Gardner D. Hiscox's movement 186 is a submerged-head vertical boiler with an enlarged water surface, a circulating diaphragm that directs water around the fire head, and a central space kept free from tubes to facilitate circulation. The calculator below uses user-entered equivalent geometry and flow only; it does not predict boiler performance or safe operation.
Submerged Head Vertical Boiler Interactive Calculator
Vary equivalent outer and central diameters, an entered circulation rate and water density. Results are exact cross-sectional and continuity arithmetic for entered values; they do not predict natural circulation, heat transfer, steam production, pressure or safe operation.
Equation Used
- The equivalent flow section is annular and the central diameter remains smaller than the outer diameter.
- Water density is treated as uniform for the entered scenario.
- Mean speed is simply entered volumetric flow divided by equivalent annular area.
- The model does not calculate pressure, heat transfer, steam rate, firing, water level, stress or safety limits.
How Hiscox's Submerged-head Vertical Boiler Is Arranged
Gardner D. Hiscox labels movement 186 a submerged-head vertical boiler. His short description establishes three distinguishing features: an enlarged water surface, a circulating diaphragm by which water sweeps the fire head, and a central space kept free from tubes to facilitate circulation.
The plate shows the lower fire-head region, the shaped diaphragm immediately above it, vertical tube rows around the sides, and the clear central passage. It supplies no dimensions, working pressure, heat rate, steam output, material specification or operating limit.
Using the Animation and Calculator
Use the cutaway to identify the fire head, diaphragm and tube-free centre. Change the equivalent diameters and flow rate to see how flow area affects mean water speed.
It is not a boiler-selection, design, inspection or operating tool. Real boiler work requires verified drawings, materials, code calculations, water-level controls, combustion and heat-transfer analysis, pressure protection, inspection and qualified professional oversight.
Equivalent Area and Continuity Arithmetic
For user-entered equivalent outer diameter D and central clear diameter d:
For entered volumetric flow Q and density rho:
The central clear-area fraction is 100 d squared divided by D squared. None of these relations predicts natural circulation.
Worked Example: Entered Equivalent Geometry
For D = 1200 mm and d = 300 mm, the equivalent annular area is 1.060288 square metres, or 10602.88 square centimetres. An entered Q of 10 L/s gives an ideal mean speed of 0.009431 m/s. At entered density 980 kg/m cubed, the mass-flow equivalent is 9.8 kg/s, and the central clear-area fraction is 6.25%.
These values describe only the entered equivalent section and flow. They do not establish actual boiler circulation or performance.
What the Calculator Includes
- Established by Hiscox: enlarged water surface, circulating diaphragm, fire head, side tube rows and a central tube-free space.
- Calculated from entries: equivalent annular area, Q divided by area, rho times Q and central-area fraction.
- Not calculated: natural circulation, pressure, heat flux, steam production, firing rate, water level, crown temperature, structural stress or any safety limit.
Frequently Asked Questions
What does Hiscox say about movement 186?
He describes a submerged-head vertical boiler with an enlarged water surface, a circulating diaphragm that sweeps the fire head, and a central space free from tubes to facilitate circulation.
Are the entered diameters historical dimensions?
No. They are adjustable dimensions for the area calculation; Hiscox supplies no dimensions.
Does the calculator predict natural circulation?
No. Q is entered by the user. The calculator only reports Q divided by equivalent area and rho times Q.
Does it calculate steam output or working pressure?
No. Heat transfer, steam production, pressure and firing are outside the model.
Can it establish safe water level or boiler safety?
No. It provides no operating or safety limit and is not a substitute for code calculations, controls, inspection or qualified engineering.
References
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