Diffusion bonding heat exchanger

A method of operating a diffusion bonding heat exchanger having a core that includes a first heat transfer plate and a second heat transfer plate that are stacked and diffusion-bonded to each other, and a header portion covering a side surface of the core,

• wherein
• the first heat transfer plate includes a high-temperature flow path that includes a plurality of first channels having a groove shape in a flow path width direction,
• the second heat transfer plate includes a low-temperature flow path which includes a plurality of second channels,
• the high-temperature flow path of the first heat transfer plate includes a connection channel portion within at least a range that overlaps a predetermined range in a stacking direction, the predetermined range being a range from a flow path inlet of the second heat transfer plate to a position downstream of the flow path inlet of the second heat transfer plate,
• each of the plurality of first channels of the high temperature flow path has a first heat transfer plate flow path inlet open on a side end surface of the first heat transfer plate at an inlet header,
• in the connection channel portion of the high-temperature flow path, a plurality of connection paths having a groove shape, each of which extends across the channels of the plurality of first channels which are adjacent to each other such that the channels communicate with each other, are formed at intervals in a direction along the plurality of first channels,
• the low-temperature flow path includes a first portion that is provided in the predetermined range of the second heat transfer plate and a second portion that is provided downstream of the first portion,
• the channels of the first portion of the plurality of second channels are not connected to one another,
• each of the channels of the second portion of the plurality of second channels are connected by connecting paths, and
• the second portion of the plurality of second channels is larger in heat transfer area than a heat transfer area of the first portion of the plurality of second channels,
• the method comprising the steps of:
• introducing a high-temperature fluid from the inlet header into the plurality of channels of the high-temperature flow path channel inlets;
• introducing a low-temperature fluid having a temperature which is lower than a freezing point of the high-temperature fluid into inlets of the plurality of second channels of the low-temperature flow path;
• and
• controlling a flow rate of the high-temperature fluid in the high-temperature flow path, a flow rate of the low-temperature fluid in the low-temperature flow path, a temperature of the high-temperature fluid entering the high-temperature flow path channel inlets, a temperature of the low-temperature fluid entering the high-temperature flow path channel inlets, or a combination of one or more thereof, such that the high-temperature fluid temperature is maintained above the freezing temperature of the high-temperature fluid in the connection channel portion in the predetermined range.