The single-blow transient testing technique considering longitudinal core conduction and fluid dispersion

Single-blow transient testing technique has been widely used to measure the thermal performance of compact heat exchangers. For compact heat exchangers with short length the effect of longitudinal core conduction can usually not be neglected. Furthermore, the flow nonuniformity in a heat exchanger has also a significant influence on its temperature response. A new conduction/dispersion model for the single-blow transient testing technique is developed to include the effects of the longitudinal core conduction and fluid dispersion. Because the axial dispersion coefficient depends on the flow pattern in the heat exchanger which is usually unknown, both the heat transfer coefficient and the axial dispersion coefficient are determined with the whole curve matching simultaneously. The experiments are conducted in an open circuit wind tunnel. Comparison is made between the experimental results and data available in the literature. The software TAIHE (Transient Analysis In Heat Exchangers) developed by the authors is applied to the data analysis to evaluate heat transfer coefficients and axial dispersion coefficients. The results show that the pulse testing technique developed in the present investigation can easily be carried out and gives good evaluated results.