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How does a heat exchanger work?

Even if it doesn’t seem like it, several of the objects we have in the house are at the theoretical level of heat exchangers; they allow the exchange of thermal energy between two fluids (which can be liquid or gaseous) without these coming into contact with each other.

In this video we will see how a heat exchanger works.
Jaes, leader in industrial spare parts for over 10 years, has become the trusted partner for all those companies that need heat exchange systems, and offers in its catalog every type of heat exchanger from the major manufacturers.

We have news of the first heat exchangers already in the Roman period. In the Roman baths, the combustion fumes of a brazier were used to heat the hot water baths, which heated stone slabs; subsequently water was passed over the slabs, allowing heat exchange.

But the first real heat exchangers were made in the Middle Ages; for the distillation of alcoholic beverages, coils were used and still are used for the condensation of the distillate.

They are shell and tube heat exchangers. To better understand the operation of the heat exchanger, let’s take a common plate exchanger and observe it inside: the plate heat exchanger consists of a sequence of plates machined in order to increase the contact surface with the fluids.

Each plate has four holes (two feed holes and two drain holes); between each pair there is a gasket which guarantees the hydraulic seal towards the outside and around the passage holes, in this way a passage chamber for the fluid is formed. These gaskets, according to their design, slide between two plates; or the hot fluid; or the cold fluid; in this way, by alternating a hot chamber with a cold chamber for the entire heat exchanger, the heat exchange between the two liquids is optimized.

It is also important that the fluids flow in opposite directions, in fact, as we can see, the gasket that allows the passage of the cold fluid, passes the flow from the lower supply hole to the upper drain hole and completely plugs the holes of the hot fluid. While the gasket that allows the passage of the hot fluid, passes the flow from the upper feed hole to the lower drain hole and completely plugs the cold fluid holes.

This "counter-current exchange" helps the circulation of fluids, improving the efficiency of the heat exchanger, because the cold fluid will decrease its density and will tend to rise, while the hot fluid will increase its density and will tend to go down.
Plate heat exchangers are very used on district heating systems.

A large power plant produces high-temperature steam, which is subsequently sent to the homes with delivery and return pipes.
Here, the heat exchangers act as an interface between the steam from the distribution network and the water from the home heating system. The entire city of New York is heated in this way, but also many other large cities.
Therefore, for their heat exchange capabilities, heat exchangers have the most varied forms and uses.

Let’s see various examples.

As we have seen in our video on the operation of a thermoelectric power plant, the whole principle of operation is based on heat exchange.
The water tube boiler, for example, is a type of tubular exchanger as are the condensers and the Deaerator thermal.

Even the cooling towers are large heat exchangers, which transfer the excess temperature of the liquid directly into the gas of the earth’s atmosphere.

It is very interesting to note that man-made machines use various types of energy to do a job; the more efficient the machine, the more the energy used is transformed into work.

The energy that has not been transformed is not lost in thin air, but is transformed into heat inside the machine, which is finally expelled into the environment. As we have seen in our video on machines this feature is very evident, in fact only about 30% of the exploded fuel is transformed into movement; all the rest is energy in the form of heat. To be efficiently dissipated into the atmosphere, the radiator, a finned pack heat exchanger, is used.

Have you ever wondered how the refrigerator works? Refrigerators and freezers use the “refrigeration cycle” by means of 2 heat exchangers (an evaporator inside, and a condenser outside).

Watch our video on how ultra freezers work! If this video was useful to you, please let us know by leaving a like and a comment, you can also share it, and don’t forget to subscribe to our channel.