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Cool treatment keeps flowers immaculate

  • marimac 

By Russell Naudé – head of engineering and mechanical technologist at FF Cooling & Engineering | All image credits FF Cooling & Engineering

One less thought-about sector of the cold chain is that of the flower market for both local and export demand.

This project, for a client that is a grower of flowers for the export market, is situated in the Cederberg area of the Western Cape. Their daily export volumes tally approximately 10 tons of fresh flowers during peak season. The facility works with proteas, pincushions and similar hardy plants.

The initial scope clarification meetings for the site were held in November 2021 whereafter the project officially commenced with the insulation portion in May of this year. Completion of the project came about at the end of July 2022.

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Design specifications/client brief of the project

This project, an upgrade to the existing facility where the client had two very small cold rooms with a precooler on the inside, included the provision of a facility with sufficient space to manually pack and stack prepacked flower boxes of 10 pallets. There was then also the requirement to force-cool the packed pallets prior to storage at a rate of four pallets at a time and then to store the cooled pallets for between one and three days. Storage duration was to accommodate the potential logistical issues  – basically allowing for a three day turnaround time. The total capacity of the storage would be 60 pallets.

The cooling solution and system used

The project essentially involved four sections that were determined in the engagements with the client and then included the following parameters and system components to achieve the requirements:

  • The sorting and pallet building room
    This section is held at 15°C by two evaporators. The packing section is kept between 12 – 15°C to start the flower cooling and the bulk of the heat is removed in the precoolers.
    The room also holds the control distribution board (DB) for all of the other rooms – including the precooler in order that the staff are able to operate the room/forced air fans from that location.
  • The precooler
    This component of the project was designed to pull down four pallets from 35°C to 2°C in a three hour timeframe. The 2°C is a commodity requirement however the three hour pull down time is based on the amount of product that gets packed and the limited space for additional pre coolers. Four suction fans and the canvas systems force the cold air through the flower boxes. The fans are controlled via Danfoss controllers in the DB situated in the sorting and pallet room of the facility. The fans switch on automatically and switch off automatically when the product reaches the determined set point. There are two evaporators in the precooler room.
  • The holding room
    Here the room load was designed to hold a maximum of 60 pallet at 2°C and also contains two evaporators in the room.
  • Refrigeration plant
    The system comprises one multiplex rack with three Dorin compressors situated in the insulated plant room which supplies the seven evaporators throughout the facility. The refrigerant used is R407c. A multiplex was chosen mainly due to the multiple temperature zones and the peak demand during the pre-cooling process. The multiplex also gives the benefit of ramping up and down based on the load requirements.
    The multiplex includes a variable speed drive (VSD) on the lead compressor to assist with capacity control of the system while a single evaporative condenser provides the heat rejection for the system. The system is monitored via a Danfoss SM 850 monitoring system.

Project dynamics

Project planning is key to keep a project on track irrespective of the size. FF Cooling prides itself in planning a project to it’s fullest in a three-dimensional environment. The holistic project was therefore conceptualised in three dimension allowing us to plan and order all of the material based on bill of quantities produced by the model.

The most challenging aspect of this project was to fit the layout within the constraints of the new buildings structure. Multiple engagements were required over WhatsApp as cell phone reception in this area was low to non-existent which created a difficult setting to co-ordinate on-site work.

Additionally, material shortage definitely played a roll when it came to keeping the project on schedule – especially for the control aspects that are essential for accuracy and efficiency.

Impact of the installation on energy efficient/sustainability

Due to the high ambient temperature, it was opted to include an evaporative cooling tower. Not only does this help during the hot days experienced in this area, but it also helps the system run at a lower condensing pressure and therefore reduces the electrical consumption.

Initial power readings have thus determined that the system is running more efficiently than the previous two simplex rooms. The true test will however come in the form of reports on the summer-month operations. The simplex rooms were on the same site and are now replaced with the new system / rooms.

Special or unique aspects of the project

This installation is certainly unique because of the product being handled. It is not every day that you see and get to work with flowers being cooled for export. The flowers are sent to Holland.

Project name: Anonymous
Name of company
Owner Anonymous
Developer N/A
Architect / Designer FF Cooling & Engineering
Project manager N/A
Consulting engineer Electrical N/S
Mechanical FF Cooling & Engineering
Wet services N/A
Civil N/A
Contractors Main building / insulation Insulated Door Systems
HVAC & R FF Cooling & Engineering
Wet services FF Cooling & Engineering
Electrical N/A
Product suppliers Product Supplier
Condenser Baltimore Air Coil
Evaporators HC Heat Exchangers
Rack HC Heat Exchangers
DBs HC Heat Exchangers
Control Danfoss
Insulation Insulated Door Systems
Suction Fans EBMpapst
Dock Seal Maxi Flex
Canvas installation SA Canvas

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