By Philip Qvarnstrom
When the University of Massachusetts Medical School unveiled its $400 million, state-of-the-art Albert Sherman Center in early 2013 on its Worcester, MA, campus, it was said that it would allow the school to “enter a new era of biomedical research, medical education and campus collaboration.” That final word — collaboration — would also play a prominent role in how the 11-story, 512,000 square foot building would be cooled during the warm and humid summer months that are quite common in the state.
That collaborative effort was driven by the needs of the University of Massachusetts Building Authority, which was responsible for the operation of the building’s cooling system, and the ability of Konvekta AG, a St. Gallen, Switzerland-based developer and provider of high performance, energy recovery systems, to meet those needs.
“When we opened the Sherman Center, we knew we would have to add cooling capacity and someone recommended Konvekta,” recalled David MacNeil, senior mechanical project manager for the Department of Facilities Management at the UMass Medical School. “We looked at their system and we liked what we saw.”
Brazed Plate Heat Exchanger Technology Chosen
In order to ensure that the Sherman Center was properly cooled when temperatures and humidities would inevitably reach summer extremes, Konvekta determined that it would need to install two dedicated air handling units for use by the facility. After reaching that determination, the next step for Konvekta was to decide which type of heat exchanger to use to properly recover the heat that would be generated during the periodic operation of the two air handling units.
In the end, Konvekta chose to outfit the units with brazed plate heat exchanger (BPHE) technology.
The design of BPHEs is what helps set them apart when compared to the performance of competitive technologies, such as gasket plate heat exchangers (GPHE). BPHEs are constructed as a plate package of corrugated channel plates that have a filler material between each plate. During the plates’ vacuum-brazing process, the filler material forms a brazed joint at every contact point between the plates, creating channels through which the media will flow. This also allows media at different temperatures to come into close proximity and enables heat or cold from one media to be transferred to the other in a highly efficient manner.
The concept is similar to other plate-and-frame heat-exchanger technologies, but without the need for gaskets and frame parts that can fail and leak, leading to potentially high cleanup, maintenance, and replacement costs.
Other advantages that BPHEs can offer in cooling applications include compact size; more efficient operation; installation flexibility; self-cleaning operation; lower life cycle cost; and the ability to be customized for the needs of an installation.
Simon Buehler, sales manager for Konvekta, recommended BPHEs for the air handling units, and specifically suggested BPHEs from SWEP, a Sweden-based supplier of BPHEs for use in the HVAC and industrial markets.
“Our business relationship with SWEP began many years ago in Germany,” said Buehler. “Today, SWEP is our main supplier of BPHEs. SWEP has an excellent SWEP Software Package (SSP) calculation platform that makes it very easy for out engineers to select the right BPHE for the project.”
In the case of the air handing units at the Sherman Center, Buehler and Konvekta recommended a pair of B50H BPHEs be installed. The B50H models were the best choice because SWEP has designed them to be used in demanding applications. With three different plate combinations and 2.5” (63.5 mm) connections, they are an ideal solution for high-volume applications that can require flow rates of as much as 56 m3/hr (246 gpm).
“SWEP B-type heat exchangers are able to optimize the use of energy, material, and space in cooling systems,” said Buehler. “They are compact, cheap when compared to other solutions, durable and have high heat-transfer performance. The B50H model is also perfect for operations with low pressure drops, high flows and where the temperature difference between the two media is typically very small. At the Sherman Center, the temperature difference between the cooling-water inlet and water/glycol outlet is only 4ºF.”
BPHE In Operation At UMass
The SWEP BPHEs began operating in conjunction with the air handling units for the Albert Sherman Center on the UMass Medical School’s campus in mid-2015 and, according to MacNeil, have performed without a hitch in the ensuing 16 months.
“We really only need them when it’s really hot out, those days when it’s 97° and humid, that’s when we get the supplemental cooling we need from the BPHEs,” said MacNeil. “They’re so simple and work well; you just install them and you very rarely have any issues. They definitely meet our needs.”
Qvarnstrom is the project development manager for SWEP North America, Inc., located in Tulsa, OK. Founded in 1983 and acquired by the Dover Corporation in 1994, SWEP is a supplier of brazed plate heat exchangers (BPHEs) for use in HVAC and industrial applications. SWEP’s North American sales network is headquartered in Duluth, GA, with the manufacturing center located in Tulsa.