HVAC for Navy Vessels

Military vessels have evolved in recent years due to the use of electronic systems, sophisticated radars, masts with lots of technology besides of the required navigation lights, powerful weapons and especially the "futuristic" shape of the hulls, such as the USS Zumwalt - class destroyer, which began to be designed in the 1990s and was built by Bath Iron Works , as well as the Littoral Combat Ships (LCS) developed by Austal Corporate for the US Navy or the Visby class stealth corvette operating in the Swedish Navy, where the angular hulls of ships is the key to "hiding" or preventing the vessel from being detected by radars.

With regards to HVAC systems, has there been any evolution?

In my understanding, the evolution lies in the use of modern screw compressors replacing the old reciprocating compressors coupled directly to electric motors and also the use of PLC's to monitor and control the HVAC systems, since the shock requirements, vibration requirements & testing and the need for NBC (nuclear, bacteriological and chemical) air filtration are the same over 40 years!

Digging into my old folders, I found these Bronswerk technical papers related to navy chillers, designed for the joint venture of the navies of France, Belgium, and the Netherlands on Tripartite class of minehunters which were conceived in the 1970s and built in the 1980s.

I also found the technical paper shown above about NBC collective protection filter unit, which is basically an interchangeable composite filter which complies with NATO requirements. In addition to being used in navy vessels, it can be used in vehicles or in permanent bunkers as it is a prevention against gas attacks.

Basically the NBC filter unit presents cyclone prefilter and composite filter of pleated aerosol media and activated carbon, four-way valve, servo operated for by-pass or filtration mode, being constructed obeying Military Standards (MIL-STD).

The unit can be manufactured for diverse air flows and static pressures, electrical supply 24 Volts DC and is suitable for different environment conditions.

In Brazil, the bid for the construction of four corvettes already has four short-listed bidders groups and the winner of the bidding will be known in early 2019.

The figure above shows the concept of the new Tamandaré Class Corvette that will be built for the Brazilian Navy.

Q: What would be the best HVAC system for navy vessels like corvettes?

A: I would say the same as used in the 80s, e.g: Chilled Water System, with few and well-known variations adopted in the preference of each bidder group / shipyard.

Considering the dimensions of the vessel, crew, calculation of the cooling & heating load and all the consumers of chilled water (AHU's, fan coils and other equipment such as some electric panels and transformers) it is known that the total system cooling capacity will vary from approximately 1300 kW (370 TR) to 1500 kW (427 TR).

Remember that in navy vessels, the air conditioning system is essential to guarantee the indoor air quality, to prevent lethal contaminants, to filter and renew the air, as well as to improve the working conditions in technical spaces.

Let's consider the total cooling capacity of the air conditioning plant for a corvette as 450 TR and two options at least should be offered to the customer.

Opition 1: System with 02 (two) Navy Chillers, cooling capacity of 225 TR each, 08 (eight) AHU's (Air Handling Units) 8000 m3/h each, distributed by the vessel and all those working with 70% fresh air and 30% recirculation.

All air intake equipped with watertight butterfly valves actuated by hydraulic actuator.

Distribution of the air at high pressure and velocity through round ducts, with the air flow being supplied into the compartments by noise attenuating terminal boxes (cabin units).

Heating during the winter season can be guaranteed by electric heaters mounted on the main ducts or alternatively an electric heater section mounted on each AHU.

Completing the system, supply and exhaust fans installed where needed, a dedicated AHU for the galley and a Gaylord or Halton hood to prevent the risk of fire.

(*) Hospital with 100% fresh air (no recirculation)!

An adequate number of citadels or bankers positioned along the ship with a collective NBC filtering system and even autonomous NBC masks for individual protection for crew members.

Opition 2: System with 03 (three) Navy Chillers at 50% of total cooling capacity, two on duty and one stand-by, 150 TR each, 03 (three) fresh air treatment AHU's 6000 m3/h each, working with 60% fresh air and 40% recirculation and at least forty additional marine baby fan-coils installed in the various compartments.

Here also all air intake equipped with watertight butterfly valves actuated by hydraulic actuator.

Heating during the winter season guaranteed by electric heating radiators installed in each cabin, technical or public space.

Fans and NBC same as in the Option 1.

Many others configurations may be used depending on the designer and manufacturer / supplier of the HVAC system.

In the past, in addition to Bronswerk, the German company Norske Kaeser stood out in the HVAC market for navyvessels.

By the end of 2017, Engie Axima, subsidiary of the Engie Group, announced the acquisition of Noske Keaser.

Talking about HVAC equipment manufacturers / suppliers, there are well-known companies like Flakt Group (Sweden), Novenco AS (Norway), Halton Marine (Finland), Heinen & Hopman (Netherlands), Lindab (Denmark), Yongsheng (China), Airmarine (Brazil), Engie Axima (France), Johnson Controls (USA), AF AeronMollier (Norway), Bronswerk (Canada) and others!

We are always looking at the future but it is always good to revisit the past years, as in this excellent movie >>> Shipboard Heating, Ventilation & Mechanical Cooling, 1952 US Navy HVAC Training Film MN-6941, published on the Web by Jeff Quitney in September, 2015 and shown on https://vimeo.com/343248978

Enjoy!