PROTO-HX™ calculates temperatures and heat transfer rates in shell and tube heat exchangers, plate frame heat exchangers and air coolers, and accurately predicts system performance. A computer-generated model of a heat exchanger enables the expediency, efficiency, and in performing evaluations under differing situations. Computer modeling can also be used to establish preventive maintenance programs and to trend current and limiting levels of fouling resistance and/or limiting cooling water inlet temperatures. PROTO-HX's built-in library of standard data takes the uncertainty out of modeling and evaluations and can help engineers address the heat exchanger concerns in the Nuclear Regulatory Commission's Generic Letter 89-13, Service Water System Problems Affecting Safety-Related Equipment.