Written by Rob Landes, Product Manager of Positive Displacement Chillers, Daikin Applied
Frost & Sullivan has selected Daikin Applied Americas as a 2017 Manufacturing Leadership Award winner for Daikin’s Variable Volume Ratio (VVR) technology.
Catering to Each Customer’s Needs; Not Only the Majority
No two buildings or their occupants are alike and no two days serve up the same conditions. With Variable Volume Ratio (VVR) technology, a building owner can relax in comfort, knowing their chiller will respond precisely and efficiently as operating conditions change. The application of VVR on an air-cooled screw chiller is a first for the HVAC industry and is engineered into each custom-designed Daikin Pathfinder air-cooled chiller. VVR allows the chiller to only compress the refrigerant just as much as is needed for the current operating conditions, which avoid efficiency-robbing over-compression as conditions change.
The ultimate benefit to the customer is that they get a chiller that is more efficient and flexible as design-conditions change, resulting in lower operating costs and carbon footprint. VVR technology sets forth a new standard for customers to get the cooling they need, with the flexibility to do so at the maximum efficiency possible, without paying the high price of over-compression.
Optimal Efficiency at Any Operating Condition
With VVR technology, the compressor senses the amount of lift needed and adjusts the compression ratio automatically to provide optimal efficiency at any operating condition. Specifically with VVR, efficiency improves the further you get from design-conditions. While it is designed to operate on the hottest day – for example, a 95-degree ambient temperature day, when the temperature drops lower, for example a 55-degree day, VVR technology provides a vast improvement in efficiency, sometimes as much as 30% better than a chiller with a fixed volume ratio that is unnecessarily over-compressing. Here’s how it works:
- In Daikin’s VVR compressor, as the gas moves from suction to discharge, it’s pressurized from low to high pressure within the screw’s flute.
- The single rotor screw’s gate rotor on either side acts as a rotating seal. As the tip of the gate rotor meshes with the screw, a gas section is trapped inside the screw flute.
- As the gate rotor continues turning, the volume of that trapped gas reduces, increasing the pressure until the gas is finally released from the flute at the discharge end of the screw.
- The pressure ratio is a function of the flute length, which can’t be changed. So Daikin’s design team focused instead on altering the effective VVR slide cover length by changing the point along the flute at which gas is allowed to discharge. When the VVR slide moves to cover the full length of the flute, it forces the gas to compress along the flute’s full length, giving the highest compression ratio. When the VVR slide moves to allow discharge at an earlier point, it reduces the compression ratio.
Our VVR technology is an industry first; no other air-cooled screw chiller can match the demands of varying conditions at optimal efficiencies. Being an industry leader, Pathfinder® with VVR also recently won the 2017 AHR Innovation Award in the cooling category.
Not only is Pathfinder’s VVR technology an industry-first, it also affects the chiller’s part load performance. This makes Pathfinder the first air-cooled screw chiller with Integrated Part Load Values (IPLV) exceeding 22.
Pathfinder’s one-of-a-kind VVR technology and 100 percent configurability, combined with other variable technologies, revolutionizes the industry with unprecedented part load efficiency levels and the best real-world performance available.
Learn more about our VVR technology by watching our video and more about Pathfinder on our website.