Effects of exit-condition, gravity, and surface-tension on stability and noise-sensitivity issues for steady condensing flows inside tubes and channels

Computational and Ground‐Based Experimental Investigations of the Effects of Specified and Unspecified (Free) Pressure Conditions at the Condenser Exit for Condensing Flows in Terrestrial and Microgravity Environments

“…In the absence of active specification of a steady exit condition, the available range of steady exit conditions is determined by the components downstream of the condenser as well as the specific nature of the hardware used in the design of the rest of the system (or flow loop). Furthermore, because of the small pressure drops (see Phan et al 6 or experimental runs reported here), when a steady natural exit condition is achieved under unspecified conditions or the specified exit condition is not too far from this natural steady exit value, vapor flows are typically close to incompressible.…”

“…This paper is a synthesis of results from a fundamental and novel experimental investigation 1 into the effects of exit conditions on internal condensing flows and computational studies 2–6 of internal and external condensing flows. Toward the end of the paper, we also present a new set of generalized results for these and other internal two‐phase flows.…”

“…This is not generally true. The attainment of natural steady flows under unspecified exit conditions requires special hardware arrangements and, even then, such flows occur more readily (over a larger‐parameter zone) for gravity‐driven condensate flows than they do for shear‐driven flows 2,3,6 .…”

“…However, this sensitivity to exit conditions, or two‐way behavior, is special and does not result from the typical ellipticity associated with slow flows and flow reversals (which are, as described in Patankar, 20 associated with the changes in the sign of local Peclet numbers). In fact, it is found (for simulations in Narain et al 4–6 ) that even when vapor and liquid flows are unidirectional and local Peclet numbers [which appear in local discretization equations for the velocity components—see Eqs. (5.61)–(5.64) in Patankar 20 ] are very large (>50,000 in both the x‐ and the y‐direction for discretizations used in exit‐condition‐sensitive simulation results reported here), the flows exhibit elliptic or two‐way behavior leading to sensitivity of interface location to exit conditions.…”

Analysis of laminar film condensation over vertical permeable hollow short fins

“…They concluded that the elliptical section tube has a clear improvement of the vapor condensation over horizontal cylinder. Recently, the stability of the condensing flows has been discussed numerically and experimentally in several works [23][24][25][26][27]. The effect of the free-stream vapor-striking angle on the condensation over a vertical plate was analyzed by Khaled et al [28].…”