Adjustment of operating conditions for centrifugal compressors with short-circuit backflow
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Regarding the issue of load adjustment for centrifugal compressors, various manufacturers state that it is possible to adjust the load of such compressors within a certain range by using the variable speed operation of turbines; below that level, bypass circuits must be used to create backflow. (I don’t know whether the return gas is taken from before or after the outlet water cooler.) Well, the gas compressed by the centrifuge must be at a higher temperature than the inlet temperature; if the production load is very low, then the amount of return gas will be large. Does this mean that the temperature of the medium inside the centrifuge will keep rising due to this return flow? Until jumping out of the car? Are there any other measures to cool the return gas?
Typical anti-surge flow curves have certain temperature restrictions; for example, the temperature must be kept within a specific range. Therefore, some systems incorporate coolers to address this issue. Another important problem is that, at low loads, the hot gas exiting the system flows back to the inlet in large quantities. Throttling from high pressure to low pressure generates a significant amount of cooling effect, and this cooling effect can even cause the inlet temperature to drop further! At the same time, when operating at low load, the load on the cooler at the compressor outlet is generally designed to be high enough to cool the compressed, high-temperature gas to the desired temperature; there is no issue as you mentioned.
It is best not to use the variable speed method of turbines to adjust the load of centrifugal compressors. Turbines achieve the highest operating efficiency at their rated speed.