Figure 11. Performance data for the cryocooler. Circles indicate the experimental data, the dotted line shows a linear fit to the data, and the dashed line indicates the operating temperature for the cryocooler in the MCD system.
These results suggest that the cryocooler was providing about 12.7 W of duty to the condenser during MCD operation, which is 3.3 W less than the manufacturer’s specifications. Reducing the condenser duty in the model to 12.7 W improves the fit with the experimental data, but there is still some disagreement. Reducing the duty in the model to 10.5 W allows the model to agree closely with the data. This additional 2.2 W difference is likely the result of parasitic heat losses (i.e., losses that result from imperfect insulation of the process).
One note about these results should be emphasized. The condenser duty in the model has only minimal impact on composition when the bottoms flow rate is small and the boil up ratio is high. Since the modeling and experiments used to determine column efficiency was performed at small bottoms flow rates, this finding about the actual condenser duty had no impact on the determination of the HETP values for each column.