1.  Field of the Invention
This invention relates generally to heat exchangers and more particularly to a heat exchanger assembly particularly useful where rapid heating of significant quantities of air for space heating purposes is needed, such as in paint spray and baking booths. 
2.  Description of the Prior Art
Paint booths are provided with air that is heated by an indirect fired or direct fired system.  In direct fired systems, the heated air may include combustion products.  In the indirect fired system, the combustion products are handled separately, and heat exchangers of conventional types are used.  When the outdoor air temperature is low, below 30 degrees F., the indirect fired systems known to me do not have the ability to provide sufficient temperature rise when handling the needed volume of air to achieve the desired spray booth temperatures.  It is desirable to expedite the temperature rise in a higher volume of air without significant increase in firing rate.  My invention is directed toward achieving this result.