The COVID‐19 pandemic has been exceptionally hard on the world‐wide cruise line industry. This highly contagious air borne pathogen has pointed out the design weaknesses of recirculating ventilation systems on ships. To better protect the safety and health of their crew and guests in the future, cruise lines will need to convert their ships with recirculating ventilation systems to a 100% single pass ventilation system.
There will be some extremely challenging redesign issues that will need to be dealt with in order to create a successful conversion. The first is the tight space conditions on most ships. All return air ducts will need to be vented to the outside through special louvers to protect from rain incursion. Finding safe places to exhaust the return air may require rerouting duct work.
Another challenging redesign factor is the cooling capacity of the existing system. A single pass system means using 100% outside air. Although most recirculating systems use some outside air as make‐up air, most were not designed to use 100% outside air. Adding additional cooling capacity will mean adding larger cooling coils or using a precooler to bring down the temperature of the 100% outside air to the desired set point. When adding additional cooling capacity consideration will need to be given to whether the ship has enough power to handle the new capacity. To accomplish the additional cooling requirements and keep the increase in power usage to a minimum, Eldridge uses a new technology that will save 60‐80% over and above traditional AC systems.
The final design challenge will to determine if the converted ventilation system will provide the correct air flow rates. A dynamic fluid flow analysis (FFA) is the only way to determine if the existing fans need to be upgraded to overcome the additional static pressure that has been added by the ventilation system redesign. Eldridge’s proprietary FFA program uses the actual fan curves to determine where the fans will be operating based on the air flow and static pressure of the converted ventilation system.
A successful ventilation system conversion will require using a design firm with significant marine ventilation system experience. Eldridge has over 70 years of marine ventilation experience. We have been designing systems and supplying ventilation equipment for the offshore drilling industry since the first rig was built in the 1950’s.