Adding a sump to your heat exchanger can help improve thermal efficiency and reduce downtime. Just listen to what our helpful heat exchanger Shane Viergutz has to say about the topic.
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The path a liquid travels through a shell and tube heat exchanger is pretty simple. One fluid travels through the tubes, while another travels through the surrounding shell. Since all sides of the tubes are in contact with the liquid in the shell, the heat transfer process is nearly 100 percent efficient.
Even though this process is naturally highly efficient, there are still ways to improve it even further. For instance, as the liquid flows through the tubes, some areas of the substance have greater exposure to the walls of the tubing being affected by heat transfer medium, located in the shell. The section of liquid at the core of the volume passing through the tube is at a slight disadvantage because it is not making as great a connection with the tube wall as the outermost layer of liquid.
“The short length of a tube prevents true and effective mixing.”
Charles Ross & Son Company, which manufactures a wide range of industrial mixers, explained that the liquid flowing through a tube will naturally mix somewhat during its journey from the beginning to the end of the tube. However, for most shell and tube heat exchangers, the length of the tube prevents true and effective mixing. A longer tube would promote additional swirling, but this solution is typically impractical for manufacturers working in limited space.
There are certain additions manufacturers can make during exchanger design, or to retrofit existing exchangers, to improve heat transfer efficiency.
Static mixers
The static mixer, sometimes referred to as a motionless mixer, is one solution to this problem. These devices are placed in the tubes themselves and alter the fluid flow. Mixers are beneficial for several different functions, including:
A static mixer typically consists of one or more long metal rods, along which several half-circle discs crisscross to agitate the fluid. It is typically the same diameter as the tube into which it will be inserted.
The number of blades included depends on the effect the manufacturer wants to encourage, as well as the abilities of the process. The more blades affixed to the mixer, the more effective it will be. However, a high number of blades will require more pressure and energy for it to work properly.
The mixers are turned by the pressure of the fluid flow itself, which is either powered through gravity or pumps. No matter the design of the static mixer, pressure will be lost when these devices are added. This is the major downside of using mixers, and is often the variable that helps manufacturers determine which mixer design is appropriate for a particular process.
Twisted tape turbulators
One unique type is the twisted tape turbulator. Unlike a static mixer that has metal rods and semicircular disks, the twisted tape turbulator is a single, flat metal sheet in a helical shape. They are thin so as to not introduce more friction into the tube than is necessary.
Though twisted tape turbulators don’t spin as static mixers do, the curved path along the metal sheet encourages the liquid to turn over more while flowing through the tube. This will allow all of the liquid to have contact with the tube walls, Fuel Efficiency, a manufacturer of turbulators, explained. This benefits the company in several ways.
A research article published in the Journal of Engineering by students and faculty at the Islamic Azad University in Iran explained the benefits of using a twisted tape turbulator in conjunction with a nanofluid as the heat transfer fluid. A nanofluid is created by adding fibers, solid particles or small tubes no longer than 50 nanometers to a traditional heat transfer fluid such as water, ethylene glycol or oil. The purpose of the nanofluid is to increase heat transfer and efficiency. First, when a higher portion of the liquid is able to come in contact with the tube walls, heat transfer becomes more efficient and effective. Second, it can help keep the tubes in good shape for longer. When there are cold or hot spots in the liquid, thermal stress can build in the tube itself. Mixing the liquid up lessens these temperature variations and reduces thermal stress and the negative effects caused by it.
The researchers found that by using the nanofluid as the heat transfer fluid without adding a twisted tape turbulator, the heat transfer coefficient went up 12 percent and the efficiency increased by 10 percent as compared to a heat exchanger with a traditional heat transfer fluid. When a turbulator is added to the tube, the heat transfer coefficient improves by 20 percent and the efficiency increases 30 percent, compared to a heat exchanger not employing either aid.
Every process is different, but no matter what a shell and tube heat exchanger is used for, efficiency is important. The more efficient the exchanger is, the better the product will be, the longer the equipment will last and the less energy is required to operate it. Twisted tape turbulators and static mixers are two options manufacturers have to increase the efficiency of their heat exchangers, reduce the size of their exchangers to save valuable floor space and therefore improve their operations as a whole.
For more information about how to use your exchanger to its full potential, reach out to the experts at Enerquip.
No matter what industry you operate in, standards matter. They are the measuring stick against which companies and consumers can measure products and choose which ones best suit their needs. They are a way of demonstrating precision and care in the manufacturing of each model of a product.
There are some industries in which meeting standards is crucial to ensuring product safety and quality. The food, beverage and dairy industries must meet guidelines set by the Food and Drug Administration to ensure products are safe for human consumption. The pharmaceutical industry must also meet these requirements so that each medicine is not only safe, but effective.
What these industries have in common is more than consumer-facing products and FDA regulations; they also rely on shell and tube heat exchangers to help make their products as safe, effective and consistent as possible. In order for these industries to produce food, beverages and medicines that are of high quality, they must use equipment that meets specific guidelines as well.
There are a wide range of standards a shell and tube heat exchanger can adhere to. Knowing what they mean and which ones apply to your industry and area of operation are important for successfully moving forward.
ANSI
The American National Standards Institute has been coordinating the voluntary standardization system in the U.S. private sector for nearly a century. Groups called standards developing organizations work together to develop and improve upon standards.
ANSI publishes Standards Actions every week, which include calls for comments on standards proposals. In it, suggestions are made along with what machinery the standard changes would apply to. As of last year, more than 240 SDOs were accredited by ANSI, and more than 1,100 American National Standards were in place.
3-A Sanitary Standards Inc.
Standards for equipment design used in the dairy industry first came about in the 1920s. There were three interest groups, or associations, that worked to develop the standards: equipment fabricators, regulatory sanitarians and processors. To highlight the three associations’ collaboration, the standards became known as 3-A.
3-A Sanitary Standards were created and are maintained to ensure that all equipment used in the food, dairy and pharmaceutical industry is kept clean so that all products coming from them are safe for consumption. According to 3-A, the ideal equipment can be mechanically cleaned through a clean-in-place or CIP system, or can be easily taken apart for thorough manual cleaning.
API 660
The oil and gas industry is another area in which standards are crucial. Petroleum is used in nearly every aspect of today’s world. It fuels vehicles and heats buildings, but it is also used in textiles, health and beauty essentials, cleaning products and many more applications.
In the oil and gas industry, there are several standards companies must adhere to. Often, it is the end user or consultant who creates demand for refineries to follow these standards. The American Petroleum Institute designed standards called API Standard 660.
A newsletter from the CoDesign Engineering Skills Academy noted that these standards were drafted based on industry experience and practical considerations. They provide specifications for the design of a shell and tube heat exchanger for use in the petroleum industry, such as how thick the tubes can be, the type of exchangers allowed in refineries and how thick the tubesheet joints can be.
As demonstrated in the newsletter’s chart, API 660 has some similar standards as TEMA, though not always. For instance, under API 660, TEMA type P and W exchangers, which have outside packed floating heads and a floating tubesheet that is externally sealed, respectively, are not allowed to be used in a refinery. However, under TEMA’s standards, these can be used in certain situations.
It’s important to note the differences in standards when working in an industry where meeting regulations can help define the quality of a product. Knowing your customer base and what they value is also critical, as this will help manufacturers determine which equipment and which standards are right for them.
If you are looking for a shell and tube heat exchanger for your operations, talk to the experts at Enerquip. Their in-house engineering team will understand your needs and be able to determine which standards your equipment needs to meet.
Heat exchanger expert, Ron, explains how to make your shell and tube heat exchangers more user friendly for your maintenance crew down the road.
Whether you’re in search of a readily available U-tube unit or a tailor-made straight tube design, Enerquip ensures the utmost quality in terms of surface finish, seamless tubing, and weld integrity. Our commitment to excellence guarantees that your 3-A exchangers are in full compliance with the stringent standards set by 3-A Sanitary Standards, providing you with complete peace of mind.
A steam bustle, or annular distributor, is an important component of a shell and tube heat exchanger when viscosity or too much direct steam heat is a concern.
In this video, we discuss the benefits and function of a steam bustle and how it can help improve the performance of your shell and tube heat exchanger.
Shell and tube heat exchangers are important instruments in a wide variety of industries. They are used in refining oil, preparing pharmaceutical products for market, ensuring that food and dairy products are safe to eat and helping breweries create the perfect pint of beer, among other use cases.
While these industries are widely diverse, they all encounter the same concern: which shell and tube heat exchanger to purchase for their operations. Heat exchangers have a long lifespan, especially when they are made with the highest-quality standards and materials. But, when it comes time to make a new purchase, it’s crucial that it is done right.
Not only does the configuration matter, but so do the codes and standards the equipment meets. Industry standards help ensure all products are built in the best way possible for customers. It prevents companies from buying subpar products. The American Society of Mechanical Engineers also pointed out that costs and training time are loweredwhen everyone adheres to the same standards and methods of design.
“Industry standards help ensure all products are built in the best way possible.”
Ensuring your shell and tube heat exchanger is designed and built in accordance to the correct industry standards is of the utmost importance for a business. If an exchanger does not meet the right criteria, the products may not be suitable for distribution, and a new exchanger or an upgrade may need to be purchased.
TEMA
One of the most widely used industry standards comes from the Tubular Exchanger Manufacturers Association. This group updates its set of standards as needed, the most recent being from 1988, according to Thermopedia.
Under TEMA’s standards, there are three subcategories:
The differences between the classes are subtle but important. For instance, the nature of working with petroleum creates a need for heavier and more durable construction, while chemical processing is better done with stainless steel and lighter equipment.
ASME
Other common standards shell and tube heat exchangers are built to adhere to are those set by the American Society of Mechanical Engineers. The ASME VIII code refers to the pressurized parts of a shell and tube heat exchanger, according to Thermopedia. These parts are the ones inside the shell, primarily the tubes.
Section VIII is the one most often applied to shell and tube heat exchangers, though Thermopedia explained sections II and V are also used occasionally. These refer to materials and nondestructive testing, respectively. There are a total of 11 sections in ASME’s standards.
“Different countries have varying rules regarding standards.”
ASME was designed to be applied to many different types of equipment, not just shell and tube heat exchangers. Many exchangers will be certified by both ASME and TEMA, as the latter was in part designed to be a supplemental level of criteria for the machines.
PED
As heat exchangers are an important piece of equipment for many industries, they are used all over the world. Different countries have varying rules about what standards equipment need to meet to be legal. Because of this, it’s crucial that equipment manufacturers and purchasers know where an exchanger is going, and what the rules are there. It’s also important that anyone buying or using an exchanger be fully aware of the regulations in the country the exchanger will be used.
The Pressure Equipment Directive is one such international standard that is required in the European Union. PED covers a wide scope of equipment, from boilers to piping to pressurized storage vessels. It also applies to shell and tube heat exchangers.
PED includes rules about:
Each of these rules is put into place to ensure workplace safety, and that products that are processed with a particular piece of equipment are safe for the public.
CRN
Another international standard is the Canadian Registration Number. This is required for any boiler, pressure vessel or fitting that will be in operation in Canada. Acquiring one ensures that the equipment is certified to be used in a specific province or territory.
The CRN is written with a multi-digit number, a decimal, and one or more numbers or letters that represent a specific territory or province. For instance, “1” indicates British Columbia, while “T” represents the Northwest Territories.
When purchasing a shell and tube heat exchanger, getting the right certifications is crucial. Enerquip’s team of engineers will know what your industry requires and will work with you to meet your needs.
A shell and tube heat exchanger is an essential part of production for many operations. These machines are built to last for years. However, some processes can be rough on the exchanger. For instance, high fluid flows can cause corrosion and vibration, which can be detrimental to the machine. Too much vibration can cause tubes to pull out and cause cross-contamination or shell or tube damage.
The Tubular Exchanger Manufacturers Association states that, in some high-velocity situations, an impingement plate is required. This is when single-phase fluids that are non-abrasive reach a dynamic pressure, or v2, of greater than 1,500. However, with other high values, TEMA recommends devices to protect the exchanger from erosion and vibration.
But installing these plates has some drawbacks. Process Heating pointed out that installing an impingement plate will increase the shell diameter because the plate is typically welded to the tube bundle, beneath the inlet nozzle. University of Kentucky professors R.K. Shah and D.R. Sekulic stated that when impingement methods like these are used, part of the opening will be blocked. Hydrocarbon Processing said these devices could also cause additional vibration problems of their own. This is why it is imperative that manufacturers thoroughly understand the problem at hand, the possible consequences of altering the exchanger and what the overall benefit will be.
Testing before investing
Of course, it can be difficult to understand the full extent of the alterations an impingement plate will make. It’s also not always easy to determine if the impingement plate is the right way to go, or if another method to reduce the risk of erosion and vibration would suit an exchanger better.
Hydrocarbon Processing explained the use of computer simulation can help to predict how a piece of equipment will affect the exchanger’s performance. Computational Fluid Dynamics uses software that combines math and physics to predict how a fluid will flow in relation to the objects and fluids it flows past, TechTarget said.
In a case study conducted by Hydrocarbon Processing, CFD simulations were compared to physical tests for the same equipment to determine whether this method would be an accurate predictor of whether impingement plates or other additions would be effective. The study found CFD was not only a reliable predictor, but it also could provide information physical testing lacked.
Exploring other options
Impingement plates aren’t the only method to decrease risk of vibration and erosion. According to Shah and Sekulic, annular distributors, impingement plates and impingement rods can all benefit a shell and tube heat exchanger operating at high velocity.
An annular distributor can be installed along with an expansion joint to save on cost and space. If an exchanger’s processes easily give way to thermal expansion, this is a good solution. The installation will help to reduce erosion and vibration, but will also help decrease risk of uneven expansion that could damage the shell or the tubes.
TEMA stated that tube-end inserts and distributor baffles can also help with issues concerning high-velocity processes.
Process Heating also explained that using a longer shell will allow the inlet valve to be moved away from the tube bundle, so it is not placed directly above the tubes. Additionally, if a manufacturer has not yet built the exchanger, a U-tube design might be worth considering. If it is determined that an impingement plate is necessary, this design does not suffer from reduced shell diameter, as in a straight tube design. Additionally, if the high-velocity process may also result in damaging thermal expansion, a U-tube exchanger does not pose risk to tube pullout or shell damage. The tubes are free to expand as needed, because they are only attached to a tubesheet at the front bonnet.
If your exchanger is running high-velocity processes and you are concerned about erosion or vibration issues, consider using one of these methods to help. The experts at Enerquip will be able to work with you to determine the best solution.
