1 If you are trying to cool the space why might you want to

1\\ If you are trying to cool the space, why might you want to bring in air from the outside that is warmer than the zone?

2\\ What are three advantages of VAV over CAV?

3\\ How does a cooling tower work?

Solution

1) If the outdoor air is cool and dry, it can cool the space nicely without using electricity for compressors and fans, and it ventilates the space with fresh outdoor air in the bargain. The same logic holds in non-residential buildings. In fact, it not only makes sense to introduce outdoor air when conditions are “right” .

Most commercial buildings have some spaces that need cooling all year long. If it’s colder outdoors than indoors, it
often makes energy-sense to “economize” by bringing in more-thanminimum outdoor air to reduce the hours of mechanical cooling system operation. A typical “mixed-air” air handler includes dampers for outdoor air, return
air, and relief air . These dampers can be controlled to provide airside economizing.

2)The VAV system offers some advantage and benefits over conventional systems as given below-
a) Fan energy savings from longhour usage at reduced volumes, also installed fan horsepower reductions.
b) Greater flexibility in respect to varying loads, which are easier zoned, resulting in occupancy controlled comfort and energysaving.
c) Reduced installation and set-up cost.
d) Reduced system energy consumption cost.
e) Single unit for easy mounting.
f) Integrated high efficiency sound attenuator.
g) Suited for mounting of all controls according to customer specification.
h) Accurate air volume control with centre averaging multi-point airflow differential cross velocity pressure sensor.

3) A cooling tower is a heat exchanger, inside of which heat is withdrawn from the water by contact between the water and the air. The heat transfer occurs through the heat exchange between air and water and through the evaporation of a small part of the water that needs to be cooled. This will allow to cool down to a temperature lower than the ambient temperature, which is an important advantage compared to dry coolers.

Consequently, a cooling tower is not a chimney producing smoke. The mist which can be seen above a cooling tower is regular steam with the same composition as a normal cloud.