Refrigerants, also referred to as refrigerant tubes, are equipment used in chemistry during the distillation process. Their task is to condense a substance or mixture by decreasing the temperature. Refrigerants have applications in many fields, they are used in industry, in industrial temperature control, in the domestic field, for example in freezers, and in laboratory chemistry.
In laboratory chemistry, refrigerants consist of glass tubes, characterised inside by two or more separate and independent sections. The characteristic composition of refrigerants allows the insertion of a refrigerant fluid inside the device, in one of the independent sections. This, separated from the substance to be cooled through the glass walls, will act as a heat exchanger by removing latent heat from the substance. A further feature of the coolers are two small side tubes, which can be found on opposite sides or on the same side of the appliance. They act as inlets and outlets for the coolant.
The Liebig refrigerant model features a vertical structure and two coaxial glass tubes. Both tubes have an inlet and outlet for the liquid inside. One contains the substance to be cooled and condensed, while the other contains the coolant.
Also referred to as a 'Claisen tube', this particular model of coolant has two 'male' and two 'female' plugs. One of the two male couplings is connected to the distillation vessel or rectification column from it, while the other consists of a diagonal coupling that connects to the condensation section. The two female couplings, on the other hand, are located in the upper part of the unit. One is generally closed, and can possibly be used for the inlet of an additional refrigerant. The other is a continuation of the elbow for housing the thermometer. The special design of the Claisen chiller allows better temperature measurement. It prevents drops condensed on the bulb from affecting it.
Allihn refrigerants consist of a long glass tube with a jacketed structure for the condenser fluid, usually water. The feature that distinguishes this model of cooler from others is a series of bulbs in the structure of the liquid to be cooled. This feature allows the Allihn refrigerant to increase the surface area over which the material inside it can condense.
Refrigerants from Davies
This model of refrigerant is similar to Liebig's, but with three concentric glass tubes instead of two. The refrigerant circulates in both the outer jacket and the innermost tube of the unit. This allows Davies' refrigerant to enjoy a greater surface area in contact with the coolant. As a result, the condensation process is less than in the Liebig model.
There are also other coolant models. Friedrichs' is characterised by a capillary tube for the refrigerant. This extends in a wide spiral along the walls of the unit. The Dimroth refrigerant, on the other hand, contains two spirals for the condenser fluid, both of which have their inlet and outlet in the upper section of the appliance. The vapours pass through the outer jacket of the refrigerant from the lower to the upper section.