Dry Cooler in the Closed-Loop Cooling System of Ocean-Going Vessel Generator Sets

Dry Cooler in the Closed-Loop Cooling System of Ocean-Going Vessel Generator Sets

In closed-loop cooling systems, dry coolers are typically integrated as a branch or alternative to the central cooler. Their operating principle is as follows:

Heat Capture: The substantial heat generated during generator operation is carried away by the cooling medium within the closed loop (usually treated freshwater or ethylene glycol solution). At this stage, the cooling medium's temperature rises (e.g., to 85-90°C).

Heat Transfer to Dry Cooler: This high-temperature coolant is pumped into the core component of the dry cooler—a heat dissipation core composed of finned tubes.

Forced Air Convection Cooling: High-power axial fans activate, forcibly blowing or drawing ambient air over the heat dissipation core. As air flows over the vast finned tube surface area, it rapidly extracts heat from the coolant through convection and conduction with the hot tube walls, dissipating it into the atmosphere.

Coolant return flow: The cooled coolant (e.g., reduced to 75-80°C) is pumped back to the generator set to begin a new cycle of heat absorption.

On ocean-going vessels, dry coolers are not always the sole cooling source; their activation follows specific operational scenarios:

Port Mode:

This is the primary operating scenario for dry coolers. When the vessel is docked at port, seawater pumps are completely shut off to prevent discharging warm seawater into the harbor basin (which may violate environmental regulations, impact marine ecosystems, or cause thermal pollution to port facilities).

The system then switches to “Full Dry Cooler Mode,” where all heat generated by the generator sets is dissipated into the ambient air via the dry coolers.

Sensitive Water Mode:

In ecological reserves, coral reef areas, or inland rivers where regulations mandate zero discharge, dry coolers are the only viable option to meet these stringent environmental requirements.

Auxiliary/Standby Mode:

In tropical waters where seawater temperatures exceed 32°C (90°F), causing reduced efficiency of seawater coolers, dry coolers can be activated concurrently to share part of the heat dissipation load, preventing generator overheating.

When the seawater cooling system (e.g., seawater pumps, piping) fails, dry coolers serve as an emergency backup system to ensure basic power supply for the vessel.

Cold Water Mode:

In polar or frigid regions where seawater temperatures are excessively low, using seawater cooling may cause generator sets to “overcool,” impairing combustion efficiency and inducing corrosion. In such cases, dry coolers are prioritized. Precise cooling intensity is achieved by controlling fan speed, facilitating easier maintenance of optimal engine operating temperatures.

To balance efficiency, reliability, and environmental sustainability, modern ocean-going vessels typically employ a hybrid central cooling system combining “seawater coolers + dry coolers.”

Normal Operation on the High Seas: Primarily relies on seawater coolers due to their high efficiency and compact size.

Port Calls or Entry into Sensitive Waters: Automatically or manually switches to dry cooler operation.

Extreme Conditions: Both systems can operate simultaneously to handle high loads or elevated temperatures.