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Compact tube-fin evaporators have been extensively used in refrigeration cassettes for light commercial applications. Such refrigeration systems are space constrained and, therefore, the heat exchangers (condenser and evaporator) must have a large area-to-volume ratio. In addition, such applications require a subfreezing evaporating temperature that induces the growth of a frost layer on the finned surface, which may block the evaporator if a proper defrost strategy is not used. Before completely blocking the evaporator, the frost layer depletes the heat exchanger performance by adding an extra thermal resistance and also by reducing the fan-supplied air flow rate. Understanding the way the frost forms on these compact heat exchangers and also the way the fan is affected by frost clogging is mandatory for the design of robust refrigeration systems and also to devise more efficient defrost strategies. In this study an experimental investigation on the frost accretion of tube-fin evaporators considering the fan characteristics is carried out. To this end, a specially designed, constructed and calibrated closed-loop windtunnel facility was used. Nine experimental tests were carried out with two different evaporator coils under different conditions. It was found that the fan characteristics play an important role in the evaporator thermal performance, indicating that for frosting conditions the fan and evaporator designs cannot be dissociated from one other.

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