Nr /9 1995 Józef Portacha, Adam Smyk and Idris A. El. Feituri Institute of Heat Engineering Warsaw University of Technology THE INFLUENCE OF THE HEAT TRANSFER COEFFICIENT VARIATIONS IN THERMAL SYSTEM ELEMENTS ON POWER AND DISTRIBUTION OF EXERGETIC LOSSES IN THE PWR NUCLEAR POWER PLANT The paper shows the results of a study on the influence of the changes of the heat transfer coefficient к on the exergetic losses in some selected equipment components of the thermal system and on the alternations of unit electric power. The changes of the к may be due to the fouling of the heat exchange surfaces or errors in the design. This research concerned with two feed-water heaters (low- and high-pressure) and the steam reheater situated behind the moisture separator. The research was conducted for the range of the ratio к (of actual to the design value of k) from 0.5 to 1.5 of its value assumed in the design. The mathematical model considers off-design operating conditions in the whole thermal system, which result from the change of the coefficient к in the selected parts of the thermal system. The decomposition method and Seild's multilevel iterative process were used to solve the problem. The research proved that the capaci- ty of the unit during operation may differ from the design value - 1000 MW - from ten to twenty MW due to alternations of the operation value of к from the design one. NOMENCLATURE к — overall heat-transfer coefficient, kW/(m 2 -K) n q = P/Q E — the ratio of the variation of the power plant capacity to the duty of the heat exchanger, kW/MW Ρ — electric power, MW q — net plant heat rate, kJ/kW-h Q E — heat exchanger duty, MW δ Π. = Π β - n pi — exergy losses in the i-th part or in the set of parts, MJ Δ - the change of the parameter к - к/k Q — ratio of actual to the design value of overall heat-transfer coefficient •Цк» Hp i — exergy losses in the i-th equipment component for the operation (Ε) and design (P) value of the coefficient к