Posted by Admin on August, 31, 2020
Heat exchangers are machines that transfer energy from one working fluid to the next in the form of heat, whether it is solids, or liquids, or gases. Such devices are important for cooling, power generation, HVAC, and much more, and come in several shapes and sizes that can either insert or remove heat. It is often difficult to understand what makes one heat exchanger special from another, so this article will help readers gain introductory information on one of the most common heat exchangers, widely accepted as the shell and tube heat exchanger.
What is Shell & Tube Heat Exchanger
All heat exchangers are based on the same concept, namely that a hot fluid flowing over or around a colder fluid must transfer its heat (and thus its energy) in the direction of cold flow. Think of when you first grabbed your steering wheel on a cold day: the temperature difference between your hand and the wheel is big at first, and you can feel how cold it is; but, if you keep grabbing the wheel, the cold wheel can absorb some of the heat in your palm, and the wheel can "warm up."
In a simple way, the Shell and tube type heat exchangers are a system that places two working fluids in thermal contact using tubes housed within the outer cylindrical shell. Typically these two integral pathways are made of thermally conductive metals such as aluminum alloys, steel, etc which allow the easy heat transfer. The tubes hold a fluid from their inlet to their outlet (the "tube-side" flow), while the shell flows a different fluid (the "shell-side" flow) through these tubes. The number of tubes, known as the tube bundle, will determine how much surface area is exposed to the shell-side flow, and therefore how much heat is transferred.
These devices are categorized among the devices giving the most effective means of heat exchange, as they are simple to create, maintain, are compact and provide excellent heat transfer. These are commonly used in industry, and are useful for a variety of purposes such as turbine coolers, condensers, preheating feed water, evaporators, and more.
How does it work?
Figure 1 above, demonstrates the standard shell and tube type heat exchanger setup, with easily readable labels. As explained previously, the fundamental purpose of heat exchangers for shells and tubes is to move a hot fluid through a cold fluid without mixing it, so that only their heat is transferred. The diagram above shows two inlets and two outlets, where each fluid begins at its respective inlet and exits the device at its outlets.
The movement of the tube-side passes through the bundle of the tube (secured by metal plates known as tubesheets or tubeplates) and exits the outlet. Likewise the shell-side flow begins at the inlet of the shell, flows through the tubes and exits at the outlet of the shell. The headers on either side of the tube bundle create tube-side flow reservoirs and may be divided into sections according to specific types of heat exchangers.
Each tube contains an insert known as a turbulator that induces turbulent flow through the tubes and prevents deposition of the sediment, or "fouling," as well as raising the heat transfer ability of the exchanger. Designers also cause shell turbulence with barriers known as baffles, maximizing the amount of thermal mixing that occurs between the fluid on the shell side and the coolant pipes. The shell-side fluid must work its way through these baffles, allowing the liquid to travel through the tube bundle repeatedly, thus transferring energy and leaving the heat exchanger at lower temperature. Some shell and tube exchangers use different heat transfer types, and others use nothing at all.
The heat exchangers for shell and tube may be single-phase, or two-phase. A single-phase exchanger keeps the phase of the fluid constant throughout the process ( e.g. entering liquid water, leaving liquid water) while a two-phase exchanger causes a change of phase during the heat transfer process (e.g. entering steam and leaving liquid water). They may also be single pass or multi pass, which simply defines how many times the flows on the side of the tube-side or shell-side pass through the system.
Types of Shell & Tube Heat Exchanger
Ablaze Export Pvt. Ltd. is a leading Shell and Tube Heat Exchanger manufacturer in India. We design Shell and Tube Heat Exchanger that can be used for various industrial purposes such as turbine coolers, condensers, preheating feed water, evaporators, and much more.
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