The use of a double-spiral heat exchanger/catalytic reactor is proposed to decompose nitrous oxide (N
2O) gas, which is widely used as anesthetic in the operating rooms of hospitals. Air contaminated with N
2O enters one spiral passage with a rectangular cross-section at the periphery of the reactor, is heated by exchange with the outflowing stream of air, and passes through an Rh/Al
2O
3 or Pd/Al
2O
3 catalyst layer in which N
2O is decomposed to N
2 and O
2. The purified air is then heated electrically in the central core and finally passes through the other spiral passage to the periphery where it is exhausted into the surroundings. With this device, a sufficiently high temperature is produced in the layer of catalyst to attain an essentially complete conversion of N
2O with a minimal electrical input and a minimal elevation of the temperature of the exiting air. The characteristics of heat transfer and the decomposition of N
2O in a double-spiral heat exchanger/catalytic reactor for this service were investigated experimentally and computationally. As an example, with an electrical heat input of 130 watts at the core and a volumetric rate of flow of 20 L/min of air plus 60 ppm of N
2O, the device produced a heat refluxing rate of over 200%, a temperature of 973 K for the air in the core, a temperature of 333 K in the exiting air, and a greater than 90% decomposition of N
2O.
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