Operational Characteristics of a Double-Spiral Heat Exchanger for the Catalytic Incineration of Contaminated Air

A temperature of about 900 K is sufficient for rapid, catalytic oxidation of contaminants in air such as carbon monoxide, hydrocarbons, organic compounds, tobacco smoke, and microorganisms. It is demonstrated in this work, both theoretically and experimentally, that such a temperature can readily be atteined with a thermal input of less than the equivalent of 80 K by the use of a double-spiral heat exchanger. The double spiral is better than other geometries in terms of minimizing heat losses to the surroundings and is more compact. The theoretical solution reveals that for a double-spiral heat exchange an optimal value of UA/wc, the number of thermal transfer units, exists forwhich the temperature rise for a given heat input is a maximum. This maximum was overlooked in prior experimental and theoretical work. A general correlation is given for the conditions and dimensions which produce this optimal performance