Equilibrium temperature of heat exchanger

AI Thread Summary
In a closed loop system with a heater and a fan-cooled finned heat exchanger, water can reach an equilibrium state but may not achieve a true equilibrium temperature. The temperature rise of the water between the heater's inlet and outlet is constant if the specific heat remains unchanged and the heat flux from the heater is constant. The efficiency of the heat exchanger is influenced by the temperature difference between the ambient air and the water, which means the water likely won't cool back to ambient temperature. After several cycles, the temperature drop at the heat exchanger may equal the temperature rise from the heater, indicating an equilibrium state, though the water's temperature continues to change. This discussion highlights the complexities of thermal dynamics in heat exchanger systems.
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In a closed loop with a heater and a fan cooled finned heat exchanger where water flows between the two, is it right to assume that the water will reach an equilibrium temperature?
If so, is there an equation that can get the equilibrium temperature?
The power of the heater and cooler, the flow rate, volume of water and initial temperature are known.
 
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I don't think the system will reach an equilibrium temperature, but it can reach an equilibrium state.

If the water doesn't boil, we can assume it has a constant specific heat, and I don't know what your specifics are, but it might also be safe to assume that the heat flux from the heater is a constant. If this is true, then the temperature rise of the water between the inlet and outlet of the heater is a constant.

So, if everything is at ambient temperature before you "switch it on," the water will start to flow and the water leaving the heater will be at some elevated temperature (ambient temperature + some constant temperature rise). The efficiency of the heat exchanger depends on the difference in temperature between ambient air and the water, so it might not (probably will not) be cooled back to ambient temperature. After several passes, the water might be hot enough that the temperature drop at the heat exchanger is equal to the temperature rise at the heater, so now your system is at its equilibrium state. But the water is still changing temperature.

-Kerry
 
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