Condenser (laboratory)

Laboratory cooler are used for the condensation of gases and vapors devices in a chemical laboratory. Depending on the application and operating temperature different types of coolers are used. The cooling effect due to heat transfer processes at the cooling surfaces of the condenser. An important criterion for the cooling effect is, in addition to the coolant temperature, the size of the cooling surface, since the transmittable quantity of heat is proportional to the area of the radiator. The cooling area is an important structural feature of a radiator. Large cooling surfaces can be achieved by means of special shapes, such as cooling coils.

From the application side, a distinction between product coolers and reflux condensers. In the former, the resulting condensate is removed in the distillation as a product. Reflux condenser, however, are intended for condensation and recycling of the vapors in the distillation flask.

Product cooler, such as Liebig condenser or coil condenser be " descending " used for the separation of the distillate that is collected in a vessel, possibly using a Sogn. Spider.

Reflux condenser are always used in a vertical arrangement. In this structure, the condensate flows back into the flask from which it rises due to extreme heating or by reaction released heat.

Cooling media

In most cases, flowing water is used as coolant. With very volatile condensates, such as acetaldehyde, the cooling water may be cooled by a cooling circulator at lower temperatures and recycled.

For High-boiling solvents with boiling points above 120 ° C is sufficient in many cases standing water. At temperatures above 160 ° C often is sufficient, the ambient air as cooling medium.

The cooling media is introduced into the condenser by the countercurrent principle.

Types of coolers

Allihn or bulb condenser

The tube of the Allihnkühlers is more spherical constricted than in the Liebig condenser and at intervals. This results in a much larger cooling surface and stronger turbulence of the steam. This also still affordable type of cooler is used almost exclusively as a reflux condenser. It is named after Felix Richard Allihn (* about 1854, † 1915).

Dimroth

The Dimroth condenser comprises a cooling coil located within a tube. This type of cooler has a large cooling surface and is mainly used as a reflux condenser, but can also be used as a product cooler. It is named after Otto Dimroth.

Liebig condenser

The Liebig condenser consists of a straight glass tube with water jacket. It is substantially used as a product cooler distillations, which can also take place under high vacuum. Thanks to its simple structure, the Liebig condenser is inexpensive, sturdy and easy to clean. Due to the small cooling surface, the cooling effect is relatively low, so it is less well suited as a reflux condenser.

Intensive condenser

A high-efficiency condenser is a combination of Liebig condenser ( cooling jacket ) and Dimroth condenser ( cooling coil inside ). This type of cooler has the largest cooling surface. It is therefore particularly suitable for working with low- media such as diethyl ether.

Air cooler

An air cooler is made of a single wall pipe in which the vapor is brought about by the cooling medium is ambient air for condensation. Air cooler can be used as a reflux condenser and product cooler for high-boiling media use (boiling point greater than 150 ° C).

Coil condenser

Due to the design of the cooler must always be operated vertically. The condensation capacity for vapors is due to relatively low due to the small surface area. Due to the long residence time of the condensate in the cooling coil is cooled to almost the coolant temperature. Therefore often other types of coolers are coil condenser with condensation better performance ( or Allihn condenser Dimroth ) downstream to cool the distillate and not used as a standalone reflux condenser.

Condensation minute quantities of substances

For condensation of minute quantities of substances the cold finger or cold finger is used. With this cooler types, sublimation can be performed. Here, the condensed product to be isolated mostly crystalline to the cooler surface.

Pictures

Allihn or bulb condenser

Coil condenser

Dimroth

Intensive condenser

Cold finger

Cooler materials

Laboratory coolers are manufactured almost exclusively from laboratory glass, for example, borosilicate glass. In special cases, for example during distillation of hydrofluoric acid -containing solutions, even cooler of PTFE are used.

For the cooling of larger quantities of material in the chemical technology special heat exchangers, such as shell and tube heat exchanger or plate heat exchangers from different materials (stainless steel, PEEK, graphite, Hastelloy, tantalum, and many others) can be used.