BIZOMAT MAKEOS · Manufacturing
Machine Coolant System Sizing
How much coolant flow, tank volume and pump power does this machine need?
Sizing of a machine-tool coolant system: the flow to carry the cutting heat away at an allowed temperature rise (as the coolant heat-flow tool), the flow the nozzles need for the jet velocity, the governing flow, tank volume for the chosen turnover time, and pump shaft power for the head and efficiency (as the pump power tool).
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Cutting power | kW | Cutting power at the spindle during heavy cuts. |
| Share of cutting heat into the coolant | % | Share of the heat carried by the coolant (most goes into chips and coolant). |
| Allowed coolant temperature rise | K | Temperature rise of the coolant you accept per pass. |
| Coolant specific heat | kJ/kg·K | Specific heat of the coolant (about 4.0 for water-based emulsions). |
| Coolant density | kg/m³ | Coolant density. |
| Number of nozzles | Number of nozzles delivering coolant. | |
| Nozzle bore | mm | Bore of each nozzle. |
| Jet velocity | m/s | Jet velocity wanted at the nozzle (higher for chip flushing). |
| Tank turnover time | min | Minutes of flow the tank holds (5–10 settles chips and releases air). |
| Pump head | m | Total head the pump must deliver (nozzle pressure plus losses). |
| Pump efficiency | % | Pump efficiency. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Cutting power
- What it is
- Power used at the cutting edge during the heaviest cuts, from a cutting power calculation or the measured spindle load.
- Units and format
- Enter a number in kW: kilowatts. The form accepts 0.000001 kW to 10000 kW. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The flow needed for heat rises in proportion.
What this means: Share of cutting heat into the coolant
- What it is
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 70% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The flow needed for heat rises in proportion.
- Get it right
- Type the percentage, not a fraction.
What this means: Allowed coolant temperature rise
- What it is
- How much the coolant may warm up in one pass through the cutting zone before it returns to the tank.
- Units and format
- Enter a number in K: kelvin (a difference of 1 K equals 1 °C). The form accepts 0.000001 K to 50 K. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 5 K as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Halving the allowed rise doubles the flow needed for heat.
What this means: Coolant specific heat
- What it is
- Heat needed to warm one kilogram of the coolant by one kelvin, from the coolant supplier’s data.
- Units and format
- Enter a number in kJ/kg·K: kilojoules per kilogram per kelvin. The form accepts 0.000001 kJ/kg·K to 6 kJ/kg·K. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 kJ/kg·K as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Check the unit: kJ/kg·K, not J/kg·K.
What this means: Coolant density
- What it is
- Mass of one cubic metre of the coolant, used for both the heat flow and the pump power.
- Units and format
- Enter a number in kg/m³: kilograms per cubic metre. The form accepts 0.000001 kg/m³ to 2000 kg/m³. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1000 kg/m³ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Number of nozzles
- What it is
- Number of nozzles delivering coolant at the same time, which with bore and jet speed sets the nozzle flow.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 200. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- 0 = no nozzle requirement: the flow is sized on heat alone.
What this means: Nozzle bore
- What it is
- Bore of the outlet of each nozzle, where the jet leaves.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Nozzle flow rises with the square of the bore.
What this means: Jet velocity
- What it is
- Speed of the coolant jet as it leaves each nozzle; faster jets flush chips better but need more flow and pressure.
- Units and format
- Enter a number in m/s: metres per second. The form accepts 0.000001 m/s to 200 m/s. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 m/s as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Nozzle flow rises in proportion to jet speed.
What this means: Tank turnover time
- What it is
- How many minutes of design flow the tank holds, giving time for chips to settle and air to escape before the coolant is pumped again.
- Units and format
- Enter a number in min: minutes. The form accepts 0.000001 min to 1000 min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 5 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Tank volume = design flow × turnover time.
What this means: Pump head
- What it is
- Total head the pump must deliver at the design flow: nozzle pressure expressed as head, plus pipe, filter and lift losses.
- Units and format
- Enter a number in m: metres. The form accepts 0.000001 m to 5000 m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Pump power rises in proportion to head.
- Get it right
- Head in metres of coolant, not bar: convert pressure with head = pressure ÷ (ρ g).
What this means: Pump efficiency
- What it is
- Efficiency of the coolant pump at the duty point, from the pump maker’s curve.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 5% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 60% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Pump shaft power is inversely proportional to efficiency.
Method and formulas
- Flow for heat Q = heat ÷ (ρ c_p ΔT).
- Nozzle flow = number × area × jet velocity; design flow = the larger.
- Tank volume = design flow × turnover time.
- Pump shaft power = ρ g Q H ÷ η.
- Example: 10 kW of cutting needs 21 L/min, a 105 L tank and a 0.11441 kW pump.
Limitations
- Average heat; through-spindle and high-pressure systems need their own pump curves.
- Tank size also depends on chip settling and filtration.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Specify a coolant pump and tank for a machine
- Check whether a coolant system keeps temperature stable
- Size a central coolant supply for several machines
Who it is for
- Machinists
- Manufacturing engineers
- Tooling engineers
What you get
- Flow for heat and for nozzles
- Tank volume
- Pump power
Interpreting the result
- If nozzle flow governs, fewer, better-aimed nozzles save pump power.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1112–1121, 1183–1190. Topic reference; no source tables or recommended settings are reproduced.
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