These are heat exchangers of fused glass construction are used for cooling and condensation. These heat exchangers are made entirely of glass i.e. the exchange tubes are fused to the jacket. This result in the following main advantage:
Units of this type are supplied in various designs with exchange areas ranging from 0.3 to 15 m2. Larger areas can be obtained by combining several exchangers.
The construction, especially of the larger units incorporates all the features required for operational safety :-
The maximum operating pressure in the coil is 3 bar gauge for the larger units. The heat exchangers are connected to the services via flexible hoses or bellows. This prevents the transmission of stress or vibration to the heat exchanger from the service pipework. Coil heat exchangers are used mainly for condensation, cooling and heating with heat transfer fluids. Heating with saturated steam is restricted to exchangers with a maximum area of 1 m2.
The overall heat transfer coefficients, k to be expected for units with an exchange area of 2.5 – 15.0 m2 are approximately as follows “
Liquid- Liquid exchange k = 120 – 175 W/m2k
Condensation k = 230 – 315 W/m2k