NO-FROST EVAPORATORS

No frost refrigerators are based on the use of finned evaporators. The scope of this kind of evaporator is to collect the humidity, continuously moved by a fan inside the refrigerated cabinets. The vapor is condensed on the fins that are cooled by a primary circuit made by tubes where the fins are in mechanical- thermal contact. The condensed vapor is transformed in ice on the fins and removed from the fin surfaces using a defrosting cycle produced by a heater element. The process is automatic. The water produced by this operation is discharged outside the cabinet. This means that the internal environment of the cabinet is totally dry and this helps with healthy preservation of the foods when properly stored in closed containers.

Material

  • Al pipe (9.52mm OD) X (wall thickness 0.7~1.0mm)
  • Fin stock aluminum foil, thickness is 0.13~0.25mm
  • Inlet and outlet tube: Al-Copper tube

THE CONSTRUCTION OF THE FINNED EVAPORATORS IS BASED ON:

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1. Fin Punching. A special press punches the aluminum foil producing the fin with two holes and a collar for each hole with flanging height. This particular construction is important because the collar then is in direct contact with aluminum tube (primary exchange) and increases the exchange area.

2. Hairpin Production. The aluminum tube is straightened and bent to realize a long hairpin. In this tube, there is a flow of the refrigerant. The U forming is performed in a multi-line machine to guarantee high productivity.

3. Assembly of the fins on tube. The fins are assembled on hairpins in specific assembling tools, then the hairpin tube is expanded in order to create a mechanical interference between the external diameter of the tube and the internal diameter of the fin collars. The tube expansion guarantees more tight contact between fins and tubes so the result is an increasing heat exchange between fins and tubes.
Fin pinches can be made based on requested cooling project.

4. Evaporator Bending. The expanded finned hairpin is then bended according to the design in order to complete the assembly including the application of mechanical flanges to guarantee the requested form and rigidity of the evaporator.

5. Final Operation and Tests. The evaporator assembly is then terminated with the proper tubes through welding or fixing of the terminal ends. The leak test is performed with different technologies like water bubble test with specific pressures and \ or with tracing gas sniffer test. After the test stage, it is possible to add the requested defrost heater element.

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