In the world of industrial engineering, the transfer of thermal energy is crucial for generating electricity, controlling systems, and manufacturing products. But how do engineers manage this energy transfer? This article explores the fascinating world of heat exchangers, devices that play a vital role in various industries.
A heat exchanger is a device that allows thermal energy to be transferred between two fluids without them mixing. These fluids can be liquids, gases, or a combination of both. For instance, if we need to heat oil, we don’t apply a flame directly to it. Instead, we use a heat exchanger to transfer heat from boiling water to the oil. The water and oil remain separate, with heat moving from the hot water through a metal wall into the oil. This process requires a temperature difference, with heat naturally flowing from hot to cold.
Heat exchangers are ubiquitous, found in air conditioning units, car radiators, and refrigerators. However, industrial heat exchangers are designed for more extreme environments, such as nuclear power plants, oil refineries, and food processing facilities. These environments often involve high pressures and temperatures, requiring heat exchangers to be made from robust materials and chemically treated to resist corrosion. They handle a variety of fluids, including water, steam, air, refrigerants, oil, chemicals, gases, and food products.
There are five main types of industrial heat exchangers, each with its own variations:
This is the most common design, featuring an inlet and outlet on the same end. A tube runs between these points, containing one of the working fluids, such as hot water. The tube is covered with thin metal sheets called fins, which increase the surface area for heat transfer. The other fluid, like ambient air, passes over the tube, transferring heat from the hot water to the air.
In this design, one fluid flows through tubes, while another fluid surrounds these tubes within a shell. Baffles inside the shell create turbulence, enhancing heat transfer. This type is common in industries like pharmaceuticals, where steam heats a chemical product, or in refrigeration systems, where water absorbs heat from a refrigerant.
Similar to shell and tube exchangers, these consist of a tube running back and forth within a shell. One fluid flows through the tube, while another flows through the shell. This design is cost-effective and commonly used in food processing and pharmaceutical production.
These consist of metal plates with patterns that create turbulent flow, enhancing heat transfer. Gaskets separate the plates, allowing two fluids to flow alternately. Plate heat exchangers are often used in heating and cooling applications, such as district heating networks.
Featuring a spiral design, these exchangers have a single channel for fluid flow, maintaining high velocity and reducing fouling. They are ideal for processing sludge-like substances, such as in anaerobic digesters, where they help release methane for energy production.
Heat exchangers are essential components in many industrial processes, ensuring efficient thermal energy transfer. Understanding their design and applications can provide valuable insights into the engineering challenges and solutions in various industries.
Work in groups to design a basic heat exchanger model using everyday materials such as plastic tubes, aluminum foil, and water. Present your design to the class, explaining the type of heat exchanger it represents and how it facilitates thermal energy transfer.
Analyze a real-world case study where heat exchangers are used in an industrial setting, such as a power plant or refinery. Discuss the challenges faced and the solutions implemented. Present your findings in a report, highlighting the importance of material selection and design considerations.
Use simulation software to model the thermal performance of different types of heat exchangers. Experiment with variables such as fluid flow rates and temperatures. Share your results and discuss how these factors influence efficiency and effectiveness.
Participate in a field trip or virtual tour of a facility that uses industrial heat exchangers. Observe the equipment in operation and interact with engineers to understand the practical applications and maintenance challenges.
Conduct research on the latest advancements in heat exchanger technology, such as new materials or designs that improve efficiency. Prepare a presentation to share your findings with the class, emphasizing the potential impact on industry practices.
Sure! Here’s a sanitized version of the transcript:
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Almost every industrial facility relies on the transfer of thermal energy to generate electricity, control systems, and working environments, and even manufacture products. So how do engineers control this? That’s what we’ll be covering in this video, which is kindly sponsored by Super Radiator Coils, one of the leaders in heat exchanger production for commercial, industrial, and even nuclear markets. All engineering design, performance testing, and manufacturing takes place in-house at one of their three divisions in Chaska, Minnesota; Richmond, Virginia; and Phoenix, Arizona. When it has to be perfect, it has to be Super. For more information, visit superradiatorcoil.com, and I’ll leave a link for you in the video description below.
A heat exchanger is simply a device used to transfer thermal energy between two fluids without them mixing. Fluids can be either a liquid or a gas, or even a mixture of either of these. Take oil, for example. We need to increase its temperature, but we don’t want to apply a flame directly to the storage unit. Instead, we will boil some water and cycle this through a simple heat exchanger. The oil is normally also cycled through the heat exchanger, where it will safely absorb the heat of the water. The thermal energy is being transferred from the hot water through the metal wall and into the oil. The water and oil never meet or mix; they are always completely separated. There must be a temperature difference for the heat to transfer, and heat always flows from hot to cold.
We could also cool the oil down by pumping cold water through the heat exchanger. The cold water will now absorb the thermal energy of the oil. We see heat exchangers used everywhere, from air conditioning units and engine cooling radiators in cars to the back of refrigerators. However, industrial heat exchangers are a little different because they often work in extreme environments, such as nuclear power stations, oil refineries, food processing plants, and factories, which all involve working in high pressure and high temperatures. Therefore, these units are built sturdier and from more robust materials. The working environments are often corrosive, so they are chemically treated to handle this. These heat exchangers will handle fluids such as water, steam, air, refrigerants, oil, chemicals, gases, and food products.
There are five main types of industrial heat exchangers, although there are many variations of each design. Let’s look at a thin tube heat exchanger first, which is probably the most common design used. A typical thin tube heat exchanger looks something like this. There is an inlet and an outlet, usually located on the same end. These connections are typically flanged, but they could be threaded or soldered, depending on the application and the pressures of the working fluids. Running between the inlet and the outlet is a tube that will contain and direct one of the working fluids, for example, hot water. The tubes will be covered with many thin sheets of metal known as fins. The fins increase the surface area of the tube wall, allowing more heat to transfer. The other fluid, for example, ambient air, will pass over the outside of this tube between the fins. The two fluids will never mix; the heat passes from the hot water through the tube wall and into the air.
In some designs, the fluid will simply flow through the entire length of the tube. Other designs will have the fluid pass through multiple tubes at the same time. These will be connected to a header at the inlet as well as the outlet to facilitate the distribution through the tubes. For example, these are used in a gas turbine power station to cool the intake air, which will be sucked into the turbine and combusted. This helps the turbine run at optimal performance in hot and humid conditions. A chiller pumps cold water to the heat exchanger, which then flows through the tubes. The warm ambient air passes over the outside of these tubes, and the thermal energy transfers from the hot air into the cold water. The air will leave cooler and enter the turbine, while the water leaves warmer and heads back to the chiller, where the unwanted heat will be rejected back into the atmosphere.
Shell and tube heat exchangers look something like this. With this design, we normally find the inlet and outlet for one fluid at the very end of the heat exchanger, known as the header. Then we have another inlet and outlet for fluid two on the main body, known as the shell. Inside the unit, we have the tubes that bend and loop around to start and finish at the tube plate, which sits between the shell and the header. The tubes will usually also pass through some baffles, which are sheets of metal. The header, as well as the tubes, can be removed for cleaning, repairs, and maintenance. Inside the header is a sheet of metal known as the divider or partition, which separates the tube ends, enabling the fluid to flow into and then out of the heat exchanger tubes. Fluid one will flow through the header into and around the tubes, then back to the header. Fluid two will enter the shell and surround the outside of the tubes. The baffles will partially block the flow, which will force the fluid to turn multiple times. This creates a turbulent flow and ensures that fluid two mixes with itself, ensuring maximum heat transfer.
For example, we might find this in a pharmaceutical factory with a boiler providing steam into the shell, which surrounds the tubes. A chemical product is then pumped through the tubes and absorbs the heat of the steam through the tube wall. This product will exit the heat exchanger much warmer, while the steam will start to condense into a liquid and flow back to the boiler to pick up more heat and repeat the cycle. Additionally, these are used in refrigeration applications, like this industrial chiller, where the water flows through the tubes and the hot refrigerant in the shell. The water will absorb the heat of the refrigerant so that it can transport this to the cooling tower, where it will be ejected into the atmosphere. The water returns cooler to pick up more unwanted thermal energy from the chiller.
We have covered how chillers work in great detail previously, so do check those out. I’ll leave a link for you in the video description below. Double pipe or tube-in-tube type heat exchangers look something like this. This is similar to the shell and tube heat exchanger because essentially we just have a tube that runs back and forth a number of times between an inlet and an outlet. This is surrounded by a shell that has another inlet and outlet. A metal frame will hold the unit in place, and typically these will all be made from stainless steel. One fluid will flow through the tube, and another will flow through the shell. The two fluids are separated by the tube wall and transfer thermal energy through this tube wall. The different configurations result in different temperature profiles and heat transfer. In this design, the bend at each end isn’t utilized for heat transfer, and heat can be wasted here. However, manufacturing this heat exchanger is cheaper and obviously easier.
Other designs, like this hairpin type heat exchanger, which is often found in oil refineries, will encapsulate the bend to fully utilize the surface area for heat transfer. This version normally uses multiple tubes to maximize the surface area and thus increase the heat transfer, although this will also increase the resistance. These are a fairly simple heat exchanger design and are very common, particularly in food processing as well as pharmaceutical production. For example, we might have a dairy product flowing through the tube, and then we have hot water or maybe even steam flowing in the opposite direction through the shell, which will warm the product up to a certain temperature before it is mixed with some other ingredients and then bottled.
Industrial plate heat exchangers look something like this. They consist of a thick metal cover on the front as well as the rear of the unit, which is typically made from mild steel. There are two inlets and two outlets, which are normally flange connections. In most designs, we find all four ports located on the front plate, as this allows the heat exchanger to be easily extended or reduced to accommodate a future change in operation. Most heat exchangers do not have this ability. Between the end covers, we find a number of plates, which are thin sheets of metal with a pattern stamped into them. Typically, these will be made from stainless steel. These patterns will help direct the fluids and create a very turbulent flow, which increases the heat transfer. Between each of these plates is a seal known as a gasket, typically made from rubber. These gaskets separate the plates, creating a thin channel between them through which fluid can then flow. On each plate, the gasket will block two of the four ports, meaning only one fluid can enter and exit. The next plate will allow the second fluid to pass. This alternates throughout the heat exchanger and keeps the two fluids completely separated; only the thermal energy will flow through the sheets. The entire unit is held together with some long bolts that compress the gaskets to form a very tight seal.
These heat exchangers are very common for heating and cooling. For example, an incinerator power plant burns household waste to generate heat. This creates steam, which drives a turbine and generates electricity. The waste thermal energy then passes through a plate heat exchanger to heat a district heating network, and other buildings will then connect to this heat network via plate heat exchangers to supply their own heating demands instead of creating their own individual boiler.
Spiral heat exchangers look something like this. We have a flanged inlet on the front face with the outlet located on the top. Then we have an inlet from another fluid also on the top, with the outlet located on the rear face. Behind the end plates, we find two sheets of metal inside, which spiral together around the interior to form a channel through which the fluids will now flow. The channel completely separates the two fluids. The first fluid enters the heat exchanger and fills the chamber, then flows around the channel and exits. Meanwhile, on the other side, the second fluid is entering via the top, flowing around the channel and into the chamber where it then exits. The two fluids enter and exit at different temperatures. This type of heat exchanger isn’t as commonly used; however, because the design has only one channel for the fluid to flow through, the velocity remains high, making it harder for fouling to occur, whereas plate and even tube heat exchangers divide the flow into multiple paths. These are ideal for installations where sludge-like substances are processed, for example, in an anaerobic digester, where the thick sludge is recirculated through a spiral heat exchanger to maintain a certain temperature. This releases methane from the digester to power an engine and then turn an electrical generator.
Check out one of these videos to continue learning about mechanical and thermal engineering. As this is the end of the video, don’t forget to follow us on Facebook, LinkedIn, Twitter, Instagram, TikTok, as well as theengineeringmindset.com.
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Heat – The form of energy that is transferred between systems or objects with different temperatures, typically flowing from the hotter to the cooler system. – In thermodynamics, engineers study how heat is transferred in order to improve the efficiency of engines and refrigerators.
Exchanger – A device used to transfer heat between two or more fluids without mixing them. – The heat exchanger in the power plant efficiently transfers thermal energy from the steam to the cooling water.
Thermal – Relating to heat or temperature. – Thermal conductivity is a crucial property in materials science, affecting how materials are used in engineering applications.
Energy – The capacity to do work, which can exist in various forms such as kinetic, potential, thermal, electrical, chemical, and nuclear. – Engineers must consider energy conservation principles when designing sustainable systems.
Fluids – Substances that have no fixed shape and can flow, such as liquids and gases. – Computational fluid dynamics is a tool used to simulate the behavior of fluids in engineering systems.
Industrial – Relating to or characterized by industry, often involving large-scale production or manufacturing processes. – Industrial engineering focuses on optimizing complex processes and systems to improve efficiency and productivity.
Applications – The practical uses of scientific principles and theories in real-world scenarios. – The applications of nanotechnology in engineering include the development of stronger materials and more efficient energy systems.
Design – The process of planning and creating something with a specific function or intention in mind. – In mechanical engineering, design involves creating detailed plans for machines and systems that meet specified requirements.
Transfer – The movement of something from one place, person, or thing to another, often referring to energy or heat in engineering contexts. – Heat transfer analysis is essential in the design of thermal management systems for electronic devices.
Processes – A series of actions or steps taken to achieve a particular end, often involving the transformation of materials or energy. – Chemical engineering processes are designed to convert raw materials into valuable products efficiently and safely.
