Shell and tube type heat exchanger

Abstract

The invention relates to a heat exchanger comprising a shell enclosing a plurality of tubes, the exchanger being configured to establish a heat exchange relationship between a first fluid circulating in the shell and a second fluid circulating in the plurality of tubes, characterized in that at least a portion of the tubes are wholly or partly made of ferritic stainless steel or duplex stainless steel. Figure for the abstract: none.

Description

Title of the invention: Shell and tube heat exchanger

[0001] The present invention relates to a shell and tube heat exchanger.

[0002] A commonly used technology for heat exchangers is shell and tube heat exchangers enclosing a plurality of tubes, also referred to as a tube / shell structure. Two fluids pass through the heat exchanger, one circulating inside the tubes and the other outside the tubes and inside the shell. Heat is transferred from one fluid to the other through the walls of the tubes, from the tubes to the shell, or vice versa.

[0003] It is known to manufacture the tubes of these exchangers in cupronickel or cupro-nickel, that is to say an alloy based on copper, predominantly, and nickel, typically between 10% and 30% by mass, and in smaller proportions of iron and elements improving the mechanical resistance of the alloy, such as manganese or silicon. Cupronickels offer good resistance to corrosion, particularly in the presence of sea water.

[0004] However, these copper alloys are not entirely satisfactory, particularly due to their high cost and the need to use a specific corrosion inhibitor. There is also a risk of galvanic corrosion at the junction with other parts of the exchanger which are generally made of carbon steel, such as the fluid collector boxes or the tube fixing plates in the shell.

[0005] The present invention aims to solve all or part of the problems mentioned above.

[0006] A solution according to the invention is then a heat exchanger comprising a shell enclosing a plurality of tubes, the exchanger being configured to put into heat exchange relation a first fluid circulating in the shell and a second fluid circulating in the plurality of tubes, characterized in that the tubes are formed in whole or in part from ferritic stainless steel or duplex stainless steel.

[0007] The invention will now be better understood thanks to the description which follows, given by way of illustrative and non-limiting example.

[0008] The exchanger according to the invention comprises a plurality of tubes arranged in a shell. Two fluids pass through the heat exchanger, one circulating inside the tubes and the other outside the tubes and inside the shell. The fluids exchange heat indirectly via the walls of the tubes.

[0009] According to the invention, all or part of the tubes, preferably all of them, is formed from ferritic or duplex stainless steel. Such materials reduce the risk of coupling galvanic. In the presence of water in particular, stainless steel has the advantage of undergoing passivation by the oxygen contained in the water, which reduces the effect of galvanic corrosion on carbon steel, while copper alloys remain active. In addition, these materials allow higher water flow speeds than those permitted by cupronickels, which facilitates the design of exchangers.

[0010] According to one embodiment, all or part of the tubes, preferably all of them, are formed from ferritic stainless steel. Preferably, an iron-chromium steel with a chromium content of at least 10.5% by mass and a carbon content of less than 1% by mass is used, more preferably, the ferritic steel belongs to the 400 series according to the AISI standard, which is the acronym in English for "American Iron & Steel Institute", in particular the steel is of grade AISI 444, also identified by the standard designation UNS S44400, where UNS is the acronym for "Unified Numbering System".

[0011] According to another embodiment, all or part of the tubes, preferably all of them, are formed from duplex stainless steel. Preferably, an iron-chromium-nickel steel is used, with a mixed austenitic-ferritic structure, composed mainly of a mixture of ferrite and magnetic austenite, more preferably the duplex steel is of UNS S32205 grade.

[0012] Note that the tubes may be solid pieces formed from ferritic or duplex steel or that the walls of the tubes may be coated, on all or part of their internal surface and / or their external surface, with a coating of ferritic or duplex steel. Note also that the exchanger may further comprise fins in order to increase thermal efficiency. The fins may also be formed from all or part of ferritic or duplex steel.

[0013] The invention applies in particular to a heat exchanger which heats or vaporizes a flow of first fluid circulating outside the tubes, in particular water, in particular sea water, by heat exchange with a flow of second fluid, in particular in the gaseous state, which cools or liquefies inside the tubes. Note that the reverse remains possible, namely water as the second fluid. Other states of the fluids, gaseous, liquid, two-phase, are also possible.

[0014] An exchanger according to the invention can in particular be used to put into heat exchange relation a first fluid and / or a second fluid comprising at least one of: neon, krypton, xenon, nitrogen, argon, oxygen, hydrogen, helium, carbon monoxide, carbon dioxide, methane, water.

Claims

[Claim 1] Claims Heat exchanger comprising a shell enclosing a plurality of tubes, the exchanger being configured to put into heat exchange relation a first fluid circulating in the shell outside the tubes and a second fluid circulating inside the tubes, characterized in that the tubes are wholly or partly formed of ferritic stainless steel or duplex stainless steel.