# Building Construction Questions and Answers – Air Conditioning – Systems and Essentials

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This set of Building Construction Multiple Choice Questions & Answers (MCQs) focuses on “Air Conditioning – Systems and Essentials”.

1. If the direction of the wind is at 90° to one of the faces, positive pressure will be produced on __________
a) Windward face
b) Leeward face
c) Two windward faces
d) Two leeward faces

Explanation: If the direction of the wind is at 90° to one of the faces, positive pressure will be produced on the windward face. Positive pressure will be produced on two windward faces if the direction of the wind is at 45° to one of the faces.

2. The rate of ventilation depends on both the wind effect and the stack effect.
a) True
b) False

Explanation: The rate of ventilation depends on both wind effect and the stack effect. In ventilation due to wind effect, the rate depends on the direction and velocity of the wind outside. In ventilation due to the stack effect, the rate is affected by the convection effects.

3. The rate of flow through an opening due to the wind blowing on the wall containing it is given by the expression ___________
a) Q = KV/A
b) Q = KA/V
c) Q = AV/K
d) Q = KAV

Explanation: The rate of flow through an opening due to the wind blowing on the wall containing it is given by the expression where Q = rate of air flow in m3/h, A = area of the smaller opening in square metres, K is the coefficient of effectiveness and V is the wind speed in m/h.
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4. If the direction of the wind is at 45° to one of the faces, negative pressure will be produced on __________
a) Windward face
b) Leeward face
c) Two windward faces
d) Two leeward faces

Explanation: If the direction of the wind is at 45° to one of the faces, negative pressure will be produced on two leeward faces. Negative pressure will be produced on one leeward face if the direction of the wind is at 90° to one of the faces.

5. The rate of flow of air arising due to the difference in temperature of outside and inside is given by the expression ____________
a) Q = 320 C.A. [h(T-t)]½
b) Q = 320 C.A. x h(T-t)
c) Q = 640 C.A. [h(T-t)]½
d) Q = 640 C.A. x h(T-t)

Explanation: The rate of flow of air arising due to the difference in temperature of outside and inside is given by the expression Q = 640 C.A. [h(T-t)]½. Here, C stands for coefficient of effectiveness, Q is the rate of air flow in m3/h, A is the free area of the inlet opening, h is the vertical height difference between inlet and outlet, T is the average temperature of inside air and t is the average temperature of outside air in degree Celcius.
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6. In the expression for finding the rate of flow of air arising due to the difference in temperature of outside and inside, the coefficient of effectiveness for general conditions is taken as ___________
a) 0.35
b) 0.65
c) 0.85
d) 1.5

Explanation: In the expression for finding the rate of flow of air arising due to the difference in temperature of outside and inside, coefficient of effectiveness for general conditions is taken as 0.65. However, it is taken as 0.50 in the case of unfavorable conditions.

7. The coefficient of effectiveness decreases with the relative size of the larger opening.
a) True
b) False

Explanation: The coefficient of effectiveness increases with the relative size of the larger opening. It depends on the direction of the wind relative to the opening.

8. Calculate the flow of air through two square openings of size 0.36 m with the wind blowing at a speed of 5 km/h. Given the value of K is 0.3.
a) 174.4 m3/h
b) 194.4 m3/h
c) 267.4 m3/h
d) 234.4 m3/h

Explanation: The flow through an opening is given by the expression Q = K.A.V. Therefore, the flow of air through two square openings of size 0.36 m with the wind blowing at a speed of 5 km/h is 0.3 x 0.36 x 0.36 x 5000 = 194.4 m3/h.

9. Ventilation arising from the temperature difference between outside and inside takes place due to ____________ effect.
a) Stack
b) Stark
c) Zeeman
d) Spark

Explanation: Ventilation arising from the temperature difference between outside and inside takes place due to the stack effect. When the temperature of the inside air is higher than the outside air, warmer air passes through the opening situated in the upper part of the room while the cooler air enters the room via the lower openings.

10. According to the Indian Standard Code IS: 3362-1977, in the case of natural ventilation, flow per unit area of the opening is greatest when the inlet and outlet openings are of nearly equal __________
a) Lengths
b) Volumes
c) Areas
d) Mass

Explanation: According to the Indian Standard Code IS: 3362-1977, in the case of natural ventilation, flow per unit area of the opening is greatest when the inlet and outlet openings are of nearly equal areas. Also, inlet openings should be located on the windward side and outlet openings should be located on the leeward side.

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