Apparatus for indirectly determining the temperature of a fluid

A technique for indirectly determining the temperature of a fluid includes directing at least a portion of the fluid around the outside of a thermally conductive body so as to produce a substantially uniform temperature therein. The fluid temperature is then determined by measuring the resulting temperature within the body. In one embodiment, the fluid is directed around the body by enclosing the body in a shell which has an inlet opening, an outlet opening, and at least one passageway connecting the inlet opening to the outlet opening. In an embodiment which is particularly useful for gas turbine applications, the body is located inside of the outer casing of the turbine and is connected to a guide tube which extends through the outer casing in such a manner that the means employed for measuring the temperature within the body is insertable into and removable from the body through the guide tube. For gas turbines having two or more turbine wheel stages, the inlet opening may be connected in flow communication with a wheelspace of a relatively forward one of the stages, and the outlet opening may be connected to a wheelspace of a stage located downstream of the forward stage, so that the pressure differential created between the stages during turbine operation causes at least a portion of the gas located in the forward wheelspace to pass into the inlet opening, through the connecting passageway, and out of the outlet opening.