SH5107: A Laboratory Fume Hood, Hood Opening Area A = 40 ft2 (3.72 m2): Industrial Ventilation Assignment, NUS, Singapore

Assignment 4 – Specific Hood

Question 1

A laboratory fume hood, hood opening area A = 40 ft² (3.72 m²), face velocity = 100 fpm (0.5 m/s), entry loss factor f = 0.5. Assume STP.

1. Determine the volume flow rate required.
2. Size the duct to give a duct velocity of nearest 2,000 fpm (10 m/s) and round off the diameter to a whole number in inches or cm.
3. Determine the hood static pressure (SP_h).

Question 2

1. A canopy hood is being used on an open-surface tank, which is not located near any walls. The hood is located 1.2 m (4 feet) above the top of the tank. If the tank is 1.8 m (6 feet) long and 0.9 m (3 feet) wide and the contents are at room temperature, what airflow through the hood is required? Assume a control velocity of 0.75 m/s (150 ft/min).
2. If a lateral slot hood is used to capture the vapor evaporated from the same open-surface tank with the same control velocity of 0.75 m³/s/m² (150 ft³/min/ft²) of tank area. What airflow through the hood is required?

Question 3

1. A high canopy hood is to be placed 5 ft (1.5 m) above a crucible furnace 3 ft (0.9 m) in diameter, what will be the diameter D_c of the rising hot air column at the hood face?
2. In question A, if the furnace temperature is 932°F (500°C) and the ambient temperature is 86°F (30°C), determine the velocity of the air column at the hood face (V_f) and the total exhaust airflow rate Q_t through the hood.

Question 4

A low canopy hood is to be installed to capture the emissions during fluxing and slagging of brass in a 1.50 m diameter ladle. The metal temperature during this operation will not exceed 800°C. The hood will be located 1.00 m above the metal surface. The ambient air temperature is 35°C. Determine the exhaust rate required. (Note: diameter of hood = diameter of source + 0.3 m)

Question 5

A die-casting machine is with a rectangular holding pot 0.50 m wide by 1.00 m long for molten metal. A low canopy hood is to be provided 0.80 m above the pot. The metal temperature is 440°C. The ambient air temperature is 30°C. Determine the exhaust rate required. (Note: length or width of hood = length or width of source + 0.3 m)