Applying Type 107 to EAW Wegracal SE 15

The TRNSYS Type 107 models a single-effect hot-water driven chiller using a lookup approach from a performance data file to predict the part load performance. With the release of TRNSYS 16 this Type was made a standard TRNSYS component. Although originally adapted to the operation and control of large scale absorption chillers (e. g. QE, rated > ~200 kW), this type and — as often expected — also the available example performance data file can be used for small capacity chillers also, since its data are normalised. Nevertheless some difficulties occurred when applying Type 107 in combination with the example performance file to the EAW Wegracal SE 15 chiller. Some of them are also mentioned in the manual of Type 107.

The example performance data cannot be used for the intended purpose since it does not suit to the operation conditions — neither to the manufacturers’ information nor to the conditions at Ebner Solartechnik. For example, the range of hot water inlet temperature (tGi) in the provided example performance file allows a range between 109°C and 116°C only; the manufacturers brochure depicts a range between 80°C and 90°C and, finally, the measured values at the solar cooling plant are often lower than 70°C.

If the chilled water inlet temperature (tEi) is too high or the available cooling capacity is too low to reach the chilled water set point (tEo, set), the part load conditions in Type 107 are calculated under the assumption of tEo, set nevertheless. Therefore the simulated cooling capacity is too low compared to what is happening in reality, since the real tEo will be higher as tEo, set.

As a consequence two steps of improvement have been carried out: A new Type — labelled as Type 307 here — was created on the basis of Type 107 and a new performance data file based on laboratory measurements has been prepared. Both will be explained in the next section.