Walter Roller developed an optimised heat exchanger fin system for CO2 deep-freeze applications, with fin spacings up to 12mm.

While CO2 has become the most important refrigerant in the grocery market it CO2 alone does not make the system energy efficient. To support the energy-efficient characteristics of CO2 in the system technology, Roller says it has developed a fin system for evaporators that optimises the energy-intensive defrosting costs in deep-freezing.

The fin spacing of an evaporator has a significant influence on the resulting heat exchanger surface, with a closer fin spacing allowing more heat transferred. However, narrow fin spacing leads to the risk of heavy, disruptive icing, which results in frequent defrosting processes and reduces efficiency.

For defrosting, direct and indirect costs must be included in the energy cost calculation, argues Roller. The direct costs in terms of the electrical defrosting of the ice from the evaporator. The indirect costs to the defrosting heat generated in the room must be reabsorbed by the refrigeration system when it restarts.

The high-performance in-line tube system with the optimum tube diameter of 9.52 mm (3/8in) for CO2 applications developed by Roller; is available with up to 12mm fin spacing. The robust fin thickness also offers the advantage of a high mechanical load capacity, necessary for cleaning work.

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