This master’s thesis is concerned with design of a heat exchanger for a unit with gas turbine. The pressurized air from the compressor is heated with flue gases from gasification and subsequent combustion of wooden biomass. Then it is led to the expansion turbine. For thermal and hydraulic calculations a program named HTRI Xchanger Suite® has been used. The thesis includes a brief description of heat exchangers, description of the used program, calculation and selection of input data, solving and conclusions. It contains also a layout of the exchanger.