temperature 5–12 o C. Pre-cooling with SW +compressor cooling;SW temperature > 12 o C Only compressor cooling(free cooling heat exchangers are equipped withbypasses).<strong>District</strong> cooling networkSupply (forward) water temperature is designed 6 o C.Return water temperature between 13–16 o C (seeFigure 4).155
The <str<strong>on</strong>g>12th</str<strong>on</strong>g> <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>Symposium</str<strong>on</strong>g> <strong>on</strong> <strong>District</strong> <strong>Heating</strong> <strong>and</strong> <strong>Cooling</strong>,September 5 th to September 7 th , 2010, Tallinn, Est<strong>on</strong>iaDue to fact that summer period soil temperature in1,5 m depth is 10 o C it is not necessary to insulate thereturn pipe of the district cooling network. Supply pipeis insulated with 10 cm nowadays heat insulati<strong>on</strong>material.The cooling plant shall have three operati<strong>on</strong>al modes:Free-cooling;Pre-cooling + compressor cooling;Compressor cooling.Optimizati<strong>on</strong> of the proposed system should be carriedout in further studies.REFERENCES[1] Vadrot, A. <strong>and</strong> Delbes, J, (1999). <strong>District</strong> <strong>Cooling</strong>H<strong>and</strong>book a Survey of Techniques, equipment <strong>and</strong>Choice of System. European market Group.Number of pages 208.[2] Feldhusen. H, Francesc. M. R, (2001). "<strong>District</strong><strong>Cooling</strong>-Present Market Assessment," Master,Kungl Tekniska Högskola, Stockholm divisi<strong>on</strong> ofApplied Thermodynamics <strong>and</strong> Refrigerati<strong>on</strong>. pp 52.Stockholm.Fig. 4 <strong>District</strong> cooling network tempCONCLUSIONThe sea water (SW) district cooling has until year 2000quite modestly developed am<strong>on</strong>g different countriesaround the World. Due to the fact that energy priceshave raised rapidly more <strong>and</strong> more researches for freeenergy resources are carried out. Wind power, heatpumps, solar energy <strong>and</strong> sea water have obtainedhuge attenti<strong>on</strong>.SW district cooling is centralized <strong>and</strong> will haveadvantages like less polluti<strong>on</strong>, less maintenanceproblems <strong>and</strong> in perspective also ec<strong>on</strong>omic benefits.Current feasibility analysis was d<strong>on</strong>e in Tallinn costalarea to define possible cooling plant load, potentialc<strong>on</strong>sumers <strong>and</strong> technical possibilities.Due low costal area it is possible to locate the coolingplant near to sea water. Further studies should addsome more ec<strong>on</strong>omic aspects to the technical soluti<strong>on</strong>.Problematic is to develop the district cooling network inTallinn area (existing tunnels <strong>and</strong> subways will easethe process).Most of the new built or renovated public buildingshave high cooling dem<strong>and</strong> due to glass walls <strong>and</strong> highinternal heat loads. In present research 21 buildingswith <strong>on</strong>ly public area were included (total coolingdem<strong>and</strong> 19,2 MW). The cooling dem<strong>and</strong> risesc<strong>on</strong>siderably when ambient air temperature exceeds16 o C. Sea water temperature 5 o C can be found indepth of 35–40 m.[3] Euroheat <strong>and</strong> Power, (2003). <strong>District</strong> Heat inEurope Country by Country/2003 Survey. BrusselBelgium.[4] Mildenstein, B. S. P, (1999). <strong>District</strong> <strong>Heating</strong> <strong>and</strong><strong>Cooling</strong> C<strong>on</strong>necti<strong>on</strong> H<strong>and</strong>book.[5] Gosney. W.B, (1982). Principles of Refrigerati<strong>on</strong>.Cambringe University Press. Published by thepress syndicate of the University of Cambridge.[6] Westin, P. E. H., (1999). Producti<strong>on</strong> Technologiesin <strong>District</strong> <strong>Cooling</strong> Systems <strong>and</strong> the Importance ofLocal Factors. New Energy Systems <strong>and</strong>C<strong>on</strong>versi<strong>on</strong>-NESC 99.). pp 6.Osaka.[7] Westin, P. E. H., Karls<strong>on</strong>, B., <strong>and</strong> Lundqvist, P,(1999). Straategies <strong>and</strong> Methods For Increasingthe Capacity of <strong>District</strong> <strong>Cooling</strong> Systems.20th<str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> C<strong>on</strong>ferenss of Refrigerati<strong>on</strong>, IIR/IIF.).pp 1-8. Sydney.[8] Nordell, B., <strong>and</strong> Skogsberg, K, (2002). Snow <strong>and</strong>ice storage for cooling applicati<strong>on</strong>s.Winter Cities2002.Japan Aomori. Luleå University ofTechnology[9] Eliadis, C, (2003). Deep Lake Water <strong>Cooling</strong> ARenewable Technology. Number of pages 3.[10] Morris, A.P, (1995). The Road to Lockport:Historical Background of <strong>District</strong> <strong>Heating</strong> <strong>and</strong><strong>Cooling</strong>. Ashrae Transacti<strong>on</strong>s: Symposia.[11] Arvids<strong>on</strong>, J, Asplund, A-L, Birgerrs<strong>on</strong>, E, (1997),Cold producti<strong>on</strong> uning low temperature wasteheat,. Kungl tekniska högskolan Kemiskapparatteknik. Pp 54, Stockholm156
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