The effects of thermal boundary condition on flow at supercritical pressure

Abstract

Fluids at supercritical pressure undergo a continuous phase from a liquid to a gas state if the fluid is heated above the critical pressure. During this phase transition the thermophysical properties of the fluid vary significantly within a narrow temperature range across the pseudo-critical temperature T pc  Tpc

(pseudo-critical temperature is defined as the temperature at which the specific heat at constant pressure (c p  cp

) attains its peak value). Figure 1 shows the variation of thermophysical properties of CO 2  2

at a thermodynamic supercritical pressure P 0  P0

= 80 bar (P critical =73.773bar Pcritical=73.773bar

) as a function of temperature (Int J Thermophys 24, 1–39 (2003)) [1]. These characteristics make supercritical fluids appealing in many industrial applications, such as: desorption, drying and cleaning in extraction processes; pharmaceutical industry; in power cycles as working fluids (Renew Sustain Energy Rev 14, 3059–3067 (2010)) [2] , (Nucl Technol 154, 283–301 (2006)) [3] and biodiesel production ( Fuel 80, 225–231 (2001)) [4].