Furnace wall ash deposit fluent phase change monitoring system

Claim 1

A heat flux measuring device, comprising: an enclosed elongate housing having air flow paths extending therethrough from an air inlet adjacent one end of said enclosure to an air outlet adjacent the other end of said enclosure, heat flux sensing means located adjacent said air outlet to permit air flowing through said enclosure to flow over said heat flux sensing means and prevent the build-up of ash thereon, elongated evacuated tube means containing water and extending generally axially within said housing from adjacent said one end of said enclosure towards said other end of said enclosure, heat sink means in heat conducting relationship with an end of said evacuated tube adjacent said other end of said enclosure, said heat flux sensing means being mounted to and in heat conducting relationship with said heat sink means, and heat exchange means within said enclosure in heat conducting relationship with the other end of said evacuated tube, whereby, upon said flux sensing means being heated by heat flux, and heat sink means conducts said heat flux to said tube means to evaporate said water in said tube while said heat exchange means cools said tube and condenses the steam formed by said water evaporation, so that heat is removed from said flux detection means.