A centrifugal exhaust head receives wet exhaust tangentially into a fixed drum. Swirling flow carries liquid droplets toward the wall, where collected liquid drains into the lower cone and bottom outlet. Vapor leaves through the upper outlet, with any remaining entrained liquid. Hiscox figure 421 shows the side inlet, drum, conical collector and drain.
Centrifugal Exhaust Head Interactive Calculator
Enter wet exhaust mass flow, inlet liquid percentage and an assumed or measured liquid-removal percentage. The animation shows the flow paths, while the calculator balances liquid entering, liquid drained and residual carryover.
Equation Used
- Steady flow, with no accumulation in the head.
- No condensation, evaporation or vapor loss through the liquid drain.
- Removal percentage is supplied by the user; no efficiency curve is inferred from speed or geometry.
- The animation illustrates flow direction, not resolved particle motion, real dimensions or residence time.
The calculator is a mass balance using an entered liquid-removal percentage. It does not predict separator efficiency, pressure drop or a suitable operating velocity. The cutaway and plan illustrate the historical tangential-entry arrangement.
How the tangential exhaust head works
Hiscox figure 421 shows a side pipe entering a drum tangentially, a conical lower collector and a bottom drain. Tangential entry makes the vapor circulate. Entrained water tends to move toward the wall, collect there and run down into the drain.
The vessel does not rotate. The plan view makes the tangent clear: the entering flow runs beside the wall rather than aiming at the center. The section shows the upper discharge and the separate path for collected liquid.
The moving markers identify these paths only. They are not a particle simulation and do not show a predicted residence time or separation rate. Remaining liquid leaves with the vapor as carryover.
Purpose of an exhaust head
This historical arrangement separates entrained liquid from exhaust vapor before discharge. The illustration explains the flow route; its proportions do not define a vessel pressure rating or a guaranteed liquid-removal percentage.
Actual selection needs equipment-specific performance and operating conditions. A mass balance is useful for estimating the drain and carryover loads once a removal percentage is known or assumed.
Liquid and total mass balances
Let m be total wet exhaust flow in lb/hr, L the inlet liquid mass percentage and η the fraction of that liquid removed, expressed as a percentage. Liquid entering = total flow × liquid percentage /100.
Liquid drained = liquid entering × η/100. Liquid carryover = liquid entering − liquid drained. Total upper-outlet flow = total inlet flow − liquid drained. It includes both vapor and residual liquid.
The vapor component is total inlet flow × (1 − liquid percentage/100), and remains unchanged under the no-phase-change assumption. Thus inlet flow equals drain flow plus upper-outlet flow.
The removal percentage is an input, not a calculated equipment rating. Velocity alone cannot establish it without applicable geometry, fluid and droplet information. Pressure drop and suitable inlet velocity require separate equipment performance data.
Example liquid balance
For 2000 lb/hr of wet exhaust containing 5% liquid, liquid entering is 100 lb/hr and vapor entering is 1900 lb/hr. If the entered liquid removal is 95%, the drain carries 95 lb/hr and 5 lb/hr of liquid remains entrained.
The upper outlet therefore carries 1905 lb/hr in total: 1900 lb/hr vapor plus 5 lb/hr liquid. Adding the 95 lb/hr drain recovers the original 2000 lb/hr inlet flow.
Changing the assumed removal to 80% gives 80 lb/hr drained and 20 lb/hr carryover. This comparison shows the consequence of an efficiency assumption; it does not establish that a particular head achieves either value.
Beyond the mass balance
Droplet size, vapor properties, inlet and vessel geometry, loading and drainage behavior can all matter to a real separator. The historical illustration does not provide a calibrated performance curve for these variables.
Condensation, evaporation, drain vapor loss and internal accumulation require additional balance terms. They are excluded here so the entered liquid split can be checked directly. The diagram is not a sizing or fabrication drawing.
Calculator questions
Does the head itself spin?
No. The body is stationary. Tangential entry causes the fluid to circulate inside it.
Where should the removal percentage come from?
Use measured performance or applicable equipment data for the operating conditions, or enter an explicitly assumed value for a comparison. The calculator does not predict that percentage.
Why is upper-outlet flow larger than liquid carryover?
The upper outlet contains vapor as well as residual liquid. Carryover refers only to its liquid component.
What do zero and 100% removal mean here?
At zero, none of the inlet liquid reaches the drain. At 100%, all inlet liquid is assigned to the drain and only vapor remains in the upper outlet. These are mass-balance limits, not claims of attainable equipment performance.
References & Further Reading
- Gardner D. Hiscox, Mechanical Movements, Powers, Devices and Appliances (1901), printed page 114, figure 421: tangential exhaust head with a lower collector and drain.
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