Formula for determining the heat dissipation of a radiator

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SUMMARY

The discussion focuses on calculating the heat dissipation of a water-cooled radiator with a fan, specifically addressing a scenario involving a 240 x 199 x 45 mm radiator volume, a 500W heat source, and various thermal properties of water and copper. Key variables include the specific heat of water (4.187 kJ/kgK), the specific heat of copper fins (0.385 kJ/kgK), and the flow rates of air (3.115 m³/min) and water (3.785 L/min). The analysis emphasizes the importance of forced convection and the Newtonian cooling model, highlighting that the heat transfer rate is proportional to the temperature difference and that empirical data, such as the Nusselt number, is crucial for accurate calculations.

PREREQUISITES
  • Understanding of forced convection principles
  • Familiarity with Newtonian cooling models
  • Knowledge of heat transfer coefficients and Nusselt number
  • Basic thermodynamics related to specific heat capacities
NEXT STEPS
  • Research the Nusselt number for various radiator designs
  • Explore empirical methods for determining heat transfer coefficients
  • Learn about steady-state heat transfer analysis
  • Investigate advanced cooling techniques for radiators
USEFUL FOR

Engineers, thermal management specialists, and anyone involved in designing or optimizing water-cooled radiator systems will benefit from this discussion.

Daringpear
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Are there any equations out there which can calculate the heat dissipation of a water-cooled radiator with a fan on it? I would assume some of the variables would include:
-Volume of the radiator (240 x 199 x 45mm)=2149200mm^3
-Specific heat of water (4.187 kJ/kgK)
-Specific heat of the copper radiator fins (0.385 kJ/kgK)
-ΔT between the temperature of the coolant (variable we are solving for), and the ambient air temperature (lets assume 20 degrees C)
-Rate at which air moves over the radiator fins (3.115 cubic meters/minute)
-Rate at which water moves through the fins (3.785 Liters/minute)
-Energy being dumped into the system (500 watt heat source)

Ultimately what I want to accomplish, is find out if said radiator can adequately radiate 500W of heat (ΔT of less than 40 degrees C) in an ideal environment. Is there some equation into which I can plug these variables? Did I leave anything out?
 
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Welcome to PF;
The short answer is "yes".

Forced convection: a good model would be "Newtonian cooling" carrying off heat on the outside. The rate of heat transfer is directly proportional to the temperature difference. The trick is determining the constant of proportionality ... which you can do experimentally, or there may be tables you can look up.
ie. http://www.engineeringtoolbox.com/convective-heat-transfer-d_430.html

The water flow is more about keeping the radiator surface at a constant temperature by moving heat from some source to the inside of the heater. So long as the flow can deliver heat at the same rate it is being dissipated you are fine.
You will be more interested in stead-state situation ... the situation as the heater warms up will be much more difficult to model and not tell you much.
For strong convection, there is a point where increasing the fan speed makes no difference to the rate of heat transfer ... which is what your description sounds like. What the fan does is blow away the warmer air close to the radiator... ie maintaining the temperature difference.
 

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