In this study, thermal treatments have been investigated for different channel angles and mass flow rates of a compact heat exchanger have been manufactured by direct metal laser sintering technique instead of a sealed and brazed one used in many areas. Boundary conditions of available heat exchanger experimental test have been used in laboratory. In this study, we have designed for compact heat exchanger of 30 degrees, 45 degrees and 60 degrees channel angle and used three different mass flow rates (0.2, 0.3, and 0.43 kg/s). Heat transfers occurring between heat channels and walls of heat exchangers for different channel angles and efficiency of heat exchangers have been calculated. As a result of the analysis, it has been determined that in order for maximum of heat transfer of a compact heat exchanger, following working conditions ought to be fulfilled: channel angle 30 degrees, hot water input temperature 60 degrees C, cold water input temperature 15 degrees C, and mass flow rate 0.43 kg/s.