With so many different types of heat exchangers available on the market for almost every industry, it can be difficult to keep track of all the different heat exchange designs and what sets each of them apart.
At IPC our engineers have been designing, supplying and installing just about every type of heat exchanger for over 20 years – so it’s safe to say we know a thing or two about the different designs, flow arrangements and industrial applications of heat exchanger systems.
From counter flow shell and tube heat exchangers, to double embossed pillow plate heat exchangers, our helpful guide will make sure that, by the end of it, you’ll understand everything you need to know about any heat exchange system on the market!
Shell And Tube Heat Exchangers
One of the most common types of heat exchangers you’ll come across today are shell and tube heat exchangers. This term covers any type of heat exchange system where fluid or gas is passed through a series of tubes enclosed in a larger metal shell.
This design is classed as a multi-tube type of heat exchanger, because of the bundle of inner tubes contained within the shell. You can also get two main types of shell and tube heat exchangers, a single tubesheet design and a double tubesheet design.
The tubesheet refers to the circular perforated plate at the end of the exchanger which supports the tubes, and the design is determined by whether it has one or two of these tubesheets at the end of the shell.
A cold or hot fluid or gas will pass through the inner tubes while a fluid or gas of the opposite temperature will pass through the larger surrounding tube, where the heat exchange will take place. As we’ll cover shortly, the flow of these liquids and gases can occur in three main directions: parallel, cross and counter flows.
These types of exchangers are typically used in high pressure applications, or in vacuums where the structure needs to be able to cope with high levels of stress.
As the substances are fully contained within the shell and tube structure, this type of heat exchange system is suitable for use with noxious, dangerous gases which need to be kept from entering the atmosphere.
They also allow for the processing of fluids that are more viscous and contain fibres or particulates, thanks to the width of the tubes. This can make it suitable for uses including the exchange of purées, lotions, medium viscosity dairy products, beverages with pulp, water for injection, oil cooling and steam generation.
Flow Directions
Cross Flow Heat Exchangers
These heat exchangers are designed so that the fluids or gases in a heat transfer system flow perpendicular to one another. This method of heat exchange is commonly utilised when one tube contains a fluid and the other contains a gas, where the gas is able to rise as the fluid is pumped vertically through the tubes.
Cross flow heat exchangers are also commonly used in steam condensers, where at the end of the process the liquid will have evaporated into a gas. Other common examples include car radiators, where ambient air is used to cool engine coolant, and air conditioner evaporator coils.
Parallel Flow Heat Exchangers
These systems, also known as co-current heat exchangers, are designed so that the fluid passing through the tubes flows in the same direction as the fluid in the outer shell. This flow is most common in double-pipe heat exchangers, but it can also be seen in shell and tube heat exchangers.
Since this design works best for fluids with a small temperature gap, a larger transfer surface area is usually required to maintain an efficient level of heat transfer. This can result in parallel heat exchange systems taking up more floor space, something not ideal for smaller scale businesses.
Not only that, but if the temperature difference at the inlet of the heat exchanger is too extreme, vibrations can occur and cause the equipment to become damaged.
Counter Flow Heat Exchangers
In a counter flow system, the fluid enters at both ends of the heat exchanger and flows in opposite directions towards each other. Also referred to as a recuperator heat exchanger, these systems are primarily used because of their high heat transfer efficiency.
As the cold fluid exits where the hot fluid enters, the rate of the heat exchange process is increased and the cold fluid can reach higher temperatures overall. This reduces the temperature difference at the tubesheets also lessens the thermal stress on the equipment, making it less likely to shake and become damaged as opposed to parallel flow heat exchangers
Double Pipe Heat Exchangers
While a shell and tube heat exchanger has a large number of parallel tubes contained within its shell, a double pipe heat exchanger consists of only two pipes, each with a different diameter.
The smaller tube is contained within the larger one, with one containing a hot substance and the other containing a cold substance. All of the heat transfer occurs inside the larger pipe through the process of conduction.
The concentric design means the heat between the liquid or gas is exchanged through a conductive barrier, such as steel or aluminium, without the substances being physically mixed together. Commonly used in counterflow systems, the designs are also able to be used in applications which require a parallel flow.
Double pipe heat exchangers generally come as monotube heat exchangers (also referred to as ‘tube-in-tube’) which contain an external shell and a single inner tube. However, depending on the industry and requirements, they can also be adapted to an annular tube model where three or four concentric tubes are used to prevent the layering of products.
These designs are typically suitable for smaller applications, where the heat transfer area is less than 45-50 square meters. As multiple units can be set up in parallel to each other or mounted vertically, double pipe heat exchangers can save on floor space while still providing a large flow rate and efficient heat transfer.
A double pipe heat exchanger is used in a variety of applications, including boilers and compressors, petroleum refineries, sewage treatment, refrigeration systems, and cooling and heating in process engineering systems.
Scraped Surface Heat Exchangers
These types of tubular heat exchanger systems are specially designed to remove product from the interior channel wall through the use of rotating blades, ensuring uniform heat transfer throughout the system.
Rotors turn the substances in the same direction throughout the exchanger, with product entering through one side and exiting through the other. The design of scraped surface heat exchangers makes them ideal for highly viscous or sticky products which may otherwise settle inside the heat transfer tubes.
The scraping blades can be made from a variety of different materials to meet various processing requirements, and are designed to handle the product gently in order to avoid damage and preserve the product’s quality and consistency
Scraped surface heat exchangers are commonly used for a wide range of applications in the food, chemical, and pharmaceutical industries, including processed foods, viscous products, heat-sensitive products, crystallising and phase changing products (such as sugar concentrates and beer), particulate products, and products with a sticky consistency like mascara and toothpaste.
Air Cooled Heat Exchangers
Air cooled heat exchangers transfer the heat from a process fluid to the surrounding ambient air. The fluid is contained within heat conducting finned tubes and electric cooling fans are used to provide either forced or induced cooling air, depending on whether the air is pushed or pulled between the tubes.
These types of heat exchangers are better for the environment than water cooled exchange systems as they do not require a constant auxiliary water supply, which can also make the running and maintenance costs lower. They also eliminate the risk of thermal and chemical pollution which can be caused by the cooling fluids used in water cooled heat exchangers.
Typically used for process cooling and/or condensing, air cooled heat exchange systems can commonly be found in nuclear power plants, oil refineries, petrochemical manufacturing plants, natural gas processing plants, compressor stations and many more industrial facilities.
Water Cooled Heat Exchangers
Water cooled heat exchange systems are designed to remove unwanted heat from a process by transferring it to water or a water/glycol antifreeze solution, keeping it at an ambient temperature.
This type of heat exchanger allows for levels of cooling which an air cooled heat exchanger can’t achieve as it is limited to the ambient conditions of the surrounding climate. They are also more efficient at transferring and removing the unwanted heat.
There are many applications for water cooled heat exchangers including steam condensing and the cooling of process liquids, oil and gas.
Plate Heat Exchangers
Also called ‘gasketed plate heat exchangers’ and ‘plate and frame heat exchangers’, these systems work by passing fluids or vapours through a series of parallel plates fitted with elastomeric gaskets compacted side by side.
The gasketed plates hang from a carrying bar and are kept vertically aligned with the use of a guide bar, and the series of plates are compressed with bolts in-between a frame plate and a pressure plate.
Hot and cold substances flow in alternating channels with heat transfer occurring from the warmer channel to the cooler channel. The gaskets control the alternating flow of the fluids over the plate surfaces.
The design of plate and frame heat exchangers mean that cleaning and flow capacity changes can be easily accommodated, as the plates can simply be removed or added when needed. Repairs and maintenance are also made easier, as any damaged clip-on plates can be removed and replaced in a process called regasketing.
Gasketed plate heat exchange systems are often found in liquid to liquid applications where the two liquids can’t mix, such as using water to cool oil, or using hot process water which contains chemicals and contaminants to heat up the clean water in a district heating system.
They also work best in the cooling and heating of low to medium viscosity products with little to no particulates, such as ice cream, milk and other beverages.
Brazed Plate Heat Exchangers
Brazed plate heat exchangers have a similar design to gasketed plate heat exchangers, however the corrugated plates are stacked together and completely sealed using a process called fusion bonding to increase the efficiency of the heat transfer.
Designed to be extremely compact, brazed plate exchangers can be up to 90% smaller than other plate type heat exchangers which makes them ideal for small spaces. The robust design and brazing of the gaskets also makes them slightly more effective by reducing heat loss, as well as minimising the risk of any leaks.
Brazed plate heat exchangers are widely used in refrigerator evaporators and condensers, compressed air coolers, water and swimming pool heating, boiler separation plates, solar heating systems, and heat pump installations due to their small volume and high heat transfer efficiency.
Pillow Plate Heat Exchangers
Also known as dimple plate heat exchangers, these heat exchangers are constructed of two metal plates fully welded together. The sheets are then inflated, a process which pressurises the two sheets and causes the material to deform, creating a cavity for the heat transfer medium.
Pillow plate heat exchangers can be single or double embossed. A single embossed pillow plate is created when the baseplate is significantly thicker than the top plate, causing the thinner top plate to deform while the baseplate remains the same. Oppositely, a double embossed pillow plate is created when both plates deform to create uniform pockets.
As the exchange system is fully welded, the risk of fluid or gas leaks is eliminated. The use of thin sheets to create the plates also make dimple plate heat exchangers a cheaper option thanks to its low material costs.
Single embossed pillow plates are suitable for heating and cooling using a wide range of agents including water, steam, glycol and oil, making them great for use in the food and processing industries. Double embossed pillow plates have a much wider range of suitable applications and can be used with agents such as freon and CO2, they can be used in immersion heaters, ice banks and many other industrial cooling systems.
Exhaust Gas Heat Exchangers
Exhaust gas heat exchangers serve as waste heat recovery units, extracting heat energy from the exhaust gases of a reciprocating diesel, gas, or biogas-powered engine and transferring it to the water circuit.
This heat exchange and recovery method is suitable for use with a variety of fuels, including natural gases, hydrogen, sewage gas and special gases, biogas, as well as diesel and most other liquid fuels.
Exhaust gas heat exchange systems, which are becoming increasingly popular due to rising energy prices, are also more environmentally friendly, helping businesses to reduce their CO2 emissions and prevent heat waste from flue gases.
Typically installed in bakeries, hardening plants and processing plants, this type of heat exchanger is also used in hazardous environments to improve safety by lowering the exhaust temperature of certain engines.
Regenerative Heat Exchangers
Regenerative heat exchangers alternate the flow of hot and cold fluids through a single tube at regular intervals, storing the heat from the hot fluid in a thermal storage medium before transferring it to the cold fluid.
This method of heat transfer greatly increases the thermal efficiency of the output heat as the amount of fuel needed for the process is reduced.
While it may seem similar to a countercurrent heat exchanger, regenerative heat exchangers use the same flow tube for both of its fluids, whereas a countercurrent system separates the fluids into two separate tubes, and the flow of both liquids occurs simultaneously.
Regenerative heat exchangers are ideal for gas to gas heat exchange where the substances don’t have to be completely separated. These types of heat exchangers are commonly used to increase the efficiency of high pressure boilers and open hearth furnaces, as well as in various chemical and industrial applications.
Industrial Power Cooling Heat Exchange Services
Hopefully, you now have a better understanding of the various types and varieties of heat exchange systems available, as well as the different applications of each one for your industry.
A new heat exchanger system can be beneficial to your business for many reasons, including improved safety, product preservation, and increased energy efficiency.
If you’re interested in having an industrial heat exchanger installed on your property you can get in touch with a member of our team online, or take a look at the different heat exchangers we offer on our website!