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“ Adding onto what Petrie and Cules have said , safety should always be a priority , particularly as heat recovery is typically best suited to larger installations . Here it is common to come across CO₂ that operates at high pressures and ammonia that is toxic . All of the correct stops , warning aspects and incident apparatus have to be included without question ,” Bell stresses .
CAN HEAT RECOVERY WORK WITH ANY SYSTEM ? With the inclusion of new technology and design methods , the short answer is yes . As already mentioned , any savings that are possible will soon be seen as essential . Savings already become possible by closing the gap on supply and demand temperatures , even if this is only a couple of degrees . This not only has an impact on operational costs , but peak energy demand can also significantly be reduced as well .
“ Although you can recover heat from any refrigeration system , plant scale is something we need to keep in mind because in theory anything can work . Heat recovery works well on large plants that typically use CO₂ or ammonia – these plants normally have stable operating conditions and accessible interface junctions . With these conditions , more heat is available with even part load conditions yielding useful amounts of recovered energy . Heat recovery always seems attractive , but as mentioned if you have to pump hot water through a long circuit to get it to the point of use , the pumping costs increase , reducing the energy savings . It then becomes more practical to consider installing an alternative solution . In my view heat recovery is then best suited for large commercial and industrial scale systems with continuous operations , where the heat source and points of use are close to each other . Heat reclaim systems are not particularly well suited to plants with seasonal operations ,” van der Merwe notes .
WHAT CAN YOU PRACTICALLY DO WITH RECOVERED HEAT ? Although the most commonly known function of heat recovery is to generate hot water for a building , many other applications are in fact possible , and this range is being expanded at a fast rate with the development of new technologies such as heat pumps that now are able to generate temperatures of up to 95 ° C . It is now possible to generate steam at 5 bar ( 145 ° C ) from a heat pump using Pentane as refrigerant . It is still in the testing phase but could be an important addition to industrial applications in the near future .
One of the first known applications of recovered heat was to increase a building ’ s temperature in colder climates . Today for commercial applications another well known technology that is widespread is variable refrigerant flow ( VRF ) systems that use the same methodology on a smaller and more controlled scale .
“ Temperatures can be varied through the heat recovery process by adjusting how the system operates , speeding up certain components or slowing things down . This obviously has a number of impacts or influence on how a system needs to be designed . However , it must be noted that heat recovery is actually a secondary function to the primary function of any refrigeration or air conditioning system and therefore any heat recovery applied should not affect the main system ’ s operation . This is most commonly seen when COPs drop and this then essentially creates inefficiency rather than savings ,” says Bell .
Other applications of recovered heat in a single stage use include washdown water that is used in facilities with fatty or oily residue where the requirement is just enough to ‘ melt ’ such products – usually around 45 ° C and clean in place ( CIP ) that can be anything from 65-70 ° C . With the addition of industrial heat pumps , steam boilers or electrical elements , recovered heat
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