The Duck Foot Heat Exchange Model (DFHXM) simulates the start up and steady-state conditions within a duck foot heat exchange system. The system consists of a heat exchanger and heating reservoir affecting a single flow of fluid. Fluid enters at a defined temperature and passes through a flat-plate, single-pass countercurrent heat exchanger. Fluid re-enters the heat exchanger after passing through a heating reservoir and exits the system near its original temperature. The DFHXM is intended to simulate systems for a variety of pasteurization applications including Legionella eradication and solar water disinfection.