COSC 325: Review questions 2

1. What is enthalpy?

2. What is the unit used for the calculation of metabolic rate?

3. What is the factor that specifies the percentage of radiated heat passing through a glass surface?

4. Name the term used for indicating the quantity of heat that is required to raise the temperature of a pound of a pound of water by one degree Fahrenheit.

5. The relative humidity an air-water vapor mixture is 100%. If the dry-bulb temperature of the mixture were 85°F, what would be its wet-bulb temperature under those conditions?

6. What is the heat transfer mode that works mainly as a cooling mechanism?

7. You have put 5 gallons of water @60°F in the refrigerator and cooled it down to 40°F. What is the quantity of heat, in BTUH, released in the process?

8. A quantity of 0.8 BTUH of heat can flow through a square foot of 1" thick plywood. What is the term you will use to indicate this particular characteristic of the material?

9. Can you find out the dry-bulb temperature of an air-water vapor mixture @70°F wet- bulb temperature and 32 BTU/lb enthalpy? If yes, how? If not, why?

10. John Doe was driving at night, with car thermostat set at 70°F. The outdoor air temperature was high at 90°F with a relative humidity of 30%. Suddenly he collided with a jaywalker, but injuries were minor. He told the police his visibility was poor due to condensation on the outside of his windshield. The police did not buy his story. What could be the scientific reason for that?

11. Two small office buildings will be constructed in El Paso and Baton Rouge, using the same design and floor area. Both the buildings will be air-conditioned. If the summer air in El Paso is 100°F @20% RH and that in Baton Rouge is 90°F @60% RH, which building would require a cooling equipment with larger capacity?

12. A building has an expected infiltration rate of 200 CFM. If indoor and outdoor dB temperatures were 70°F and 10°F respectively, what would be the quantity of sensible heat loss due to the effect of outside air?

13. Solar heat gain inside a building through a 100 sq. ft. double-glazed window with color drape on the south (orientation at 40° N latitude on July 21 @ 10 a.m.) is 4,095 BTUH. If the solar factor (SF) were 63 BTUH/sq. ft., what would be the shading coefficient of the window material?

14. What is ventilation in HVAC terms? 15. What are the factors that influence Equivalent Temperature Difference (ETD) used to determine the quantity of heat flow through a material?

16. Assembly of materials of a wall consists of 12” concrete block (R = 2.27), 4-inch air space (R = 1.01), and two layers of gypsum board (R = 0.45 per gypsum board). What is the U-value of the wall? (Assume R = 0.17 for outside air film and R = 0.68 for inside air film.)

17. ½” roofing slate has a U-value of 30. What is the resistance (R) of the material?

18. Rate of infiltration in a room (50’ long, 30’ wide, and 10’ high) is 0.5 ACH. Indoor dry bulb temperature is 75°F @ 45% RH and outdoor dry bulb temperature is 90°F @ 60% RH. What is the latent heat gain inside the room due the infiltration of outside air?

19. Find the approximate enthalpy of an air-water vapor mixture @80°F dB and 30% RH.

20. What is the function of a vapor barrier in construction?

21. Define U-value..

22. How much heat will be released if you cool down a pound of water from 51°F to 50°F?

23. When does condensation occur on the surface of a material?.

24. What is radiation?.

25. What is dew-point temperature?

26. What properties of atmospheric air can be read from a psychrometric chart?.

27. What is latent heat?

28. What is latent of fusion?

29. What is latent heat of evaporation?

30. What is infiltration in HVAC terms?.

31. What is one of the important means of maintaining acceptable indoor air quality in buildings?

32. What is sensible heat?

33. What is convection?

34. When is the driving force for heat flow?

35. Increase of what property of a material adds to its insulation value?

36. What factors are taken into account to calculate latent heat gain in a building due to the effect of outside air?

37. What factors are taken into account to calculate sensible heat gain in a building due to the effect of outside air?

38. What is the difference between TD and ETD?

39. What is the unit used for quantifying infiltrated or ventilated air?

40. What does one air change per hour (ACH) mean?

41. What other factors, apart from building materials and outside air, have an affect on heat gain in buildings?

42. When air temperature is less than skin surface temperature, body heat can be lost by?

43. What is a common winter problem, related to dew point temperature, on single glass windows?

44. On which side of the construction vapor barriers are installed to prevent vapor penetration and minimize internal condensation problems.

45. Which air/water vapor mixture will occupy the larger volume? 90 ° F db, 70 ° F wb or 80 ° F db, 75 ° F wb?

46. Calculate infiltration air quantities in summer for a 10,000 square foot school classroom building, with 12 feet high conditioned space and total population is 320 students and teachers. Expected air changes in summer is 1.5.

47. Find the heat loss through a 180 sq ft window if its U value is 1.1, the indoor temperature is 80 ° F, and the outdoor temperature is 20 ° F?

48. Find the heat loss through a 1,500 sq ft wall if its U value is 0.1, the indoor temperature is 75 ° F, and the outdoor temperature is 0 ° F?

49. Calculate infiltration air quantities in summer for a 10,000 square foot school classroom building, with 12 feet high conditioned space and total population is 320 students and teachers. Expected air changes in summer are 1.5.

50. The two air/water vapor mixtures below have the same dry-bulb temperature. Which one has the higher relative humidity, 80 ° F db, 60 ° F wb or 80 ° F db, 50 ° F wb?