Analysis of Variation in Properties and its Impact on Heat Transfer in Sub and Supercritical Conditions of Water/Steam

Thermal power plants use water and steam as main working medium. The properties of water and steam depend on operating pressure and temperature. The present work analyses the variation in heat transfer due to changes in properties of water and steam such as, dynamic viscosity, specific heat, density and thermal conductivity in the pressure and temperature ranges of 100 to 1000 bar and 5 to 700 degree C respectively. Microsoft Excel version of IAPWS IF-97 (The International Association for the Properties of Water and Steam Industrial Formulation-97), has been used for invoking the transport properties for the given pressure and temperature. Trends of predominant properties in the above mentioned pressure and temperature ranges have been plotted and analyzed. The variation in heat transfer coefficients, calculated using Dittus Boelter equation, for a typical case has also been plotted. The present work gives an idea for heat transfer equipment designers about the conditions to be carefully handled to avoid metal temperature increase and the conditions that could be exploited to gain maximum heat transfer for cooling applications. The study also identifies the critical zones of property variations in sub and supercritical conditions which have direct impact on heat transfer.