apparatus for monitoring , characterizing , and testing coolant recirculation systems has , in combination , a heat load , a flow meter measuring flow rate of the coolant , inlet and outlet thermometers , and a data recorder connected to the flow meter , inlet thermometer , and outlet thermometer for recording their data outputs . the data recorder has an output representing flow rate , coolant inlet temperature , and coolant outlet temperature , whereby the coolant - recirculating heat exchanger system is characterized . a computer connected to the data recorder output is operable for computing heat removal capacity . the apparatus is specially adapted for methods of monitoring , characterizing , and testing coolant recirculation systems , including determining their maximum heat removal capacities .