GPSA Ch. 14
| Parameter | Range |
|---|---|
| Economizer Pressure | Geometric mean of Pcond & Pevap |
| Flash Fraction | 10–25 wt% |
| Power Savings | 5–15% |
| COP Improvement | 5–20% |
| Liquid Retention | 3–10 min |
Flash Fraction:
Where hin = enthalpy of subcooled liquid entering economizer, hf,econ = saturated liquid enthalpy at economizer pressure, hg,econ = saturated vapor enthalpy at economizer pressure.
COP Improvement:
The economizer reduces compressor work by routing flash gas to an intermediate compression stage, avoiding re-compression from the lowest suction pressure.
Vessel Sizing: The economizer vessel is sized as a flash drum to separate vapor from liquid at the intermediate pressure. Diameter is set by vapor disengagement velocity (Souders-Brown), and length by liquid retention time with the specified L/D ratio and design margin.
Understand economizer design, flash gas separation, and refrigeration cycle optimization
An economizer flashes high-pressure liquid refrigerant at an intermediate pressure, routing flash gas directly to the compressor interstage. This subcools the remaining liquid before the evaporator and reduces overall compressor power per GPSA Ch. 14.
By flashing refrigerant at intermediate pressure, the economizer reduces the mass flow through the low-pressure compressor stage. The calculator quantifies power savings and COP improvement compared to a system without an economizer.
The calculator supports propane, ethane, propylene, and ammonia economizer systems. Each refrigerant's thermodynamic properties determine the flash fraction and resulting power savings at the specified intermediate pressure.
Vessel dimensions are calculated based on the flash gas and liquid flow rates, required retention time, and allowable vapor velocity for liquid-vapor separation. The calculator determines diameter and length per GPSA Ch. 14 guidelines.