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use our global experience that exceeds more than 50 years and also get the user to pass onto us the type of challenges they have encountered with their existing system to enable us to see what design changes can be implemented or how the product can further be optimised to avoid or minimise failures in the future . This could be an efficiency challenge or a material type failure . Secondly training on any HE product is critical because most HEs look so simple , so users may attempt maintenance without being familiar with a particular unit , causing irreparable damage ,” Modibela says .
COMMON DESIGN ERRORS “ Common issues seen are incorrect pipe sizing , incorrect expansion valve sizing and fitment ( especially the bulbs ), incorrect placement of coils ( for example fitted above doorways ) or too close to walls . A further critical consideration in unit performance is the air distribution in a room which is closely linked to fan selection and coil placement ,” says van Rooyen .
According to both Modibela and Kutelya , their experience related to design mistakes start with the actual versus the designed parameters . Modibela states that this , “ mostly ends up with an over specified system because of high margins added at a feed stage . This includes provision for future expansions . If we have all the information up front , we can size the HE very accurately with the result of less problems from an HE point of view ”.
Another major design error is the flaw of assuming fluids have the same properties or will act like water . A simple example is a brine solution , although this may look similar to water , its thermal properties are vastly different . It is important to provide information on the fluids to ensure that the correct physical properties are used , and compatible material is selected .
Kutelya adds , ” Plate HEs are becoming increasingly popular in a variety of applications due to the potentially lower purchase cost , a high heat recovery ( up to five times more efficient than a shell and tube application ), a close temperature approach ( up to 1 C ), small installation footprint , the flexibility of using various types ( gasketed , semi-welded , welded , spiral ), and ease of maintenance .
“ Developement of a completly new range of gasket plate heat exchangers ( GPHE ), where the latest innovation is offered on the heat exchanger market is part of new trends . New GPHE has a combination of new features that ensures higher heat transfer efficiency , better reliability and greater serviceability . Environmentally-friendly refrigerants are also big elements of the trends we see today as products are driven to be as compact as possible .
Danfoss
The latest seizures include R410A , R32 and R404A .
TRENDS Product footprint has become a significant factor in recent years as available plant room space becomes smaller . Suppliers now offer several products to maximise the usage of floor space on sites . “ Our range now includes dedicated containerised plant rooms to outdoor racks with the addition of integrated condensers . These give our clients flexibility and offer large cost benefits against building the traditional dedicated plant room ,” notes van Rooyen .
Further , market design trends are focusing on the use of natural or low GWP synthetic refrigerants , with significant attention being given to low charge systems . In the wider market , the trends have moved towards customers preferring full end-to-end solutions that minimise points of responsibility and localise all project design considerations . This approach means that each individual design decision and implementation is made with cognisance of its impact on the whole project , and therefore the best overall outcomes can be achieved while limiting expenses and errors .
www . hvacronline . co . za RACA Journal I February 2021 27