Shell and Tube Condenser

Condensation inside a Shell and Tube Condenser — ANSYS Fluent CFD Simulation

Description

This project simulates condensation inside a shell and tube condenser using ANSYS Fluent, modeling the phase change that occurs when water vapor releases its latent heat and converts to liquid upon reaching saturation temperature — here set at 46°C, with a mass-transfer time-frequency coefficient of 0.1. The condenser is a horizontal shell-and-tube heat exchanger, with hot saturated steam flowing through the shell at 10 m/s while cooling water flows through four rows of internal tubes at 5 kg/s and 20°C. As the shell-side steam contacts the outer surface of these cold tubes, it loses heat, drops below its saturation temperature, and condenses into liquid water. Within the Mass Transfer: Beginner CFD Training Package, this project isolates condensation in a real industrial device, building on the heat-pipe case toward a single-phase-change application.

Methodology

Given the exchanger's symmetric structure, only a semi-model is drawn, built in 3D in Design Modeler with two baffles inside the shell directing the hot flow, and meshed in ANSYS Meshing with an unstructured grid of 342,486 elements. Since both liquid water and water vapor are present and thoroughly intermixed rather than existing as distinctly separated regions, the Mixture multiphase model is used to represent the two phases together. Condensation itself is defined through an evaporation-condensation mass-transfer mechanism, which governs how vapor converts to liquid as it cools past the saturation point on contact with the cold tube surfaces.

Analysis

The results include 2D and 3D contours of pressure, velocity, temperature, water vapor volume fraction, liquid water volume fraction, and the mass-transfer rate between vapor and liquid. These fields show the hot steam cooling as it exchanges heat with the cold tube bank, dropping below the saturation temperature exactly where contact with the tubes is strongest. This temperature drop drives the phase change directly, and the resulting condensation and liquid-water production are visible in the volume-fraction and mass-transfer-rate contours, confirming the condenser is performing its intended heat-exchange and phase-change function. By the end of this project, you'll be able to set up a Mixture multiphase model with an evaporation-condensation mass-transfer mechanism, define saturation conditions and cooling boundaries in a shell-and-tube geometry, and interpret the volume-fraction, temperature, and mass-transfer-rate fields that characterize condensation in a condenser.