manualul pentru incalzire danfoss - chapter8

7/29/2019 Manualul Pentru Incalzire Danfoss - Chapter8

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8 STEPS - CONTROL OF HEATING SYSTEMS

CHAPTER 8 TECHNICAL DATA, FORMULAS AND CHARTS

161

TECHNICAL DATA, FORMULAS AND CHARTS

Diagram for local district heating plants and heating and power plant . . . . . . . . . . . . . . .162

Diagram for heating and domestic hot and cold water . . . . . . . . . . . . . . . . . . . . . . . . . . .163

Heat emission from radiators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164

Conversion chart for radiators in one-pipe systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165

Reduction of heat emission from radiators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166

Heat losses from uninsulated pipes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167

Pressure drops in steel pipes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168

Resistance in heating systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169

Sizes of steel pipes for heating systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169

Flow chart for thermostatic radiator valves in one-pipe system . . . . . . . . . . . . . . . . . . . . .170

Flow chart for thermostatic radiator valves in two pipe system . . . . . . . . . . . . . . . . . . . . .171

Flow chart for p control valves for risers or circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .172

Flow chart for control valves in heating systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173

Flow chart for control valves in district heating systems . . . . . . . . . . . . . . . . . . . . . . . . . . .174

Flow chart for p control valves in district heating systems . . . . . . . . . . . . . . . . . . . . . . . .175

Heat requirements for domestic hot water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177

Flow limiters for one-pipe circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .178

Calculation of one-pipe systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .180

Calculation of two-pipe systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182

SI-units, Greek alphabet, Physical properties for water . . . . . . . . . . . . . . . . . . . . . . . . . . . .184


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162 8 STEPS - CONTROL OF HEATING SYSTEMS

130 C

70 C

130 C

130 C

70 C

70 C

130 C

130 C

70 C

70 C

130 C

130 C

70 C

70 C

Diagram for local district heating plants connected to a heating and power plant.

Heating andpower plant

Local heating plant

Flue gascooler

Safetyvalve

Exp. tank

Boiler

Safetyvalve

Heat exchanger

Accumulator

Heat meter

Flue gascooler

Safetyvalve

Exp. tank

Boiler

Safetyvalve

Heat exchanger

Accumulator

Heat meter

Flue gascooler

Safetyvalve

Exp. tankBoiler

Safetyvalve

Heat exchanger

Accumulator

Heat meter


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163

6

120-70 C

90 C65 C

Diagram for heating and domestic hot and cold water.

Expansion tank

p - control

Flow meter

Domestic hot water

Domestic cold water

Flowmeter> 6 storeys

Heat meterDomestic hot water 60

Domestic cold waterCirculation

Control valve< 6 storeys

Storeys


4/25

40 30 25 20 16

0

1,0

0,9

0,8

0,7

0,6

0,5

0,4

0,3

0,2

0,1

1,1

1,2

0 1,0 2,0

90

60

70

80

50

0,5 1,5 2,5

1

2

4

5

6

3



Heat emission from radiators.

Two-pipe system with thermostaticvalves.Measured 1 : tflow 75 oC, t 8 oCHeat requirement : 0,83, Q = 2,47

tflow 80o

C : 2 t 16o

C, Q = 1,23Every point along the horizontal line0,83 gives the same heat emission.

The influence of gravity forces on heat emission from a radiator in a two-pipe systemFor a correctly sized radiator 3 ( with manual radiator valve in a two-pipesystem ) the heat emission will increases only by 5% when the flowincreases by 23%, 4 , depending on gravity forces. The temperature dropacross the radiator however will decrease by 5 oC and that is significant,because it reduces the capacity of the whole system all the way down tothe heating and power plant.

Resuls t for one- and two - pipe circuits, and required pump capacitywhen thermostatic valves utilize internal and external heat gains.

Two-pipe circuit One-pipe circuitPoint Heat Flow t Circuit resi- Pump ca- Flow t Pump ca-

gain % % oC stance % pacity % % oC pacity %

3 0 100 25 100 100 100 25 100

5 10 66 33 44 29 100 22,5 100

6 20 47 39 22 10 100 20 100

n = 1,3 troom = 20 oC tflow = 90 oC t = 25 oC

t oC

Heat

emission

Q

12

10

8

6

5

4


5/25

165



0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

1,7

1,8

1,9

2,0

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

90

85

80

75

70

60 65

21

Conversion chart for radiators in one-pipe circuits.

Conversion chart for panel and section radiators in one-pipe circuits.Enter the current tflow and temperature drop and find the conver-

sion factor, Fc.

Multiply the heat requirement by Fc and select size of the radiator

according to the new value.

Example.Calculated heat requirement: 1.230 W.

tflow : 82oC, t: 15 oC, 1

Fc = 1,16 2Converted heat requirement: 1.230 x 1,16 = 1.427 W.

Formula for calculating Fc:

49,33 x ln

t1 - t2[ ]t1 - tr n

t2 - tr( )n

Panel radiator 1,28Section radiator 1,29Convector 1,3 - 1,33

F =

tflow oCFc

to

C


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a

The control unit has to sense the room temperature to be able to control it.

No enclosure0%

Shelf withopening0%

Shelf close tothe wall10 -2%

Open frontedrecess with ashelf12 -6%

Encased withgrille in front> -15%

Encased withsmall grille infront. Notrecommended.> -30%

Acceptablecabinet. -8 - 10%

Reduction of heat emission from radiators fixed in some type of enclosure

Radiation from a radiator depending on the treatment of thesurface.

Material Surface treatment Radiation %

Steel, cast iron 100

Oil paint 100

Aluminium orcopper bronzes 75

Zinc white 101

Lead white 99

Enamelled White 101

Matt green 96

Aluminium 8

10 - 100 mm 30 - 100 mmAlternativeopenings a+40

>

100mm


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167

0

100

200

300

400

0

20 40 60 80 100 120

80/89 65/76

50/6

40

32

25

20

1015



Heat losses from uninsulated horizontal pipe.

For vertical pipe reduce by 20%

One-pipe above another reduce by 12%

Three pipes above each other reduce by 20%

Temperature above room temperature oC

Heat emissionW/m pipe DN/0


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5 7 10 20 30 mmWG/m

,05 ,07 0,1 0,2 0,3 0,4 0,5

kPa/m

25

15

20

32

40

80

50

100

125

150

,01,015

,02

,03

,04,05

,07

,1

,15

,2

,3

,5

,4

,7

1

1,5

2

3

457

10

4050

15

20

30

1,0

2,0

10

100

1000

10

100

1,5

2

3

45

7

15

20

30

4050

70

150

200

150

200

300

400500

700

70

5040

15 40 50

0,15

65

3,0

m/s0,

2

0,3

0,4

0,5

k = 0,00003 m

Density = 1.000 kg/m3

Pressure drop in steel pipes for heating installations.

m3/h DN mm l/s

l/h


9/25

0,1

0,20,30,5

1,02

3

,01 ,02 ,03 ,05 0,1 ,2 ,3 ,5 1

1

2

64

3

2 3 4 5 107

169



p for values at differnt rates.Symbol Units Coefficient of resistance,

Branch tee 1

Through tee 1

Elbow, smooth 0,2

Bend 1

The values for the coefficient of resis-tance for tees, elbows and bends.

The pressure drop is calculated from:p = 0,5 2 ,

Recommended portion of pipe losses for different systems or part ofsystems.

Type of system Unit Friction %

Heating Small buildings 50 - 60

Large buildings 60 - 70

Sub-stations Primary and secondary side 20 - 30

Distribution pipe net work Primary side 80 - 90

valuem/s

p kPa

Sizes of steel pipes for heating systems. Working pressure 1,0 MPa (10 bar)Nominal diameter External diameter Wall thickness Internal diameter

mm inch mm mm mm8 1/4 13,50 2,25 910 3/8 17,00 2,25 12,515 1/2 21,25 2,75 15,7520 3/4 26,75 2,75 21,2525 1 33,50 3,25 27,0032 1 1/4 42,25 3,25 35,7540 1 1/2 48,00 3,50 41,0050 2 60,00 3,50 53,0065 2 1/2 75,50 3,75 68,0080 3 88,50 4,00 80,50100 4 114,00 4,00 106,00125 5 140,00 4,50 131,00150 6 165,00 4,50 156,00


10/25

30

5070100

200

300

5007001000

0,1 ,2 ,3 ,4 ,5 ,7 1,0 2 3 kPa

0,01 ,02 ,03 ,07 ,1 ,2 ,3 mWG

,001 ,002 ,004,006 0,01 ,02 ,03 Bar

,01

,02

,03

,05,07,1

,2

,3

,05

4 5 7 10 20

,7 1 2

,04 ,06 0,1 ,2

,5

15

2025



Flow chart for RTD-G 15, 20 and 25

RTD - G 15, 20 and 25

l/h l/sValve size

pvalve


11/25

171



3

5710

20

30

5070100

,001

,002

,003,005

,007,01

,02

,03

1 2 3 4 5 7 10 20 30 kPa

0,1 0,2 ,3 ,4 ,5 ,7 1 2 3 mWG

0,01 ,02 ,04 ,06 0,1 ,2 ,3 Bar

,1

,05,07

500

300

200N

1

23

45

67

3

5710

20

30

5070100

,001

,002

,003

,005,007,01

,02

,03

1 2 3 4 5 7 10 20 30 kPa

0,1 0,2 ,3 ,4 ,5 ,7 1 2 3 mWG

0,01 ,02 ,04 ,06 0,1 ,2 ,3 Bar

,1

,05,07

500

300

200

N

1

23

456

7

Flow chart for thermostatic valves in two-pipe system

l/hl/sPre-set value

pvalve

Pre-set value 1 2 3 4 5 6 7 N

kv values 0,04 0,08 0,12 0,20 0,27 0,36 0,45 0,60

Pre-set value 1 2 3 4 5 6 7 N

kv values 0,10 0,15 0,17 0,25 0,32 0,41 0,62 0,83

l/hl/sPre-set value

pvalve

RTD - N 15

RTD - N 20 - 25


12/25



0,1

0,2

0,3

0,5

0,71,0

23

5710

0,1

0,2

0,3

0,50,7

1,0

2

3

,03

,05,07

1 2 3 4 5 7 10 20 30 40 60 80 kPa

0,1 0,2 ,3 ,4 ,5 ,7 1 2 3 4 5 7 mWG

0,01 ,02 ,04 ,06 0,1 ,2 ,3 ,4 ,5 ,7 Bar

520

8

,8

1,62,54,06,3

10

1

Flow chart for p control valves for riser or circuit in heating systems.

ASV-P, PV 15-40 and ASV-M 15-40

m3/h l/skvs-value

pvalve

Working range:

ASV-P 10 kPa

ASV-PV 5 - 25 kPa.

Minimum available p for good functioning: 8 kPa.

Example

Q: 300 l/h. p riser: 7kPa. p radiator including valve: 5 kPa.p-control kv 1,6. pvp = 3,4 kPa, 1Necessary p = 7+5+8 = 20 kPa.


13/25

173



0,1

0,2

0,3

0,50,71,0

23

5710

0,1

0,2

0,3

0,50,71,0

23

,03

,05,07

1 2 3 4 5 7 10 20 30 40 60 100 200 kPa

0,1 0,2 ,3 ,4 ,5 ,7 1 2 3 4 5 7 10 15 20 mWG

0,01 ,02 ,04 ,06 0,1 ,2 ,3 ,4 ,5 ,7 1,0 1,5 2 Bar

10

5

7

150

50

30

20

100

200

20

30

50

,4

,631,0

1,62,54,06,3

1016

25

40

6310014

5

Flow chart for control valves in heating systems.

m3/h l/skvs-value

pvalve

Formulas.

p : bar. Q: m3/h. kv = ; p = ; Q = kv p ;Q

pQ

kv( )2

p : kPa. Q: l/h. kv = 0,01 ; p = 0,01 ; Q = 100x kv p ;Q

pQ

kv( )2

p : kPa. Q: l/s. kv = 36 ; p = 36 ; Q = p ;Q

pQ

kv( )2 kv

36

Q

Q

Q


14/25



0,1

0,2

0,3

0,50,71,0

23

5710

0,1

0,2

0,3

0,50,71,0

23

,03

,05,07

1 2 3 4 5 7 10 20 30 40 60 100 200 kPa

0,1 0,2 ,3 ,4 ,5 ,7 1 2 3 4 5 7 10 15 20 mWG

0,01 ,02 ,04 ,06 0,1 ,2 ,3 ,4 ,5 ,7 1,0 1,5 2 Bar

10

57

150

50

30

20

100

200

20

30

50

,4

,631,0

1,62,54,06,310

16

25

40

6310014

5

Flow chart for valves in district heating systems.

m3/h l/skvs-value

p

valve


15/25

175



0,1

0,2

0,3

0,5

0,71,0

23

5710

0,1

0,2

0,3

0,50,7

1,0

2

3

,03

,05,07

1 2 3 4 5 7 10 20 30 40 60 80 kPa

0,1 0,2 ,3 ,4 ,5 ,7 1 2 3 4 5 7 mWG

0,01 ,02 ,04 ,06 0,1 ,2 ,3 ,4 ,5 ,7 Bar

520

8

,8

1,62,54,06,3

10

1

m3/h l/skvs-value

pvalve

AVP 15 - 32

Flow chart for p control valves in district heating systems.


16/25



0,1

0,2

0,3

0,50,71,0

23

57

10

0,1

0,2

0,3

0,50,71,0

2

3

,03

,05,07

1 2 3 4 5 7 10 20 30 40 60 100 200 kPa

0,1 0,2 ,3 ,4 ,5 ,7 1 2 3 4 5 7 10 15 20 mWG

0,01 ,02 ,04 ,06 0,1 ,2 ,3 ,4 ,5 ,7 1,0 1,5 2 Bar

10

57

150

5030

20

100

200

2030

50

,631,0

1,62,54,06,3

10

16

25

50

80125

20

Flow chart for p control valves in district heating systems.

m3/h l/skvs-value

pvalve

IVD-IVFS kvs 0,63 - 25,0 m3/h

AFP kvs 50 - 125 m3/h

p-regulator, working range: IVD 5 - 50 and 20 - 250 kPa.AFP 20 - 120 and 50 - 250 kPa

Maximum p valve IVF kvs: 0,63 and 1,0 = 1.000 kPa2,5 = 630 kPa4,0 - 25 = 800 kPa

Maximum p valve AFP: 1.200 kPa


17/25

177



0

0,5

1,0

1,5

2,0

2,5

050100150

200250300

350

400

1 10 50 100 150 200 250

Heat requirement for hot water according to the Swedish Board of District Heating

Domestic hot water, Q L/s. Effect, P kW

Number of apartments.


18/25



0,07

0,1

0,15

0,2

0,3

0,4

0,5

0,6

0,7

0,8

1,00,9

20 30 40 50 60 70 80m /h

3p kPav

0,2 0,3 0,4 0,5 0,6 0,7 0,8

p Barv

1

2

3

4

5

8

6,5

0,2

0,3

0,4

0,5

0,7

2,0

1,5

1,00,90,8

0,6

20 30 40 50 60 70 80m /h

3p kPav

0,2 0,3 0,4 0,5 0,6 0,7 0,8

p Barv

10

1214

2

4

6

8

Flow limiter, ASV-Q 15, Flow limiter, ASV-Q 20

Set values

Set values

ASV-Q Capacity l/h Set value

15 100 - 800 1 - 820 200 - 1400 2 - 1425 400 - 1600 4 - 1632 500 - 2500 5 - 30


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179



2,0

1,7

1,5

1,2

1,00,90,8

0,7

0,6

0,5

0,4

30 40 50 60 70 80m /h

3p kPav

0,3 0,4 0,5 0,6 0,7 0,8

p Barv

10

12

14

16

4

6

8

4,0

3,0

2,0

1,5

1,2

1,00,90,80,7

0,6

0,5

0,4

m /h3

30 40 50 60 70 80p kPav

0,3 0,4 0,5 0,6 0,7 0,8

p Barv

5

15

10

20

25

30

Flow limiter, ASV-Q 25, Flow limiter, ASV-Q 32

Set values

Set values


20/25



Calculation of one-pipe system

6

31 m

6 m6 m6 m6 m

1200

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1200

1200

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1200

1200

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1200

1200

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1200

6 m 6 m 6 m

1200

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1200

1200

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1200

1200

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1200

1200

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1200

3x12=

36m

1,5 m

0

2345

2345

6

789

1

10

10 m


21/25

181



Calculation of one-pipe system


22/25



Calculation of two-pipe system

12001200 1200 120012001200 1200 1200

1200 12001200 12001200 12001200 1200

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

3 m 6 m 6 m 6 m

12345

6

7

8

9

10

11

12

13

14

15

16

17

3m

3m

31 m


23/25

183



Calculation of two-pipe system


24/25



SI-units.Effect, P. Pressure, p.

W kcal/h Pa kPa bar mWG

1 0,85985 1 0,001 0,00001 0,0001

1,163 1 1.000 1 0,01 0,1

100.000 100 1 10

10.000 10 0,1 1

Flow, Q (). Temperature, t ().l/s m3/h Kelvin K Celsius oC

1 3,6 0 -273,150,278 1 273,15 0

373,15 100

Greek alphabet.

alfa beta gamma delta epsilon seta eta theta iota

kappa lamda my ny xi omikron pi ro sigma

tau ypsilon phi chi psi omega

Physical properties for water.

Temperature Pressure Density Isobaric heat

oC p kPa kg/m3 capacitivitycp J/ (kg x K)

0 - 999,84 421810 - 999,70 419220 - 998,205 418230 - 995,65 417840 - 992,2 4178

50 - 998,14 418160 - 983,21 418470 - 977,78 419080 - 971,80 419690 - 965,33 4205100 1,3 958,35 4216110 43,26 951,0 -120 98,54 943,1 4245130 170,11 934,8 -140 261,36 926,1 4287150 375,97 916,9 -


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manualul pentru incalzire danfoss - chapter8

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