What is the Workflow of a Dry Cooling Tower with Adiabatic Cooling?

What is the workflow of Dry Cooling Towers with Adiabatic Cooling?

The workflow of Dry Cooling Towers with Adiabatic Cooling is a segmented process of "adiabatic pre-cooling → dry cooling heat transfer → discharge".

Air Entry and Adiabatic Pre-cooling Section (optional)

Ambient Air Introduction:

The outside ambient air (temperature varies seasonally, e.g. 35°C in summer, 5°C in winter) enters the system through the air inlet at the bottom or side of the tower, and first flows through the adiabatic pre-cooling section (usually located below the dry cooling section or at the inlet).

Adiabatic pre-cooling (only high-temperature conditions start):

If the ambient temperature is high (e.g., more than 25 ℃ in summer), the adiabatic section is started: a small amount of water is sprayed to the air through the spraying system (or evaporation of the wet film), using the latent heat of evaporation of the water to absorb the heat of the air, so as to lower the temperature of the air (usually reduced by 5-15 ℃, for example, air at 35 ℃ down to 25-30 ℃), and at the same time, the humidity of the air rises slightly (but far from being saturated, to avoid condensation). (but far from saturated, to avoid condensation).

If the ambient temperature is low (e.g. below 15°C in winter), the adiabatic section is closed and the air goes directly into the dry cooling section (pure dry cooling mode operation).

Heat exchange in the dry cooling section (core cooling link)

The pre-cooled air (or low-temperature air entering directly) enters the dry cooling section and exchanges sensible heat with the high-temperature mass in the tube bundle:

Inflow of work material:

High-temperature work material to be cooled (such as turbine exhaust steam, process cooling water, heat transfer oil, etc., the temperature is usually 40-150 ℃) enters into the finned tube bundle of the dry cooling section through the pipeline (the fin design can increase the contact area of the air to strengthen heat transfer).

Apparent heat exchange process:

When the low temperature air flows through the surface of the finned tube, heat transfer occurs with the high temperature work material inside the tube: the temperature of the air absorbing heat increases (e.g., from 25℃ to 35℃), and the temperature of the work material releasing heat decreases (e.g., from 100℃ to 40℃).

In this process, the air and the mass is not in direct contact (no moisture exchange), only through the solid wall (tube wall) heat transfer, is a pure apparent heat exchange.

Air Discharge and Work Mass Output

Air Discharge:

The warmed up air (e.g. 35-40℃), which has completed the heat exchange, is discharged out of the tower through the axial fan at the top of the tower or the natural ventilation power, and it will not produce the “white mist” of the wet-cooled tower (due to the unsaturated humidity).

Output of cooled work material:

Work material cooled to the target temperature (e.g., turbine exhaust steam condensed to water, process cooling water down to 30℃) leaves the dry cooling tower through pipeline and returns to the original system (e.g., turbine reheat system, process equipment) for recycling.

Flow summary (in summer high-temperature working conditions, for example)

Ambient air (35℃) → adiabatic section water spray pre-cooling (down to 25℃) → into the finned tube bundle of dry-cooling section → and the high-temperature work material in the tube (such as turbine exhaust steam at 100℃) apparent heat exchange → the air is warmed up to 35℃ and then discharged → the work material is cooled down to 40℃ and then returned to the system.