The relationship between hot and cold is a complicated one. Where we humans may have become accustomed to simply flicking a switch in our homes and receiving hot or cold air instantly or putting all out trust in our vehicles to maintain the correct heat, the process is much more involved than the average person might consider. No, it is not magic, but something known as a heat exchanger. These devices are seemingly everywhere we look, yet many of us fail to realise it.
What is a Heat Exchanger?
A heat exchanger is a device that transfers heat between two liquids, two gasses or a mixture of the two. Generally, one of the substances is at a lower temperature to the other, thus transferring the heat from one to the other. There are various designs for this device, but the main concept is to transfer heat from either hot to cold or vice versa. Heat exchangers are used in air conditioners, power plants, automobiles, chemical plants, for sewer treatment, natural gas processing, and a variety of different avenues. Essentially, anywhere that requires additional heat, or additional cold, you can rest assured a heat exchanger is involved.
Classifications of Heat Exchangers
Although there are various types of heat exchangers on the market today, there are actually only two classifications of this device.
Parallel-Flow Heat Exchangers – The two fluids or gasses are exchanged at either end in a parallel fashion where all liquids and gasses move in the same direction
Counter-Flow Heat Exchangers – One of the two fluids or gasses is moving one way while the other is moving in the opposite direction.
Different Types of Heat Exchangers
Shell and Tube Heat Exchangers
With a shell and tube heat exchanger, the interior smaller tubes have one liquid running through while the surrounding space maintains the other temperature liquid. The beauty of shell and tube heat exchangers is that they are available for remarkably high temperatures. Some can take temperatures over 260°C without cracking. However, manufacturing a shell and tube heat exchanger calls for many features to be taken into account such as…
- Tube Diameter – The diameter of a shell and tube heat exchanger is a factor as making the outer tubing smaller will aid in its compact nature, but will drastically limit its ability to heat or cool properly and the extremely small interior tubes can foul up easily with little ability to clean the unit. Generally, shell and tube heat exchangers maintain a larger diameter for much bigger applications due to the necessity to clean the interior.
- The Tube’s Thickness – The thickness of the shell and tube heat exchangers should be taken into account to allow for corrosion in certain instances, but also to allow for vibration resistance. Essentially, the thickness must be able to withstand the intense pressure produced by higher temperatures, yet still allow a decent amount of energy to pass through.
- Length of Tube – Expense of shell and tube heat exchangers rises when the tubing is smaller in diameter with a longer shaft. Due to its expected longer length, shell and tube heat exchangers are not always practical for every application.
- Pitch of the Tubes – Pitch between tubes is something to consider when constructing a shell and tube heat exchanger. The reason this is so important is that an increased pitch will lead to a larger and more expensive heat exchanger. Generally, pitch should be no more then 1.25 times the outside diameter of the interior tube.
- Corrugation of Tubes – Performance of your shell and tube heat exchangers largely depends on the level of tube corrugation to transfer heat effectively throughout the entire unit.
- Layout of the Tube – Tube layout is extremely important within a shell and tube heat exchanger. There are three general layouts including triangular, rotating triangular, square, and rotated square. Triangular based patterns are used for more effective heat transfer. They use force to provide substantially more heat. Square style patterns are effective but must be cleaned often.
- The Baffle Design – The baffles within shell and tube heat exchanger are essentially the holders of the interior tube pattern. These holders or baffles must withstand the heat, pressure, and girth of the entire apparatus. The space between each baffle is important as more space can lead to less economic heating and sagging of the interior components. Setting the baffles to close tends to provide adequate heating but can produce too much pressure.
Plate Heat Exchangers
Plate heat exchangers utilise surface area to produce heat. The plates are larger and not tubular, but flat pieces that maintain a small space between each plate. The arrangement of the plate design can either hinder or heighten the unit’s heating effectiveness. Plate heat exchangers are generally used in refrigeration applications as they can be made to be smaller and wider allowing them to be placed in thin, out of the way locations. However, they have also been known to be used in water to water heat exchange and, in vehicle applications, coolant or oil to air heat exchange.
Adiabatic Wheel Heat Exchangers
An adiabatic wheel heat exchanger uses in interior wheel comprised if fine threads rotating with hot and cold liquids for heat exchange. Heat is moved through the wheel and out the opposite side of the heat exchanger.
Plate Fin Heat Exchangers
Plate fin heat exchangers carry a lot of advantages that the other styles simply do not have. Due to its large size and ability to transfer heat a bit more effectively, higher heat is able to be utilised with a larger transfer ability. Many plate fin heat exchangers are comprised of aluminum alloys which can help reduce their overall weight by up to 5 times while the design can handle far more pressure than other styles. The only disadvantages to the plate fin heat exchanger design is that clogging can happen due to narrow pathways and cleaning can be a great challenge with the narrow channels as well. A plate fin heat exchanger is generally used for low temperature services and within transportation industries such as aircrafts and vehicle motors.
Manufacturing costs are always on the rise and heat exchanger manufacturing is certainly no exception. The costs of materials and paying countless workers to upkeep and run machines, not to mention the high cost of maintaining manufacturing machines, themselves, keeps the cost of manufacturing high, but there is a solution. More and more people are embracing the beauty of 3D Printing heat exchangers as it solves many of these ongoing problems.
Intricate Design Needs
As we can plainly see in the above illustrations, heat exchangers are not all one in the same. Each one has their own set of needs and intricate pieces that go into their design. Manufacturing each piece in the traditional sense, can be a nightmare especially with the tiny diameters and small spaces between each piece.
3D Printing heat exchangers can take a lot of the worry out of their manufacture. A 3D Printer is ideal for designing even intricate pieces as the system is controlled through a computer for pinpoint accuracy. The results are as perfect as the output information given by the computer, so there is little room for human error or manufacturing issues with even the most intricate heat exchanger design format.
No Extra Machines Required
Manufacturing heat exchangers requires a lot of machinery. Each piece must be manufactured individually and then placed together. However, 3D Printing heat exchangers gives the manufacturer more room for progress as there is no longer a need to use individual machines for each piece. The 3D Printer can be the main avenue for manufacture reducing the cost of upkeep and maintenance on various machines.
Labor Cost Reduction
Labor can be an enormous expense in any manufacturing facility. There is a job for everything from cleaning and maintaining equipment to actually putting pieces of heat exchangers together, but again, 3D Printing can drastically reduce labor costs. With the use of 3D Printers in a heat exchanger manufacturing facility, there is no longer a need to maintain the manufacturing equipment and the act of welding pieces together becomes an autonomous task for the 3D Printer during the manufacturing process as opposed to after the fact.
Higher Efficiency Output
Possibly the best way 3D Printers can assist with manufacturing heat exchangers is the level of high efficiency output they can produce. Time will no longer be wasted with human errors or machine downtime as each 3D Printer can work independently producing heat exchangers 24 hours a day. More output equals more money for the manufacturer.
3D Printing solves many problems and its ability to assist in the manufacturing of heat exchangers and many other applications makes it a viable option for those looking to streamline their manufacturing processes. Any facility would do well to modernise their manufacturing machines to updated 3D Printers. Not only can the facility benefit from the cost effective measures listed above, but by designing a heat exchanger and testing it in a computer format first, they can offer a variety of new designs to improve the overall efficiency of the heat exchangers they manufacture.