What the result helps you understand
Reservoir volume influences residence time, deaeration, contamination control and thermal behaviour. Tight packaging can shift more of the cooling duty onto an active heat exchanger.
Pumps & Hydraulics
Hydraulic Reservoir Sizing Calculator
Estimate a starting reservoir volume from pump flow and screen whether the exposed tank surface can dissipate the entered heat load.
“How large should the hydraulic tank be, and is passive heat loss likely to be enough without an active cooler?”
Core formulae
Reservoir sizing and heat screen
Usable volume starting point
V_use = Q_pump × multiplierTotal tank volume
V_total = V_use × (1 + headspace%)Passive dissipation
Q̇_passive = h A (T_oil − T_ambient)Thermal balance
Balance = Q̇_passive − Q̇_heatThe volume multiplier is a screening starting point, not a universal design rule. Confirm deaeration, residence time, contamination control, duty cycle and cooling requirements.
Simple arrangement sketch
Reservoir volume and exposed surface
1
Set a starting reservoir volume
Use a project-specific basis when one exists. The presets are only starting points for early sizing.
Why volume alone is not enough
Real reservoir performance also depends on duty cycle, deaeration, baffles, return-line arrangement, contamination control, suction conditions and the amount of heat rejected elsewhere in the system.
2
Screen passive heat dissipation
Compare the entered heat load with a simple natural-convection estimate for the exposed reservoir surface.
Results
Reservoir sizing screen
Recommended total tank volume198 L
Usable oil volume180 L
Oil-to-ambient temperature difference30 K
Estimated passive dissipation0.84 kW
Screening heat shortfall3.16 kW
The entered heat load exceeds the estimated passive capacity
Screening shortfall: 3.16 kW. An active cooler or a different thermal design basis may be required.
Method
Usable volume = pump flow × selected multiplier. Total volume adds headspace. Passive dissipation = h × exposed area × (oil temperature − ambient temperature).
Job-file record
Save the calculation, not just the number.
Copy a permalink that reloads these inputs, or download a PDF record with inputs, visible results, assumptions, a sensitivity note, date and disclaimer.
Know where the quick calculation stops
This is a starting-point volume and heat-dissipation screen, not a full thermal or fluid-cleanliness design. Duty cycle, return arrangement, baffles, filtration and cooler performance are not resolved here.
Important boundary
A calculator can show the arithmetic. It cannot establish every requirement that applies.
Confirm the actual equipment, loading, materials, condition, jurisdiction, contractual requirements, standard edition and current project documentation before using the result for design, repair, testing or lifting decisions.
Ask an engineer about this calculation →