Design and Analysis of High Pressure Feedwater Heater

Abstract

Heat exchanger is an essential part of any engineering system which works on thermal gradient principle. High Pressure Feedwater heater is one of the important component for supplying feedwater to the steam generator. It reduces temperature di erence, avoid thermal shock to boiler, reduces fuel consumption, improves ther- modynamic gain of the regenerative steam cycle by means of utilizing bled-o steam. It is highly necessary to critically design the di erent components of feedwater heater as it is subjected to varying pressure conditions (i.e. 8 MPa to 34 MPa) and varying temperature from ambient temperature to 189oC. These variation make it more critical as di erent zones namely desuperheating, condensation and subcooling are formed in the same shell which creates even high thermal gradients. Various International Codes such as ASME, TEMA, HEI are available for designing such heat exchangers.Commonly heaters are designed to sustain around 150 bars pressure.Hence designing of a special purpose,187 bar, heater as a whole from basic fundamental is highly essential. As it is coming under non-conventional equipment category, it is di cult to pre- dict its behaviour in the working condition.The analysis of shell to nozzle, tube to tubesheet is critical due to discontinuity stresses and local stresses. This analysis be- comes a requirement for such heaters as thermal shock and pressure di erences make the joints even more vulnerable to failure. Mechanical Design Calculations are carried out in accordance with ASME Section VIII Div.1. Further, analysis of shell to nozzle junction(steam inlet/outlet and feed- water inlet/outlet), tubesheet using FEA tool is carried out and results, conforming to ASME standards, is within the allowable limits. Design of leg support has been carried out for horizontal Channel Shell.