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Design

Without a doubt , the heat exchanger is an essential and critical component in all thermal systems , whether for industrial use ( chemicals , petrochemicals , iron and steel , food processing , energy production , etc .), for the automotive , aeronautical and aerospace industries , or also for the building industry ( residential or commercial ).

About the authors

Christophe Weber , PhD , is a thermal engineer and heat exchanger expert with more than 10 years experience and has been the GRETh association ' s CEO since 2017 .

Quentin Blondel , PhD , has been an R & D thermal engineer within GRETh since 2021 and is notably in charge of technical and scientific studies and related report writing .

By Christophe Weber and Quentin Blondel , GRETh – Heat Exchanger Research Group

Indeed , it is generally agreed that more than 90 % of the thermal energy used in industrial processes passes through a heat exchanger at least once : it is therefore an essential and ubiquitous element for the proper operation of processes but also in the energy performance strategy framework . First of all , as a reminder : a heat exchanger ’ s main function is to transfer thermal energy , generally from one fluid to another at different temperature levels . The heat exchanger functions are extremely different and varied . Among others , we can mention the following main application cases :

• Liquid or gas heater or cooler ;

• Heat recovery system ;

• Thermal heater ( as radiator );

• Dehumidifier or partial moist air condenser ;

• Evaporator or condenser ;

• And many more It should be highlighted here again that all these functions are performed by a single component type : the heat exchanger .

Efficiency and pinch minimization From an energy point of view , the most efficient heat exchanger will be the one that will allow transfer of the most important thermal power amount through it ( notion of pinch minimization , i . e . the lowest temperature difference between the two fluids within the heat exchanger ) with a minimal heat transfer surface ( thus considerations of material and volume ) and at the same time minimizing the pressure losses which affect the consumptions of the auxiliaries necessary for the fluid ’ s circulation ( pumps , fan , compressor ). However , pinch minimization leads paradoxically to an important increase of the heat transfer surface ( and therefore the quantity of heat exchanger material and its cost ) as well as very often the pressure losses ( more heat transfer surface and therefore potentially more heat transfer length and thus more pressure losses ). From a more concrete point of view , and based on the simple example of a tube-in-tube heat exchanger , it can be observed and understood , thanks to the figure below , the following points :

100

Cold Fluid Temperature Hot Fluid Temperature

Temperature (° C )

Heat Exchanger temperature evolution according to the exchanged thermal power ( tube-in-tube heat exchanger co-current flow ).

100

Cold Fluid Temperature Hot Fluid Temperature

Temperature (° C )

80 60

Pinch

40 20

20 Heat Exchanger World April 2023 www . heat-exchanger-world . com