Help needed: two-phase cross-flow in a heat exchanger
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In heat exchangers where phase changes occur, such as condensers and reboilers, what does cross-flow between the two phases inside the heat exchanger mean? Does it refer to the gas in the shell layer undergoing phase change to form liquid, with the liquid and solid flowing in cross-flow, or does it mean that the fluid in the shell layer and the fluid inside the tubes flow past each other without any phase change?
This post was last edited by wiseboy on 2011-9-17 21:20, version 1. “The term “turbulent flow” has an ambiguous meaning that sparks various interpretations. The term \"turbulent flow\" in two-phase flow of phase-change heat exchangers does not refer to the turbulent flow of the fluid relative to the equipment (tube bundles, tube walls, etc.), but rather to the relative motion between the two-phase fluids. For example, condensation in horizontal pipes: liquid accumulates at the bottom of the pipe, while gas is present at the top. Gases move faster than liquids, resulting in relative motion at the gas-liquid interface: cross-flow ； 2. The cross-flow at this phase interface generates a frictional force at the gas-liquid interface, and this frictional force is the main driving force for the liquid to move forward. If the tube is perfectly horizontal with no inclination, this frictional force is the only force that drives the liquid forward.
Reply to 2# wiseboy: Thank you for your explanation; I understand now.