Abstract: A heat exchange arrangement (40) for a gas turbine engine (10). The arrangement (40) comprises a first conduit (46) for an engine component cooling fluid and a second conduit (44) for a second fluid. The arrangement further comprises a heat exchange portion (42) in which fluids flowing through the first and second conduits (46, 44) are in a heat exchange relationship. A valve 48 is provided, which is configured to moderate the mass flow rate of one of the fluids through the heat exchange portion (42). The arrangement comprises a temperature sensor (50) configured to sense a temperature of one of the fluids after said fluid has passed through the heat exchange portion (42) and a controller (52). The controller (52) is configured to control the valve (48) in response to a rate of change of the temperature with respect to time of the fluid sensed by the temperature sensor (50).

Abstract: A bidirectional water turbine comprising: an upstream rotor module and a downstream rotor module, each of the upstream and downstream rotor modules carrying a rotor comprising a plurality of blades; wherein the upstream and downstream rotor modules are individually removable from the turbine, the turbine being configured to operate with one of the upstream and downstream rotor modules removed.