Water Cooling Wattage Calculator - Flow, Delta T & Reverse

Water Cooling Wattage Calculator using Q=m-dot cp Delta T with L/min, gpm, m3/h, glycol/custom fluids, required flow, and reverse Delta T.

Solve for

Required: coolant properties, volumetric flow, and coolant temperature change.

Method: heat-transfer rate equals density x volumetric flow x specific heat x temperature change.

Coolant or fluid

Custom density

Density unit

Custom specific heat

Specific-heat unit

Volumetric flow

Volumetric-flow unit

Mass flow

Mass-flow unit

Coolant temperature change

Temperature-difference unit

Heat load

Heat-load unit

Process direction

Entering temperature

Entering-temperature unit

Leaving temperature

Leaving-temperature unit

Heat-result unit

Flow-result unit

Temperature-change result unit

Mass-flow result unit

Temperature-result unit

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Water Cooling Wattage Formula

In base units, the calculator uses water heat transfer with flow in L/min and temperature difference in °C.

Q = 69.7333 \times F \times Δ T

F = (Q) / (69.7333 \times Δ T)

Δ T = (Q) / (69.7333 \times F)

Q = cooling wattage, in watts
F = water flow rate, in liters per minute
ΔT = temperature difference between inlet and outlet water, in °C
69.7333 = water heat transfer factor based on water specific heat and density

The factor assumes liquid water with a specific heat of about 4184 J/kg·°C and a density of about 1 kg/L. Temperature difference in °F is converted as 1°F difference = 5/9°C difference. Results will change if you use glycol mixtures or another coolant.

Water Cooling Unit Conversions

These are the conversions used before and after the main calculation.

Quantity	Conversion	Use
Power	1 W = 3.41214 BTU/hr	Convert watts to BTU/hr
Power	1 BTU/hr = 0.293071 W	Convert BTU/hr to watts
Flow rate	1 GPM = 3.78541 L/min	Convert gallons per minute to liters per minute
Temperature difference	1°F difference = 5/9°C difference	Convert a Fahrenheit temperature rise or drop

Cooling Wattage per 1 L/min of Water Flow

Use this table as a quick check. Values scale linearly with flow rate.

Water ΔT	Cooling at 1 L/min	Cooling at 1 L/min
1°C	69.7 W	237.9 BTU/hr
2°C	139.5 W	475.8 BTU/hr
5°C	348.7 W	1,189.8 BTU/hr
10°C	697.3 W	2,379.7 BTU/hr

Example Check

If water flows at 3 L/min and rises by 4°C, the cooling wattage is:

Q = 69.7333 \times 3 \times 4 = 836.8 W

A larger temperature difference means each liter of water carries away more heat. A larger flow rate means more water is carrying heat away each minute.