An important part of the research on the dynamics of a heat exchanger discharge temperature control system is the investigation on the dynamics of the heat exchanger alone. This study considers, through analysis, experiment and computer simulation the dynamic behavior of a commercial tube and plate-fin, serpentine, water-to-air heat exchanger. The behavior of particular interest is the dynamic response of the discharge air temperature to changes in the hot water flow rate. This corresponds to the common configuration of the control system whereby a flow-modulating water valve, driven by a controller having its temperature sensor in the duct downstream of the hot water coil, is used to control the discharge air temperature.