Numerical and experimental investigation of buoyancy effects in a plate heat exchanger

► Heat transfer of a chevron-type PHE under mixed convection was studied. ► Aiding and opposing buoyancy experiments performed for Re = 100-400. ► Heat transfer is improved under aiding mixed convection conditions. ► Aiding buoyancy forces cause higher pressure losses. ► Opposing buoyancy deteriorates the flow symmetry inside channels.