Thermal exchange: FAQ
All what you ever wanted to know about heat exchangers! Read our FAQ and discover the answers to the questions most frequenlty asked to our team of thermal engineers.
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- Thermal exchange: FAQ
WHAT IS A HEAT EXCHANGER?
A heat exchanger is a device used to transfer thermal energy from one fluid to another, without any direct contact between or mixing of these fluids.
What does heat recovery involve?
A distinction is made between heat recovery at high temperature (above 90°C), often from combustion products (stack gases) and recovery at low temperature (below 60°C), from water cooling circuits, waste water, or process effluents, hot air from drying or compression, or poorly insulated surfaces.
How should a heat exchanger be chosen?
The choice of a heat exchanger is determined by many criteria: the fluids involved (liquid/liquid, liquid/vapor, gas/gas, etc.) and their nature (clean, fouling, viscous, corrosive, etc.), the temperatures (temperature pinch, temperature difference, temperature cross, thermal exchange coefficient, etc.), the pressures involved (maximum service pressure and design pressure, acceptable loss of head, etc.), the required ease of maintenance (FDA standards, pharmaceutical exchanger, etc.), the level of maintenance (frequency of cleaning, for example).
Based on these various parameters, our heat engineers select the best heat exchange technology for your application and your industry: Shell and tube heat exchangers (with straight, corrugated, twisted, or spiral tubes), gasketed plate heat exchangers, or welded plates heat exchangers, and the appropriate materials (steel, 304 or 316 stainless steel, cupro-nickel, duplex, Hastelloy, titanium, etc.).
What are the advantages of the Platular® heat exchanger?
The Platular® (the name is trademarked) is a heat exchanger invented by Barriquand in the 1950s that has since then been steadily improved. It is a welded plate exchanger (so there are no gaskets between the plates) that can operate up to a pressure of 30 bars and at temperatures as high as 500°C.
Its unique design features near-perfect counter-current exchange combined with unequal fluid flow rates on the two sides, made possible by very different flow areas, with no points of contact for the more fouling fluid.
Its maintenance is by chemical cleaning in place (CIP) or by mechanical cleaning using a jet of pressurized water through quick-opening ports, with no dismantling of the piping. This makes maintenance very simple, with no need for replacement parts other than the simple gaskets of the ports). Stronger than a plate and gasket exchanger, it is also very compact.
What is a condenser?
A condenser is a device that allows to move fluid from the gaseous state to the liquid state by condensing.
A heat exchanger is very well suited to this function and allows, by cooling the gas with another colder fluid to condense it. In this case, the latent heat released by condensation, as well as the power of a possible de-superheating, are used as energy to heat another colder fluid. According to the thermal programme, the power can be increased by a sub-cooling of condensate in a suitable design. This gaseous fluid may be the main fluid to be treated or can be the fluid that brings heat.
If the gaseous fluid is pure and the heat exchanger design is well done, all of the gas will be condensed and transformed into liquid. The resulting condensates are in thermodynamic equilibrium (pressure and temperature) with the gas phase. If the gaseous fluid is a mix or includes non-condensable gases, the condensed quantity will depend, among other things, of the mass fractions and the outlet temperature of the heat exchanger. In this case, it will be necessary to foreseen the non-condensable gas extraction.
Is Barriquand a builder of heat exchangers?
Barriquand makes plate heat exchangers (in particular the Platular® heat exchanger) and shell and tube heat exchangers. These devices are produced entirely in France, in our plants at Roanne and Saint-Priest in Auvergne-Rhône-Alpes region, giving us complete control of their design and execution.
Is the Barriquand company ISO9001-certified?
All of our heat exchangers are made to order under quality assurance as per CE, ASME, ISO 9001 or other standards.
Are there software programs to design heat exchangers?
Barriquand has developed, in-house, proprietary software to design its Platular® welded plate heat exchangers. For work on the other technologies, such as shell and tube heat exchangers, our engineering design department uses well-known industry standard software solutions such as ASPEN or HTRI.
The major strength of Barriquand’s thermal engineers is their expertise in the use of these programs, thanks to a database of several thousand installed exchangers.
What maximum temperature can a heat exchanger gasket withstand?
The maximum temperature plate exchanger gaskets can withstand depends on the material they are made of. Barriquand will help you choose according to your application.
HOW IS A PARTICLE-LADEN, FOULING, OR VISCOUS FLUID MADE TO PASS THROUGH AN EXCHANGER?
Barriquand calls on its 80 years of experience with fouling, viscous and otherwise “difficult” fluids to decide with you on a custom-designed technology. The basic objective in this case is to maintain speeds and rheologies (Reynolds numbers) compatible with good thermal exchange.
For this type of product, the Platular® heat exchanger, which allows different flow widths between the process fluid and the heating or cooling fluid, may be ideal.
WHAT IS RHEOLOGY?
It is the science of fluid flows in a given environment. The term “fluid mechanics” is also used. A flow regime may be laminar, transient, or turbulent and is characterized by a dimensionless Reynolds number.
IS IT POSSIBLE TO DRY AIR WITH A HEAT EXCHANGER?
Barriquand heat exchangers let you recover the energy in moist air, in vapors, or in a gas. In a condenser (Shell and tube, Platular®, plate and gasket, etc.), the water vapor contained in the air is condensed (in the presence of non-condensables) to an equilibrium point defined by the moist air diagram (or psychrometric diagram).
However, attaining perfect dryness will necessarily mean using other technologies as well.
WHAT IS THE PSYCHROMETRIC DIAGRAM?
Also known as the “moist air diagram“, it is a diagram giving the principal characteristics of moist air at a given atmospheric pressure, namely the relative and absolute humidity, the dew point, the dry- and wet-bulb temperatures, the enthalpy, and the specific volume.
WHAT TEMPERATURES AND PRESSURES CAN A HEAT EXCHANGER WITHSTAND?
They range up to 1000°C and 1000 bars. It all depends on the technologies used.
WHAT IS THE MINIMUM PRESSURE DROP OF A HEAT EXCHANGER?
Barriquand heat exchangers are custom-designed: we therefore meet the pressure drop requested by our customer.
But bear in mind that reducing the necessarily pressure drop means making the exchanger larger. The design will therefore be a trade-off.
WHAT PRODUCTION CODES AND CERTIFICATIONS APPLY TO EXPORTS OF EXCHANGERS?
The certifications Barriquand has obtained and systematically renewed, covering the design, production, and installation of heat exchangers, enable it to satisfy all normative, administrative, and regulatory requirements, whatever the construction code concerned and the country of destination.
We hold the following certifications:
- Certification of pressure vessels compliant with PED 2014/68/UE, module H/H1 for the European market (linked to the CODAP construction code),
- Stamp-U certification for the world market (linked to the ASME construction code),
- SELO certification for the Chinese market,
- HP0 certification for the German market (linked to the AD-Merkblatt construction code).
WHAT MATERIALS SHOULD BE CHOSEN FOR WHAT FLUIDS (CORROSION)?
Barriquand proposes, depending on the technology, the following metals: steel, stainless steel, cupro-nickel, duplex, super-duplex, Hastelloy, titanium, etc. As stated in our offers, the choice of materials is the responsibility of the customers, who know the compositions of their fluids.
Thanks to our 80 years of experience, we are however in a position to provide references and guidance for some applications. On request, we can also provide samples to enable our customers to perform corrosion resistance tests in situ.
HOW IS A HEAT EXCHANGER HANDLED?
Heat exchangers are generally fitted with welded lifting rings (or ears) or with holes for the same purpose, which must be used when handling the equipment with slings, as described in the installation manual provided by Barriquand. In some very particular cases, a slinging drawing may even be provided.
WHAT KINDS OF TESTS AND INSPECTIONS ARE PERFORMED ON HEAT EXCHANGERS?
We perform all the necessary tests required by the production codes, and also all our customers deem necessary for their applications: hydraulic test, penetrant examination, radiography, air- or helium-tightness test, etc.
WHAT ARE THE LEAD TIMES FOR INSTALLING A HEAT EXCHANGER?
Depending on the technology and the application, Barriquand may propose exchangers from stock, with very short delivery times (48h in metropolitan France), or custom heat exchangers with longer lead times (a few months).
WHAT SERVICES DOES BARRIQUAND PROPOSE?
Barriquand is in a position to offer a complete service, from design to the maintenance of your installations. Our regional sales representatives can discuss your plans with you, and the thermal optimization of your processes or your utilities. Depending on your requests, our heat engineers design the heat exchangers and give you an estimate with production and delivery times.
Once your order has been placed, our engineering design department produces the drawings of your exchangers and possibly adapts them as you request. Subsequently, Barriquand archives the technical documentation on your heat exchangers, making it possible to adapt them in the future as your processes evolve. We also supply original-equipment spare parts and provide maintenance in the shop or on site.
HOW IS A PLATE-AND-GASKET EXCHANGER DISMANTLED?
The procedure for dismantling a gasketed plate heat exchanger is described in the maintenance manual provided by Barriquand.
The main steps are:
- Make sure that the exchanger is cold, not pressurized, empty, and isolated from the rest of the network
- Before dismantling the vessel, note and record the distance between the two plates with a view to clamping during reassembly
- To open the exchanger, gradually loosen the clamping tie rods, uniformly and in a staggered pattern so as to keep the plates parallel
- Push the mobile plate, keeping it as vertical as possible, against the rear upright, without tilting it (hold it if it is not stable)
- Free the plates on by one
WHAT GUARANTEES DOES BARRIQUAND PROVIDE?
Barriquand commits to the thermal performance and mechanical ruggedness of its heat exchangers. These guarantees are described in our offers.
WHAT IS THE PAYBACK PERIOD ON THE INSTALLATION OF A EXCHANGER FOR HEAT RECOVERY?
The payback period on a heat exchanger depends of course on the application on which it is installed. If it is unavoidable energy that is recovered, the power of the exchange (in KW, MW,…), valued at the cost of the energy recovered, gives an immediate estimate of this payback period, often highly advantageous (a few months).
In the case of thermal exchanges in connection with production processes or utilities, the focus will be on the savings compared to the older technologies already installed, both thermally and in terms of the running costs of maintenance.
WHAT IS UNAVOIDABLE ENERGY?
It is the energy produced by a process intended to produce something else; this energy is often lost if it is not recovered or upgraded.
WHAT IS THE HEAT TRANSFER COEFFICIENT?
It is the quantity of heat exchanged per unit of area per unit of time. It is expressed in W/m².°K or kcal/m².°C. It is the inverse of the thermal resistance.
WHAT IS THE APPROACH TEMPERATURE?
It is the smallest difference between the temperatures of the cold and hot streams. For example, if you heat a cold fluid from 80°C up to 100°C using a hot fluid at 105°C, the approach temperature of the heat exchanger is 105-100 = 5°C. The lower approach, the higher heating area.
WHEN DO WE SPEAK OF A TEMPERATURE CROSSING?
There is temperature crossing when the outlet temperature of the cold stream is higher than the outlet temperature of the hot stream.