Heat exchanger differential oil temperature determination

A method of operating a gas turbine engine comprising:

• moving an accessory fluid to a component in a gas turbine engine;
• fluidly downstream of the component, passing the accessory fluid through a heat exchanger via a fluid inlet of the heat exchanger and out of a fluid outlet of the heat exchanger;
• sensing a strain of the heat exchanger at the fluid inlet and sensing a strain of the heat exchanger at the fluid outlet;
• determining a temperature differential across the heat exchanger based on the strains at the fluid inlet and the fluid outlet;
• and
• utilizing the determined temperature differential for a diagnostic purpose;
• and
• wherein the strain at each of the fluid inlet and fluid outlet is determined with a conductor member mounted on a substrate and a voltage applied across the conductor member, such that as the substrate expands and contracts the conductor member is deformed and a voltage change can be determined and a difference between a voltage change at the strain gauge at the inlet compared to a voltage change at the strain gauge at the outlet can be utilized to determine the temperature differential.

A heat exchanger comprising:

• a heat exchanger operable to cool a fluid and the heat exchanger having an inlet and an outlet for the fluid;
• and
• a strain gauge associated with the fluid inlet and operable to produce a signal indicative of a temperature at the fluid inlet and a strain gauge associated with the fluid outlet and operable to produce a signal indicative of a temperature at the fluid outlet, and a controller for determining a temperature differential across the heat exchanger by utilizing the signals from the fluid inlet and fluid outlet;
• and
• wherein each of the strain gauges at the fluid inlet and the fluid outlet include a conductor member mounted on a substrate and a voltage applied across the conductor member, such that as the substrate expands and contracts the conductor member is deformed and a voltage change can be determined and a difference between a voltage change at the strain gauge associated with the fluid outlet compared to a voltage change at the strain gauge associated with the fluid inlet can be utilized to determine the temperature differential.