Page 235 - Analysis, Synthesis and Design of Chemical Processes, Third Edition
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Example 8.4
Using Figure 8.4, calculate the relative costs of providing refrigeration at 5°C, –20°C, and –50°C. From
the figure, the ordinate values are given as follows.
Therefore, compared with cooling at 5°C, cooling to –20°C is 0.257/0.144 times as expensive, and
cooling to –50°C is 0.426/0.144 times as expensive. This analysis assumes that the two refrigeration
systems operate equally efficiently with respect to the reversible limit and that the major cost is the power
to run the compressors.
In Example 8.5, a real refrigeration system is considered and operating costs are estimated.
Example 8.5
Obtain a cost estimate for a refrigerated cooling utility operating at 5°C.
Consider a single-stage refrigeration system to provide refrigeration at 5°C, using 1,1 difluoroethane (R-
152a) as the refrigerant. The process flow diagram and operating conditions are given in Figure E8.5 and
Table E8.5, respectively.
Figure E8.5 Process Flow Diagram for Simple Refrigeration Cycle of Example 8.5
