All the data signals are collected and converted by a data acquisition system (a hybrid recorder). The data acquisition system then transmitted the converted signals through GPIB interface to the host computer for further operation. During the experiments, the water inlet temperature was held constant at 60.0 ± 0.2 C, and the tube side Reynolds number was approximately 38,000. Frontal velocities of inlet air ranged from 1 to 4 m/s. The energy unbalance between air side and tube side was within 2%. The water side resistance (evaluated as 1/ hiAi) was less than 10% of the overall resistance in all cases. The test fin-and-tube heat exchangers are tension wrapped having an ‘‘L’’ type fin collar. Thermal contact
conductance provided by the manufacturers ranged from 11,000to 16,000 W m2K1.
To obtain the heat transfer coefficient and pressure loss characteristics of the test coil from the experimental data, the e-NTU method is applied to determine theUA product in the analysis. Detailed reduction can be seen from previous work (e.g. Wanget al. [27] ).