Ammonia Liquid Overfeed & Recirculation Calculator
Model pumped ammonia liquid overfeed circulation ratios, pump flow rates, evaporated mass flow, and low-pressure receiver (LPR) surge vessel sizing.
Evaporator System & Temperatures
Coil Holdup & Vessel Retention
Pump Flow & Circulation Rates
Low Pressure Receiver (LPR) Sizing
Hydraulic & Cavitation Advisory
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
What is a liquid overfeed (recirculation) ammonia refrigeration system?
In a liquid overfeed system, mechanical pumps circulate liquid ammonia through the evaporator coils at a rate significantly higher than the evaporation rate (typically 3 to 4 times the evaporation rate). The excess liquid ensures that every square foot of internal coil surface remains completely wetted, maximizing heat transfer coefficients.
Why are expansion valves not required on individual evaporator coils in overfeed systems?
Instead of delicate thermostatic or electronic expansion valves prone to superheat hunting and freezing, overfeed evaporators use simple fixed hand expansion valves or orifice plates to distribute liquid. The flow rate is determined by the central liquid pump pressure.
What is the role of the Low-Pressure Receiver (LPR) surge drum?
The LPR acts as both a liquid pump reservoir and a gravity vapor-liquid separator. Wet return vapor and un-evaporated liquid from the coils enter the vessel; the liquid drops down into the pump suction sump, while clean dry vapor rises into the compressor suction header without danger of liquid slugs.
Why must liquid ammonia pumps have substantial static suction head?
Because the liquid in the LPR is at its boiling saturation point, any minor pressure drop in the pump suction line causes the liquid to flash into vapor, resulting in cavitation, seal damage, and lost flow. Elevating the drum 4 to 6 feet above the pump provides the necessary Net Positive Suction Head Available (NPSHA).