2.1.1. Prediction power requirement in multi-level refrigeration cycle: two heat sources and a single heat sink

The power demand in the multi-level cycle is estimated, for the case data given in Table 2, by representing the multi-level refrigeration cycle as a two parallel simple cycle, as shown in Figure 2(b). It is clear from the results in Table 3 that the refrigeration model is under predicting


Table 2. Case data – two heat sources and one sink.


Table 3. Predicted shaft work requirement for multi-level cycle – two heat sources and a single heat sink using HYSYS and new shortcut model [3].

the compression shaft work requirement by 325 kW. The error between the refrigeration model and HYSYS predictions for the overall shaft work is about 10%. This error occurs because of the mixing of the saturated stream from the low-pressure evaporator with the superheated compressor outlet from the low-pressure compression stage [2]. The superheated inlet conditions to the high-pressure compression stage lead to an overall increase in the power requirement when compared with two simple cycles operating in parallel, as shown in Figure 2(b).
