Adapted control systems for house service connection stations of huge performance – domestic hot...

Adapted control systems for house service connection stations of huge performance – domestic hot water supply based on continuous flow system

Faculty of Mechanical Engineering Institute of Power Engineering,

Second Euroheat & Power RTD WorkshopBrussels, 2-3 February 2006

Dipl.-Ing. Norbert Wünsche, Dr.-Ing. Karin Rühling TU Dresden, Institut of Power Engineering

This presentation is based on a research project financially supported by the German Federal Ministry of Economy within the PROgramm “INNOvationskompetenz mittelständischer Unternehmen” (KF 0100804KMH3)

Professorship of Energy System Engineering and Heat Economy

Brussels, 2 February 2006 Huge DHW supply based on continuous flow systemWünsche/Rühling

Slide 2

MOTIVATION

Domestic hot water supply in the range of 100 kW to 1 MW

Standard installations temporary mostly as storage systems favourable conditions for growth of Legionella

Cause of high quality standards (TrinkwV, DVGW W 551) special solutions with considerable high efforts necessary

Sto

rage c

harg

ing s

yst

em

Sto

rage o

f D

HW

Sto

rage s

yst

em

Sto

rage o

f D

HW

T

M

T

DHW

DW

supply

returnM

T

DHW

DW

supply

return

T

DHW

DW

supply

return

T

DHW

DWM

T

supply

return M

a b

c d

storage system - storage of DHW storage charging system - storage of DHW

Continuous flow system - without storage Continuous flow system with primary storage - storage of heating water


Slide 3

OBJEKTIVE

Check, if continuous flow system can be applied simple hydraulic circuit

primary storage for heating water

domestic hot water temperature control system based on speed control of electronic pumps

Conti

nuous

flow

syst

em

w

ith p

rim

ary

sto

rage

Sto

rage o

f heati

ng w

ate

r

Conti

nuous

flow

sy

stem

Wit

hout

stora

ge

T

M

T

DHW

DW

supply

returnM

T

DHW

DW

supply

return

T

DHW

DW

supply

return

T

DHW

DWM

T

supply

return M

a b

c d

storage system - storage of DHW storage charging system - storage of DHW

Continuous flow system - without storage Continuous flow system with primary storage - storage of heating water


Slide 4

Tested basic configurations on DHW side

Two-stage principle – during tapping treturn , as no mixing circulation/cold DW

primary storage

of heating water

supply

return

DHW

DW

circulation


Slide 5

Basic configurations for charging the primary storage

Contr

ol sy

stem

wit

hout

auxili

ary

pow

er

dem

and

Therm

o m

ech

an

ical valv

e

Thre

e-p

oin

t co

ntr

ol

Moto

r co

ntr

ol valv

e

dir

ect

charg

ing

Tw

o-p

oin

t co

ntr

ol

Moto

r co

ntr

ol valv

e

Thre

e-p

oin

t co

ntr

ol

Moto

r co

ntr

ol valv

e

indir

ect

charg

ing

Adjusted charging temperature


Slide 6

Choice of the pump

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6 7 8

flow rate in m³/h

pres

sure

hea

d in

m H

2O

100%

90%

80%

70%

60%

50%

25%12%

design point 250 kW

200 kW

150 kW

Limit of control range


Slide 7

Set-up of the laboratory test facility

SIKA-Strömungskontrollschalter Temp.KW

Temp.RL Zirk

Temp. WÜEintritt

Temp. WÜAustritt

Temp. TWWmitFühlerkopf-transmitter

Rückschlagklappe

temp. HX inlet

temp. DHW with sensor head trans-mitter

temp. circ. return

SIKA flow control switch temp. DW nonreturn valve

temp. HX outlet

Single-stage realisation

Qth, design = f(tstorage)

= 100 …150 kW

Switching the mixing valve via flow control switch

0 .. 12 l/min tHX,in=65 °C

> 12 l/min tHX,in= tstorage

Control pump Grundfos TPE 25-90R (smallest available)

Plate HX SWEP B28 x 30

Rudert DW-storage 200 l


Slide 8

Key aspects of the laboratory tests

Test of different hydraulic circuits

Measuring the time constants of different temperature sensors

Placement of DW-temperature sensor in heat exchanger

Examination of the control range of the electronic pump

Dimensioning the admix-quantity

Choice of proper mixing valve

Choice of appropriate flow control switch

Optimisation of pump control parameters


Slide 9

Selected results of the laboratory tests with 72 °C storage temperature

40

45

50

55

60

65

70

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 min

Te

mp

era

tur

in °

C

0,0

0,5

1,0

1,5

2,0

2,5

3,0

Vo

lum

en

str

om

in

m³/

h .

+3K

-3K

Umschaltpunkt: SIKAHigh: 99% / Low: 75%Pumpe: kp=4,0 / Tn=10sMax: +2,2K Min: -3,6KMittleres DJ:+0,3/-1,2K

PD

16

09

02

.XL

S

VolumenstromKaltwasser

Temperatur Trinkwarmwasser

40

45

50

55

60

65

70

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 min

Te

mp

era

tur

in °

C

0,0

0,5

1,0

1,5

2,0

2,5

3,0

Vo

lum

en

str

om

in

m³/

h .

+3K

-3K

Umschaltpunkt: SIKAHigh: 99% / Low: 75%Pumpe: kp=4,0 / Tn=10sMax: +5,5K Min: -6,3KMittleres DJ:+0,7/-1,1K

PD

160903.X

LS

Temperatur Trinkwarmwasser

VolumenstromKaltwasser

Load profile

Step curve

Load profile

Jump function


Slide 10

Selected results of the laboratory tests

Load function /storage temperature

Maximum values

Minimum values

average positivedeviation

average negativedeviation

Step curve 72 °C +2,2 K -3,6 K +0,3 K -1,2 K

Jump function 72 °C +5,5 K -3,6 K +0,7 K -1,1 K

Step curve 80 °C +2,1 K -1,9 K +0,2 K -0,4 K

Jump function 80 °C +6,5 K -5,7 K +0,5 K -0,7 K


Slide 11

Field test – Objectives

Prove under praxis conditions

uninterrupted service,

dimensioning of performance,

stability of control,

effectiveness of primary storage (coverage of peak demands)

as well as

low return flow temperatures and thus

function of complete system

Single-stage realisation


Slide 12

Field test – Conditions of application

For 53 living units two-stage DW-heating first operation period single-stage and

later two-stage operation mixing loop as independent

temperature control circuit no cold water flow sensor data logging

11 temperature sensors

3 flow rate sensors

average value logging (2 or 5 s–pulse)

8 weeks save and convenient supply of tenants

V´DHW,max = 2,95 m³/h (Comparison: DIN 4708 4,8 m³/h)


Slide 13

Field test - Selected results – Daily average values

Remarkable higher control stability in the two-stage realisation (± 2K)

50

52

54

56

58

60

62

64

66

68

20.02.05 27.02.05 06.03.05 13.03.05 20.03.05 27.03.05 03.04.05 10.04.05 17.04.05 24.04.05

tem

per

atu

re in

°C

single-stage two-stage

Sum

men

date

i Ber

lin.X

LS

daily average value temperature DHW

daily maximum value temperature DHW

daily minimum value temperature DHW


Slide 14

Field test - Selected results – Daily course; two-stage

0

5

10

15

20

25

30

35

40

45

50

55

60

65

0:00

1:00

2:00

3:00

4:00

5:00

6:00

7:00

8:00

9:00

10:0

0

11:0

0

12:0

0

13:0

0

14:0

0

15:0

0

16:0

0

17:0

0

18:0

0

19:0

0

20:0

0

21:0

0

22:0

0

23:0

0

0:00

time

tem

per

atu

re in

°C

0,00

0,25

0,50

0,75

1,00

1,25

1,50

1,75

2,00

2,25

2,50

2,75

3,00

3,25

flo

w r

ate

in m

³/h

Monday, 11 april 2005

temperature DHW

flow rate DHW


Slide 15

Field test - Selected results – Peak demand; two-stage

10

15

20

25

30

35

40

45

50

55

60

65

70

75

6:30

6:35

6:40

6:45

6:50

6:55

7:00

7:05

7:10

7:15

7:20

7:25

7:30 time

tem

per

atu

re in

°C

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0

5,5

6,0

6,5

flo

w r

ate

in m

³/h

Monday, 11 april 2005

temperature DHW

flow rate DHW

flow rate primary pump


Slide 16

Field test - Selected results – Frequency distribution DHW demand

0,0

0,5

1,0

1,5

2,0

2,5

3,0

0 10 20 30 40 50 60 70 80 90 100Zeit in %

Vo

lum

enst

rom

in

m³/

h .

Verteilungsfunktion: WarmwasservolumenstromTestobjekt: Berlin Ziethenstraße 17Zeitbereich: 25.02 bis 21.04.2005max. Volumenstrom : 2,948 m³/h

Auswertung Berlin 1.XLS

Volumenstrom eines flächengleichen Rechtecks: 0,134 m³/h

Verteilungsfunktion

DHW-demand only 32 % of the time only during 10 % of the time demand > 0,5 m³/h dimensioning of primary storage = f (circulation demand, operation

parameter of heat exchanger, mixing loop, storage temperature ..)

program for dimensioning

frequency distribution

flow rate of area-equivalent rectangle: 0,134 m3/h

time in %

flow

rate

in

m3/h

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