Box Cooler

Box Coolers Bloksma K-type

Unique characteristics


A Box Cooler is a cooling system which finds growing application both for inland and sea going ships. Cooling water is forced through a U-tube-bundle, which is placed in a sea-chest having inlet- and outlet-grids. The cooling effect is reached by natural circulation of the outboard water in the sea-chest or by a circulation due to the speed of the vessel. The outboard water is heated and rises by its lower density, thus causing a natural upward circulation.

  • Bloksma box cooler
    Bloksma box cooler
  • Bloksma box cooler
    Bloksma box cooler

Box coolers compared with other cooling systems such as plate heat exchangers or conventional shell & tube coolers provide the following advantages:

  • Elimination of complete outboard secondary cooling water circuit on board. So there is no need for a cooling water pump, filters, valves, and pipelines etc. - parts that are sensitive for maintenance.
  • We have a well-equipped Research and Development department which ensures a design according to the latest developments and techniques.
  • The box coolers are much less susceptible to corrosion and fouling compared with any other solution.
  • Energy saving (secondary pump) - in a conventional cooling water system, the secondary pump of approximately 15 kW consumes approx. 3 litres fuel per hour. At a yearly operation level of 5000 hours this means a saving of 15000 litres.

Box coolers are virtually maintenance free. Therefore operational costs are much lower than for any other cooling system. Analyses of seawater flow and ñtemperatures around the box cooler by CFD (Computational Fluid Dynamics) calculation to improve cooler design.

In case of Bloksma coated coolers, the sea-chest is protected against galvanic corrosion by a coating covering all noble surfaces. A long lasting and (intrinsic) reliable insulating effect is ensured, because local damage to the coating results in a small galvanic drain only. Damage to larger surfaces can be taken care of by installing some sacrificial to anodes. The solution is not sensitive for corrosion caused by stray currents. ICCP (Impressed Current Cathodic Protecting) and ICAF (Impressed Current Anti Fouling) systems have no influence on the box cooler.

The unique combination of support baffles and anti-vibration-strips bonded by the coating has been proven to be a solid solution for this problem.

In case the coolers are uncoated, protection of the sea-chest is also a must. Here it is obtained by insulating the numerous joints between the ship and the bundle and it should be checked each time after (re-) assembling. Any fault results in complete failure of the protection mechanism. Sacrificial anodes can give only partial protection or are consumed fast. Stray currents may cause pitting attack of the bundle.

Corrosion occurs also when vibrations induced by uncontrolled flows of the outboard water or by mechanical sources can cause the tubes to rattle in their supports. The protective oxide layer of the tube will be scuffed away locally and as a result pitting corrosion will cause leakage.

  • In general the box cooler system is a maintenance free system for most applications. However depending on the area of sailing and on several operational conditions biological fouling can occur.
  • The type of organism most responsible for biological fouling on box coolers is mussels.
  • Biological fouling can appear on coated as well as un-coated box coolers.
  • In case of severe biological fouling the thermal performance of the box cooler is deteriorated.
  • To avoid this biological fouling an anti fouling system is recommended.
  • When some bio-fouling has settled on the box cooler, the negative effect on the thermal performance is hardly noticeable. Only when the box cooler is totally covered with bio fouling, causing a blockage of the flow between the tubes, the thermal performance will be influenced. Due to the external coating on the tubes of the Bloksma box cooler, bio-fouling and other deposits cannot cause the so feared under deposit corrosion.

To prevent the box cooler from biological fouling we recommend the ICAF (Impressed Current Anti Fouling). This system is reliable, effective under all circumstances and virtually maintenance free.

Anodes of pure copper are mounted under the box cooler in the sea chest. A constant current is applied between the anodes and the sea chest, which caused copper to dissolve in the sea-water. These CU ions create a continues toxic environment for biological growth, preventing the attachment and growth of marine organisms.

These anodes are to be mounted directly under the box cooler. In case of separate anodes the supports for the anodes are welded onto the sea chest. (See picture.)

Alternatively the anode system can be integrated into the box cooler. With these integrated anodes - see figure -  the cabling is fed through the box cooler to ease installation. The extra weight of the anode-rack does not influence the mechanical stability of the cooler, even under heavy seagoing conditions.

Retrofitting an ICAF system
In case the thermal performance of a box cooler has deteriorated, due to marine growth, retrofitting an ICAF system is possible in most cases. Contact us in case retrofitting is considered.

Compared to other systems box cooling is very suitable for sailing under ice conditions. There is no danger for damage due to freezing water.

Bloksma box coolers fully comply with classification requirements under ice-class.

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