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Strengthening a Heat Exchanger

A heat exchanger is an essential thermal machine used for industrial cooling, with several types existing: shell and tube, plate exchangers, spiral heat exchanger, block and fin heat exchangers.

These exchangers are crucial equipment for industrial thermoregulation but also required in residential and commercial air-conditioning plants, achieving heat transfer between two fluids with different temperatures. Heat exchangers are indeed passive thermal machines, allowing the transfer of heat energy between fluids due to an existing temperature gap.

In a plate heat exchanger, the fluids are separated by a thin metallic screen, a plate, which allows the heat transfer between the two fluids flowing on its sides separately. Corrugated plates increase thermal transfer, extending exchanging surface area and boosting energy dissipation thanks to turbulence prompted in flowing fluids and higher transmission coefficients.

The cold fluid gets heated in contact with the plate, gaining heat from the fluid to be cooled, and is then carried to a cooling system (a chiller, or dry cooler or evaporative towers, for example), bringing the fluid at a lower temperature.

Plate heat exchangers offer several advantages, being compact and smaller, and easily sizable, also to fit new and changed working project conditions leading to a higher thermal duty, with an increased thermal load to be managed. Strengthening a heat exchanger is indeed achieved simply adding new plates, in order to answer a growth in production, and then a growth in the quantity of heat generated, or due to changes in the thermal conditions of the cooling cycle, for example laking of cooling air or water at a certain temperature, meaning a loss in dissipating capacity of the cooling system itself.

It is true that is possible to strengthen an existing heat exchanger only in case of an openable and inspectable gasketed exchanger. If a brazed plate exchanger was the first project choice, it would not be possible to increase the thermal load capacity once it is installed, and an alternative solution would need to be found to manage an increased thermal duty (adding others exchangers, more powerful or bigger exchangers).

In a plate inspectable heat exchanger, it is easy to vary the thermodinamic state of the machine, adding new plates to the existing ones, increasing thermal transfer surface area having extra dissipating capacity. Transfer heat surface area needed to perform the thermal duty in a heat exchanger is usually calculated in function of exchange process characteristics and thermophysical properties of the fluids. Speaking of strengthening an existing heat exchanger, the kind of fluids and thermal processes are supposed to remain the same, and the only variable is the amount of heat load the machine has to dissipate, or also a new temperature gap between the fluids.

Strengthening a plate heat exchanger is then a quite simple operation, only requiring a correct evaluation of the new thermal load or the new fluids temperatures, in order to determine the right additional thermal transfer surface area and the number of plates that can be inserted to obtain the thermal performance needed.

Strengthening a heat exchanger requires a series of operations, that at the same time allow the checking of operability and affordability of the exchanger, as well as regenerating it cleaning and changing damaged parts (gaskets or corroded plates), ensuring the best performances of the thermal machine at the end of the operation.

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