Heller Dry Cooling Tower

Heller Dry Cooling Tower CFD Simulation

Description

This project simulates the airflow and heat transfer inside a Heller-type dry cooling tower — the indirect cooling system used in thermal power plants to reject heat from the working fluid to the ambient air without evaporative water loss. After leaving the condensers, the hot water is pumped through a ring of air-cooled heat exchangers at the base of the tower; cooling air is drawn through them by natural draft, created by the density difference between the warm air inside the tower and the cooler air outside.

The core physics governing tower performance is the temperature driving force: the larger the gap between the working fluid and the ambient air, the stronger the natural draft and the more effective the cooling. This is also why dry cooling towers lose efficiency in summer — as the ambient temperature rises, the driving force shrinks, forcing the plant to cut power output and increase water consumption to maintain cooling. This simulation makes that buoyancy-driven mechanism directly visible and quantifiable.

Methodology

The model includes the cooling tower, the heat-exchanger (radiator) ring, the surrounding flow domain, and the air inlet. The geometry is built and meshed in GAMBIT software with an unstructured mesh of 1,343,988 cells.

The case is solved as a steady-state problem using a pressure-based solver. Gravity is enabled at −9.81 m/s² in the Y direction — an essential setting, since the natural draft is entirely buoyancy-driven. The energy equation is activated, and turbulence is modeled with the standard k-ε model with standard wall functions.

The boundary conditions reproduce the natural-draft configuration: the inlet is defined as a pressure inlet at 0 Pa gauge total pressure (normal to boundary), and the outlet as a pressure outlet at 0 Pa gauge with a backflow temperature of 303 K. The heat-exchanger ring is modeled as a heated radiator surface at 318 K with a heat generation rate of 14,861.52 W/m³, with its shadow face at 313 K. The tower walls are stationary with zero heat flux.

The solution uses SIMPLE pressure–velocity coupling with first-order upwind discretization for the momentum, energy, and turbulence equations (standard scheme for pressure and density), initialized at 303 K.

Analysis

At the end of the solution process, contours of velocity, pressure, and temperature are extracted, along with flow streamlines through the tower. Together, these results reveal the complete natural-draft mechanism: ambient air is drawn in through the heat exchangers, heats up as it crosses the radiator ring, loses density, and rises through the tower — sustaining the draft without any fan or external power.

The temperature field across the radiator ring shows the cooling capacity available to the plant, directly linking the simulation results to power plant performance. By completing this project, you will learn to set up a buoyancy-driven natural-draft flow, represent a heat-exchanger ring using a heated radiator surface with a volumetric heat generation rate, configure a steady pressure-based solver with the energy equation, and interpret cooling-tower performance from temperature and streamline fields.