Dimensioning standard for domestic hot water

1. Dimensioning standard for domestic hot water Euroheat&Power RTD Workshop 2.-3.2.2006 Brussels Mirja Tiitinen Finnish Energy Industries Mirja Tiitinen

2. Research project, years 2004 – 2005“The design flow and temperature criteria of hot tap water in respect of the microbiological water quality in district-heated residential buildings”Finnish Energy IndustriesMinistry of the EnvironmentHelsinki EnergyE.On Finland OyjVantaa EnergyHelsinki University of Technology Mirja Tiitinen

3. Objectives • To establish temperature criteria for hot tap water based on the growth temperatures of microbes in the hot-water network • To supplement and specify earlier studies carried out on the subject • To produce a new design principle for the design flow of hot tap water as the basis for an official standard • To compare the new design principle with criteria used in Finland and Sweden Mirja Tiitinen

4. Increase Decrease Number of bacterial colony pmy/l] Example of increase / decrease in various temperatures Time [h] Number of bacteria colonies of Legionella as a function of temperature and time Mirja Tiitinen

5. Research locations • 26 locations in the Helsinki region • Different types of residential buildings with district heating • Number of apartments 6-220 • 9 terraced houses, 5 small apartment buildings, 6 medium-sized apartment buildings and 6 large apartment buildings Mirja Tiitinen

6. Measurements Apartment building Tele network Copper HelenMetering ADSL modem PC Sofware DVD Measuring data HUT Data analysis District heating heat exchanger Domestic hot water Mirja Tiitinen

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9. Number of apartments: Over 100 51 – 90 20 - 50 Flow l/s Under 20 Time [%] Flow duration curves Mirja Tiitinen

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12. Suggested design flow • Equation for the new design principle qAS.MAX is the mean location-specific maximum flow (Usually 0.5 l/s,location or 0.6 l/s,location) Θ is the probability that qAS.MAX is used during maximum consumption (0.005) Q is the sum of the standard flow of the connected water taps A is the factor that takes into account how often design flow q is exceeded (2.8) Mirja Tiitinen

13. Summary of the research project • The design flows currently used in Finland don't correspond with the measured flows • in smaller buildings measured flows were higher • in bigger buildings measured flows were lower • The maximum flow, the 30-second maximum flow and the 1-minute maximum flow were very close to one another • The mean values of the water temperatures going into the network were reasonably good • The return temperature of circulation was too low in most locations Mirja Tiitinen

14. Dimensioning of the dhw control valve,example : • Effect 310 kW • Flow 1,65 l/sec. • Pressure difference available 250 kPa • (in normal operational conditions) • heat exchanger 20 kPa • pipelines 5 kPa • Available for the valve 225 kPa Mirja Tiitinen

15. ”Old” dimensioning custom • Effect 310 kW • Flow 1,65 l/sec. • Pressure difference given 60 kPa • -heat exchanger 20 kPa • pipelines 5 kPa • Dimensioning pressure difference • for the valve 35 kPa Mirja Tiitinen

16. Valve: flow 1,65 l/sec, 35 kPa Mirja Tiitinen

17. Result Mirja Tiitinen

18. Valve: flow 50 % = 0,83 l/sec,35 kPa Mirja Tiitinen

19. Result Mirja Tiitinen

20. “Correct” dimensioning • Effect 310 kW • Flow 1,65 l/sec. • Pressure difference given 250 kPa • -heat exchanger 20 kPa • pipelines 5 kPa • Dimensioning pressure difference • for the valve 225 kPa Mirja Tiitinen

21. Valve: flow 1,65 l/sec, 225 kPa Mirja Tiitinen

22. Result Mirja Tiitinen

23. Conclusions • Domestic hot water valve shall be dimensioned with correct flow and correct pressure difference • Correct flow is the actual maximum flow which can be expected to occur during normal conditions • Correct dimensioning Δp is the pressure difference during normal operational conditions Mirja Tiitinen