When I started the Facebook group last fall, I posted a series of short articles derived from my blog about refrigeration cycle diagnostics daletrossi/. There were very few members then. I am going to re-post the series now for the benefit of most members that didnt see it. Number 12 Heat transfer We will consider three service-related factors that affect heat transfer through the air cooled condenser. One factor that affects heat transfer is the amount of surface area available. We understand that there is more heat transfer when there is more contact between the thing you are cooling and the thing you are cooling it with. The aluminum fins in air-cooled condensers provide more surface area between the warm copper coils and the air used to cool it. Another factor effecting heat transfer in an air-cooled condenser is the volume of air being pulled past the fins. The more air that moves through the condenser coil, the more heat is transferred to the environment. Still another factor effecting heat transfer is the ΔT, or the difference in the temperature between thing being cooled and the thing we are cooling it with. A good way to visualize that third factor is to consider an ice cube in a frying pan. The ice cube will melt at some rate because of the heat transfer between the ice and the pan. If we were to put a fire under the pan and increase the ΔT, the ice cube would of course melt at a different faster rate because of the additional heat transfer offered by the increased ΔT. When some technicians hear ΔT they assume we are talking about the difference in the air temperature before and after it has been through the condenser. That is a useful calculation as we will see later, but that is not the subject here. Next: Heat transfer in the condenser, continued I will post another installment each weekday.
Posted on: Wed, 05 Mar 2014 13:27:01 +0000
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