Glossary

Some simple notions even for non-technicians.

All about cooling technologies. Technical solutions, components and accessories, physical notions: the terminology of evaporative and adiabatic theory from A to Z.

R

Adiabatic Cooling
Reduction of the air temperature by forced increase of its relative humidity, but without heat exchange (isenthalpic).
Evaporative Cooling
Heat dissipation from a fluid, generally water, by evaporation of a small part of the same fluid (latent exchange).

S

Spraying
Water sprayed out of the air inlet openings (leaks).
Thermal Difference
Difference between the temperature of the hot water entering and leaving the cooler.

A

Adiabatic humidifier
A device which allows to increase the relative air humidity to lower the temperature.
Air cooling system
System that uses air as a fluid to remove heat. This usually heappens by means of a coil of finned tubes.
Air liquid cooler
Heat exchanger usually consisting of a coil with copper tubes and aluminium fins. These last are aimed at increasing the contact surface with the air.
Ambient air
It is the air introduced into the cooler. It is taken from the environment and used for the thermodynamic operation of the cooling system.
Approach
It is the difference between the chilled water temperature and the ambient air wet bulb temperature.
Adiabatic Cooling
Reduction of the air temperature by forced increase of its relative humidity, but without heat exchange (isenthalpic).
Adiabatic Cooler
A device that uses adiabatic air cooling to increase sensible heat exchange efficiency in finned coil heat exchangers.
Ambient Noise
It is the sound level due to any source external to the cooling system.

B

Basin or Collection Basin
Basin collecting cooled water of a tower.

C

Closed circuit
See “closed circuit cooling towers”.
Components of the Cooling Tower
  • Casing.
  • Fill pack or filling material or heat exchange surface, formed to produce a contact between water and air.
  • One or more fans for generating air stream with the required characteristics (flow and pressure).
  • Cold water collection basin.
  • Drop eliminator to avoid excessive water losses due to dragging in the air flow.
Concentration
Quantity of solid or liquid elements unrelated to the treated water contained therein.
Cooling Tower
“It is a heat rejection device that rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or, in the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid to near the dry-bulb air temperature” (Source: Wikipedia).
  • Centrifugal cooling tower: device that uses a centrifugal fan to move the air which is necessary to perform forced evaporation. Generally preferred when there are noise problems, need for air ducting or when sound-absorbing silencers are needed.
  • Closed circuit cooling towers. Tower in which the process fluid which is cooled (often not water, but a cooling fluid) does not come into contact with the cooling water. This is distributed on the outer surface of a tube-bundle or of linked plates and circulates between the distributor and the basin.
  • Crossflow cooling towers (against the current). Towers in which the air flow goes in opposing directions.
  • Counterflow cooling towers. “In a counterflow design, the air flow is directly opposite to the water flow. Air flow first enters an open area beneath the fill media, and is then drawn up vertically. The water is sprayed through pressurized nozzles near the top of the tower, and then flows downward through the fill, opposite to the air flow” (Source: Wikipedia).
  • Factory-assembled cooling tower: small and medium-sized, totally factory assembled in 2 or 3 main sections with dimensions that are compatible for road or sea transport. No assembly time or a few days for modular systems.
  • Field-erected cooling tower. Generally large, in order to reduce transport costs. It is transported completely disassembled and assembled directly at the installation site. Assembly times are roughly variable between 20 and 60 days.
  • Mechanical draft cooling towerEvaporative cooler in which the water is cooled by partial evaporation through contact with a mechanically driven air stream.
  • Open circuit cooling towers. Evaporative system that cools water through direct exchange with air.
Cooling
Process by which the temperature of a gas, a liquid or a solid object, is changed by lowering it. In the case of the liquid, cooling may take place by mainly latent exchange using an evaporative system, or by sensible exchange by contact between two elements at different temperatures: for instance, in air cooling.
Cooling Technologies
Different methods, based on different functional principles, for removing heat derived by the production processes of various kinds. The choice for best technology must be made based on the user’s real needs and the environmental conditions of installation place.

D

Distribution Manifold
System of channels that distribute hot water to the filler material.
Distribution System
The water entering the tower should be divided into droplets and distributed evenly over the fill to obtain the maximum yield from the cooling tower.
Dragging
Droplets dragged out of the tower by the air stream.
Drop Eliminator or Drift Eliminator

System of baffles or fins placed inside the tower. It is intended to reduce the amount of water droplets getting dragged outside.

E

Evaporative Cooling
Heat dissipation from a fluid, generally water, by evaporation of a small part of the same fluid (latent exchange).
Evaporative Cooler
A device that performs the evaporative cooling in a forced and efficient way, optimising the latent exchange of the fluid to be cooled with the air.

F

Fill Pack or Filling material or Heat exchange surface.
Set of sheets or grilles of plastic material that separate the water in the tower and activate the contact between the fluids and therefore the cooling process. The fill pack’s purpose is to divide the air and water flows in the most uniform and targeted way possible. This would allow the most extensive contact between the fluids. The other purpose of a filling material is to slow down the fall of the water to allow a time when water can remain in the tower, thus creating a thorough cooling. There are two main types of fill packs, defined by the way in which they produce a large contact surface between water and air: film and spray.
  • Film fill pack. This type of fill pack distributes the water over a large surface dividing it into thin films or dispersed droplets. The film fill can be constituted by mobile or grating packs.
  • Spray fill pack. This type of filling material is formed with grates or bars arranged in horizontal planes over which the water falls, breaking into numerous droplets. These, by falling from one level to another, divide further. The grates or the levels below, are placed so as to continuously break the fall of water droplets.
Flow
See the next entries.
  • Air flowIt is the total amount of air, including the dissolved water vapour, which flows into the tower.
  • Inlet water flowQuantity of hot water or other liquid that enters the cooling circuit.

H

Hybrid Cooler
A device which, in a single solution, has an evaporative cooling and an air function. The former is used during summer, the latter during spring, autumn and winter periods.

M

Make Up
Water added to the circuit to compensate for liquid leaks from the circuit by evaporation, spray entrainment, water drains and various losses.

N

Nozzle
A device through which the flow of liquid is sprayed onto the filling material.

O

Open Circuit
See “open circuit cooling towers”.

P

Power
See the next entries.
  • Thermal power. See “Thermal power”.
  • Power absorbed by the fan motorPower measured at the control axis of the fan, excluding the only motor losses.
Plume
Cloud or column produced by the steam contained in the air exiting from the tower. It condenses on contact with the colder ambient air.

S

Scale Deposit
Deposits normally due to the mineral salts, or other solids present in the water or, in cases where an adequate water treatment has been provided.

T

Thermal Difference
Difference between the temperature of the hot water entering and leaving the cooler.
Thermal Power
Heat quantity subtracted from the liquid flowing into the tower. It is disposed of in the air.

W

Water Treatment
Without proper management and chemical treatment, the circulating water in a cooling tower would soon adversely affect the cooling system and decrease the exchange yield of both the tower and the entire circuit.
Water Cooling System
System or circuit that uses water as a fluid to remove heat, usually from another fluid or directly from a production process. The heat exchange can take place indirectly (in a closed circuit through a tube-bundle or plate exchanger), or directly through an evaporative open circuit tower.
Water Drain
Water discharged from the circuit to control the concentration of salts or other impurities in the circulating liquid.
Wet Bulb Temperature
Average air wet bulb temperature at the inlet to the tower, including any air recirculation effect. It is an essential concept for operation.