Experimental investigation of thermal contact resistance in plain-fin-and-tube evaporators with collarless fins

The thermal contact resistance between fins and tubes in a plain-fin heat exchanger has been studied. The test coils have aluminum fins and tubes with no fin-collars. The heat-exchanger configuration under investigation was selected because this fin–tube joint is commonly used in refrigeration applications. Two coils were examined: one in the as-manufactured condition, and the other with brazed fin–tube joints—providing an intimate, metallurgical, bond between fins and tubes. Both heat exchangers were examined under dry and frosting conditions. The results show significant contact resistance in the production heat exchanger when operating under dry conditions. When frost is formed on the surface, the contact resistance is dramatically reduced to an insignificant value.