**4. Conclusions**

The experiments performed for three considered cross-flow heat exchangers have shown that the air inflow non-uniformity range may be significant and its form depends on the air volumetric flow rate in the considered configuration. The experimental data allowed for determination of the total heat flow rates transported between the agents in the heat exchangers.

The computational results, as it was expected, have shown significant decrease in the heat flow rates comparing with the exchanger with fully uniform air inflow. The average deterioration factor is about 15%. Two aspects should be taken into account while evaluating the numbers from Table 5: the measurements errors and the accuracy of the code HEWES. Taking into account accuracy of the measuring instruments the maximum measurements error has been determined to be of ±4%. The uncertainty of numerical results has been assessed during the validation of the code - see (Bury et al., 2008a; Bury et al., 2008b) for more details - and the differences between numerical and experimental results may reach almost 11%. These two numbers and the fact that the numerical results are always underestimated allow to conclude that the air inlet maldistribution has significant impact on a cross-flow heat exchanger performance.

Following final conclusions and remarks can be pointed for summarizing this study:


The author realizes that the combination of experimental tests and numerical simulations to assess the impact of inequality for the work of the heat exchangers may be the subject of some criticism. The best solution would be to do all the analysis by means of measurements. However, to obtain a homogeneous air flow on the described testing rig, while maintaining the appropriate parameters, it is impossible due to technical limitations. Some attempts to implement this idea has been taken in (Bury et al., 2009b), and although it failed to get the full homogeneity of the flow, it was noted the positive effects.
