HC Heat Exchangers supplied 91 glycol coils to the Pick ' n Pay Distribution Centre refrigeration project , with 62 of those coils being of the same type in a single area .
INCORPORATING COLD CHAIN
PROJECT
Where efficient design meets practical implementation
By Gert van Rooyen , HC Heat Exchangers mechanical engineer , and edited by Eamonn Ryan
HC Heat Exchangers supplied 91 glycol coils to the Pick ' n Pay Distribution Centre refrigeration project , with 62 of those coils being of the same type in a single area .
Distribution centres in themselves are not novel , says Gert van Rooyen , HC Heat Exchangers mechanical engineer , but improvements in design and improvements in operation are what make them interesting .
He notes that a full set of designs was done on each potential type of refrigerant to find the one that was the best price , the best energy consumption and the best fit for client .
The project was prefaced with multiple design iterations and engineering models to ensure the best fit for purpose solution was proposed and ultimately installed . Design guidelines were centred on product quality , plant efficiency , personnel safety and life cycle cost without deviating from a commitment to minimise the environmental impact and maximise the space utility .
The solution for this project is a 7.2 MW installed ammonia refrigeration plant divided into two suction regimes to ensure the operating spaces are served by the most appropriate glycol supply . The ammonia plant ensures a high efficiency zero GWP ( Global Warming Potential ) engine that drives the cooling for the entire facility coupled with a non-hazardous secondary refrigerant loop to maintain highly controlled cooling in all serviced areas . The selection of the glycol option was followed by some further iterations of design to ensure it was as efficient as possible .
All photos by © Eamonn Ryan Cold Link Africa
The HC Heat Exchangers factory . Factory large coil assembly .
“ Due to safety and as a result of the size of the facility the decision was taken early on in the design phase to use secondary refrigerants in the field and limit the ammonia charge to the plant room . Noting the congestion in the roof void and the travel distances it was a prudent decision and greatly increased the safety aspects of the overall facility and roof void ,” says van Rooyen .
This project ultimately draws from the best of the available technologies to produce a final product that plays to the strengths of the parts .
The heat from the spaces ( with the future ambient area incorporated ) is removed by means of 80 coils of 74kWR each in the 2 ° C
space , 24 coils of 76kWR each in the 14 ° C space , and 4 coils of 73kWR each in the chocolate box . The coils were designed at tight temperatures : larger coils that were aimed at saving on energy usage over the life of the plant .
“ The brief called for glycol coils with stainless steel tube and aluminium fins , designed for a big open space with a fair amount of thermal volume and fluid flow with stringent pressure drop requirements through the coil . We consequently had to refine the design of the coils especially considering the flow regimes through the coil whether a turbulent , laminar or transition .
“ In this project , we ' re using waste heat from the compressors to heat up the glycol to pump through the coils to defrost them for an efficient and quick defrost . The compressors ’ energy has to go somewhere , so it might as well as be used to heat water . It ’ s almost free water heating because you have to have the cooling to run the distribution centre . The waste heat that comes out of that can be efficiently and economically used for other things like crate washing , staff showers or just to wash their hands ,” suggests van Rooyen .
GLOBAL TENDER WITH LOCAL SOLUTION
Effective cooler design was of paramount importance to ensure the facility is able to operate at its design capacity – allowing for the realisation of the project ’ s goals . It is with
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