Air Coolers

Air Coolers

Similar to other pumps, a Liquid Ring Vacuum Pump (LRVP) has a bladed impeller attached to a center hub.

TAn air cooled heat exchanger, or ACHE, is simply a pressure vessel which cools a circulating fluid within finned tubes by forcing ambient air over the exterior of the tubes. A common example of an air cooler is a car’s radiator.

Air coolers are used in industrial applications when reliable source of water is not available. Even if water is available, in some cases, air cooled exchangers are favored for economic & operational reasons – because dedicated cooling water circuits, pumps, water cooling systems & water conditioning system add complexity & capital cost, as well as operating & maintenance cost.

In moderate climate, air cooler will be a best choice for minimum process temperature above 65ºC & water cooling for minimum process temperature below 50ºC.

Advantages of using air coolers

Air is always available.
Maintenance cost normally less than for water cooled systems.
In event of power failure they can transfer some heat because of natural convection.
Mechanical design is normally simpler due to pressure on air side always being closer to atmospheric.
Fouling on air side can normally be ignored.
No problem arising from thermal & chemical pollution of cooling fluids.

Disadvantages of air coolers

Noise – Low noise fans are reducing this problem but at cost of fan efficiency & hence higher energy costs.
May need special features for cold weather protection (high pour point liquids freezes in cold weather).C
an not cool to same low temperature as cooling tower.

Types of air coolersForced draft type air cooler:

Forced draft type air cooler

Figure 2 - Forced draft type air cooler

Low power requirement for air Temperature rise greater than 10ºC.
Adaptable for winterization, pour point Recirculation schemes.
More readily accessible for maintenance.
Exchangers are easy to remove for repairs.
No mechanical equipment
exposed to hot air. Whereas induced draft is subjected to much higher temperature.
Less structural support required.
Isolated support for mechanical equipments.

Induced draft type air cooler:

Figure 3 - Induced type air cooler

Requires less power for an air temperature rise less than 10 ºC.
Less hot air circulation as exhaust air velocity Is about times that of forced draft.
Offers bundle protection from adverse weather.
Better suited for cases with close approach temperatures between inlet air & outlet fluid.
Air distribution over exchanger is better.
Will transfer more heat by natural convection because of stack effect.
Connecting piping usually less

Figure 4 - Types of tube bundle or manifold arrangements for air coolers