www . refrigerationandaircon . co . za RACA Journal I June 2023 31
Project
While the project is predominantly a refrigeration one , so significant is its scale that the lesser HVAC component nonetheless represents a major project .
The development covers 36ha of state-of-the-art infrastructure and is currently being commissioned . It is part of a larger project to position the Eastport Logistics Park , near OR Tambo International Airport in Gauteng , and the broader R21 area , as South Africa ’ s prime logistics hub as allied industries and businesses seek proximity and rational integration into the country ’ s leading logistics ecosystem .
However , the complexity of the HVAC & R project stemmed less from its size as in having multiple different cold rooms , multiple different temperatures and multiple different smaller areas each with different considerations . This distribution centre is an undoubtedly sizeable one with large areas catering to massive amounts of product .
The Pick ‘ n Pay Distribution Centre project at OR Tambo International Airport in Johannesburg is a state-of-the-art facility that serves as a hub for the distribution of goods to Pick ‘ n Pay stores across the region . The project was designed to be highly energy-efficient , incorporating a range of innovative technologies to reduce energy consumption and minimise its impact on the environment . One key component of the project was the HVAC system , which was designed to be highly efficient and environmentally friendly .
The project serves as a model for sustainable building design and demonstrates the potential for the HVAC industry to contribute to a more sustainable future .
HVAC CONSIDERATIONS During the design of this facility special care and time were taken to optimally design the air side of the facility . As with most facilities or cooling designs where the heat is removed from the space via air , the flow and distribution as well as selected conditions of the air comprise a critical and often overlooked consideration .
The facility in its final configuration has 80 coolers in the + 2 ° C area and 24 coolers in the + 14 ° C area ; each cooler is equipped with four 700mm EBM EC fans capable of delivering 18 850 m ³/ h ( 5.236 m ³/ s ) of air . This results in a total of some 545m ³/ s of air being displaced in the facility , at a peak fan power consumption of 145kW , to provide the cooling required . It is clear that careful consideration is to be given as to how this air is distributed and optimised to provide the cooling to the facility .
As this facility was extremely high , some 18.9m at the centre and 11.6m at the dock faces , the air volume in the centre of the facility is much larger than at the dock faces . This was advantageous as the coils were equally spaced and thus created a higher air change rate at the dock faces where the instantaneous heat load could be quite high at times due to the infiltration loads .
EVAPCO AMC Engineers
These are induced draft , counterflow , belt drive axial fan two stage evaporative condensers .
Primary and secondary hot water heat recovery pump sets .
The design allowed an air change rate of some 16AC / h at the dock faces resulting in an average distribution velocity of 0.27m / s which sufficiently deals with the high peak infiltration loads . The inner half of the warehouse was designed to have slightly lower air change rate of eight air changes per hour and an average distribution velocity of 0.22m / s .
Crucial consideration was the actual airflow interaction between coils – initially the coils were placed in a three-row spine row orientation with two back-to-back coolers in the middle of the facility and a single row at each dock side , all blowing towards the dock . During the detail design phase it was recognised that there might be poor cooling by the dock row of coils as the cold air from the centre row will be blowing into the rear of the dock row of coils . This might result in a higher dT over the product and possible warm spots below . It was decided to move the centre back-to-back row towards the dock rows and rather make two back-to-back rows of coils on either side of the facility as shown in the schematics below . This resulted in a better air distribution in the space and completely eliminated the middle pipe run and pipe bridge .
www . refrigerationandaircon . co . za RACA Journal I June 2023 31