Patent ID: 7069981

Claim:
A method of operating a recuperative heat exchanger that transfers heat between a first fluid and a second fluid having a maximum operating mass flow rate through the heat exchanger, the first and second fluids having mass flow rates that are substantially proportional to each other, the method comprising the steps of: a) flowing a first fluid through a first pass of a first flow path of the recuperative heat exchanger; b) flowing a second fluid through a second pass of a second flow path of the recuperative heat exchanger, the second pass of the second flow path adjacent the first pass of the first flow path and the temperatures of the first and second fluids closely approaching or attaining a common temperature at the exit of their respective passes at the maximum operating mass flow rate; c) flowing the first fluid through a second pass of the first flow path of the recuperative heat exchanger after the first fluid has flown through the first pass of the first flow path; and d) flowing the second fluid through a first pass of the second flow path of the recuperative heat exchanger prior to the second fluid flowing through the second pass of the second flow path, the first pass of the second flow path adjacent the second pass of the first flow path and the temperatures of the first and second fluids closely approaching or attaining a common temperature at the exit of their respective passes at the maximum operating mass flow rate.