The rear gap position is the worst in the smallest gap range. Fin discontinuity in the front of the tube causes the smallest reduction of the heat transfer rate in comparison to the ideal tube-fin contact, especially for thin slits. Blocking of heat flow by the gap leads to the reduction of heat transfer rate. Velocity and temperature fields for cases with air gap were compared with ideal thermal contact cases. Different locations and sizes of an air gap spanning 1/2 circumference of the tube were considered for the range of airflow velocities. Several numerical simulations were carried out for a symmetric section of plate fin-tube heat exchanger to study the influence of air gap on heat transfer under periodic flow conditions. Various errors made in the manufacturing process can result in the formation of an air gap between the tube and fin.
Plate fin-tube heat exchangers are widely used in air conditioning and refrigeration systems and other industry fields.
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