Steam Basics Armstrong International, Inc.

Transcription

1 Steam Basics Armstrong International, Inc.

2 Steam Basics - Overview What is Steam? Why is Steam Used? How Do We Create Steam? How Do We Identify Steam Properties? 2

3 This Is Not Steam! Steam is a vapor form of water, and is colorless, tasteless, and odorless 3

4 What is Steam Used For? Steam is Used to Transfer Heat Energy From One Location to Another 4

5 Why Use Steam? Steam is an efficient heat transfer medium Steam is easily controlled We have a lot of knowledge concerning steam We have already developed the equipment and expertise to design and install steam systems for many different applications 5

6 How We Create Steam Steam is created by adding Heat Energy to water. Heat Energy is expressed in Btu s. 1 Btu is the amount of Heat Energy required to raise the temperature of 1 pound of water by 1 F. 6

7 How We Create Steam The Heat Energy required to create steam has two forms: Sensible Heat Latent Heat 7

8 Heat Energy (Sensible Heat) Sensible Heat is the amount of Heat Energy required to raise the temperature of water from 32 F to the boiling point (saturated liquid) at a given pressure. (Sensible Heat raises the temperature of the water and can be sensed with a thermometer.) 8

9 Adding Sensible Heat 1 lb. of Water at 32 F Btu's of SENSIBLE HEAT = 1 lb. of Boiling Water at 212 F. Btu's Atmospheric Pressure 9

10 Heat Energy (Latent Heat) Latent Heat is the amount of Heat Energy required to transform water at the boiling point (saturated liquid) to steam. (Adding Latent Heat does not raise the temperature saturated liquid and steam have the same temperature for a given pressure.) 10

11 Adding Latent Heat 1 lb. of Boiling Water at 212 F Btu's of LATENT HEAT = 1lb. of Steam at 212 F, and 0 psig with a TOTAL HEAT content of 1150 Btu's. Btu's Atmospheric Pressure 11

12 What Is The Effect Of Pressure? Increased Pressure: Increased the Heat of Saturated Liquid Increases the Steam Temperature Temperaure of Steam F psig 15 psig 50 psig 100 psig 12

13 What is the Effect of Pressure? Increased Pressure: Decreases the amount of Latent Heat Increases the amount of Sensible Heat 13

14 What Is The Effect Of Pressure? Latent Heat BTU/lb Sensible Heat BTU/lb 0 psig 15 pig 50 psig 14

15 Steam Pressure Latent Heat Sensible Heat Specific Volume What Is The Effect Of Pressure? 15

16 What Is The Effect Of Pressure? Increased Pressure: Decreases the Specific Volume 26.8 Specific Volume of Steam ft 3 /lb psig 15 psig 50 psig 100 psig 16

17 Identifying Steam Properties Steam Tables 17

18 Steam tables allow us to identify all of the important properties of steam, given either the steam temperature or the steam pressure 18

19 Example: Steam at 250 o F is at 15 psig, with 945 Btu s/lb of Latent Heat Steam at 5 psig is at 228 o F, with 196 Btu s/lb of Sensible Heat

20 Now That We ve Made Steam What Do We Do With It? 20

21 Since Steam is used to Transfer Heat Energy From One Location to Another... 21

22 It only makes sense that we take the heat energy back out and use it to do work. 22

23 Removing Latent Heat 1 lb. of Steam at 212 F, with a TOTAL HEAT content of 1150 Btu/lb. 970 Btu s of LATENT HEAT = 1 lb. of boiling water (Saturated Liquid) at 212 F with a heat content of 180 BTU s/lb. Btu's Atmospheric Pressure 23

24 REMEMBER: The Latent Heat added at the boiler is what we have available to do work in our equipment BUT... When we remove Latent Heat we create Condensate 24

25 FLASH STEAM Steam created when condensate of a higher pressure/temperature is discharged to a lower pressure system. To maintain the p/t relationship the condensate cools by converting some of it s sensible heat to latent heat and flashes back to steam. This flash steam has the same characteristics as boiler generated steam. 25

26 FLASH STEAM CHART 26

27 Latent Heat can be removed intentionally, in a piece of heat exchange equipment, or unintentionally, from radiation heat loss in piping 27

28 What Does This Unintentional Heat Loss Mean to Your Steam System? Condensate Steam Vapor 50.3 psig F 100 psig F PRV Trap Trap Trap Trap Trap Trap Vent 28

29 It Means: The Steam System is Constantly Being Filled With Water (Condensate) 29

30 It Means: Your Steam System is Subject to Corrosion ( CO 2 + H 2 O = H 2 CO 3 ) Subcooled Condensate + CO2 Forms Carbonic Acid 30

31 It Means: Your Steam System is Subject to Water Hammer 31

32 It Means: Your Heat Exchange Equipment is Less Efficient 32

33 It Means: Your System Must Be Properly Piped 33

34 It Means: Your Equipment Must Be Properly Trapped 34

35 35

36 INVERTED BUCKET 36

37 INVERTED BUCKET cont. 37

38 FLOAT & THERMOSTATIC 38

39 THERMODYNAMIC 39

40 BI-METALLIC (thermostatic) 40