Plate vs. Shell-and-Tube Heat Exchangers for Ships

We’ve long been told that shell and tube heat exchangers are king in ship engine rooms, they’re reliable, well-understood and have been around for donkey’s years. However, the development of space-efficient, high performance Plate Heat Exchangers (PHEs) has put them on the radar for ship owners, designers and technical superintendent alike. Each offers its own merits and drawbacks and the selection process requires careful consideration based on vessel type, operational demands, maintenance practices and available space. Here at SME Group, drawing on 20+ years of marine engineering experience and with a range of ICCP, MGPS, SED & PHE solutions in our armory, we look at the options in comparison

1. Thermal Efficiency and Footprint Comparison

When it comes to heat transfer capacity, PHEs win hands down. The flow induced through the corrugations in the plates causes high turbulence at all but the very lowest flow rates and gives PHEs the highest overall heat transfer coefficients, typically three to five times higher than a shell and tube unit. This greater capacity means a PHE needs around a third to half the space required for a shell and tube for the same duty. On today’s modern vessels where engine room space is always at a premium, this saving is significant.

On the other hand, shell-and-tube exchangers use a straight tube flow path with baffles to guide shell-side flow. These exchangers offer robust and predictable performance, but poor efficiency necessitates larger surface area and physical footprint. If the application has plenty of room and a less critical approach, as in some auxiliary cooling applications, that might not be a problem. However, in a core cooling application (such as, main engine jacket water or charge air cooling), the higher PHE efficiency leads to better temperature approach, less pump power and more fuel economy.

2. Maintenance and Cleaning Considerations

But when the maintenance philosophy enters the fray, this can be the determining factor in favor of either technology. Shipboard crews are, historically, much more comfortable cleaning shell-and-tube units, You can rod or brush a tube bundle or apply a chemical easily enough. But getting to the tubes means taking off big end covers, and to replace tubes you usually have to go to a yard, which is a very expensive proposition. And it’s not easy to clean the shell side without a lot of effort and even dismounting.

SME's plate heat exchangers, PHEs, provide another maintenance philosophy. It is possible to disassemble the plate pack, inspect and clean it in a few hours with standard tools. Individual plates if found to be corroded and damaged, instead of scrapping the whole assembly. Gaskets are considered consumables which should be replaced roughly every four or six years, but with modern, clip on gasket types, SME ensures that this is made even easier. The drawback, however, is that PHEs require a bit of care in cleaning to avoid damage to the relatively thin plates (made from either stainless steel or titanium), and special care training is needed for crews. SMEs offer both in-depth maintenance manuals, on-site training and can ensure that genuine gaskets and spare plates are shipped to vessels at all of the main shipyards across mainland China.

3. Operating Pressures, Temperatures, and Fluid Compatibility

Shell and tube exchangers are a long established choice for high pressure, high temperature environments. The cylindrical shape of the shell, coupled with the heavy-duty tube walls allows this type of heat exchanger to cope with working pressures above 40 bar and it finds a home in steam, fuel oil and hydraulic oil cooler applications, in addition to fluids with particulates present (as straight tubes are less prone to blockage or fouling).

Limitations Though our PHE designs are becoming more powerful every day, there are limits in applications for PHEs. The typical design pressure of PHE’s may be in the region of 25-30 bar maximum, whilst temperature limits usually reach approximately 200°C (depending on the gasket material). The other drawback for PHE’s is that they do not tolerate particulate in fluids, for instance, seawater that carries sand and debris can damage the plates and can also block the narrow channels where the heat transfer takes place. This is where an integrated solution, as delivered by SME with its associated MGPS (Marine Growth Prevention Systems) and suitable strainers protecting the PHE from both biological and particulate growth, comes into play. For higher pressure, applications can be serviced by SME providing a semi-welded or a fully welded PHE, thus avoiding gasket leakages, but retaining the smaller footprint size of a PHE. We make sure to select the most appropriate solution based on the fluid, whether that be fresh or seawater, oil, fuel, and more.

4. Total Lifecycle Cost and Fleet Standardization

Consideration should also be given to the overall lifecycle costs in addition to initial purchase prices. Shell-and-tube units can have lower first costs in small and medium size applications, however, the pumping power required is increased through higher pressure drop and greater quantities of cooling water are needed. The thermal efficiency will fall off as fouling occurs, and retubing is a capital intensive task.

While initially more expensive (especially when using titanium plates), PHEs can save operating costs by using less pumping energy, require less seawater pump capacity, and enable faster maintenance times. Additionally, you can simply add or remove plates to match required capacity or for future changes. For fleet owners with several vessels, standardization offers benefits by allowing the same type of PHE to be installed on similar sister ships, a simplification of spare parts stocking, training and repair routines. SME assist with comprehensive installation guidelines, use consistent plate design regardless of the model and our technical team is readily available to assist with fleet-wide retrofit projects. Whether you prefer the tried-and-tested design of a shell-and-tube exchanger or the up-to-date design of a plate heat exchanger, SME offers both, together with the corresponding ICCP (Cathodic protection), SED (Shaft earthing) and MGPS (Cathodic protection of seawater intakes). Every year we complete more than 500 new projects, a quality reflected in our ISO-certification, to go beyond your concerns.

Plate vs. Shell-and-Tube Heat Exchangers for Ships

We’ve long been told that shell and tube heat exchangers are king in ship engine rooms, they’re reliable, well-understood and have been around for donkey’s years. However, the development of space-efficient, high performance Plate Heat Exchangers (PHEs) has put them on the radar for ship owners, designers and technical superintendent alike. Each offers its own merits and drawbacks and the selection process requires careful consideration based on vessel type, operational demands, maintenance practices and available space. Here at SME Group, drawing on 20+ years of marine engineering experience and with a range of ICCP, MGPS, SED & PHE solutions in our armory, we look at the options in comparison

1. Thermal Efficiency and Footprint Comparison

When it comes to heat transfer capacity, PHEs win hands down. The flow induced through the corrugations in the plates causes high turbulence at all but the very lowest flow rates and gives PHEs the highest overall heat transfer coefficients, typically three to five times higher than a shell and tube unit. This greater capacity means a PHE needs around a third to half the space required for a shell and tube for the same duty. On today’s modern vessels where engine room space is always at a premium, this saving is significant.

On the other hand, shell-and-tube exchangers use a straight tube flow path with baffles to guide shell-side flow. These exchangers offer robust and predictable performance, but poor efficiency necessitates larger surface area and physical footprint. If the application has plenty of room and a less critical approach, as in some auxiliary cooling applications, that might not be a problem. However, in a core cooling application (such as, main engine jacket water or charge air cooling), the higher PHE efficiency leads to better temperature approach, less pump power and more fuel economy.

2. Maintenance and Cleaning Considerations

But when the maintenance philosophy enters the fray, this can be the determining factor in favor of either technology. Shipboard crews are, historically, much more comfortable cleaning shell-and-tube units, You can rod or brush a tube bundle or apply a chemical easily enough. But getting to the tubes means taking off big end covers, and to replace tubes you usually have to go to a yard, which is a very expensive proposition. And it’s not easy to clean the shell side without a lot of effort and even dismounting.

SME's plate heat exchangers, PHEs, provide another maintenance philosophy. It is possible to disassemble the plate pack, inspect and clean it in a few hours with standard tools. Individual plates if found to be corroded and damaged, instead of scrapping the whole assembly. Gaskets are considered consumables which should be replaced roughly every four or six years, but with modern, clip on gasket types, SME ensures that this is made even easier. The drawback, however, is that PHEs require a bit of care in cleaning to avoid damage to the relatively thin plates (made from either stainless steel or titanium), and special care training is needed for crews. SMEs offer both in-depth maintenance manuals, on-site training and can ensure that genuine gaskets and spare plates are shipped to vessels at all of the main shipyards across mainland China.

3. Operating Pressures, Temperatures, and Fluid Compatibility

Shell and tube exchangers are a long established choice for high pressure, high temperature environments. The cylindrical shape of the shell, coupled with the heavy-duty tube walls allows this type of heat exchanger to cope with working pressures above 40 bar and it finds a home in steam, fuel oil and hydraulic oil cooler applications, in addition to fluids with particulates present (as straight tubes are less prone to blockage or fouling).

Limitations Though our PHE designs are becoming more powerful every day, there are limits in applications for PHEs. The typical design pressure of PHE’s may be in the region of 25-30 bar maximum, whilst temperature limits usually reach approximately 200°C (depending on the gasket material). The other drawback for PHE’s is that they do not tolerate particulate in fluids, for instance, seawater that carries sand and debris can damage the plates and can also block the narrow channels where the heat transfer takes place. This is where an integrated solution, as delivered by SME with its associated MGPS (Marine Growth Prevention Systems) and suitable strainers protecting the PHE from both biological and particulate growth, comes into play. For higher pressure, applications can be serviced by SME providing a semi-welded or a fully welded PHE, thus avoiding gasket leakages, but retaining the smaller footprint size of a PHE. We make sure to select the most appropriate solution based on the fluid, whether that be fresh or seawater, oil, fuel, and more.

4. Total Lifecycle Cost and Fleet Standardization

Consideration should also be given to the overall lifecycle costs in addition to initial purchase prices. Shell-and-tube units can have lower first costs in small and medium size applications, however, the pumping power required is increased through higher pressure drop and greater quantities of cooling water are needed. The thermal efficiency will fall off as fouling occurs, and retubing is a capital intensive task.

While initially more expensive (especially when using titanium plates), PHEs can save operating costs by using less pumping energy, require less seawater pump capacity, and enable faster maintenance times. Additionally, you can simply add or remove plates to match required capacity or for future changes. For fleet owners with several vessels, standardization offers benefits by allowing the same type of PHE to be installed on similar sister ships, a simplification of spare parts stocking, training and repair routines. SME assist with comprehensive installation guidelines, use consistent plate design regardless of the model and our technical team is readily available to assist with fleet-wide retrofit projects. Whether you prefer the tried-and-tested design of a shell-and-tube exchanger or the up-to-date design of a plate heat exchanger, SME offers both, together with the corresponding ICCP (Cathodic protection), SED (Shaft earthing) and MGPS (Cathodic protection of seawater intakes). Every year we complete more than 500 new projects, a quality reflected in our ISO-certification, to go beyond your concerns.

99.71%

https://app.originality.ai/share/1k8ygfz956bod2iv