Compressor Volumetric Efficiency
Compute a compressor's volumetric efficiency, ηv = (actual suction flow / volumetric displacement)·100%, the fraction of the piston-swept volume that actually pumps gas. Losses come from clearance volume (gas that re-expands), suction reheating and leakage. It drops as the compression ratio rises. It is a key indicator of compressor performance. Enter the actual suction flow and the volumetric displacement.
Result
—
Compressor volumetric efficiency
A reciprocating compressor never draws in the whole volume its pistons sweep — a few losses are unavoidable. The volumetric efficiency ηv = (actual suction flow / swept volume)·100% measures that effective fraction. The losses come from several sources: the clearance volume (the small space left at the top of the cylinder when the piston reaches the end of its travel — the gas compressed there re-expands on the downstroke, taking up room that should be drawing in fresh gas); the reheating of the cold gas as it enters the hot cylinder (which expands it and cuts the mass taken in); leakage past the valves and the piston rings; and pressure drop in the suction line. The most influential factor is the compression ratio: the higher it is, the more the clearance gas re-expands, and the more ηv falls — at very high ratios ηv can drop so far that single-stage compression becomes impractical (hence two-stage machines at low temperatures). ηv links the theoretical displacement to the real flow and therefore to the effective refrigerating capacity of the system. Enter the actual suction flow and the swept volume.
Related Tools
Compressor Volumetric Displacement
Compute the volumetric displacement of a reciprocating compressor, Vd = (π/4)·D²·L·n, the volume swept by the pistons, from the cylinder bore (D), the stroke (L) and the number of cylinders (n). It is the compressor's 'displacement' — the theoretical volume aspirated per revolution, which, multiplied by the speed and the volumetric efficiency, gives the actual flow. It defines the compressor capacity. Enter the bore, the stroke and the number of cylinders.
Real COP / Carnot Efficiency
Compute a refrigerator's second-law efficiency, η = (real COP/Carnot COP)·100%, comparing the measured real COP with the theoretical Carnot maximum for the same temperatures. It shows how close to thermodynamic perfection the system operates: real systems are typically at 40–60% of Carnot, due to compression irreversibilities, pressure losses and finite temperature differences in the heat exchangers. Enter the real COP and the Carnot COP.
Superheat Degree
Compute the superheat of a refrigeration system, ΔT = T_suction − T_evaporation(saturation), how much hotter the refrigerant vapor is than its saturation temperature at the evaporator pressure. Proper superheat (typically 5–10 °C) ensures only vapor (no liquid) reaches the compressor, protecting it from liquid slugging. Too much superheat reduces capacity. It is controlled by the expansion valve. Enter the suction and saturated evaporation temperatures.
Breguet Range (Jet Aircraft)
Calculates a jet aircraft's cruise range with the Breguet equation: speed divided by thrust specific fuel consumption, times the aerodynamic efficiency, times the natural logarithm of the ratio between weight at the start and at the end of cruise. Valid for cruise with V, specific fuel consumption and L/D held constant — in practice the cruise-climb, at fixed Mach and lift coefficient, or step-climb flight. Enter the speed, TSFC, L/D and both weights.
Compressor Work (Isentropic)
Compute the specific compression work in an ideal refrigeration cycle, W = h₂ − h₁, the enthalpy difference between the compressor outlet and inlet (isentropic compression, at constant entropy). It is the energy the compressor adds to the refrigerant per kilogram — the cycle's 'electricity bill'. Together with the refrigerating effect, it defines the COP (COP = refrigerating effect/work). Enter the outlet and inlet enthalpies.
Screw Degree of Fill
Calculate an extrusion screw's degree of fill, η = (actual flow ÷ drag flow) · 100, from the actual production flow and the screw's theoretical drag flow. Degree of fill measures how much of the screw's theoretical pumping capacity (the drag flow, which would occur with no back-pressure) is actually delivered as real flow — the difference is 'lost' to pressure flow (backflow from die resistance). It is thus a measure of the extruder's volumetric EFFICIENCY and operating point on the characteristic curve: a high fill (near 100%) means little back-pressure (open die, simple product); a low fill means strong back-pressure (restrictive die), with much internal backflow. In gravity-fed (flood-fed) extruders the screw runs full, and degree of fill reflects the drag-pressure balance; in metered-feed (starve-fed, common in twin-screw) extruders, degree of fill is deliberately controlled by the feed rate, decoupling flow from speed and giving independent control of residence time and shear. Knowing the degree of fill helps diagnose the process and optimize productivity. Enter the actual flow and the drag flow.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.