Confronto tra raffreddamento ad aria e raffreddamento a liquido:
Progressi nella gestione termica per l'elettronica di potenza


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Negli ultimi decenni, i settori dell'elettricità e dell'energia risultano essere le due industrie in più rapida crescita per quanto riguarda l'elettronica. La conversione, l'inversione e la rettificazione di potenza, così come le tecnologie della batterie e delle pile a combustibile, sono diventate parti integrali della crescita tecnologica in tutti i settori industriali.

Poiché i sistemi elettronici diventano sempre più complessi e necessitano di campi di potenza sempre più elevati, i fattori di forma diventano sempre più piccoli, rendendo il calore uno dei maggiori limiti alle possibilità produttive. Per gestire la quantità di corrente che deve essere dispersa, le soluzioni di raffreddamento dell'aria devono essere ottimizzate e sviluppate per eliminare adeguatamente il calore eccessivo. In alcuni casi, le dimensioni diventano un fattore limitante per le soluzioni di convezione forzata. In questi casi in cui le dimensioni o il peso di un sistema di raffreddamento ad aria ne rendono poco pratica l'installazione, il raffreddamento a liquido sta diventando il metodo alternativo più diffuso.

Il passaggio da un sistema raffreddato ad aria a uno raffreddato a liquido non è una decisione che possa essere presa velocemente o alla leggera; ci sono molti fattori e possibilità da considerare per consentire alla gestione termica di far fronte a carichi di calore più intensi. Sebbene le tendenze del mercato indichino che il raffreddamento completamente a liquido diventerà lo standard industriale per il raffreddamento dell'elettronica di potenza, sono disponibili molte opzioni e soluzioni ibride che riescono a fornire i benefici di entrambe le tipologie mentre si procede allo sviluppo o aggiornamento del proprio sistema. Nel caso in cui i limiti legati ai bilanci preventivi o alle scadenze di produzione siano tali da non consentire il passaggio a un sistema di raffreddamento a liquido, l'ottimizzazione della convezione forzata attraverso miglioramenti del design o attraverso l'introduzione del raffreddamento bifase o di componenti liquidi, rappresenta una valida soluzione provvisoria.

Engineers have been developing liquid systems that are complimentary to existingair cooled solutions that can be expanded to fully replace the air cooled systemsover time. This is done by focusing on the electronic devices that can gainimmediate benefit with liquid cooling. Utilizing fluid couplings, reliable pumpsystems, and compact heat exchangers, the system removes heat from the air flowto the liquid where it is transferred and managed elsewhere. In other cases,engineers are opting to fully replace their air cooled systems with liquid cooled toimmediately enable higher power outputs and optimize thermal performance.

As you consider the switch to liquid cooling in order to improve the performance of your power electronics devices andfacilities, there are several key determining factors:

• Quali sono l'altezza, il peso e i requisiti termici richiesti?

• È possibile ottimizzare ulteriormente l'attuale sistema di raffreddamento ad aria?

• Per quanto tempo ancora un sistema di raffreddamento ad aria sarà una soluzione termica praticabile per la propria applicazione?

• Ci sono limiti alla disponibilità di volume o di liquidi?

• Quanto tempo ci vorrà per realizzare un ritorno sull'investimento nel raffreddamento a liquido in termini di prestazioni ed efficienza?

• Come può essere implementato o progettato il raffreddamento a liquido nella propria applicazione? Quale sarà l'effetto che subirà la tua applicazione/il tuo impianto considerando i tempi di fermo?

• Come e quando sarà avviato il processo?


Raffreddamento con dissipatore di calore con ventola

I benefici del raffreddamento ad aria


I sistemi di raffreddamento ad aria sono significativamente meno costosi di quelli a liquido. They do not require regulated or specializedfluids and they are comprised of fewer components that are more economical than components for liquid systems. Asthey have no liquids to leak and less components to break, they also have less modes of failure. In addition to havinghigher reliability and lower cost, air cooled systems are also easier to modify or upgrade.



I limiti del raffreddamento ad aria


In typical applications, air cooling systems are comprised of an extrudedor bonded fin heat sink and often a fan. When reliability is a significantfactor, engineers may forgo a fan and instead opt for passive solutions.

Sia la convezione naturale che la convezione forzata hanno dei limiti. Natural convection islimited by the total surface area needed to dissipate heat, thisnecessitates large, heavy solutions that are often impractical.

Le soluzioni a convezione forzata sono limitate dal calo della pressione. Heat sinks withlarge surface areas in feasible volumes create a high amount of airresistance that hinder the amount of flow and therefore heat transfer thata fan can produce. Larger forced convection solutions also require largeror more fans, increasing the amount of noise generated by the solution.

Tuttavia, il più grande limite delle soluzioni di raffreddamento ad aria è la prestazione termica. Air does not have the same capacity asliquid to absorb and transfer heat. At a certain threshold, air cooling becomes an insufficient solution and liquid coolingis necessary.

Modifiche al raffreddamento ad aria e soluzioni ibride


Ci sono tre metodi comuni per migliorare il proprio sistema ad aria. The first is to optimize your heat sink design andfan selection. Generating more air flow, optimizing your fin geometry, or increasing your heat sink volume are ways toimprove upon your air cooled solution without introducing additional technologies. The second is to introduce twophase cooling into your design. Heat pipes may be integrated to spread higher power densities or move the heat to anarea where it can be more easily dissipated. The third most common method of increasing the performance of an aircooled solution is to start introducing elements of a liquid system such as a passive thermosiphon.

Vedi la pagina del prodotto Raffreddamento ad aria



L'efficacia del raffreddamento a liquido


Il liquido ha la capacità di trasferire il calore fino 4 4 volte in più rispetto all'aria con la stessa massa. This enables higherthermal performance in a smaller solution. A liquid cooling system is a hydraulic circuit that typically consists of a coldplate that interfaces with the heat source and device, a pump that circulates the fluidthrough the system, and a heat exchanger that rejects the heat absorbed by the liquidfrom the device. Liquid cold plates have a much smaller working envelope than a heatsink that would be used in air cooling for the same application. Additionally, multiplecold plates can be connected to the same exchanger with minimal impact onperformance. Liquid cooling grants an additional level of control over the coolingsystem because it controls inlet temperature to the cold plate as well as flow rate.

Potenziali rischi e benefici del raffreddamento a liquido


Some have been reticent to adopt liquid cooling because of the additional complexity and the fear of leakage.Complexity often increases the cost of the solution and the amount of maintenance required to keep the systemrunning. However the additional costs are mitigated in that the improved cooling performance will increase the lifetimeand reliability of your device.

Because of its complexity, liquid cooling requires better planning and design to incorporate into your power electronics.Although the cold plate is much smaller than an extrusion or heat sink, the overall solutions tends to occupy morevolume once the heat exchangers, tubes, reservoir, and pumps are all taken into account. Engineers must take all of thisinto account during the initial design phase in order to avoid complications later on. With proper foresight, thecomplexity of the systems can be beneficial as there is more flexibility in system design.

Soluzioni di raffreddamento a liquido


AAVID Hydrosink


The Aavid HydroSink system is a configurable method of combining astandard set of optimized heat exchangers, fans, pumps, valves, reservoirs,fittings, sensors, and control boards with custom cold plates to design thebest possible liquid cooling solution for given requirements.

HydroSinks offer more flexibility in design and installation than standardliquid cooling systems because they are configurable and more easilyadapted to design requirements. Sealing and connecting of the liquid coldplate, control board, and customer machine controls within the enclosureare also customizable.

As Aavid HydroSinks are largely comprised of a set of standard optimizedcomponents, they are more cost effective than traditional custom liquidcooling and their air cooled counterparts.

Attualmente HydroSink di Aavid è disponibile in due versioni di base compatte: piccola e media. Actual size of thefinal customer HydroSink system varies by configuration. Sizes are based around fan size and cooling performance.Small operates at a temperature rise 7-20 °C per kW, while the Medium operates at a rise of 3-9°C per kW.

Clicca per ulteriori informazioni sul sistema HydroSink™ di Aavid.

Piastre di raffreddamento a liquido Aavid


Le piastre di raffreddamento a liquido Aavid sono parte integrante del sistema HydroSink. Aavid offers four distinct, innovativecold plate designs developed to optimize the overall system based on application and requirements. All Aavid cold platesare constructed for worry-free liquid cooling utilizing specialized certification procedures to ensure leak-free, reliablesolutions.

Piastre di raffreddamento con manicotto Hi-Contact


Piastre di raffreddamento con manicotto Hi-Contact™
Aavid Hi-Contact tube liquid cold plates feature a high performanceassembly utilizing a continuous tube press fit into an extruded aluminumplate. The patented geometry used in the Aavid Hi-Contact process movesthe fluid closer to the device generating heat, achieving the best thermalperformance from a tube cold plate. To further increase the performance ofAavid's Hi-Contact liquid cold plates, a thermal epoxy is applied to the jointto provide a gap free thermal interface between the tube and the plate. Hi-Contactplates are easy to customize and are available in standard sizes.

Piastre di raffreddamento Blister


Blister technology stamps channels into the base plate, eliminating channelmachining and greatly lowering manufacturing costs. A leak free joint is createdbetween the base and cover plate and the blister channels to allow greaterflexibility to drill mounting holes in the topside of the cold plate without regardfor the location of the liquid channels.

Piastre di raffreddamento a liquido Vortex


Aavid Vortex Liquid Cold Plates are designed to cool extremely high powerapplications. These cold plates were initially developed for applications where ahigh compressive load may be applied such as when cooling SCR type devices.Using patented flow path geometry, both sides of Vortex Liquid Cold Plates areevenly cooled; therefore they can provide equal and consistent performanceacross both surfaces and lend themselves to creating more predictableenvironments.

Piastre di raffreddamento a liquido con superficie estesa


Aavid Extended Surface Liquid Cold Plates have increased internal surface areawhich allows for better overall heat transfer. Innovative technologies andmanufacturing processes are used to increase the liquid to plate contact areawithin the liquid cold plate. Their vacuum brazed construction ensures leak freejoints while maintaining high thermal conductivity. Aavid Extended SurfaceLiquid Cold Plates are specially fabricated to improve design flexibility and canbe easily customized for optimized flow paths for application designs.

Vedi la pagina del prodotto Raffreddamento a liquido



Considerazioni finali


The key to effective design for liquid cooling and optimized air cooled systems is to consider your thermal managementas early in the design phase as possible. Aavid offers design, engineering, and testing services that can come in at anyphase and develop the best possible solution based on requirements, constraints, timeline, budget, and any othercritical factors.

With design centers around the world, Aavid can provide any customer the necessary engineering services to design andmanufacture a fully optimized system. Engineers are available at every phase from analyzing if there is a need for liquidcooling or air cooling, to developing an optimized, integrated system, to reliability and validation testing of the entiredevice.

To request a free consultation about your current cooling solutions or for help finding the right thermalsolution for your Power Electronic Applications click here.

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