Document Type: Full Lenght Research Article
R&D, High Pressure Boiler Plant, Bharat Heavy Electricals Limited, Trichy, India.
National Institute of Technology, Trichy, India
Mechanical engineering, NIT Trichy,Tamilnadu, India.
A study of heat transfer characteristics at supercritical pressure fluid flowing in a uniformly heated vertical tube has been carried out. In order to reduce the thermal emissions and to increase the thermal efficiency, supercritical boilers were developed at various sizes. Above supercritical pressure, the distinction of liquid and gas phases disappears. This eliminates the problem of critical heat flux and dry out phenomenon which occurs in subcritical pressure. However, the study of heat transfer behavior above supercritical pressure is indeed necessary since heat transfer deterioration occurs at high heat flux to mass flux ratio. In the present work, numerical simulation has been carried out to study the effect of various parameters such as heat flux to mass flux ratio, diameter and pressure that causes heat transfer deterioration. Shear Stress Transport k-ω model has been used for all the computations. It is observed that the metal temperature predicted by numerical simulation is more accurate than the empirical correlations available in the literature. A Visual Basic Program has also been developed to assess the empirical correlations in the context of predicting metal temperature under 5280 different operating conditions. Tube sizes of 10, 15 & 20 mm inner diameter with 4 m length, pressure between 225 and 280 bar and heat flux to mass flux ratio between 0.27 and 0.67 has been chosen to study the effect of diameter, pressure and heat flux respectively.