Understanding Shell and Tube Heat Exchangers, Their Functions, and Applications
When we talk about industrial heat exchange services and applications, shell and tube heat exchangers are pretty much the leading choice. Shell and tube exchangers are the workhorses of heat transfer, used in a multitude of sectors for cooling and heating fluids. Their robust and versatile design makes them a top choice for industrial processes when temperatures and pressures get serious.
Shell and Tube Heat Exchangers: The Core Concept
At the heart of a shell and tube heat exchanger, as the name implies, is a shell with some tubes. The shell is essentially a pressure vessel containing a bundle of tubes. One fluid flows through the tubes, and another flows over the tubes (within the shell), allowing heat to transfer between the two. It’s similar to washing your hands in cold running water, with the cold water pulling heat away from your warm hands.
The Working Principle of a Shell and Tube Heat Exchanger
Let’s break down how heat exchangers work. Two fluids at different temperatures flow through the heat exchanger. One, the tube-side fluid, flows inside the tubes. The other, the shell-side fluid, goes around the outside of the tubes inside the shell. The tube walls separate the fluids, so they never mix, but heat can jump across from the hot fluid to the cold, thanks to our good old pal, thermal conductivity.
Heat transfer in a shell and tube heat exchanger occurs primarily via two modes: conduction (the heat travelling through the tube wall) and convection on both sides (the heat being carried away by the moving fluids). The efficiency of heat transfer is influenced by stuff like the process fluids used, the total surface area of the tubes, and the velocities of the fluids, among many other factors.
In the tubes and the shell, fluids can flow in a smooth or turbulent manner. Turbulent flow is actually a good thing in heat exchangers because it mixes the fluid against the tube walls, which helps transfer more heat. Thermal Design Engineers tweak things like tube counts and baffle configurations to improve fluid velocity, turbulence, and maximize heat transfer relative to exchanger cost.
You want your heat exchanger to be efficient, meaning you get as much heat as possible from the hot side to the cold side without oversizing the exchanger. Factors like the design of the exchanger, the temperature difference between the fluids, and the properties of the fluids themselves all play into how efficient and compact an exchanger can be.
Once the fluids have exchanged heat, they’ve got to exit the heat exchanger. The tube-side fluid may leave from the same end it entered (in a multi-pass exchanger like a BEU type) or the opposite end (in a single -pass system typical of a NEN or BEM TEMA type). The shell-side fluid will usually exit at the top if being heated, or the bottom of the shell if being cooled, but it depends on the process design.
Co-Current and Counter Flow
There are two common arrangements for the flow of fluids in a shell and tube heat exchanger: co-current and counter flow. In co-current flow, both fluids go the same direction. In counter flow, the fluids head in opposite directions. Counter flow is typically more desireable because it can achieve greater heat transfer due to a larger temperature difference between the fluids. Quite often, shell & tube heat exchangers have a mix of co-current and counter-current flows due to the multiple tube-side passes inside the shell.
Different Applications for Shell and Tube Heat Exchangers
Oil Refineries and Gas Processing
Shell & Tube heat exchangers are used throughout oil refineries, upgraders, and SAGD facilities due to their robust construction and ease of maintenance and cleaning. Shell & Tube is also commonly found in gas processing and gas transmission industries as they are well suited to high-pressure applications.
In petrochemical plants, these exchangers are used to condense, cool, or heat various chemicals in the refining process. They have to be tough to handle corrosive substances and high pressures.
Power plants use shell and tube heat exchangers to condense steam back into water after it has spun the turbines. They’re a key part of recycling steam and keeping efficiency up.
The food industry uses these exchangers to heat or cool products gently and evenly. Pasteurization of milk is a classic example, where you have to heat the milk just enough without scorching it.
Contact Altex Industries for Shell and Tube Heat Exchanger Manufacturing and Design Services
If you’re in the market for a shell and tube heat exchanger, or you need one designed to fit unique requirements, contact Altex Industries. We’ve got the expertise to craft exchangers that fit all sorts of specs and can handle just about anything you throw at them. Whether you’re in oil and gas, petrochemical, or just about any industry needing reliable heat exchange solutions, we’re ready to walk you through the design process, build a quality exchanger, and provide the support you need to keep things running smoothly.