We all know that the fuel we use in cars comes from crude oil. But have you ever thought about the process that turns the dark-coloured liquid into many forms of fuel? Or how geothermal power stations transmit electricity to our homes? All this is made possible by using heat exchangers that transfer energy as heat from one fluid to the other. And what makes a heat exchanger unique? The tubes! These tubes facilitate heat transfer in mediums for heating and cooling processes. They also have multiple components that react differently to perform optimally. Here is everything you need to learn about heat exchanger tubes.
What is a Heat Exchanger Tube?
This is a device that transfers heat from one medium to the other in heating and cooling processes. It separates the medium inside the shell and tube exchanger to transfer heat through the tubes through conduction.
The mediums used in these pipes are gas, liquid or vapour. The tubes can be plain, finned, external or internal, with the finned ones having a higher heat transfer surface than plain tubes. Their diameters range from 6mm to 40 mm depending on the diameter and construction material.
Types of Heat Exchanger Tubes
U-Tube Exchanger Tubes
These tubes bend to form a U shape and hold onto the shell with one tube plate. The coolant flows from the header’s top half through the u-tubes and then exits at the header’s half bottom. The bend facilitates thermal expansion without using expansion joints. These tubes are available at different leg lengths, with their ends deburred. They are also of great quality, and their shapes are flexible to meet the customer’s needs.
Straight Tubes
Straight tubes have their two ends mounted onto one tube sheet of a shell and tube heat exchanger. One fluid medium enters the tube while the other goes through the shell. As a result, they have extraordinarily high fouling qualities, making them perfect for processes that frequently cross high temperatures. In addition, these straight tubes are easily washable, unlike u-bent tubes.
How do Heat Exchanger Tubes Work?
Heat exchanger tubes should pass hot fluid through cold fluids to transfer heat without mixing them. They have two inlets and two outlets, and each fluid must enter the system at their respective inlets and exit at their outlets.
The tube bundle facilitates the tube-side flow where the liquid exits at the outlet. The shell-side flow begins at the shell inlet and passes through these tubes to exit at the shell outlet. Helixchanger heat exchanger has baffles at an angle to create a helical flow.
The tubes have turbulator inserts that create a turbulent flow to prevent depositing sediments. This flow also improves the heat transfer capacity. Some pipes also have “baffles”, which are barriers that maximise thermal mixing between the coolant pipes and the shell-side fluid. The fluid on the shell side must go past these baffles to create a repetitive pass over the tube bundle. It, therefore, ensures energy transfer while exiting the heat exchanger and lowering the temperature.
Classification of Heat Exchanger Tubes
Heat exchanger tubes are classified by their characteristics, the flow type being one of them. The flow type is broken down into three;
- Parallel
- Cross
- Counter
Parallel Flow
Parallel flow happens when the tube and shell side mediums enter the exchanger from the same end to flow in opposite directions. The liquids undergo equal temperature changes, and their output temperatures converge.
Counter Flow
Counter flow shell and tube heat exchangers allow two mediums to flow in a counter direction. These mediums enter the exchanger at both ends and exit at opposite ends. This happens because the cooling medium is discharged from the counter flow heat exchanger at the entry point of the hot medium.
Cross Flow
Cross-flow heat exchangers have a medium flowing perpendicularly across the other. For example, steam condensers let the steam enter a turbine’s shell side. Cool water flows through the tubes to absorb heat from the system turning it into water.
Application of Heat Exchanger Tubes
Heat exchanger tubes are products of stainless steel 304, which makes them adaptable to various industries. They are common in chemical industries, oil refineries, hydrocarbon manufacturing, and aerospace.
So far, you already know what it takes to keep a heat exchanger running. Inspection of these tubes is essential to keep their surfaces in good shape. Any form of corrosion or damage may affect the performance of the tube. You can always contact a heat exchanger dealer to guide you on making your heat exchanger pipes last longer.
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