Heating and cooling needs aren’t quite as straightforward in the industrial and commercial sectors as they are in residential situations. Whether heating a space or cooling machinery, heat exchangers have to perform at exceptional rates and need to be as efficient and cost-effective as possible. One of the most common types of heat exchangers is the shell and tube heat exchanger, and here you’ll find out about the different types of shell and tube heat exchangers, their functions, and the pros and cons of this form of heat exchanger.
Types and Functions:
The general function of all shell and tube heat exchangers is to transfer heat from one liquid to another. The exchanger performs this function by acting as a container where heated liquid can enter through pipes, where it’s passed over by cooler liquid. Within the exchanger, heat is transferred from the hot water pipes to the cold water. This allows for two functions: the return of formerly heated water to machinery where, now cooled, it can pull excess heat from in order to cool the machinery; or the formerly cold water can circulate back to a space where it can now, in heated form, warm the space.
Two common types of shell and tube heat exchangers are u-tube and straight-tube exchangers. In a u-tube system, pipes enter at one end and bend into a u-shape at the other in order to exit back at the same end they entered from. Liquid is passed through the heat exchanger on one end and exits out the other in order to remove or introduce heat to the pipes. For a straight-tube system, the pipes enter the heat exchanger at one end and exit at the other.
No matter the type or configuration of shell and tube heat exchanger, all of them utilize baffles. Baffles are essential for optimizing heat transfer, and, without them, the system would not only work less efficiently, but would also be more susceptible to damage. These components control how water circulates over the pipes that enter the heat exchanger and can be implemented in three different ways: single segmental; double segmental; and disc and doughnut.
Single segmental baffles create an up and down movement of water over the pipes in the exchanger. Double segmental baffles also create an up and down movement, but it’s in a counter flow pattern, whereas in the single segmental system water moves up, then down, then up, and so on. In the double segmental system, water flows up and down in the same motion, flowing up and down away, and then up and down head-on. With disc and doughnut baffles, water is forced to move in a circular motion over the pipes.
The baffles come in different designs not because there are conflicting beliefs about which works best for all heat exchangers, but because different baffle designs work better depending on the temperature and pressure present in the system. Understanding these ratios allows engineers to determine which arrangement will yield the best exchange of heat within the system.
Pros and Cons of Shell and Tube Heat Exchangers:
Pros – These exchangers are less expensive to install than other varieties – such as plate heat exchangers – and offer more versatility in terms of temperature and pressure endurance. They can also be repaired more easily than other types of heat exchangers, as it’s easier to ascertain where a leak is and easier to repair it.
Since this type of heat exchanger is so common, it’s easy to find a professional service that not only can properly install the system, but can also properly clean and repair it on a regular basis. This reduces the likelihood that crucial components of the system will be overlooked or mishandled, leading to costly damages or even workplace injury.
Cons – These exchanger systems are susceptible to vibration problems, caused by the water flowing through the pipes. However, the baffles are meant to hold pipes in place and reduce the effects of vibrations. They’re also not as efficient at other models in terms of heat exchange and heat yield.
Some corrosion issues are also possible with this type of exchanger, mostly due to the fact that it contains inactive zones where water is able to pool and remain relatively stationary. One of the biggest cons to this system, though, has to do with the size of the heat exchanger. Compared to other heat exchangers, tube and shell heat exchangers take up more space and are therefore bulkier.