How to calculate bendedcurved Coils Heat Exchangers

In many applications, engineers need to find new ways to arrange the internal components of a unit in order to reduce the size of their embedded HVAC systems. There are situations where only bended or curved coils heat exchangers can fit into the unit: a typical example could be a remote condenser used in a lot of common air conditioning plants, where the coil is usually U-shaped and the fan, placed over the finned pack, intake the air from the outside.

Because of this particular shape and the fan position, the resulting airflow distribution is not homogeneous along the coil. For example, right across the curved area the crossing airflow is less, resulting in a low performance of the exchanging surface of that area.

Because of this, if we simulate this coil like any other linear coil, the capacity estimated by UNILAB COILS could be higher than the measured one.

In UNILAB COILS, this problem can be easily fixed. In the software, in fact there is a special factor that you can change so that the calculation will consider all these evaluations: it is the “Security Factor”. In general, you can set the security factor to 0.85 as a “first attempt”, but you can change it if the results are still far from your expected capacity. For example, if you have some experimental measurements, you can calibrate the calculation results changing the value of this factor.