Feature
Standard catalogue coils installed and running
Gasketed plate heat exchangers are supplied in a variety of configurations according to the design needs .
The new heat exchangers are now also supplied with a U-turn separator . The U-turn separator was developed to ensure efficiency and to achieve smaller overall dimensions for easier and more compact installations . This new concept in flooded evaporators , offers enhanced separation efficiency via gravity and centrifugal effects , insignificant internal pressure losses , compact design , low ammonia charge and reduced hold-up , short vertical ammonia driving columns to allow for small temperature approaches and high system efficiency and reduced height and
HC Heat Exchangers Alfa Laval compact profile allow for this packaged evaporator system to be installed in one piece in narrow spaces ,” says Modibela .
WHAT IS A PLATE HE ? A compact heat exchanger ( plate HE ), depending on the technology and design parameters , is a set of thin heat transfer plates compressed together to form a plate-pack which forms the heat transfer area . Each compact technology has headers and followers which hold the plate packs together . The inner working of a plate heat exchanger is to transfer thermal energy between two fluids , without the fluids mixing together .
“ As for gasketed HEs , there are different numbers of plates according to the required flow rate and pressure drop . Hot mediums go through one pair of plates ( between the first and second plate ), and cold mediums go through the second and third plate , and so on – so each alternating plate thereafter will be hot and cold respectively . Cold and hot mediums exchange heat through a thin plate that is most commonly 0.5mm thick . This same technology works for welded units , but these don ’ t have gaskets between the plates . These plates are welded by a laser machine ,” Kutelya notes further .
Within a gasketed HE , the plate material is thinner so heat transfer is higher , thus resulting in a high heat transfer coefficient . Each channel plate has an efficient distribution area and plates chevrons that utilise the pressure drop fully . The result is high turbulence which results in high wall shear . The additional benefit of turbulent flow is minimised fouling on the plate surface .
WHY PLATE HES WERE DEVELOPED According to Kutelya , plate heat exchangers have been around since the 1920s and revolutionised methods of indirect heating and cooling of fluids . They were developed as an alternative to the shell and tube technology in some industries and applications .
There are also different tasks for different industries and this technology was designed for a corresponding solution . In these different industries , varieties in parameters also differ between countries . For instance in most countries , the quality of water is completely different . Flow rates and system pressure also depends on a facility ’ s capacity which can be different at every location and so plate HE offered a new method .
Plate HEs , having a now wider application use are also generally smaller and so transportation and installation cost became lower , maintenance is easier and they are much higher in efficiency to the traditional shell and tube system . RACA
REFERENCES : 1 . Alfa Laval 2 . Danfoss 3 . HC Heat Exchangers
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RACA Journal I February 2021 www . hvacronline . co . za