Condensers in cooling centers
The condensers liquefy the refrigerant vapor compressed by the refrigeration compressor. The power is adjusted either step by step, by starting and stopping the fan motors – or straight forward with the frequency converter. Air and liquid cooled condensers are most commonly used and possibly also water cooled if preferred water is available.
Air-cooled condenser or air condenser
An air condenser is a low-cost option in northern conditions up to 1MW.
- easy maintenance
- no risk of freezing
- greater need for space
- higher refrigerant charge
- louder sound
The condenser cell is most commonly made of aluminum lamellae and copper tubes. Condensers made of steel tubes are used with ammonia fillings.
In the industrial climate, e.g. epoxy coated or copper lamellae.
Shell material: most commonly painted or plastic-coated galvanized steel.
A liquid-cooled condenser is used when:
- refrigerant filling should be kept to a minimum
- the distance between the compressor and the air-cooled condenser would be too great
- condensing heat is utilized at several sites
An antifreeze liquid such as a mixture of ethylene glycol and water is used as the medium.
A water-cooled condenser is the most common in industrial use, where the so-called industrial water. Liquid and water-cooled condensers are designed: multi-tube condenser, coaxial condenser or plate heat exchanger.
Multi-tube condenser construction
In a multi-pipe condenser, the refrigerant flows in the jacket and the condensing liquid in the pipes inside the jacket. The steam from the compressor is led from the connection at the top of the jacket to the condenser. The condensed liquid leaves the lower part of the jacket again. When the volume of the inner part of the condenser is large enough, the condenser can also act as a fluid tank for the machinery.
The condensing liquid is led to the condenser tubes from its lower part. With the turning chamber at the end, the flow is turned along the others back to the inlet end.
Depending on the desired temperature of the liquid, the liquid flows back and forth 1-2 times, finally leaving the top of the end.
The multi-tube condenser is easy to clean because the ends can be opened.
Plate heat exchanger type condenser
Condensers of the plate heat exchanger type are much smaller than multi-tube condensers of similar power. They are also significantly smaller in internal volume.
The condenser is built of corrugated sheets. The plates are soldered together with copper or nickel. Refrigerant flows in every other plate and condensing liquid flows in every other plate. Refrigerant vapor is passed to the heat exchanger from the top of the condenser and the condensed liquid leaves the bottom. The exact design depends on the type of plate heat exchanger used.
The condensing liquid is led to the heat exchanger from its lower part. The heated liquid leaves the top.
Plate heat exchangers can be welded, sealed or semi-welded. In a semi-welded, the refrigerant-containing plate pair is welded and the liquefied-containing plate pair is again provided with a seal.
Welded plate heat exchangers meet the requirements of demanding applications, whether corrosive liquids, gases or mixtures thereof are used as media. They operate in conditions and media unsuitable for sealed plate heat exchangers.
Want to know more about plate heat exchangers?
Get acquainted with : plate heat exchanger flow and heat transfer modeling thesis, Kalle Vähätalo, Tampere University of Technology, 2015