Case study by Dr.Azhar Iqbal Sabri

profile HVAC/R ENGINEERING

YORK Puts the Air in Miami International Airport ®

had to be notched out to accommodate a column that was part of the building. In those cases, we actually built the AHUs around columns.”

Meeting NC40 Sound Criteria

Miami International Airport’s multi-billion dollar capitalimprovement program includes a major HVAC installation.

Miami International Airport is in the midst of a $5.4 billion capital-improvement program. Scheduled for completion in 2007, the five-year project includes the addition of a fourth runway and a new concourse that will increase by 55 percent the 4.7 million square feet of existing space. This will boost airport capacity to 48 million passengers annually.

Increased Cooling Demand To meet increased cooling demands within the expanded concourse, plans called for the installation of 24 new air-handling units (AHUs) ranging in capacity from 75,000 to 125,000 CFM, for a total capacity of 2.2 million CFM. Each unit needed to meet strict sound criteria of NC40, and utilize dual supply fans so that a minimum of 70 percent airflow was produced, even if one fan was off-line because of service or failure. To date, 18 mechanical rooms have been approved and built, and each houses a YORK® custom AHU. According to Victor Baumzweig, YORK zone sales manager, none of the 18 rooms are alike. “Each room presented footprint constraints that YORK needed to address with the unit we supplied. In fact, some of the units

Just as unusual footprint constraints demanded the attention of YORK engineers, so did the airport’s exacting specifications for thermal and sound performance. According to Tony Spohn, senior YORK project manager, the airport required AHUs to meet NC40 sound criteria in order to ensure effective operation of the public-address system and provide acceptable sound levels in the office spaces used by airport-operations staff. “Normally, this would not be a difficult sound level to achieve,” said Spohn. “But, in this particular case, when you couple the space constraints with the large size of the AHUs, meeting the NC40 requirement presented another unique challenge for us.” YORK met the challenge with its exclusive P91 plenum fan. Its fully welded, all-aluminum wheel is aerodynamically designed and tested. Each extruded blade is precisely positioned within the wheel, ensuring quiet and predictable performance. To minimize vibration noise, the fans are mounted on a welded (not bolted) and isolated steel base. Direct-drive of the fans further reduces vibration by eliminating the beltand-pulley mechanism. “The fan is so quiet,” remarked Spohn, “that it has been used for years in clean rooms where low sound and vibration levels are critical.” In addition to sound benefits, the P91 fans also offer design benefits that the originally specified vane-axial fans cannot. “This project required 13 AHUs to be built around a structural corner notch in the building,” explained Spohn. “Because vane-axial fans

require uniform air inlet conditions in order to properly load the fan blades and prevent destructive vibrations within the blades, it would have been very expensive and somewhat risky to accomplish uniform inlet loading on the notched units using vane-axial fans. The P91 plenum-type fans eliminated that risk.”

P91 Fan Flexibility

In order to meet Miami International Airport’s increased cooling demands within the expanded concourse, plans call for installing 24 new airhandling units, like the one shown above.

According to Matthew Shaub, YORK marketing manager, the P91 plenum fans also offered installation advantages. “The vane-axial fans required extensive customization to accommodate dual supply fans. With the P91 plenum fans, both supply ducts are supplied, whether one or both of the fans is operating, making the installation of ductwork easier and less costly.” Specifications also required the AHUs produce a minimum of 70 percent airflow, regardless of failure or service to either the motor or fan. The YORK P91 plenum fans met this requirement as well. “By demanding a minimum of 70 percent of airflow from the system rather than the normal 50 percent,” explained Spohn, “the airport is in a position to cover itself in the event of a single fan’s failure. With twin fans, if one fan is down for repair, the remaining fan can be ramped up to provide an additional 40 percent of its airflow, which is 70 percent of the original design total, and that’s important here. These large AHUs provide air-conditioning for a large indoor environment, where a tremendous amount of air-travel business takes place. If one of these high-capacity units is off-line for repair, a good bit of business is affected, especially in the sub-tropical conditions of Miami.” Complementing the twin-fan system is the P91 Econo-Disk™. The Econo-Disk, located

Tele. 800-861-1001 www.york.com

in the inlet of each P91 fan, safely isolates the inactive fan from the backdraft airflow caused by the adjacent operating fan, in the event of a fan or motor failure. YORK’s patented P-Cone airflowmeasurement system, also available on the P91 fan, offered additional advantages to the Miami Airport project. The airport expansion includes a building automation system (BAS) that monitors air volume and reports motor and fan failures, often indicated by fluctuations in airflow. The P-Cone system provides an accurate, quiet and affordable method to measure airflow. Unlike traditional transverse airflow-measurement stations that increase noise and reduce airflow when placed in a fan’s inlet cone, the P-Cone has no impact on noise levels or airflow, and it measures inlet airflow with more than 98 percent accuracy.

Passing Performance Tests As part of its contract with the airport, YORK was required to conduct a fully operational performance test of its AHUs, witnessed by representatives from American Airlines, TurnerAustin Airport Team (the construction manager) and William A. Barry Associates (the consulting engineer). YORK built an entire AHU, mounted it on a test stand and put the unit through its entire operational spectrum, measuring the amount of sound the unit emitted and its airflow performance. The unit was tested in conditions simulating the airport site, with return-air, outside-air and supply-air ducts connected. Sound-baffle walls were used to measure the sound coming off these openings. “We hit every sound test within 1 decibel of where we needed to be,” Shaub recalled. “And we adhered to a very stringent shipping schedule,” added Baumzweig. “A unit of this size usually has a substantially long lead-time to fabricate and ship. We had to meet a much shorter lead-time in order to accommodate construction schedules, and we did.” YORK designed and delivered, on-time, custom AHUs that met strict space, airflow, and sound requirements. When construction is complete, these same units will provide quiet, dependable comfort to passengers and airport employees throughout the new facility.