What is a design point?
The design point specifies the conditions based on which the compressor is designed for. These conditions are:
- Ambient temperature (of the air intake)
- relativ humidity (of the air intake)
- barometric pressure defined by the elevation above sea-level
- Required pressure rise by the compressor
- Required airflow from the compressor
Usually the compressor design uses these conditions as a maximum requirement and determines the mechanical and electrical components accordingly.
The design point describes then the maximum possible performance (flow/ pressure) under the given (maximum) conditions.
This will determine the sizes of components like diameter of cone diffuser, motor size, maximum discharge temperature and selection of materials, as well as exact impeller and gear design.
The next very important step is to define and evaluate the off-design operating points, as your compressor will seldomly run in the (maximum) design point.
These off-design points are usually lower airflows during regulation, expressed in %-air-flow of design point airflow. Also the ambient conditions will differ
from the design point. The power consumption of these is determined by a smart choice of the design point.