28MW NJ Data Center — Rooftop Chiller Plume Recirculation CFD
Rooftop chiller plume recirculation under NW wind. Public-source inputs. Screening-level.
What This Page Covers
This page presents a screening-level exterior CFD analysis of a rooftop air-cooled chiller and rooftop generator data center located in Clifton, NJ. The facility was designed by a national MEP engineering firm with a dedicated mission-critical practice. The analysis examines rooftop plume behavior — chiller exhaust dispersion, generator-yard interaction with the chiller array, and recirculation patterns — under a wind case that exposes the rooftop configuration's most demanding orientation.
Facility Context
The facts below are derived from public sources including public satellite imagery of the Clifton site. No proprietary drawings, specifications, or operational data are used.
Location. Clifton, NJ.
Owner-operator. A major colocation operator (facility originally developed for a regional carrier-neutral provider).
Building configuration. Two- to three-story shell with all heat-rejection equipment and standby generators positioned on the rooftop.
Cooling. Rooftop air-cooled chiller array. Visible per public satellite imagery as parallel V-coil banks across the long axis of the roof.
Standby power. Rooftop diesel generators. Generator enclosures are visibly taller than the adjacent chiller banks — an important geometry input for the wind analysis.
Surroundings. Adjacent industrial structures to the northwest of the building exceed the facility's roof height, creating a non-trivial upwind obstruction for northwesterly wind conditions.
Wind Case Modeled (Worst-Case Rooftop Recirculation)
Wind direction. 315° (NW).
Wind speed. 10 mph.
Operating scenario. N + R — all generators and all chillers running concurrently (full plant load).
Ambient. 108°F (high-end design summer day; bracketing the upper end of the chiller derate curve).
Why this case. Northwesterly wind combines two unfavorable geometry effects at this facility: (a) upwind taller buildings act as a windbreak that depresses local airflow over the chiller array, and (b) the rooftop generator enclosures, themselves taller than the chillers, further deflect what wind does reach the array. The model evaluates whether this combination is enough to drive chiller intakes into the temperature regime where the array's derate or shutdown setpoint is triggered.
Observed plume behavior
Two phenomena emerge from the model under the worst-case wind orientation. Both are screening-level qualitative observations from a public-source model; quantitative outputs — per-chiller intake temperature distributions, time-resolved recirculation magnitudes — are not published here. They are shared directly with the engineer of record on request. If you are interested in these results, please contact us.
Upwind obstruction creates a recirculation zone over the chiller array.
Under 315° NW wind at 10 mph, the rooftop generators and the neighboring industrial buildings — both taller than the chillers — act as a combined windbreak. Local airflow over the chiller bank deflects and recirculates rather than dispersing chiller exhaust downwind. The recirculation cell occupies the central portion of the chiller array.
Chiller exhaust recirculation to neighboring chillers.
Within the recirculation cell, flow patterns develop that pull one chiller's exhaust into adjacent chillers' intakes. Under the modeled ambient (108°F) plus full plant load, this is a condition that can drive chiller intake temperatures above ~130°F — the regime where shutdown setpoints engage on many commercial air-cooled chiller platforms. The number and position of affected units depends on the specific chiller bank spacing and generator-enclosure geometry, which would benefit from confirmation against the as-built drawings.
Methodology
The methodology applied here is the same standardized exterior CFD approach applied to every facility in the cohort — cylindrical far-field domain, logarithmic atmospheric boundary layer inlet, polyhedral mesh in Siemens STAR-CCM+, realizable k-ε RANS baseline, paired mass-flow/velocity boundaries on heat-rejection equipment. Full domain setup, boundary conditions, solver choices, and stated limitations are documented at the Methodology page. Core terms (recirculation, k-ε, ASHRAE design conditions, etc.) are defined at Key Terms and FAQ.
For the Engineer of Record
The full per-facility figure set — additional wind cases at 0°, 45°, 90°, 135°, 180°, 225°, 270°; per-chiller intake temperature distributions; and a one-paragraph quantitative summary — is available on request. We share these directly with the named engineer of record, not with building owners, operators, or other parties. Contact stewart@resolvedanalytics.com and reference this Clifton, NJ facility.
About the Author
Stewart Bible, Principal, Resolved Analytics. Resolved Analytics is a Computational Fluid Dynamics consulting practice and authorized Siemens STAR-CCM+ reseller, with a long-standing service line in mission-critical facility exterior analysis. Contact: stewart@resolvedanalytics.com.
Disclosure
This is independent research conducted by Resolved Analytics without engagement, sponsorship, or input from the building owner, operator, or MEP firm of record. All inputs are derived from cited public sources; no proprietary drawings, specifications, or operational data are used. Results represent idealized exterior conditions and do not represent the actual as-built performance of any facility. No claims are made regarding life-safety, code compliance, or operational performance. All firm and project references have been anonymized. This material is not engineering services rendered to any party.
Exterior CFD output for a Clifton, NJ data center under the worst-case rooftop recirculation scenario modeled: 315° NW wind at 10 mph, ambient 108°F, all generators and chillers operating at N+R. Surface coloring on the chiller intakes shows local intake temperature; red intakes are running at or above shutdown threshold.
Observation 1: Top-down streamline view above the chiller array. Upwind taller buildings and the rooftop generator enclosures combine to depress local airflow and form a recirculation cell over the central portion of the array.
Observation 2: Elevation view of the affected chiller bank. Surface coloring shows per-unit intake temperature; intakes shaded red are running at or above the ~130°F shutdown threshold from re-ingested neighbor exhaust.