10 Questions
Difficult to use variable ______ flow, as spray characteristics may be negatively affected.
water
Cross flow is a design in which the air flow is directed ______ to the water flow.
perpendicular
Air flow enters one or more vertical faces of the cooling tower to meet the ______ material.
fill
Water flows (perpendicular to the air) through the ______ by gravity.
fill
A distribution or hot water ______ consisting of a deep pan with holes or nozzles in its bottom is located near the top of a cross flow tower.
basin
Gravity distributes the water through the ______ uniformly across the fill material.
nozzles
Gravity water distribution allows smaller ______ and maintenance while in use.
pumps
The air flows horizontally and the water falling downwards meets the air at different ______.
temperatures
Low pressure head on the distribution ______ may encourage orifice clogging and less water breakup at spray nozzle.
pan
M3 – m4 = mass of ______ evaporated (or make of make-up water).
water
Study Notes
Cooling Towers
- A special type of heat exchanger that allows water and air to come in contact to lower the temperature of hot water.
- Evaporative cooling occurs as small volumes of water evaporate, lowering the temperature of the circulating water.
Applications of Cooling Towers
- Cooling condenser water in power and refrigerating plants.
- Water-cooled refrigerating (chiller) systems.
Types of Cooling Towers
Natural Draft Cooling Towers
- Use natural air flow direction to cool water.
- Two main types:
- Cross flow tower: air is drawn across the falling water and the fill is located outside the tower.
- Counter flow tower: air is drawn up through the falling water and the fill is located inside the tower.
Mechanical Draft Cooling Towers
- Use fans to circulate air mechanically.
- Advantages:
- Smaller size for the same capacity.
- Capacity control possible by controlling fan speed.
- Can be located inside a building.
- Disadvantages:
- Requires more power to run.
- Increased maintenance costs for fans, motors, and controls.
Types of Mechanical Draft Cooling Towers
According to Fan Location
- Forced draft cooling towers: fan is located near the bottom and forces air from bottom to top.
- Induced draft cooling towers: fan is located at the top and takes suction from the tower.
According to Flow
- Counter flow cooling towers: air flow is directly opposite to the water flow.
- Advantages:
- Breakup of water in spray makes heat transfer more efficient.
- Coldest water comes in contact with coolest and most dry air.
- Disadvantages:
- Typically higher initial and long-term cost.
- Difficult to use variable water flow.
- Advantages:
- Cross flow cooling towers: air flow is perpendicular to the water flow.
- Advantages:
- Gravity water distribution allows smaller pumps and maintenance.
- Typically lower initial and long-term cost.
- Disadvantages:
- Heat transfer is not always optimized.
- Low pressure head on the distribution pan may encourage orifice clogging.
- Advantages:
Learn about the fundamentals of cooling towers, a type of heat exchanger that allows water and air to come in contact to lower the temperature of hot water. Test your understanding of their working principles and functions.
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