Buffer heat exchangers for hydrogen engines

A method for heating hydrogen in a hydrogen powered aircraft engine;

• comprising
• flowing engine oil through a first engine fluid conduit of a first heat exchanger;
• flowing engine compressor bleed air through a second engine fluid conduit of the first heat exchanger;
• flowing the hydrogen through a hydrogen conduit of a second heat exchanger;
• flowing a buffer fluid through a first buffer fluid conduit of the first heat exchanger and a second buffer fluid conduit of the second heat exchanger, wherein the first engine fluid conduit, the second engine fluid conduit and the first buffer fluid conduit are fluidly isolated, wherein the hydrogen conduit and the second buffer fluid conduit are fluidly isolated;
• transferring heat from the engine oil and the engine compressor bleed air flowing through the first and the second engine fluid conduits to the buffer fluid flowing through the first buffer fluid conduit of the first heat exchanger;
• transferring heat from the buffer fluid flowing through the second buffer fluid conduit to the hydrogen flowing through the hydrogen conduit of the second heat exchanger;
• flowing engine turbine exhaust through a third engine fluid conduit of a third heat exchanger;
• flowing the buffer fluid exiting from the second heat exchanger through a third buffer fluid conduit of the third heat exchanger, the third buffer fluid conduit fluidly connected to a fourth buffer fluid conduit of the second heat exchanger, whereby the buffer fluid enters a first buffer inlet of the second heat exchanger to pass through the second buffer fluid conduit and exits the second heat exchanger through a first buffer outlet, the buffer fluid flows from the first buffer outlet to the third heat exchanger to flow through the third buffer fluid conduit, and the buffer fluid flows from the third buffer fluid conduit to a second buffer inlet of the second heat exchanger to pass through the fourth buffer fluid conduit to a second buffer outlet of the second heat exchanger;
• transferring heat from the engine turbine exhaust flowing through the third engine fluid conduit to the buffer fluid flowing through the third buffer fluid conduit of the third heat exchanger;
• and
• transferring heat from the buffer fluid flowing through the fourth buffer fluid conduit to the hydrogen flowing through the hydrogen conduit of the second heat exchanger.