Box Cooler / Boxcooler – Marine Sea Chest Heat Exchanger for Engine & System Cooling

A boxcooler is a U-shaped tube bundle heat exchanger installed inside a sea chest on a ship. It uses seawater as a cold source to cool the ship's main engine, auxiliary engines, generators, hydraulic systems, etc. It eliminates the need for a seawater pump, saves engine room space, and operates through natural convection combined with forced circulation during navigation.

U-shaped tube bundle: The heat exchange core, commonly made of aluminum brass/copper-nickel alloy, which is corrosion-resistant and has good thermal conductivity.

Tube sheet + flange: Secures and seals the tube bundle, installed and fixed from the engine room side.

Sea chest: A closed cavity outside the hull, with a bottom inlet and top outlet grille to allow seawater to flow over the outside of the tube bundle.

Working Principle (Thermosiphon + Forced Convection)

Internal Circulation (Fresh Water/Coolant): High-temperature fresh water (for main engine/lubricating oil cooling) is pumped into the U-shaped tubes, flowing within the tube bundle and releasing heat.

External Circulation (Seawater, Cold Source):

During Navigation (Forced Circulation): As the ship moves forward, seawater rushes into the seawater tank through the bottom grille, laterally scouring the outer wall of the tube bundle. After absorbing heat, it is discharged through the top grille. The flow rate is high, and heat exchange is strong.

When Moored (Natural Convection/Thermosiphon): After absorbing heat, the seawater becomes less dense and automatically rises and is discharged. Cold water continuously replenishes the bottom, forming stable convection, eliminating the need for a pump.

Heat Transfer: Heat from fresh water inside the tubes → heat from the tube wall → heat from seawater outside the tubes. The fresh water cools and returns to the equipment for circulation; the seawater absorbs heat and is discharged into the sea.

Applications:

Main engine/auxiliary engine cooling, generator fresh water/lubricating oil cooling; bow thruster, hydraulic system, air conditioning system cooling.

Applicable ship types: small and medium-sized cargo ships, oil tankers, tugboats, fishing boats, ferries, supply ships, icebreakers, etc.