local exhaust ventilation

1-How changes in velocity, velocity pressure and duct diameter can affect duct friction loss?

2-Review ABIH 9-e table, and use your own words to describe how changes in curvature (R/D) and the transition (pieces) of round elbow can affect the loss factor K.

3-What’s the range of recommended entry angles: __________

4-If the duct diameter, air temperature and humidity are same throughout a LEV system, you perform the SP and VP measurements at two different points (#1 and 2) of the duct: At a point (#1) of the upstream of air cleaner you get SP1 and VP1, and at another point (#2) of the downstream of air cleaner (but before fan) you have SP2 and VP2. Please determine the following relationship between two values using the symbol > (greater than), = (equal), or <(smaller than). SP1 ___________ SP2; VP1 ___________ VP2; TP1 ___________ TP2; V1 ___________ V2; Q1 ___________ Q2; air density (1) ___________ air density (2); Air mass (1) ___________ air mass (2);

5-What is the friction loss when air flows through a round galvanized duct with duct diameter of 5 inches and the length of 10 ft, and at an average velocity V = 4,000 fpm? Assume STP and df=1. The result should be rounded to 2 decimal places, and appropriate unit should be included for full credits. Hint: use equation 25 and 26 in textbook.

6-What is the 90-degree elbow loss factor (K elbow) where the elbow radius of curvature is R/D = 1.0 in a smooth transition elbow?

7-Cyclone can be used as an air cleaning device in LEV system. Use your own words to discuss how cyclone can work to clean contaminated air.

8-What is the ACGIH entry?

9-Use your own word to explain what the vena contracta is, and where it is located in the LEV system.

10-Use you own words to discuss why and how energy losses occur in local exhaust ventilation system. At least 4 factors need to be discussed.

11-What are two major functions of static pressure? Please explain where static pressure losses occurs in the LEV system?

12-The energy from SP losses is usually converted to some less valuable or useless types of works, such as ____________, ______________ and _____________.

13-What are the basic components of local exhaust ventilation? Please briefly explain the primary function(s) of each component?

14-We have discussed several different losses including duct friction loss, elbow loss and branch entry loss. Why these losses are the square function of velocity (V^2)?

15-If the conversion efficiency of SP to VP in the LEV system is less than 100%, there will have____________

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