Heat exchangers are equipment that is present in all types of industrial processes. In this sense, it is common to see them in industrial air conditioning installations, steel plants, refineries, food processors, the pharmaceutical industry, nuclear power plants, etc. Temperature is a critical variable in any industrial process. Therefore, it must be controlled very precisely both for safety and to guarantee the quality of production.
What are heat exchangers?
Heat exchangers are equipment that facilitates the transfer of heat between two fluids or gases, without mixing. This is possible thanks to two sealed and independent circuits, which are very close to each other and are made of materials with high thermal conductivity.
Thermal conductivity is a property of matter that is calculated by measuring the speed with which heat passes through it. Therefore, in the International System of Units, thermal conductivity is measured in watts per meter per degree Kelvin (W/(m × °K)).
Diamond is the material with the highest thermal conductivity, which reaches 2200 W/(m × °K). This is followed by silver (430), copper (398), gold (315), aluminum (280), brass (120), steel (50), etc. On the other hand, it is convenient to mention both water and air, since they are substances widely used in industry for heat transfer. In this sense, the air has a thermal conductivity of 0.02 W/(m × °K). However, the conductivity of water is higher than that of air, reaching up to 0.6 W/(m × °K).
In general, the exchangers are made of metallic materials such as copper, aluminum, brass, bronze, iron, or steel. The selection of such materials is not only carried out for their thermal conductivity but also for their resistance to temperature, pressure, stress, price, etc.
What are the most frequent uses of heat exchangers in the industry?
In industrial processes, both cooling and heating are necessary, depending on the needs of each stage of said process. That is, a thermal or heat exchanger can be used to cool or heat a certain point of an industrial process. For this reason, it is very common to find many heat exchangers distributed throughout any production process.
For example, it is essential that machine gear and bearing lubrication systems have thermal systems that can cool the oil. Normally, each machine must have a heat exchanger, since otherwise the lubricating oil would get too hot and lose its properties.
Hydraulic systems for power transmission also need thermal systems to cool the hydraulic oil. If the cooling is not efficient, it will cause damage to the seals of the main hydraulic cylinders, in addition to the deterioration of the solenoid valves and a general malfunction.
The examples mentioned above refer to cases of cooling of substances (oils). However, on many occasions, it is necessary to add heat to a process. This is the case of food processing industries that need to add heat to sauces and jams. In this way, its processing and packaging are facilitated.
In industrial air conditioning thermal systems, the use of heat exchangers is essential for the Mollier thermodynamic cycle to function correctly. Thus, in air conditioning systems, both the condenser and the evaporator are basically two heat exchangers. These exchangers will be responsible for producing heat or cold, respectively.
What types of heat exchangers are there and how do they work?
All heat exchangers work thanks to the thermal interaction of two fluids or gases that are at different temperatures. In other words, if there is no temperature difference between both fluids or gases, the heat exchanger would be totally useless equipment.
Within the heat exchangers, heat transfer by conduction and convection is used. The efficiency of heat exchange in exchangers depends on their design, the effective exchange area and the materials used. For this reason, the equation that summarizes the operation of this equipment is the following: Q = C × A × ∆T. In this equation Q is the amount of heat, C is the transfer coefficient, A is the effective area and ∆T is the temperature difference.
When the direction of the fluids inside the exchangers is taken into account, they are classified as parallel, counterflow and transverse. However, in this post we will only talk about the shell and tube heat exchanger, the plate heat exchanger and the air heat exchanger. This classification is based on its structure or physical configuration.
Shell and tube type heat exchanger
This equipment is composed of an elongated cylindrical casing, inside which there is a set of tubes. The internal fluid circulates inside the tubes, and the external fluid circulates inside the casing. Therefore, the structure of this equipment is quite robust.
The shell and tube heat exchanger is used in chillers, which use water as a secondary coolant.
Plate type thermal systems
These types of exchangers have a group of corrugated and stacked plates, which replace the tubes of the previous model. The plates offer independent and tight paths to the liquids involved in heat transfer. Therefore, their structure is very different and they have the great advantage of offering higher performance. However, they have the disadvantage that they do not guarantee a reliable seal when working with relatively high pressures.
Air exchanger
This exchanger has a different design from the ones described above since it uses air as a second cooling fluid. Therefore, it does not require two sealed circuits, but a single circuit for the other fluid. This type of exchanger is made up of a tube coil with fins, through which a fluid circulates, and a fan. The fan creates a current of air that passes through the coil to speed up heat exchange.
Intersam, manufacturer of exchangers for industrial air conditioning systems
Depending on the industrial application where they are going to be used, heat exchangers must be manufactured with a specific design and suitable materials. At Intersam we are specialists in the design and manufacture of exchangers for industrial air conditioning, tailored to the needs of your company.
In the design and manufacture of heat exchangers for air conditioning systems, it must be taken into account whether they will be used as a condenser or an evaporator. In addition, the capacity of the industrial air conditioning system, type of refrigerant, and working pressure must also be considered, in order to select the appropriate materials. At Intersam we guarantee long-lasting, efficient exchangers at low prices.