| 摘要 |
A regenerative air heater is comprised of a matrix of heating surface elements contained in a compartmented housing with heat transfer being effected by alternately exposing the heating surface elements to hot gas and cooler air, thereby heating the exiting air stream. Un-burned products of combustion present in the gas may collect on the heating surface and, under certain operating conditions, ignite spontaneously in one or more local areas. In some instances, the local combustion can become severe enough to cause the heat transfer surface itself to burn, seriously damaging the heat exchanger. An elongated expansion element, made of a material having a high coefficient, of thermal expansion relative to the compartment structure, is used to sense the presence of a hot spot in any air heater compartment. The resulting thermal initiated expansion of the element activates a device to indicate the presence of a hot spot in the heat exchanger.
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