HVAC Systems for Cruise Ships

A Good Question: Is a Marine HVAC-R Engineer able to design a complete Air Conditioning Systems for Cruise Ships, even though this type of vessel is not one of their specialties?

Yes, I'll justify my answer!

I strong believe that any engineer who works or has worked with Offshore HVAC-R is able to master design or installation for any other type of vessel, even more if he has extensive experience in shipbuilding and is aware about IMO (International Maritime Organization) / SOLAS (Safety of Life at Sea) regulations and those main International Association of Classification Societies (CLASS) as American Bureau of Shipping (ABS), Bureau Veritas (BV), Det Norske Veritas Germanischer Lloyd (DNV GL) and Lloyd's Register of Shipping (LR).

Fig.1 – Some types of vessels and facilities where marine HVAC is required.

Imagine a Mechanical Engineer with a very long career, going through different areas such as Shipbuilding, Oil & Gas industry and HVAC-R, with vast experience in designing, building and maintaining air conditioning systems on O & G production platforms, Offshore drilling rigs, Offshore support vessels, FPSOs, Bulk carrier ships, VLCC, Navy Ships, Submarines, Ferries, Sailing boats and Yachts.

Fig.2 – Since 1979, inside a hull learning from the experienced people technical details about marine ventilation and air conditioning.

On top of that, consider also that HVAC and mechanical ventilation systems for offshore units whether it is drilling , production and / or accommodation units are far more complex than for larger Cruise and/or Ro-Pax ships, as rules and regulations for calculation of heat loads and system design are surrounded by far more rigorous rules than for cruise ships.

Heat load calculations, Chilled water flow calculations, distribution of Air handling units and Fans within each fire zone as well as duct design and air distribution are all more or less theoretically identical whether it is an accommodation platform or a vessel carrying passenger.

Automation systems can vary in operation functionality with lot of different features based on demands for stand alone and/or integrated system with higher safety in offshore than on ships, as fire and explosion risks are significantly more risky in offshore facilities than on board ships.

You might doubt the ability of anyone who is not familiar with Cruise Ships and ask about specificities such as “Atrium space”.

All right! An Atrium (architecture luxury design) is a large open and vey tall space within a building or structure, often featuring a glass roof, which is particularity found in cruise ships, which do not exist in other types of vessels or offshore facilities.

On a cruise ship we also have many other public areas like large cinemas, restaurants and other special spaces where the use of ducts for ventilation and air conditioning should be minimized and hidden by the architecture or even avoided and the air stream can not bother the passangers, then the speed and noise level of the air diffusion must be strictly observed and guaranteed!

I fully agree, and all requirements can be met if different air conditioning methods use the appropriate air diffusion devices and equipment for each specific space or area in the cruise ship.

Let's begin our assessment with some basic questions and answers.

1) What are the most common types of systems available for air conditioning on ships?

A: The most common systems found on ships are the direct expansion system (DX) and the chilled water system, which may have several combinations between the refrigeration section and the air conditioning and filtration section. Depending on the space to be conditioned, one or other can be used, and it is up to the designer/ engineer to choose the best option to meet the needs and specifications of the shipowner, always observing the efficiency and functionality of the installation and the costs involved.

2) What is a direct expansion system (DX) and a chilled water system?

A: A direct expansion system (DX) is the same as that found in a simple window air conditioner apparatus. It is a self-contained equipment where all the components necessary for the conditioning the air such as the compressor, the condenser, expansion device, evaporator (cooling coil), heater, fan, air filters, refrigerating fluid piping, filter drier , liquid sight glass, solenoid valve, pressure controllers, thermostat and manometers are contained in the same housing. It can also be splited in two parts, one being the evaporator unit and the other the condensing unit.

The condensation of the refrigerant can be done by air or by water, depending on where the equipment will be installed.

Fig.3 – Typical Vertical Self-Contained Unit.

Generally, direct expansion systems use equipment known as self contained units, which can be vertical or horizontal type. In technical compartments such as main engine control room, workshop and warehouse, these are preferred because they can blow the air into the space through a “plenum box” or small branchs of ducts for air distribution, are easy to maintain and relatively inexpensive compared to the chilled water system with equipment, various balancing and control valves and more sophisticated electronic controllers.

Fig.4 – Water Screw Compressor Chiller manufactured by Jiangsu Zenya in Taixing - China.

A chilled water system is a system where fresh water is cooled by the refrigerante fluid in a shell & tube type heat exchanger. The chilled water is pumped and distributed through pipes to the various AHU's (Air Handling Units) where the cooling coils are located. The air is drawn in or blown through the finely tapered face of the cooling coil, which has the chilled water circulating in its tubes. Talking about air treatment, it is an ongoing process that may or may not involve air recirculation, as some compartments need 100% fresh air to meet standards and especially indoor air quality. In this system the main equipment is the chiller, usually some installed, which normally use the sea water for the condensation of the refrigerante fluid, can also be used plate heat exchangers to fresh water / sea water (which proves problematic over time) or air-condensed chillers in some areas where location allows them to be used.

Fig.5– Typical horizontal marine Air Handling Unit manufactured by Flakt Woods in J?nk?ping - Sweden.

3) Where to use a system with high air velocity / high static pressure and system with low air velocity / low static pressure?

A: Imagine a tight space between the ceiling and the deck plate above, and through this space you need to install several cable trays, various pipes, main ducts and their branches to distribute the air through several cabins and other spaces to be conditioned. You do not have many alternatives, or you will have to use several branches of spiroducts (round ducts) or oblong ducts, conducting and distributing a massive air flow with high speed and pressure. In addition you will have to use special cabin units, suitable for air distribution and noise attenuation. Optionally these cabin units may have a built - in reheating device controlled by a local ambient thermostat to "fine tune" the air temperature in the cabins.

Fig.6 – Typical Spiroducts installed on a ship deck.

In some places of the ship, where reasonable space is available, conventional rectangular ducts combined or not with spiroducts can be installed. Generally those ducts carry large volume of air at low speed and pressure.

4) How does the air conditioning system on cruise ships work?

A: The HVAC system on cruise ships can be centralized, decentralized and/or a mix of both systems. Depending on the intended areas, the DX (direct expansion) system with several horizontal self-contained units can carry air to the various compartments of the ship through various spiroducts distributed across the decks and areas to be air conditioned.

In the large areas a low pressure system is generally used for the reason that it transports a big volume of air.

As an alternative, instead of using DX self-contained equipment, several medium or large AHU’s (air handling units), as many as needed, can be used to air conditioning the diverse areas.

The chilled water is pumped from the chilled water plant and distributed to the various AHU's spread across the various decks on the ship.

Leaving the AHU’s located in technical compartments along each deck, many branchs of spiroducts carry the air at high pressure and velocity to the desired areas.

Special attention should be given to the cabin areas which are usually serviced by a high pressure and decentralized system that is either completely self-sufficient or one that makes use of chilled water circulation, due to ease of maintenance.

On decentralized system each cabin can control the indoor air temperature individually. In this way each one can adjust the climate in own cabin as desired, without affecting or being affected by the other cabins.

Depending on the shipowner's request, even ductless fan-coil units can be used.

5) What are the key points that should be observed when choosing marine HVAC for cruise ships?

A: The options, combinations and sophistication of the systems are many, but five fundamental points must be observed by the HVAC system designer to make the right choices:

•  The purchasing costs;
•  Efficiency and quality of equipment used;
•  The deadlines for the manufacture of equipment and installation of the HVAC system;
•  Energy consumption and efficiency of the HVAC system;
•  Environmental impact.

Energy efficiency on the ventilation, heating & cooling (air conditioning) systems onboard cruise ships must be taken into consideration, due to the high energy consuption of these systems and the amount of savings that can be gotten from making those systems more eficient.

The cost and fuel consumption to move giants like cruise ships are immense, so any contribution to energy savings should be evaluated in all onboard systems, including primarily the HVAC system.

6) What are the possible variations that can be used in marine HVAC systems?

A: Find some combinations below, but many other combinations can be implemented depending on the observation and imagination of the designer. Remember that air distribution equipment can be either a large DX self-contained unit or a chilled water AHU (air handling unit), blowing high pressure air through lots of spiroducts, or distributing air at low pressure through conventional rectangular ducts, as also the possibility of mixing the two types of ducts for air distribution.

The most known are: Constant airflow, Constant airflow with reheating, Variable airflow, Variable airflow with reheating, Dual duct system, Dual duct system with energy recovery and Ductless fan-coil.

I will briefly describe the DUOVENT + VAV + REGOTERM (Dual duct system with energy recovery and variable airflow) system designed by former Flakt Marine, nowadays known as Flakt Woods.

The installation of Regoterm rotary heat exchanger is a documented method of effective energy conservation. The first installation was undertaken as far back as 1975. Since then thousands Regoterm units have been installed throughout the world.

The rotary heat exchangers are regenerators with rotating heat accumulators, where the heat-dissipating and heat-absorbing air flows heat or cool the rotating, air-permeable storage accumulator.

Depending on the air conditions and the surface of the accumulator material, humidity may also be transferred in the process. Supply and exhaust air must therefore be brought together and flow through the heat exchanger.

E.g.: Installation of Regoterm Rotary heat exchanger and VAV (variable air volume) system combined with Flakt’s Duovent ventilation system.

The VAV system senses the temperature cabins, messes and other areas and continuously regulates the air flow through the supply air fan in the system.

With a duct carrying cold air and other hot air, these arrive in the Duo or Dual-Duct cabin units, where temperature adjustment can be done individually in each cabin or specific area.

Fig.7 – From Safe Air Technology magazine (May 1986) - Flakt Marine, the classic Dual Duct System with energy recovery.

From Flakt Air Technology Magazine: “One of the most importante requirements of the job is a knowledge of how the need for on-board ventilation and refrigeration fluctuates. Both among different parts of the vessel and at different times of the day or night. Large amount of energy and money can be saved by adapting capacity to actual needs. Comprehensive studies have been made of various vessels types and engineers are today much aware of how needs vary and which capacity the climate contol system needs to have.

If this information is not acessible, the installation must be so rated that it is able to meet simultaneously peak demand in all areas of the vessel. Since we know how needs vary, we also aware that all areas never experience peak load at the same time; so we have also been able to scale down the total refrigeration capacity. We can use smaller units that need less energy and less space and which weigh less. This all results in a lower total cost even before the installation is in operation. If additionaly you make use of the energy in the exhaust air and continuously regulate capacity in line with needs, then you get a really efficient and low energy climate control plant without having to lower the standard of confort.”

 7) What are the main companies that provide equipment and accessories for marine and offshore HVAC?

A: In the past the main companies in marine HVAC business were Bronswerk B.V, Sabroe Hi-Press, Novenco and Flakt Marine.

(*) My old school was Bronswerk Stork – Brazil.

New companies have emerged, some mergers, name changes have taken place and today several marine & offshore HVAC companies are in the market, the main ones being; Flakt Woods (Sweden), Flakt Marine AB (Sweden), Novenco AS (Norway), Halton Marine (Finland), Heinen & Hopman (Netherlands), Wilhelmsen (Norway), Yongsheng (China), Airmarine (Brazil) and Carrier Marine & Offshore (USA).

8) Is shipbuilding knowledge important to the marine HVAC Engineer?

A: Knowing the methods of shipbuilding well is one of the obligations of those who works with marine HVAC.

Know where and how bulkheads and decks can be penetrated, what types of protection and reinforcements are needed and which rules to obey according to Class is a must!

Fig.8 - Photo of bridge deck during construction of a vessel in Nantong - China.

You should be familiar with the evolution of methods in shipbuilding, especially those used in the construction of accommodation, mainly in the cabin area on large ships of the new generation.

In modern shipbuilding, construction panel-to-panel is a detail of outdated projects.

The modern method of accommodation erection is, after the installation of ducts, cable trays, thermal insulation of the bulkheads, ceilings and floor preparation in each deck, is time to make the cabins hauling.

The usual way of installation is to lift the cabins in a cage to the level of the deck where each cabin will be installed. Through an opening in the bulkhead, the cabins are slid into the deck.

Fig.9- Cabin positioned to be slid into the accommodation structure.

The cabins are slid one by one to their position on a deck free of obstruction.

Fig.10 - Cabin being moved to the final position.

After that the cabins are positioned side by side forming the corridors according to the designed general arrangement.

There are many companies in the world that manufacture and install this type of cabin in the living quarters of modern vessels, but without a doubt, Almaco from Turku in Finland is one of the best that I know.

9) Is it important to participate in the FAT of the equipment you designed, specified and purchased?

A: When you are a Senior Engineer, Master or Expert, in addition to designing, you generally witness the Factory Acceptance Testing (FAT) across manufacturers around the world.

10) What is the best part of a marine HVAC Expet job?

A: The best part of the job is to travel and to be working around the world, meeting very different people and learning from their habits and behavior.

It is fantastic to visit amazing factories and technical development labs, meet face to face each people you are talking on the phone at the other side of the world. 

It is easy also to ask, answer and clarify any technical doubt or commercial pending when you are around there.

Conclusions:

As we can see, there are several methods for air conditioning systems in ships, a simpler and cheaper, others more sophisticated, but much more expensive.

In a forum on Marine HVAC Technology you can ask which is the best system to use in Cruise Ships?

Probably you will get several different answers from HVAC Experts!

Mine would be: "The better answer will come from the Shipowner, because he is the one to talk about the available Budget to spend on the HVAC system, the degree of sophistication he wants in the automation and control of energy saving (mainly fuel) , if he is concerned about the environment and the time he wants to wait to have the ROI accomplished”.

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