chapter 10

1. Heat supplied or taken away from a substance that causes a change of state without a change in temperature is called: a. Latent heat b. Sensible heat c. Convective heat d. Accumulated heat e. Evaporative heat

a

14. The ratio of the heat energy required to make steam to the heat energy supplied by the combustion of fuel in a boiler is called: a. Boiler efficiency b. Factor of evaporation c. Heat rate d. Combustion efficiency e. Equivalent evaporation

a

19. The total amount of heat, in kJ, that is absorbed by the water/steam in a boiler in a given period of time is called the: a. Heat rate b. Factor of evaporation c. Equivalent evaporation d. Total enthalpy e. Latent heat of the transformation.

a

2. The heat necessary to change a unit mass of liquid to the vapor state without any change in the temperature and pressure is the: a. Latent heat of evaporation b. Boiling temperature c. Sensible heat d. Enthalpy of fusion e. Fusion energy

a

20. From the Steam Tables the symbol "hg" means: a. Heat gained by the steam b. Heat generated by the boiler. c. Hot gaseous temperature. d. Total heat of the steam e. The heat gained in converting water to steam.

a

22. For steam point corresponding to the temperature of 374.12°C and pressure of 22,090 kPa on the temperature-enthalpy diagram is called the: a. Critical point b. Boiling point c. Superheat pressure and temperature d. Steam-water saturation point e. Point of absolute temperature and pressure.

a

23. Steam that is superheated: a. Has a greater volume than saturated steam. b. Has less heat than saturated steam at the same pressure c. Contains more energy but has the same temperature as saturated steam. d. Has a volume equal to that of saturated steam. e. All of the above.

a

26. Wet steam: a. Contains insufficient latent heat b. Contains extra sensible heat in the form of water. c. Has a greater volume than dry steam at the same pressure. d. Contains insufficient sensible heat e. Contains all of its sensible and latent heat.

a

27. Critical pressure, critical temperature and critical volume are the terms given to those points in the state of a substance at which: a. Liquid and vapor have identical properties. b. Liquid and vapor have different properties c. The critical temperature and pressure are the same d. Vapor properties are exactly double liquid properties e. Critical pressure and critical volume are the same.

a

28. Equivalent evaporation is determined by: a. Factor of evaporation times the actual evaporation. b. Factor of evaporation times net heat added per kg c. Actual evaporation divided by the factor of evaporation d. Factor of evaporation times the volume of steam generated per hour. e. Actual evaporation times the specific heat of the dry steam.

a

37. The dryness fraction, also called steam quality, is the percentage: a. By weight of steam in the mixture b. By volume of water to steam of the mixture c. By volume of steam in the mixture d. Of water by weight in the steam e. By weight of steam and water in the mixture.

a

4. Steam at its boiling point with no water particles present is called: aa. Dry saturated steam b. Supersaturated c. Superheated d. Vaporized e. Wet saturated steam

a

16. The temperature at which water boils is dependent upon the: a. Heat content b. Acting pressure c. Total boiler heating surface d. Absolute volume e. Dryness fraction

b

17. The ratio of the equivalent evaporation of the boiler to the actual steam flow rate is called the: a. Heat rate b. Factor of evaporation c. Equivalent evaporation d. Boiler efficiency e. Boiler evaporation ratio

b

25. The total heat for wet steam can be determined by: a. Multiplying the "hf" value from the Steam Table by the dryness fraction. b. Using the entropy - enthalpy diagram for steam. c. Subtracting the volume of water from the volume of steam and multiplying the result by the dryness fraction. d. Multiplying dryness fraction by the "hf" then adding the "hfg". e. Multiplying "hg" by the dryness fraction.

b

29. Saturated steam is steam saturated with at a particular temperature a. Water b. All its latent heat c. A percentage of "hfg". d. Sensible heat e. A percentage of "hf".

b

33. The quantity of saturated water contained in a unit quantity of steam is indicated by the: a. Partial pressure b. Dryness fraction c. Saturation index d. Steam temperature e. Moisture index.

b

35. From the Superheat Tables the symbol "v" means the specific: a. Viscosity of the steam b. Volume of the steam c. Velocity of the steam d. Volume of the water e. Velocity of the water.

b

38. At the critical pressure and temperature the total heat is made up of _____ and requires no latent heat to change water to steam. a. Internal energy b. Reheat c. Entropy d. Superheat e. Sensible heat.

b

12. The mass of water that would be evaporated in one hour, from feedwater at 100°C into dry saturated steam at 100°C, by the same amount of heat that is required, per hour, to produce steam at the actual boiler condition is called the: a. Heat rate b. Factor of evaporation c. Equivalent evaporation d. Total enthalpy e. Latent heat of the transformation

c

24. The ratio of the amount of heat absorbed per kg of steam in the boiler, to the amount of heat absorbed in producing 1 kg of steam at 100°C from water at 100°C is called the: a. Dryness fraction b. Equivalent evaporation. c. Factor of evaporation d. Efficiency of steam generation e. Latent heat of fusion.

c

3. Addition of sensible heat to a substance: a. Results in a change of state from solid to liquid b. Cannot be read on a thermometer c. Causes a rise in temperature d. Is the sum of the latent heat plus heat of evaporation e. Results in a change of phase from liquid to vapor

c

34. In the steam tables "vf" is: a. Cubic m per kg of the saturated liquid b. Grams per cubic cm of the saturated liquid c. Cubic cm per gram of the saturated liquid d. Kg per cubic m of the saturated liquid e. Cubic cm per kg of the saturated liquid.

c

15. Superheated steam is steam at a certain pressure, which temperature is above the: a. Combustion gas temperature b. Radiant steam temperature c. Fusion temperature d. Saturation temperature e. Critical temperature

d

30. From the Steam Tables the critical pressure is: a. When boiler pressure exceeds safe operating limits. b. At the corresponding boiling point c. When the temperature equals the boiling point. d. At 22090 kPa e. At a negative pressure or vacuum.

d

31. Steam with a percentage of wetness is said to have insufficient: a. Temperature b. Sensible heat c. Total enthalpy d. Internal energy e. Latent heat.

e

32. Steam at the temperature of evaporation corresponding to the pressure is: a. Wet steam b. Superheated steam c. Dry steam d. Sub-cooled steam e. Saturated steam.

e

41. If the temperature from the Temperature Tables of the Steam Table is known then: a. Corresponding absolute pressure can be determined b. Heat of the liquid can be determined c. Total enthalpy of the steam can be determined d. Specific volume of the gas can be determined e. All of the above.

e