Which Materials are the Best for a Heat Exchanger Application?
Heat exchangers are critical components in a range of industrial and commercial systems. Heat exchangers basically allow the transfer of heat from one gas or liquid to another, without the two coming into direct contact. It can be liquid-to-liquid, gas-to-liquid or gas-to-gas. Heat exchangers can heat a cool substance and cool a warm substance, which is important for systems that need to maintain a steady temperature.
How Do Heat Exchangers Work
To put it simply, heat exchangers will circulate two substances (which can be either gas or fluid) alongside each other, but in separate pipes, plates or containers. One of these substances will be hot and the other will be cold. As they circulate through the heat exchanger, heat will transfer from the hot substance to the cold one until they reach the desired temperature. Thus heating the cool substance up and cooling the hot substance down.
Types of Heat Exchanger
The best type of material for a heat exchanger will really depend on its application. There are quite a few different heat exchanger types, which can be used in different ways. Take a look below.
Air Cooled Heat Exchanger
A finned tube heat exchanger or air cooled heat exchanger, uses air to cool a liquid or gas contained in the pipes. These air cooled heat exchangers are more environmentally friendly and cost-effective than water cooled heat exchangers, as there’s no need for a running water supply.
Water Cooled Heat Exchanger
This type of heat exchanger runs water in one pipe and the liquid or gas in the other pipe. The water is typically used as a coolant, to remove heat from the process media. It can be more expensive than an air heat exchanger, but it offers more control as air is affected by the surrounding climate.
Shell and Tube Heat Exchanger
A shell and tube heat exchanger is basically any heat exchanger where liquid or gas is passed through tubes enclosed in a metal shell. This type of heat exchanger can be used to heat or cool. It’s also suitable for use with noxious gases, as it’s contained within a metal box. It’s most often used in high pressure applications, like oil and gas or chemical industries.
Double Pipe Heat Exchanger
This type of heat exchanger has a smaller pipe inside a larger pipe. One pipe will hold a hot substance and the other will have a cold substance. This type of heat exchanger is a great way to save floor space, as it is quite compact.
Plate Heat Exchanger
Also known as a gasket plate heat exchanger, these heat exchangers have a series of plates lined up together, with hot or cool fluids passed through the plates alternatively. So one plate will have a hot substance and the next will have a cool substance, and heat will transfer between the two.
Scraped Surface Heat Exchanger
A scraped surface heat exchanger is often used when there is a sticky or viscous material in use, as is often the case in the food industry. Basically, there is a cylinder, surrounded by a jacket and vacuum. Steam or a hot gas is circulated in the vacuum between the jacket and cylinder to heat the material in the cylinder. Inside the cylinder is a rotating scraper blade which stops the material getting stuck to the side and makes sure heat is distributed evenly throughout the material.
Material Properties to Consider
When selecting materials for use in a heat exchanger, it is important to consider the following factors:
1. Thermal Conductivity
The most important factor when choosing a material for heat exchangers is thermal conductivity. Thermal conductivity is how well a material can conduct heat. Materials with high thermal conductivity are more effective at transferring heat, which makes them the perfect choice for heat exchangers. Materials with high thermal conductivity include copper, aluminum, and brass.
2. Corrosion Resistance
Heat exchangers are often exposed to corrosive environments, which can compromise their structural integrity and performance if you choose the wrong material. That’s why we recommend corrosion-resistant materials. If you’re working with chlorides or hydrogen sulfide, for example, you’ll need a material that is resistant to chloride induced stress corrosion cracking.
The cost of the material is also an important consideration when selecting materials for use in a heat exchanger. While materials such as copper and aluminum have high thermal conductivity, they can be expensive, making them less cost-effective for certain applications.
It’s important to ensure that the material used in the heat exchanger is compatible with the liquids or gases it will be in contact with. You’ll have to consider the liquids or gases you want to treat and find a compatible alloy. Otherwise corrosion could render your heat exchanger unusable in a matter of months, if not weeks! Our metallurgists can help you find compatible metals.
Fabrication is also important when selecting a material for a heat exchanger. You should consider that heat affected zones or welded sections could affect performance. Plus, some materials are harder to work with than others, which can impact the overall cost and lead time for your heat exchanger.
The Best Materials for Heat Exchangers
Here at NeoNickel, we stock a great supply of alloys suitable for use in heat exchangers. Take a look at some of our recommended alloys below:
Alloy 600 has excellent heat resistance and oxidation resistance up to temperatures of 1093°C. It’s often recommended for use in the heat treatment industry (like furnace doors or rollers), but would be suitable for heat exchangers too.
Alloy C276 is one of the most corrosion resistant alloys, which also demonstrated good thermal conductivity. We’d recommend it when one of the treated gases or liquids is particularly corrosive, like in the petrochemical or chemical processing industry.
Alloy 321 Stainless Steel
Alloy 321 is a stainless steel with great heat resistance at temperatures of up to 870°C, which makes it perfect for application in heat exchangers. It also demonstrates good thermal conductivity.
Overall, the best material for a heat exchanger will depend on the specific application. You should consider important factors like thermal conductivity, fabrication and cost to make sure you choose the appropriate alloy. NeoNickel hold and supply countless alloys, suitable for application in thermal heat exchangers.
If you’d like more advice on choosing the correct alloy for a heat exchanger, please get in touch with us here.