On the basis of heat transfer mechanism of heating surface of heat recovery steam generator(HRSG) and combining with actual operation data of the combined cycle unit

the sensitivity analysis model of the efficiency of the HRSG was established through support vector regression(SVR). Moreover

the effects of several factors on the efficiency of the HRSG

such as the change of the heat transfer performance of each heating surface

the ambient temperature and the unit load

were analyzed. The results show that

the root mean square error of the HRSG efficiency sensitivity analysis model is 1.38×10~(-3) in the test set

which is in good agreement with the HRSG efficiency calculated by the heat balance diagram of the manufacturer

and the prediction accuracy is high. The HRSG efficiency decreases with the decrease of the ambient temperature

the increase of the exhaust gas flow of the gas turbine

and the degradation of the heat transfer performance of the heating surface. The medium and high pressure boiler system evaporator of each heating surface and the change of performance of high pressure evaporator and superheater has a great influence on the efficiency of the HRSG. The efficiency of the HRSG decreases by about 0.4% and 0.2% respectively for every 1.0% degradation of heat transfer performance of the heating surface of high pressure evaporator and superheater. The research results can provide theoretical support for the fault diagnosis and maintenance of HRSG.