Wind tunnel optimization of FluxScale cooling

We are obsessed with energy efficiency and reliability at GrowFlux. When our engineers set out to squeeze every last bit of efficiency out of our FluxScale LED fixtures, they took a very close look at the cooling fans.  

FluxScale uses two high performance IP68 waterproof ball bearing fans to provide cooling to the 318 tunable LEDs, allowing these devices to efficiently convert electricity to photons. FluxScale automatically adjusts the speed of these fans in real time based on an array of temperature sensors placed among the LEDs. The fans are hosted on a user serviceable fan tray which interfaces to the cooling fins within the fixture - the aerodynamics of these assemblies has a significant impact on fan performance. Minor design adjustments can result in enhanced airflow, allowing FluxScale to operate the fans at lower speeds, improving the energy efficiency and reliability. 

  FluxScale features a removable fan assembly, making it the only horticultural lighting fixture in the industry designed to facilitate rapid maintenance of cooling fans. FluxScale is designed for very low fan failure rates, however in the rare occurrence of a fan failure, fixtures can be serviced on site in minutes. 

FluxScale features a removable fan assembly, making it the only horticultural lighting fixture in the industry designed to facilitate rapid maintenance of cooling fans. FluxScale is designed for very low fan failure rates, however in the rare occurrence of a fan failure, fixtures can be serviced on site in minutes. 

Assessing these design features can be done with computational fluid dynamics (CFD) simulation tools, however nothing compares to real world measurements on physical hardware. GrowFlux worked with engineers from ebm-papst, a world leader in cooling fans and motors, to optimize the performance of the the removable fan assembly and cooling fins. 

  FluxScale 600AC instrumented and connected to a wind tunnel at ebm-papst. This tunnel precisely measures airflow; laser tachometers measure fan speed, and other instruments measure power and thermal performance.

FluxScale 600AC instrumented and connected to a wind tunnel at ebm-papst. This tunnel precisely measures airflow; laser tachometers measure fan speed, and other instruments measure power and thermal performance.

The first step in assessing the cooling performance of the fans within FluxScale is to instrument the fixture with temperature sensors attached to various components inside the fixture; lasers are directed at the fan blades to allow optical tachometers to measure actual fan speed.

In addition to these instruments, every FluxScale fixture is able to internally measure 9 temperature points across the LED array as well as real time fan speed - in normal operation these measurements are reported to the GrowFlux Cloud Control solution for quality assurance within our PrecisionPAR management service. 

  Pressure plot showing the relative performance of various fans and fan speed settings against the system airflow resistance within FluxScale.

Pressure plot showing the relative performance of various fans and fan speed settings against the system airflow resistance within FluxScale.

ebm-papst engineers then attached FluxScale to a calibrated wind tunnel.  The wind tunnel is designed according to AMCA210, a standard which establishes laboratory methods to assess the aerodynamic performance of fans. The principle of the chamber is to measure the differential pressure through an array of nozzles. The differential pressure, along with the geometry of the nozzles, is used to calculate a volumetric flow rate of the air moving through FluxScale. An auxiliary blower on the chamber is used to remove any pressure drop caused by the air flow chamber. This assures that FluxScale is being measured at its true operating conditions. Input power, current draw and fan speed are all recorded during the measurement. Subtle design changes were made to the FluxScale fan assembly to fully optimize performance.  

  Thermal image showing the LED array within FluxScale operating at full power, indicating effective and uniform cooling due to the low board temperatures and absence of a central hot spot in the middle of the LED array.

Thermal image showing the LED array within FluxScale operating at full power, indicating effective and uniform cooling due to the low board temperatures and absence of a central hot spot in the middle of the LED array.

The detailed analysis of fan selection, fan speed, and design for optimal airflow using these tools is a small part of the work GrowFlux has done to ensure optimal cooling of its LEDs. Effective cooling of LED emitters improves energy efficiency and longevity, allowing our customers to save more energy for a longer period of time.