Two new energy-efficient Trane chillers were recently installed at Newlands on Main by the HVAC experts at SFI, along with new energy-saving pump sets for the condenser and chilled water, plus IoT sensors for improved energy management.
Newlands on Main – one of Growthpoint Properties’ A-Grade office spaces in Cape Town – is a highly sought-after space offering tenants incredible mountain views, modern features, and close proximity to Cavendish Square and other convenience stores.
“Newlands on Main has been our client for 25 years,” says Edward Hector, MD of SFI Group. “With their previous chillers being in operation for over a quarter of a century, it was time to upgrade. This was not only to solve the numerous component failures and call-outs caused by age and wear and tear, but also for the clear benefits of energy-efficient optimisation for this 14000m2 site now supplied by a 1600kW cooling plant.”
The chillers were decommissioned as they had reached end of life, and were using outdated R22 refrigerants. Additionally, these old chillers were of the flooded type evaporator heat exchanger, unlike the new chillers, which have the more efficient falling film evaporator.
Falling Film Evaporator Replaces Evaporator Heat Exchanger
The advantages of a falling film evaporator are based on the kinds of work that a chiller evaporator does. The evaporator is where liquid refrigerant boils into a gas as it contacts tube surfaces heated by warm return chilled water. Functioning as a large heat exchanger, the efficiency of an evaporator is a function of tube surface area and how the refrigerant and return chilled water interface with the outer and inner tube surfaces, respectively.
In a traditional flooded evaporator design, the tubes are covered with refrigerant. The liquid refrigerant passes through a variable orifice, enters the bottom of the evaporator and fills the evaporator shell with liquid refrigerant to ensure that refrigerant adequately covers all the tubes. As the refrigerant boils off the tubes, it is drawn through a baffle assembly and up into the compressor to continue the vapor-compression cycle.
The refrigerant and return chilled water interface differently in falling film evaporators. In a falling film evaporator design the shell is not filled with refrigerant to submerge all the tubes. Instead, a thin film of refrigerant only covers the surface of the upper tubes. Liquid refrigerant passes through the variable orifice and is sent to a header at the top of the evaporator. From there, liquid refrigerant is evenly distributed and sprayed down over the evaporator tubes. Approximately half of the sprayed refrigerant is instantly evaporated. The other half is collected at the bottom of the evaporator. There, the remaining refrigerant is boiled off from the submerged tubes, just as with a flooded design. The evaporated refrigerant passes through baffles along the side of the shell ensuring no liquid is carried over as the gas is drawn into the compressor.
About the Installation
SFI’s team of experienced technicians went to the site to handle the installation of the two new chillers.
First, the two chilled water supply lines feeding the three buildings were frozen with dry nitrogen to allow for alterations to be made to accommodate the new machines.
Then, the plant room brickwork was opened up to allow for the safe and easy removal of the old chillers, and installation of the new chillers.
Additionally, the two plinth supports had to be altered and made larger to accommodate the new machines, and structural supports were installed throughout the two levels of parking to accommodate the 6-ton weight of each new chiller.
Finally, a new KwH meter was fitted in the plant room board to monitor power consumption, and new ioT Sensors were added, allowing building managers and stakeholders to access the consumption information for both energy and water remotely, as this data is stored in the cloud. This empowers decision-makers with the data they need to ensure the building’s resources are used optimally.
- More efficiency. Heat transfer in falling film evaporators is very efficient. The evaporation of a thin refrigerant film covering a tube happens more easily than with submerged tubes. The high heat transfer coefficient boosts these chillers efficiency.
- Zero ODP and lower GDP. The R134a refrigerant used in the new chillers ozone depletion potential (ODP) is zero compared to the previous chillers R22 refrigerant, which has an ODP of 0.05.
- Less energy, reduced spend. The new chillers rated current draw at full load is 225 amps vs 264 amps for the previous chillers, and with the new premium efficiency pumps deliver an energy saving of 15%.
- Greater clarity and control. The IoT sensors and full BMS integration give facility managers the data they need to track and manage the building’s energy consumption, from anywhere at any time.
“In all, it was a highly successful project,” says Edward, “and I am proud of how our team, together with suppliers and riggers carried out their tasks with excellence, dedication, and expertise. Retrofit projects in occupied buildings is a core part of our business and we always aim to turnaround each project as fast as possible to minimize downtime” Getting that thank you email from the client was affirmation of a successful execution.
Backed by the on-going support and expertise of the SFI team, the new chillers are sure to keep the tenants of Newlands on Main comfortable and cool for the next quarter century!