Let’s Talk about Smart Air Valves
We’ve all heard the saying that “If at first you don’t succeed, try, try again.” Inspirational advice. But on the other hand, performing the same function repeatedly — while expecting different results every time — might just indicate insanity. And many mechanical/HVAC engineers are doing just that in their approaches to airflow.
Let me explain. Consider that most of our clients identify the following goals for their design teams:
- Decarbonize the building construction.
- Reduce carbon emissions from operations.
- Improve sustainability and energy performance.
- Design for current or future electrification.
- Improve speed to market.
- Reduce unexpected costs/variance to budget.
- Support health and wellness within a space.
- Improve flexibility of space.
- Improve experience of space for employees, students, patients, staff, etc.
In order to achieve these goals, HVAC engineers have flexed to include heat pumps, energy recovery, displacement ventilation, demand-controlled ventilation and other design strategies. However, the baseline components, decision-making, and sizing strategy around air distribution have remained the same for decades.
More specifically, airflow control technology has been limited to use of either differential pressure measurement, vortek shedding, thermal dispersion, or factory calibrated springs/cones in venturi valves. Airflow control capability is described in terms of “turndown,” or device maximum controllable flow divided by device minimum controllable flow. These devices have yielded 4-1, 8-1, 10-1, and maybe 16-1 turndown with increases in pressure drops, energy costs, installation costs, and, in many instances, lead times as we increase the turndown capability.
Regardless of the device, the design is the same. A branch duct is funneled into an air valve with a transition. Air is measured and controlled and routed through a vertical reheat coil, then transitioned to the branch duct again, many times through a sound attenuator. By the way, all of these control devices are round in geometry while the majority of our ductwork is rectangular.
It’s time to rethink and simplify all of this. First, let’s design a rectangular airflow-control valve. Eliminate transitions, cost and associated pressure drops. The rectangular inlet condition allows us to re-orient the reheat coil to the upstream side of the airflow control valve. Let’s also change the angle of the reheat coil and increase the surface area for heat transfer without incurring additional air-side pressure drops.
Potential performance results:
- Reduction in overall length of airflow control valve
- Improvement in airflow reading by using the coil as a flow-straightening device
- Reduction in construction cost of pressure drop of transitions
- Potential reduction in supply water to hot water reheat by improving heat capacity of coil without Increasing air-side pressure drops
- Decrease in the number of rows of reheat coil, reducing air-side pressure drops
Second, let’s incorporate new flow measurement and control technology into the VAV market. New technology is being introduced to the VAV market that allows for 100-1 turndown in airflow capacity control, utilizing variable-orifice-flow technology versus today’s traditional differential pressure and static-flow coeffiecient-based technology. These new air valves are being marketed as “Smart Air Valves.” Their benefits are a “one-size-fits-all” approach to airflow control. Additional benefits include:
- Improved airflow flexibility
- Reduced lead times
- Reduced construction and installation cost
- Reduced time and cost risk
- Reduced installation mistakes and rework
- Reduced balancing and commissioning time
- Removed transitions and sound attenuation
Concerning the reduction in lead times, this smarter VAV box also eliminates on-site labor constraints and your supply chain issues as well. Check our previous post about it.
Other results, and more important to the operating needs of our clients, include the ability to make the HVAC system more flexible and supportive of the smart-office, smart-lab and smart-healthcare needs present in the market today. Smart offices are designed to improve employee productivity and experience. Productivity gains, as seen in many studies, stem from improved indoor air quality, which is many times at odds with energy cost. However, new smart building technologies allow buildings to know precisely how many occupants are in any given area. But how many HVAC systems can turn up or down enough airflow to each area to accommodate this smart building capability?
Smart healthcare systems are focused on enhancing patient experience and patient outcomes. The pandemic clearly showed the market the need to have inherent airflow flexibility to change room use cases. 100-1 turndown smart air valves provide this inherent flexibility for future adaptability. In addition, patient experience is impacted by perception of noise. Smart air valves provide the ability to reduce noise below code requirements without the use of terminal unit sound attenuation. More importantly, smart air valves can positively impact patient outcomes when employed in ORs throughout perioperative care. Surgical staff comfort can be accommodated while automated smart healthcare routines can utilize additional heating capacity of diagonal coils and low-pressure-drop air valves with 100-1 turn-up capability.
Smart air valves also enable more flexible laboratory design. Spaces can be controlled with low flow today and inherent flexibility to add VAV hoods in the future due to the 100-1 capacity of control capability within the smart air valve. Decarbonizing laboratory design also requires the use of intelligent systems to actively determine proper ACPH setpoint on a per lab basis, based upon dynamic air-quality measurement. Smart-lab sensing systems need more flexible HVAC control than is on the market today with traditional components. Smart air valves provide this flexibility with no impact to fan pressure requirements.
Few clients ask us to use VAV boxes, Venturi Valves, or bladder/dual blade dampers. But our clients do require more cost-effective designs that require less energy to operate, require zero direct carbon-based energy into the building, and have a positive effect on the building occupants. Smart air valves enable us to accomplish these goals. Let’s use these tools to stop the insanity – and instead come up with solutions that are insanely good.
Written By Richard Nowak