Centrifugal compressor
A centrifugal compressor raises gas pressure by transferring energy to a continuous flow. It is a dynamic machine, not a sequence of sealed shrinking chambers.
Guide
ContentsImpeller, diffuser and stages
The rotating impeller adds energy and directs flow outward. A diffuser slows the flow and converts part of its velocity energy into pressure. One or several successive impellers can provide the required lift. The number of stages describes successive compression, not the number of separate compressors in a plant.
Operating map and surge
Flow, pressure lift and speed must remain within the model’s stable operating map. At unsuitable low-flow conditions, surge can cause large pressure and flow oscillations, sometimes with reverse flow. Capacity control and protective logic must respect the map throughout the expected load and temperature range.
Bearings and modulation
Constructions can use lubricated or oil-free bearing arrangements, including magnetic bearings in some models. These properties require exact model confirmation. Speed control and inlet guide vanes are possible methods of modulation; their effect depends on the compressor and required pressure lift.
Comparison within a chiller
Assess cooling output and power at actual chilled-fluid and heat-rejection conditions. Compare the compressor together with heat exchangers, auxiliaries and controls using the same calculation boundary. A favourable compressor operating point does not by itself establish a whole-chiller seasonal result.
Prepare a compressor request
Pressure conversion and pressure-ratio calculation · model selection unavailable
The pressure tool converts the supplied values and calculates the absolute discharge-to-suction pressure ratio. The request form records other requirements. Neither function selects a compressor, calculates capacity or confirms a refrigerant cycle, diagnosis or interchangeability.
For a technical review, identify the exact model and refrigerant, duty and rating conditions, electrical supply and control, oil, dimensions/connections, and the reason for replacement or service. Missing information remains unknown.
Selection / replacement · Service
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Absolute pressures and pressure ratio
Use suction and discharge pressures for the same stated operating condition and compatible measurement definitions. This is a pressure calculation; it does not check whether a compressor can operate at those pressures.
Method: 1 bar = 100 kPa; 1 MPa = 1000 kPa. Convert each input to kPa. For gauge pressure, p(abs) = p(gauge) + p(atm). For absolute pressure, use the entered value directly. r = p(discharge, abs) / p(suction, abs); r has no unit.
Both absolute pressures must be positive. Enter a positive absolute atmospheric pressure whenever either input is gauge. A negative gauge reading is allowed if its absolute pressure remains positive. Atmosphere is never assumed.
Example: suction 2 bar absolute and discharge 8 bar absolute give 200 kPa, 800 kPa and r = 4. The same result follows from 1 bar gauge and 7 bar gauge with an explicitly supplied atmosphere of 1 bar absolute.
The calculation does not provide cooling capacity, power, discharge temperature, an operating envelope, refrigerant/oil compatibility, diagnosis or a replacement model. Pressure sources, measurement uncertainty, operating stability and model limits remain unverified. Displayed results are rounded; extreme values outside finite numeric precision are rejected.