Quote:
Originally Posted by rick-l
The more I think about that, it makes sense.
The latent heat of evaporation is 600 cal/gram. The specific heat of ice is .5 cal/gram. The latent heat of fusion (melting) is 80 cal/gram.
So once the sensor/evaporator get a coating of ice on it the temperature rapidly goes down below freezing but the fan is still blowing hot air over it sucking out 600 calories per gram until it melts. I bet it isn't ice for long.
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I suspect that's why the factory placement for the T-stat capillary sensor tube is at the "warmest" point, last to freeze over, of the evaporator core.
My "vision" of a frozen over evaporator core doesn't allow for much, if any, "warming" airflow. Actual experience bears this out.
Ask any orchardist what the effects are of a coating of ice.
Modern day heat pump controls place a defrost control sensor in a area MOST likely to freeze over. Once that happens the sensor's temperature no longer reacts to the cooling refrigerant flow and a defrost cycle is triggered.