Condenser Performance, Control, and Heat Transfer Enhancement Issues Resulting from Elliptic-sensitivity of Shear Driven Internal Condensing Flows

This paper presents unsteady computational simulation results and supporting experimental evidence that show a certain fundamental feature of a purely shear driven annular/stratified internal condensing flow with respect to its sensitivity to boundary conditions. This feature is termed “elliptic sensitivity.” Shear driven condensing flows occur in 0g, horizontal channels, and micro-meter scale ducts of any orientation and they often have, or are designed to have, a significant annular/stratified regime. This fundamental feature of the flow allows imposition of several possible values of the mean pressure-difference (unlike the usual situation of having only one pressure difference value) for a given set of quasi-steady values of mass-flow rate, inlet or outlet pressure, and a steady cooling approach for the condensingsurface. By a quasi-steady time-varying flow variable, it is meant that the variable exhibits a steady-in-the-mean value with suitable time periodic fluctuation (s) superposed on it. For most common cooling approaches, when a quasi-steady value of the pressure-difference is changed (even by an amount in the range of 5 – 200 Pa) in time to another quasi-steady value, it often triggers significant changes in the mean condensate thickness, heat transfer rates which induces significant thermal transients, and system characteristics outside the condenser. However if the