Abstract: The present invention provides a heat exchanger for a fryer having a vat or tank filled to a selected level with a cooking medium such as shortening or oil. The heat exchanger includes a plurality of heat transfer tubes each having an inlet end and an outlet end, and at least one of the plurality of heat transfer tubes extending at a first angle, at least one of the plurality of heat transfer tubes extending at a second angle generally opposite to the first angle, and at least one of the plurality of heat transfer tubes extending horizontally. At least one mixing plenum having a plurality of inlet openings and a plurality of outlet openings is also provided, and at least some of the heat transfer tubes are sealingly connected to the mixing plenum. The plurality of heat transfer tubes and the mixing plenum are disposed within the vat of shortening in order to maximize the exposed heat transfer surface and thereby increase the heat transfer to the shortening.