Special Edition – Mind Tweezer

Once in a while a question comes up that I can’t think my way through.  Here is one.  Within an insulated system there is air passing over a heat source that constantly produces a certain number of BTU’s per hour.  In the process, the air is heated from the inlet temperature to an elevated temperature at the outlet.  If the air flow is increased, the outlet temperature will decrease – agreed?  Does it necessarily follow that the surface temperature of the heat source is reduced as well?  Is cooling improved (lower source temperature) or are the BTU’s removed just distributed over a larger amount of air thereby producing a lower temperature at the outlet?

I really don’t know the answer on this one and hope someone can help me.  I’ll let you know how things come out.

3 comments on “Special Edition – Mind Tweezer

  • John Fuchs says:

    Maybe I should have asked the question in a different way. Let me try. Is the outlet temperature an absolute indicator of the temperature of the heat source? OR, is there a direct relationship between the outlet temperature and the temperature of the heat source? My thought is that one would have to know more about the heat source to establish this relationship. More specifically, the surface area of the heat source and the turbulent flow characteristics resulting from increased airflow. Does that change things? JF

  • Darnocbard says:

    Heat transfer is described as BTUs per sq ft ,per degree difference (TD) ,per hour.If the air exiting (from the system has the same heat content in both systems (constant BTUs) the(TD) would have to be reduced for the BTUs to remain constant

  • Darnocbard says:

    An increase of air flow will cause an increase of energy transfer.Therefore the constant heat source would have to have a reduced temperature.If the constant heat source was to remain the same temperature the BTUs would have to increase.

Leave a Reply