Size the coolant loop: enter the heat load and the coolant temperature rise you can accept across the cold plate or heat exchanger, pick the coolant, and get the required flow rate.
The diagram is labeled with the same symbols as the input fields below.
Liquid moves heat with startling efficiency compared with air: one liter per minute of water absorbing a 5 C rise carries about 350 W. That density is why cold plates dominate power electronics, lasers, EV chargers, and increasingly AI compute racks. The flow equation is the same sensible-heat balance as the airflow case - only the fluid properties change, which is exactly why the glycol selection matters.
A 50-50 ethylene-glycol mix - the standard freeze-protected loop - carries about 20% less heat per liter than pure water and is several times more viscous, so it costs both flow AND pump head. Designing on pure-water numbers and then filling with glycol in winter is a classic path to an undersized loop. Oils and dielectric fluids give up even more, trading heat capacity for electrical safety in immersion systems.
The step this estimate cannot take: the temperature of the DEVICE also depends on the cold plate's internal resistance, the flow split between parallel plates, and transient events like pump failure ride-through. Those questions belong to a loop-level network simulation - cold plates, lines, heat exchanger, pump curve, and control together.
Water with a 5 C rise needs about 2.9 L/min per kW (0.76 GPM). A 50-50 glycol mix needs about 3.6 L/min per kW for the same rise. Halving the allowed rise doubles the flow.
Yes. A 50-50 ethylene-glycol mix has roughly 20% lower volumetric heat capacity than water, so it needs about 20% more flow for the same load and rise - and its higher viscosity raises pressure drop further. Always size at the actual winter mixture.
3-5 C is typical for precision cold plates (tight device gradients); 8-10 C suits energy-conscious loops where the downstream heat exchanger benefits from the warmer return. Tighter rise costs flow and pump power; looser rise costs device temperature uniformity.