27.1.2006 mirja tiitinen 1 dimensioning standard for domestic hot water euroheat&power rtd...
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27.1.2006Mirja Tiitinen
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Dimensioning standard for domestic hot water
Euroheat&Power RTD Workshop2.-3.2.2006 Brussels
Mirja TiitinenFinnish Energy Industries
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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
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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
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Number of bacteria colonies of Legionella as a function of temperature and time
Increase
Decrease
Nu
mb
er
of
ba
cte
rial c
olo
ny
pm
y/l]
Time [h]
Example of increase / decrease in various temperatures
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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
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Measurements
HelenMetering
DVD
Measuring data
PC
Sofware
HUT
Data analysis
Tele network
Apartment building
Copper
ADSL modem
District heating
heat exchanger
Domestic hot water
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Maximum flows
0
1
2
3
4
5
6
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230
Number of apartments
flow
[l/s
]
D1 design 0,8 l/s,apartm.
D1 design 0,5 l/s,apartm.
Measured maximum flows
F:101 design 2004
Isännöitsemänne kohde
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Maximum flows of different durations
0
0,25
0,5
0,75
1
1,25
1,5
1,75
2
2,25
2,5
2,75
0 20 40 60 80 100 120 140 160 180 200 220
Number of apartments
Flo
w [l
/s]
Max 30 s max 60 s max
Mean value curve for maximums 30 s mean value curve for maximums 60 s mean value curve for maximums
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Flow duration curvesF
low
l/s
Time [%]
Over 100
51 – 90
20 - 50
Under 20
Number of apartments:
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Outgoing and return temperatures (average)
40
42
44
46
48
50
52
54
56
58
60
EK4K17 K2 K4 K3
K14 EK1EK6 K5 K8
EK2K10 K11 K20 K19 K12 K13 K6
K18 K9 K7K16 EK3
Tem
pera
ture
[°C
]
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Suggested design flow
0,0
1,0
2,0
3,0
4,0
5,0
6,0
0 50 100 150 200 250
Number of apartments
Flo
w [
l/s]
Maximum flows
New design flow
D1 design flow
FVF:101 design 2004
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• 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)
MAXASMAXASMAXAS QqAqQqq ... )(
Suggested design flow
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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
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Dimensioning of the dhw control valve,example :
Effect 310 kWFlow 1,65 l/sec.
Pressure difference available 250 kPa(in normal operational conditions)-heat exchanger 20 kPa-pipelines 5 kPaAvailable for the valve 225 kPa
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”Old” dimensioning custom
Effect 310 kWFlow 1,65 l/sec.
Pressure difference given 60 kPa-heat exchanger 20 kPa-pipelines 5 kPaDimensioning pressure difference for the valve 35 kPa
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Valve: flow 1,65 l/sec, 35 kPa
0
1
2
3
4
5
6
0 10kv-value
flow
, l/s
ec
300 kPa
250 kPa
200 kPa
150 kPa
100 kPa
50 kPa
35 kPa
kvs-value10,0
pressure difference:
1,65 l/sec
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Valve: flow 50 % = 0,83 l/sec,35 kPa
0
1
2
3
4
5
6
0 2 4 6 8 10
kv-value
flow
, l/s
ec
300 kPa
250 kPa
200 kPa
150 kPa
100 kPa
50 kPa
35 kPa
kvs-value5,0
pressure difference:
0,83 l/sec
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“Correct” dimensioning
Effect 310 kWFlow 1,65 l/sec.
Pressure difference given 250 kPa-heat exchanger 20 kPa-pipelines 5 kPaDimensioning pressure difference for the valve 225 kPa
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Valve: flow 1,65 l/sec, 225 kPa
0
1
2
3
4
5
6
0 2 4 6 8 10
kv-value
flow
, l/s
ec
300 kPa
250 kPa
200 kPa
150 kPa
100 kPa
50 kPa
35 kPa
kvs-value4,0
pressure difference:
1,65 l/sec
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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