Application 101: Shell & Tube Coolers

Shell & Tube Coolers - An Overview 

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Extracting waste heat from air and liquid streams in moving vehicles is commonly performed with radiator-style heat exchangers, but what about engines where cool, high-volume airflow isn’t readily available? Think of applications such as marine vessels, stationary engines, and backup generators – these systems are typically tucked away from ambient air, immobile, and mission-critical. To properly cool these types of engines, we turn to advanced mechanical solutions known as Shell & Tube heat exchangers.

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In principle, shell & tube coolers function the same as radiators and other finned heat exchangers.  The hot media to be cooled flows through one circuit in the heat exchanger, while cool media flows through the other circuit.  These two circuits or zones do not physically contact each other.  In the same way that a radiator exchanges energy from coolant contained inside of the radiator’s tubes to air flowing over these fins, shell & tube coolers exchange energy from media on the “tube side” to media on the “shell side” as they flow through the cooler.  The cooler’s thin internal tubes keep the two medias separate but offer substantially more energy transfer potential in smaller sizes than standard radiators.  A diagram of flow through a shell & tube cooler is below:  

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Shell & Tube Cooler Applications

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Generally speaking, shell & tube coolers serve applications where standard finned radiators cannot physically fit or reach the required heat transfer levels.  In addition, shell & tube coolers tend to offer the highest performance in liquid-to-liquid applications, though they can certainly serve air-to-liquid uses as well.  To give a broad sampling of use-cases where shell & tube coolers are often found, let’s use three application groups:

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• Vehicle Cooling – high-performance vehicle cooling circuits include such use-cases as turbodiesel aftercoolers, transmission fluid coolers, and brake fluid coolers.  These applications involve higher total temperature ranges that require rapid, consistent, and continuous heat extraction, often tied directly into a central coolant water loop.  Racing vehicles, construction equipment, and long-haul freight trucks all fit into this category.  

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• Marine Cooling – marine engines, lubrication systems, and hydraulic systems are often installed deep within vessels and away from free-flowing, cool ambient air.  For this reason, shell & tube coolers are ideal for locally dumping heat into a cooling water loop fed from external marine water or a recirculated cooling compressor.  

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• Stationary Equipment – fixed equipment such as fire water pumps, backup generators, mining conveyors, and air compressor plants all require cooling that a normal radiator cannot provide.  Shell & tube coolers serve these applications quite well, cooling intake air, oil, or lubricants with recirculated coolant or single-pass cooling water.  

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Across all of these application categories, shell & tube coolers serve the goal of removing waste heat from a fluid or air stream, discharging that heat into another media where it can be promptly removed from the system.  For example when serving as a turbodiesel charge air cooler, a shell & tube cooler pulls out excess heat added by the turbo so that the air is lowered to a more suitable temperature for combustion within the engine.  As another example when cooling engine oil for a stationary backup generator, a shell & tube cooler must quickly cool the lubricant so that it remains in its ideal viscosity range to protect the engine from friction-driven damage.  

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Key Considerations in Selecting an Engine Shell & Tube Cooler 

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Heat exchangers – as an overarching family of engineered mechanical components – can be configured in hundreds if not thousands of different ways, depending on the application, industry, and media involved.  For engine cooling, fortunately we have a much smaller number of design styles to work from, though that number is expanding as technologies evolve.  In general for engine cooling, we can break shell & tube coolers down into two design styles:

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1. Straight Tube Design – in this design, a shell & tube heat exchanger utilizes internal tubes that travel straight down the housing’s length.  With any heat exchanger, the potential energy exchange is largely a function of the available surface area through which energy can pass.  In a straight tube cooler, this surface area is proportional to the housing’s length – for more area, a longer housing and more tubes are required.  Construction of a straight tube unit is relatively simple, performance moderate, and installation options wide (by being able to position shell-side ports both on either end or one end only).  

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2. U-Tube Design – as opposed to the above straight tube design, a U-tube design consists of a tube bundle where the internal tubes are rolled with a “U” shape at their end.  Tube-side media flows in and out of the bundle on the same housing end, in effect offering twice the housing’s length per tube in surface area.  These units typically allow for larger surface areas in shorter housing lengths than straight tube designs, but are often larger in diameter.  U-tube designs are a slightly more complex design, but offer even higher performance.  
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When selecting a shell & tube cooler, buyers will need a bit more technical information about their application available than when sizing standard radiators.  Flow rates, pressure, temperatures (in and out), fluid densities, and other characteristics will all be needed to properly calculate a shell & tube unit’s size.  In addition, material types, chemical compatibilities, and installation details should all be covered in a unit’s initial sizing and design.  To help buyers understand the various options they’ll want to consider in specifying their next shell & tube cooler, please consider the following:    

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• Technical Design:  any Shell & Tube Cooler purchase discussion should begin with full engineering specifications on the engine, cooling load, and operating conditions that make up the application, which will drive the selection of the correct unit to begin with.  

• Construction:  tube style, removable heads, connection styles, mounting brackets, tube sheet positions, baffles, and port orientations are just a few construction details to be thoroughly reviewed.   

• Materials:  all-aluminum materials offer the best combination of low weight, high thermal transfer, and economical cost.  Media compatibility and temperature ranges may drive more advanced selections such as steel, stainless steel, bronze, and even titanium options.   

• Cleaning:  both pre-and post-assembly, Shell & Tube Coolers should receive a thorough cleaning pass inside and outside of the unit to ensure proper fabrication and in-vehicle performance.

• Assembly:  Shell & Tube Coolers are engineered for a specific heat transfer target based on airflow, surface area, and temperature delta, which means that each unit should be assembled to very exact dimensions and tolerances in order to achieve the expected design point.

• Brazing and Welding:  tube brazing and welding must consider the temperatures, pressures, and fluid compatibilities in play, and must be performed with the goal of serving a long life under the stresses and aggressive demands expected in the application.   

• QC:  to assure that the assembly process was a complete success, every unit should be fully checked prior to shipment for dimensional accuracy, brazing and weld penetration, pressure holding, joint integrity, and zero leakage.  

• Packaging: tube bundles are inherently robust but can still be damaged during shipment, so all Shell & Tube Coolers must be fully protected for shipment by carefully packaging the assembly.  

• Customer Support: after the purchase, buyers should expect full and readily available support should they have any questions around installation, operation, and troubleshooting concerns, at any time during the long life of the cooler.    

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Mission-critical vehicles and equipment in over a dozen infrastructure sectors rely on heat transfer components manufactured by Cincinnati Radiator. CR works directly with Original Equipment Manufacturers and Aftermarket service channels to supply premium-grade, long life radiators, coolers, and full cooling packages into extreme applications all over the world.  With our expanding inventory and fabrication space at our Fairfield, Ohio facility, we pride ourselves on having a personal touch, ultra-fast lead times, and one-off custom design capabilities.  

For your next vehicle or heavy equipment heat transfer project, call us at (513) 874-5555, email us at sarslan@cincyradiator.com, or visit our website at https://cincyradiator.com/