Heat exchangers are vital components in various industries, efficiently transferring thermal energy between two fluid streams. Among the different types, shell and tube heat exchangers are commonly used due to their versatility and reliability. To optimize their performance and reduce energy loss, insulation jackets play a crucial role. Here, we’ll explore the significance of insulation jackets for shell and tube heat exchangers, their applications, and how they are utilized to enhance efficiency and safety.
With so many factors to consider in choosing a material for your shell and tube heat exchanger, you may have a lot of questions. To start, you’ll need to decide which criteria are most critical to your operation. Criteria like:
thermal efficiency
cost
availability
corrosion resistance
cleanability
durability
You can then weigh the pros and cons of the options that best meet your priorities, since there is typically more than one good alternative. For example, the best material for heat transfer may not be sanitary enough for your application; or the most corrosion-resistant option may far exceed your budget. In most cases, there is a heat exchanger material option that can balance most of your priorities.
Here are a few tips and suggestions for evaluating the heat exchanger material options based on these common criteria.
A mechanical contractor for a Chicago-based liquid-foods packager had an interesting and challenging cooling application. An important client planned to award the foods packager a large contract for packaging soup if they could satisfy one stipulation: The company had to guarantee that the product would be cooled from 198°F (92°C) to precisely 77°F (25°C) before packaging.
In addition to the tight temperature requirements, process flexibility was required. The contract was for various types of soups, so the packager had to be able to cool products having different thermal properties. At the same time, the packager needed to be able to clean the system easily between batches to avoid any carry-over from different soup types. The cooling point had to be met precisely. If the soups were too warm when packaged, spoilage potentially could occur. If they were too cool during packaging, the containers could sweat, and the labels would not properly adhere to the packages.
In addition, the packager had to accomplish this within a physical area with space limitations. The entire cooling system had to fit within a 14-by-6’ footprint and fit under a 12’ ceiling. Additionally, in order to minimize utility costs, the packager wanted to take advantage of ambient water from their cooling tower to perform the bulk of the cooling. A glycol/water mix through a chiller would be used for final cooling. Another factor considered in the design was the requirement for a sanitary food-grade system that met the 3-A sanitary standards for polished surface finishes and cleanability.
Dual-Stage Heat Exchanger Design Selected
After exploring the options, the food packager selected a designer of shell-and-tube heat exchanger systems. Often when designing shell-and-tube heat exchangers, multiple configurations can perform the duty requested. The best design is selected based on surface area, utility service provided, regulatory preferences and customer priorities. Working together in a collaborative process, the heat exchanger designer and food packager pursued the best option balancing all of the conditions.
In order to provide a fairly simple solution, the first design presented was for a pair of 24” by 10’ long BEM-style straight tube exchangers in series. The soup product would flow through the tubes of the first exchanger while being cooled by cooling tower water in the shell. After the first exchanger, the soup would flow through the tubes of the second exchanger while being cooled by 45°F (7°C) glycol/water mix in the second shell. Both exchangers were inclined to allow the units to drain out when not in use between batches. The two heat exchangers were designed with davit swing-arm assemblies to help facilitate removal of the bonnets for periodic inspection and manual cleaning when needed.
This dual exchanger approach, despite the advantage of simplicity, had several drawbacks. First, the cooling performed in the first exchanger was limited to the temperature that the cooling tower water was being heated to on the shell side. In other words, when the soup entering the exchanger at 198°F (92°C) met the cooling tower water entering the shell at 70°F (21°C), it heated up the cooling tower water to around 120°F (49°C). The soup could not be cooled below this level of 120°F (49°C), which is known as the temperature cross or temperature pinch. This would then put most of the burden on the glycol/water chiller to perform the bulk of the cooling, requiring a larger and more expensive chiller unit.
The other issue that presented itself was the ability to completely clean the unit between batches of product. Although the exchanger could be cleaned by backflushing the tubes with water and cleaning solution, there was no way to accelerate the wash water to the preferred velocity (5 ft/sec) needed for adequate cleaning. This was limited by the size of the onsite cleaning clean-in-place (CIP) system (200 gal/min). With the sheer size of the exchangers and number of tubes, it would have taken a CIP system using 1,500 gal/min to reach the proper cleaning velocity. These factors led to a redesign to a more complex yet more effective solution.
In order to allow for a smaller tube field that would provide the 5 ft/sec velocity for cleaning, the exchanger diameter was reduced from 24” to 6”. Because of the reduction in surface area per heat exchanger, it was necessary to add more exchangers to the set. The first, large unit being cooled by the cooling tower water was replaced by six smaller exchangers. For the final cooling utilizing the chiller, the larger exchanger was replaced by two of the smaller units.
As the design simulations unfolded, other benefits started to show themselves. By restricting the flow of the product to a smaller number of tubes, the velocity of the product also increased. This improved the heat transfer when cooling the soup product. It also allowed the cooling tower water to be split into a fresh stream flowing into each of the six shells, avoiding the temperature cross experienced in the larger unit. During winter months, when their cooling water was colder than 70°F (21°C), it was possible to shut down the glycol/water chiller and perform all of the cooling with just cooling tower water, saving utility costs.
The smaller diameter exchangers were easier to construct and polish to meet the 3-A sanitary requirements. They were efficient to clean using the onsite CIP system, and they were simpler to take apart to inspect due to the smaller, lighter bonnets on each exchanger.
The eight exchangers were stacked on a custom rack with all of the interconnecting product jumpers, utility piping and the contractor’s manual valves. During design, it was decided to leave enough space to mount two more of the same size exchangers on the rack, allowing for future growth in batch size, or for tough-to-cool products requiring more surface area. The units were all pitched slightly to allow for full draining of the product and cleaning fluids from the tubes. Another advantage was that spare parts like gaskets and tri-clamps were less expensive and more readily available for the smaller exchangers than with the two original, large exchangers. An added bonus is that the parts are interchangeable between the eight exchangers in the set.
The new system of stacked heat exchangers in series still fit within the packager’s space limitations, and it ended up costing about the same as the two larger custom units. This allowed the food package to stay within the budget and timeline for the project. The stacked set approach of smaller heat exchangers in series performed consistently. This allowed the packager to win the contract while enjoying the benefits of lower utility costs, increased regulatory compliance and automation of the maintenance process for the system.
GENERON is the world leader in the design and manufacture of custom process air and gas separation systems including nitrogen generators for onshore and offshore platforms, floating production, storage and offloading units and transport tankers for the oil & gas market. GENERON has an expanded product base which includes primary compression, instrument air and post compression packages.
GENERON can design and manufacture standard systems or custom engineered packages. For over 40 years, GENERON has provided thousands of systems worldwide to the oil and gas, marine, and industrial service industries that meet stringent customer and third-party society specifications. GENERON® systems are designed for all areas of classification, from Safe to Hazardous Areas, Class I Division 2, Zone 1 and 2, potentially explosive atmospheres, CE / PED, as well as other European standards.
GENERON has a wide variety of clients that require nitrogen generation systems, including drilling and service contractors like Schlumberger, Weatherford, and Halliburton; engineering companies like Alliance Engineering, Wood Group, McDermott, Fluor, and Petrofac; and major oil companies like Exxon-Mobil, Shell, Chevron, Total, and British Petroleum.
High Expectations
GENERON’S dedicated research and development team in California is constantly working to improve product offerings.
Most recently, the GENERON® Dehydration Hollow Fiber Membrane, was re-developed to reduce the weight and size of overall systems, while maintaining instrument quality air. Innovations like this, along with the complete GENERON® product line, continue to elevate the standards and expectations of clients.
GENERON’s facilities in Houston, Texas and Pittsburg, California allow the hands-on monitoring of quality control while delivering the most cost effective products. Both are certified by certified by DNV to ISO-9000 standards, the American Society of Mechanical Engineers, the Pressure Equipment Directive, GOST, and Underwriters Laboratories and the Canadian Standards Association. High quality and high standards are expected from not only their company, but the companies they partner with.
For nearly a decade, GENERON has trusted Enerquip to provide stainless steel shell and tube heat exchangers for these systems. GENERON turns to Enerquip multiple times a year to fulfill the needs and expectations of a growing customer base. The shell and tube heat exchangers Enerquip develops are integral in the nitrogen generation and natural gas compression and processing packages. GENERON relies on the high standards and integrity of Enerquip’s products and services to fulfill this need.
Industry Standards
GENERON relies on Enerquip’s commitment to meet all necessary compliance standards. Enerquip produces shell and tube heat exchangers that are code compliant and follow the regulations set by the Tubular Exchanger Manufacturers Association (TEMA’s) Classes B, C and R; the American Society of Mechanical Engineers (ASME); the Pressure Equipment Directive; the Ministry of Manpower; 3-A; as well as the codes set forth by the American National Standards Institute. Enerquip also fabricates to American Petroleum Institute (API) and Canadian Standards Association (CSA) standards. Enerquip is able to produce heat exchangers that are customized to GENERON customers’ specific needs. Many have unique requirements for various sizes, models and capacities. While many other shell and tube heat exchanger suppliers provide standard pieces of equipment, Enerquip is able to tailor each product to the unique applications for which it will be used. This is because Enerquip has in-house engineers who develop solutions for GENERON’s clients’ needs.
“We often require more customized equipment,” explained Sergio Gonzalez, the Americas Sales Director at GENERON.
“That’s why we turn to Enerquip. They have the engineering and manufacturing capabilities and facilities.”
Enerquip can produce shell and tube heat exchangers ranging from two inches to four feet in diameter, and it has access to a variety of alloys with which to create the equipment. Using the right material is important to GENERON’s clients to ensure the longest lifespan of the equipment as possible. Using the wrong metal can cause corrosion or won’t be able to withstand the pressure or other conditions of the operations.
Quick Turn-Around and On-Time Delivery
Delivery time is another key factor GENERON appreciates. Enerquip prides itself on providing fast deliveries to clients for whom time is a critical factor. GENERON clients sometimes need to put in rushed deliveries for various systems that GENERON provides. However, the company cannot deliver unless it works with a supplier that can provide them with the necessary equipment in a short period of time. Gonzalez explained that even when GENERON clients need a system to be expedited, Enerquip is eager to accommodate the short time frame whenever possible.
GENERON also values the time Enerquip takes to answer questions and give feedback about various products and orders. Gonzalez explained the contact person he has at Enerquip, Shane Viergutz, is always available to talk and is helpful.
“Every time I call them, even if it’s after hours, he answers the phone or returns my calls,” Gonzalez said.
Sometimes GENERON’s customers need a heat exchanger but don’t need a full system for gas compression, production or processing. Other times, they’ll indicate they need an exchanger or system for an application that GENERON doesn’t specialize in. In these instances, Gonzalez explained, he steers them directly to Enerquip. This is because he knows Enerquip’s engineers will be able to work with them to create the right solution for their needs.
“I’ve recommended Enerquip to some of my clients when they only need the heat exchanger, or when it’s not our market,” he said. “When they are working on a different application that we are not directly involved with, I send them directly to Enerquip.”
In getting connected with GENERON’s trusted supplier, the clients know GENERON is looking out for their best interests and will help them succeed in the future.
GENERON plans to continue working with Enerquip for years to come. The company knows Enerquip and its engineers are dependable, efficient, and will work hard to create the best solution for the many systems GENERON provides to its clients.
Simply put, said Gonzalez, “Overall, Enerquip gives good service to us, good products, and good quality.”
Lambertiprovides specialty chemicals to a wide variety of industries. From ceramics to agrochemical to PVC additives, 14 different industries rely on Lamberti for necessary chemicals to enhance product quality for their customers. Located in 17 different countries allows Lamberti to work with a diverse group of clients.
Bill Ruder is a product manager at Lamberti Systems USA, a division of Lamberti, in Chattanooga, Tennessee. The Tennessee facility specializes in ethoxylation and propoxylation technology. It produces such chemicals as surfactants, polyols and block copolymers, as well as combinations of these.
Companies in the textile, oil, cosmetic, agrochemical and ceramic industries utilize these products. The facility needed a way to heat large storage tanks without altering their complex system already in place. Many of the chemicals are produced in batches to ensure accuracy and quality. It is essential that the chemicals are able to heat and cool properly to the necessary temperatures to maintain their quality before being distributed to clients. However, installing large equipment could hold up production and alter the workflow of the production area.
Reaching Out To A Trusted Company
Mr. Ruder decided to contact a company Lamberti had done business with before, Enerquip. For the past three years, Lamberti has worked with Enerquip to customize shell and tube heat exchangers for its operations. Ruder has always been impressed with Enerquip’s ability to provide affordable, high-quality exchangers to its facilities in Tennessee and Texas. Even though Enerquip is located in Wisconsin, more than 900 miles north of Chattanooga, the exchangers have always arrived quickly and safely at Lamberti’s various locations.
Lamberti has purchased 11 shell and tube heat exchangers from Enerquip. The engineers at Lamberti have always been impressed with the exchangers bought from Enerquip. Ruder also appreciates the extent of knowledge everyone at Enerquip displays about Lamberti’s needs and of the chemical processing industry in general. The person he regularly speaks with, Ron Herman, Enerquip’s director of sales and marketing, has always been able to answer his questions about the equipment Enerquip provides.
“Ron was more knowledgeable on the technical side than most marketing professionals,” he explained.
This is why Ruder thought of them first when he decided to invest in an immersion heater. He learned that Enerquip had a new line of bayonet heaters, so he decided to ask Enerquip about them.
The liquid that Lamberti needed to heat was being stored in vessels. After talking to Enerquip, Ruder learned that the manways located at the top of the vessels were perfect for Enerquip’s bayonet heaters. The bayonet heater could be attached at the manways, which would allow for easy removal when needed. Ruder explained this is necessary because Lamberti’s policy states that equipment must be inspected periodically
A Solution Is Found
Ruder and others at Lamberti liked the bayonet heater because it has direct contact the fluid in the vessel. Because of this, there is no need for extra piping or an external loop. No existing equipment needed to be moved or altered to accommodate the new heater, because it goes right into the vessel itself. This saved Lamberti money and time in the long run.
The raw material can also be heated before being fed into the unit. Once inside, the material needs to be heated to high temperatures. When the fluid is heated before entering the unit, the machine performs less work and the liquid reaches the desired temperature faster. This saves reaction time as well as the energy it would take to heat the material from a lower initial temperature.
Lamberti has been using the bayonet heater for several months now and has enjoyed its space-and cost-saving properties. It is easy to use and simply removed from the vessel for inspection and cleaning purposes. It has been able to heat the necessary liquids to the correct temperature without any problems.
Ruder says he would recommend other companies work with Enerquip because they are fast, reliable and willing to help clients customize their exchangers to provide the best solution to meet their unique needs.
Honey is a shockingly versatile ingredient. Used in dishes ranging from fried chicken to kale chips, honey can be a nice complement to nearly any meal.
More people are incorporating honey into their diets. According to Bee Culture, a magazine dedicated to all things beekeeping, the U.S. consumed 1.61 pounds of honey per person in 2016. Just six years prior, that number was 1.2 pounds per person.
American consumers want clean-looking honey
As more consumers search grocers’ shelves for this golden ingredient, it’s important that honey producers understand what qualities most consumers are looking for. According to the National Honey Board, most shoppers seek out liquid honey that has a bright, clear appearance. Generally speaking, consumers don’t want things like pollen or wax, and especially not bee parts, left suspended in their honey.
Additionally, they don’t want their honey to crystallize quickly. Though crystallization isn’t an indication of anything wrong with the honey (and all honey will crystallize eventually), the look of solid or discolored honey doesn’t appeal to many U.S. shoppers, NPR reported.
Filtration and pasteurization produce attractive honey
Though crystallization will eventually happen to all honey if given the time, the process can be slowed by taking out foreign particles and pollen, and by removing any tiny air bubbles in the product. These goals can be accomplished with two steps: filtration and pasteurization.
There are many ways to filter honey. According to NPR, Dutch Gold uses dichotomous earth and a series of large filters that remove:
Dust.
Pollen.
Bee wings and other insect parts.
The dichotomous earth.
This is one of the more common filtration methods, and is very effective in producing a clear, unadulterated product.
“Heating honey to 160 degrees Fahrenheit is enough to pasteurize the honey and ward off crystallization.”
After that, the honey can be pasteurized. Sanitary shell and tube heat exchangers are an excellent option for this. Honey is very temperature-sensitive and heating it up too much can scorch the product, affecting both taste and color. By using a shell and tube heat exchanger, which will heat up the honey by way of a heat transfer medium such as water, the honey won’t be exposed to as much risk of heat pockets or being heated higher than what the manufacturer wants. Manufacturers can dissipate the heat, thus decreasing risk of localized heat pockets, even more by adding steam bustles to their unit.
According to John Skinner, of the University of Tennessee’s department of entomology and plant pathology, heating honey too much will lower the quality of the product and cause the loss of many important components. Heating it rapidly and over direct heat are the most detrimental to honey’s many nutritional qualities.
However, some heat will rid the product of tiny air bubbles, lengthen the time for which the honey will remain liquid, and ultimately create a more beautiful product. Deb Terrill explained in The Daily Journal of Kankakee, Illinois, that heating honey to 160 degrees F is enough to pasteurize the honey and ward off crystallization for a while, but still keeps the healthy compounds intact.
Designing a shell and tube heat exchanger involves many decisions that must be made carefully and intentionally. One crucial choice that’s important to every exchanger is the material from which it’s made.
Engineers have a wide variety of options when choosing the right material from which to build a shell and tube heat exchanger. Steels and alloys come in various compositions, each with their own unique properties, benefits and disadvantages.
What makes one material more suited for an exchanger over another largely depends on how the equipment will be used – including what chemicals will be introduced to it, the temperature and pressure settings it will be subjected to, and what kind of environment it will be housed in. In addition, the composition material must be cost-effective and easily acquired by the manufacturer.
Many manufacturers find duplex stainless steel to be an ideal material for shell and tube heat exchangers in a wide variety of industries, including the pharmaceutical, oil and gas and biotechnology industries. Duplex stainless steels are composed of ferrite and austenite, and thus can withstand high-stress applications.
Ferrite and austenite
Stainless steels come in many forms. Austenitic stainless steels are the most popular, as they are the most versatile. They are very weldable, according to the American Welding Society, but they do have a tendency to crack when overheated or under too much pressure.
“Duplex stainless steels can withstand high stress applications.”
Ferritic stainless steels are another good option for a variety of applications. Though they aren’t as durable as austenitic steels, they have high resistance to corrosion and are fairly formable, making them a versatile solution.
When combined to create duplex stainless steel, the best properties of both the austenite and ferrite come out. Austenite lends its strength while ferrite resists corrosion and cracking.
Duplex stainless strength
Since duplex stainless steels are so strong, engineers have found they can reduce the weight and thickness of materials made from it while still maintaining durability and corrosion resistance. According to Process Heating, duplex stainless steels usually have double the strength of austenite stainless steel. Thinner tubes mean less material is needed, reducing the building cost of the equipment. The exchanger may also be able to be more efficient because of the lower weight.
In addition to having a strong, efficient exchanger, manufacturers seek out those that can resist corrosion best. Corroded or pitted tubes become weak in time and can eventually spring a leak. A cracked tube is never a good thing, and can cause:
Fouling
Cross contamination
Damaged tube sheets, shells or other important features of the exchanger.
Damaged tubes are also difficult and expensive to replace.
Corrosion can occur anytime a substance is introduced to the exchanger that naturally reacts with the chemical composition of the tubes or shell. Chlorine is a common cause of pitting, and can be a major concern for manufacturers operating in a chlorine-heavy environment with an austenite stainless steel heat exchanger. Duplex stainless steels, on the other hand, resist the ill effects of chlorine well and are sought after in industries that work with chlorine frequently.
Duplex stainless steels’ ability to withstand high temperatures also make them a prime choice for shell and tube heat exchangers. When chloride and tensile stresses are both at play, it only takes a temperature of 150 degrees Fahrenheit to endanger austenitic stainless steel, according to the International Molybdenum Association. When duplex stainless steels are in use, however, temperatures can rise to around 250 degrees before they become risky.Rouging is another problem that some industries need to fend off. Rouging refers to the oxygenation of the metal, represented through a rainbow of colors including red, blue, gold, gray and dark brown. However, IMOA noted that the causes of rouging aren’t always completely understood, but can be greatly affected by the grade of steel equipment is made from.
When rouging builds up on equipment in the pharmaceutical and biotechnology industries, it’s imperative that it gets cleaned to prevent product contamination. The biggest challenge in this is the time and money that goes into this process. Choosing a rouging-resistant material to build equipment is ideal. IMOA explained that the 316L grade of austenitic stainless steel is a favorite among the pharmaceutical industry because it is resistant to rouging to a certain extent. However, duplex stainless steel has also been found to be just as resistant to it, if not more so.
Cost benefits
In addition to information about how well one alloy performs in operation compared to another, manufacturers also need to know whether the material is available to them, how difficult it is to obtain it and how much it costs. Process Heating noted that duplex stainless steels have lower nickel and molybdenum contents compared to austenitic stainless steels, bringing down their price point. It also protects the alloy from a volatile raw materials market, which can cause alloy and metal prices to swing upward dramatically at times.
“Lower nickel and molybdenum contents bring down the price point of duplex stainless steel.”
Additionally, since the stronger duplex stainless steel can be made durable with less material than an austenitic or ferritic steel, the cost to build it can be reduced.
Manufacturers also need to look at cost comparisons over the long term. For example, a material that costs less upfront but has weak properties will eventually cost more in the long run through maintenance and replacement costs. Since duplex stainless steel can stand up to higher temperatures and pressures, as well as more corrosive materials, than austenitic or ferritic stainless steels, less maintenance would theoretically be needed to keep the exchanger in working order.
Using equipment that is made from the proper elements is crucial to having a healthy and productive manufacturing operation. If you’re in the market for a long-lasting shell and tube heat exchanger,
Your shell and tube heat exchanger could be one of the most important pieces of equipment in your business. In the food, beverage and dairy industries, a heat exchanger will protect customers from contaminated products. The pharmaceutical industry relies on heat exchangers to ensure medicines are top quality.
If a heat exchanger fails, product is contaminated and lost. This could decrease productivity, and in some cases, could result in a reputation-damaging recall. To prevent failure, it is critical that the heat exchanger is reviewed and serviced regularly. Chemical Engineering Magazine explained that, without proper maintenance, heat exchangers are prone to corrosion and fouling, which could lead to leaks. This will cause the product to mix with the cooling or heating fluid and ruin the batch. Corrosion and other deposits collecting on the floor of the exchanger will decrease the efficiency of the exchanger. This could prevent the liquid from reaching the desired temperature.
“If a heat exchanger fails, product is lost or contaminated.”
Corrosion leads to bigger problems
A shell and tube heat exchanger is a machine that is expected to have to be repaired or replaced eventually. The nature of its use will wear on it and eventually, corrosion will occur. The goal is to keep the exchanger in operation as long as possible. According to MTS Systems Corporation, a heat exchanger could last up to 20 years with the right maintenance. This includes careful, regular inspections of the machine and all its parts.
MTS said it is important to make sure the heat exchanger is sanitary from the beginning of its life to the end. Before the first use, be sure to look it over thoroughly to make sure everything is secured properly and the tubes and shell have not been contaminated by dirt, dust or other foreign substances.
Corrosion is a process that occurs over time regardless of proper maintenance schedules. It is the result of chemical reactions in or around the heat exchanger. Different metals will react with different substances differently. Stainless steel is a good material to use in exchangers when the substances used within could be harmful to other metals, such as copper alloys. According to the Stainless Steel Information Center, the material can resist corrosion from most acidic, alkaline and chlorinated substances when it is a high-alloy grade. However, the British Stainless Steel Corporation explained that while the metal is highly resistant to corrosion, it will begin to wear over time.
“Stainless steel is resistant to corrosion from many substances.”
Water monitoring
MTS explained the best way to prevent corrosion is to make sure only the best substances for the exchanger’s material makeup enter the machine. Using the correct chemicals to treat and clean the tubes is essential. This information should be obtained before you begin using your heat exchanger to ensure you are prepared for its maintenance from the get-go.
Many heat exchangers use water as the heat transfer liquid. Tap water is generally of an acceptable quality to use in the machine. However, it is important to double check the water before putting it into the exchanger. The pH should be neutral and the water shouldn’t be polluted or have any bacteria or other contaminates in it. If the water comes from a natural source, is should be treated before entering the tubes.
If the water isn’t treated or inspected before entering the exchanger, debris could enter the machine and block the chambers. To prevent this from happening, screens or filters can be installed to keep particles out. If they do enter, they will wear against the tubes and cause corrosion.
Monitoring the health of your heat exchanger will help to identify early signs of failure before fouling or contamination become a larger issue. MTS explained that checking on the water quality is a good way to see if failure is a risk or is already happening. Cloudy water indicates the fluid is no longer pure. Taking notes on temperature and pressure changes will reveal problems beginning to form. Reduced efficiency could be a sign of scaling, a solid precipitate resulting from chemical reactions. Scale build-up will lead to fouling and corrosion over time. Checking other aspects of the exchanger, such as tube thickness, will also give indications of emerging problems.
If you find that you need to replace all or part of your heat exchanger, contact the helpful heat exchanger experts at Enerquip who specialize in designing custom shell and tube heat exchangers, and drop-in replacement exchangers.
When processing liquids in a shell and tube heat exchanger, it is critical that everything is in order. If a small part of the exchanger is broken, flawed or contaminated, the entire batch of liquid will not be suitable for consumption. According to UK Essays, shell and tube heat exchangers are adaptable to many different industries, and are therefore the most popular style of heat exchanger. Shell and tube heat exchangers are used in a variety of consumer-directed industries, such as dairy, food and beverage, and pharmaceuticals. It is essential that consumers can trust that the processing procedures are adequate in keeping them and their families healthy.
“Maldistribution is the uneven flow of liquid through tubes.”
A common problem among shell and tube heat exchangers is maldistribution. Maldistribution is defined as an uneven flow of liquid through the various tubes comprising the tube side of the heat exchanger. This problem has several causes, but one main effect: It can cause the tubes to pull out of their designated space on the tube sheet, explained Chemical Processing. They can also become warped and damaged in the process, according to Wermac, a website dedicated to piping education and information.
Maldistribution causes problems
Once the tubes pull out of the tube sheet, heat-transfer liquid can leak into the solution being processed. Some of the product can also be lost to the heat-transfer liquid. This results in an impure product not suitable for use or sale. The problems associated with this type of error can be costly and time-consuming in many ways. First, there is the cost and time it takes to repair or replace the damaged parts. Then, the question of fixing and preventing the relapse of the maldistribution. Finally, the time and cost of reproducing another batch of product will result in profit losses.
UK Essays also explained that maldistribution would cause the heat exchanger to cease operating at top performance. Heat is not transferred as well when maldistribution occurs and the problems that cause it exist.
The best way to avoid the issue of tube damage and pullout is to prevent maldistribution from happening. There are several common problems that lead to this malfunction.
Thermal expansion
Chemical Processing reported inconsistent temperatures can lead to thermal expansion. When the shell side heats up rapidly but the tube side remains cool, the shell is prone to expansion. The tubes are then left behind as the tube sheet expands, causing the tubes to be removed from their place in the sheet.
“Inconsistent temperatures can lead to thermal expansion.”
Wermac explained this problem can be avoided with the installation of an expansion joint. An expansion joint can be installed either on the shell side or the tube side of the heat exchanger, though the least expensive option is to install it into the shell pipe.
Evenly dispersed flow
UK Essays examined the flow of a shell and tube heat exchanger to discover another cause of maldistribution. When a company uses a heat exchanger, it is expected that the liquid being heated will be evenly divided among each tube. However, there are some things heat exchanger operators should be aware of to make sure this is the case.
UK Essays found that when the flow rate, or Reynolds number, is increased, maldistribution is more likely to occur. To balance this out, the pressure drop needs to be increased. This can be done with a longer header part of the heat exchanger. Another way would be to decrease the velocity of the liquid.
Liquid distribution systems
Chemical Processing described another potential cause of maldistribution. When liquid is dispersed among the tubes using a spray system, it is crucial the pressure is high enough to evenly distribute the product among all tubes available. Furthermore, it is important the liquid is kept at a constant temperature and has low possibility of vaporization. When this occurs, there are bound to be temperature inconsistencies. This will cause localized thermal expansion, causing maldistribution.
The best way to ensure the liquid is able to be dispersed uniformly among all tubes via a spray nozzle is by using a bottoms recirculation system.
Maldistribution can be caused by a variety of issues in the design and the use of a shell and tube heat exchanger. Regardless of how it is caused, maldistribution can lead to serious consequences and a failed product batch. To prevent this from happening, companies should invest in custom stainless steel shell and tube heat exchangers and learn about additions that could help prevent maldistribution, such as expansion joints and bottoms recirculation systems.
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