Senior Mechanical Systems Engineer

Senior Systems Engineer – Mechanical

Fleet Data Centers designs, builds and operates mega-scale data center campuses. Fleet provides its customers flexibility and predictability to meet their upside demand forecasts, addressing a key need in the market as traditional leased models are struggling to keep pace with the demand for new Cloud and AI infrastructure. Fleet is led by a team of industry veterans that have already made a lasting imprint on the evolution of global digital infrastructure and are committed and uniquely capable of upleveling data center development scale and operations in the face of rising demand. Fleet is well positioned to bring in-house design, engineering and operational capabilities to collaborate with customers on tailored solutions for campuses of 500MW+. This unique model enables Fleet to provide the world's largest and most sophisticated customers a seamless extension of their own data center fleets with constant access to design innovation. Fleet is headquartered in Denver, Colorado, with satellite offices in Seattle, WA and Arlington, VA.

Position Overview:

We are seeking a Senior Systems Engineer – Mechanical to own the detailed design validation, analysis, and ongoing optimization of Fleet's data center cooling topology from campus level through the rack. This role requires a deep understanding of Fleet data center cooling topology, including air-side and liquid-side systems (fan walls, CRAHs/CRACs, chillers, dry coolers, pumps, heat exchangers, distribution manifolds, in-rack cooling components), and how these components interact under a variety of operating and failure scenarios.

The ideal candidate will pair strong mechanical engineering fundamentals with practical data center cooling experience, ensuring that the air-to-liquid mix and cooling configuration for each deployment match rack layouts and rack SKUs, that CFD and failure-mode simulations are routinely used to de-risk deployments, and that cooling system behavior is well understood and systematically improved. This role is accountable for end-to-end thermal system integrity, including aisle-level optimization, fan wall octet configuration, failure-mode simulations (e.g., CRAC outage, dry cooler outage), and impact assessment for infrastructure upgrades and expansions, with the goal of optimizing uptime SLAs and minimizing cooling stranding.

We have a hybrid policy, and candidates can sit in Seattle, WA, Denver, CO, Austin, TX, or Alexandria, VA

Responsibilities:

• Cooling Topology Ownership & Rack-Level Alignment:
• Develop and maintain a deep understanding of Fleet data center cooling topology, including air-side systems such as fan walls, CRAHs/CRACs, air handlers, ducting, containment, and filters
• Develop and maintain a deep understanding of liquid-side systems including chillers, dry coolers, pumps, CDUs, heat exchangers, headers/manifolds, and valve trains
• Develop and maintain a deep understanding of rack-level solutions including liquid-cooled cold plates, rear-door heat exchangers, in-rack manifolds, and hybrid air/liquid configurations
• Determine the air-to-liquid mix needed to support a given rack layout and density, considering rack SKUs, aisle configuration, containment, and site constraints
• Ensure cooling topology and capacity at room and aisle level support current and forecast rack deployments and density targets
• Rack SKUs, Cooling Requirements & Data Accuracy:
• Understand the air and liquid cooling requirements for each rack SKU, including inlet temperature and humidity ranges
• Understand liquid flow, pressure, and temperature ranges for cold plates and rear-door heat exchangers
• Maintain structured mapping from rack SKUs to required airflow per rack and aisle
• Maintain structured mapping from rack SKUs to required liquid flow per rack, manifold, and loop
• Maintain structured mapping from rack SKUs to special constraints such as mixed air and liquid aisles and maximum delta T
• Ensure specifications and counts for cooling components including fan wall modules, CRAHs/CRACs, CDUs, pumps, valves, manifolds, piping sizes, and coils are accurate, documented, and provided to capacity planning and procurement
• CFD & Thermal Analysis:
• Perform CFD analysis at room and aisle level to validate that planned rack placement does not create hot spots
• Perform CFD analysis to confirm that airflow patterns, pressure profiles, and temperature distributions are within allowable limits
• Identify and mitigate cooling stranding where cooling capacity exists but cannot be effectively delivered to IT load because of placement or topology
• Use CFD and thermal modeling tools to evaluate different rack arrangements and containment strategies
• Use CFD and thermal modeling tools to test sensitivity to changes in IT load, fan speeds, supply temperatures, and air-to-liquid mix
• Quantify margin to thresholds such as maximum rack inlet temperature and maximum component temperatures
• Translate CFD results into actionable design rules, placement constraints, and deployment guidelines for capacity planners and operations
• Aisle-Level Optimization & Fan Wall Configuration:
• Optimize cooling for each aisle based on actual and forecasted IT load distribution
• Optimize cooling based on air-to-liquid split for the racks in that aisle
• Optimize cooling based on containment strategy including cold aisle, hot aisle, full containment, and partial containment
• Recommend fan wall octet configurations and other fan wall module configurations per deployment
• Ensure configurations deliver required airflow and pressure with redundancy
• Maintain redundancy and margin for failure and maintenance scenarios
• Minimize energy use while maintaining thermal headroom
• Work with operations to tune setpoints including supply temperatures, fan speeds, differential pressure, and chilled water temperatures to support uptime SLAs and reduce cooling stranding and over-provisioning
• Failure Mode Simulations & Uptime Optimization:
• Conduct failure mode simulations and analyses for mechanical systems including CRAC/CRAH outage scenarios, dry cooler outage scenarios, and pump or valve failures
• Evaluate transient and steady-state temperature excursions at the rack and component level
• Evaluate time-to-threshold for safe temperature limits
• Evaluate impact on redundancy, load shedding requirements, and achievable uptime
• Recommend design improvements such as additional redundancy, loop segmentation, and capacity rebalancing
• Define operational responses and MOPs including load shedding priorities and setpoint changes
• Optimize uptime SLAs while minimizing cooling stranding, especially in mixed air and liquid deployments and high-density aisles
• Infrastructure Upgrades & Expansion Impact Analysis:
• Lead or support infrastructure upgrades and expansion impact analyses for cooling systems including adding or resizing fan walls, CRAHs/CRACs, dry coolers, chillers, pumps, CDUs, and distribution headers
• Support increasing liquid cooling fraction as AI-heavy racks grow in share
• Support changing setpoints or operating modes including supply temperatures and economization strategies
• Quantify effects on current and future thermal capacity and headroom
• Quantify changes in aisle-level and room-level airflow and liquid flow distribution
• Quantify impact on PUE, water usage, and operating costs
• Provide mechanical engineering input into MOPs and risk assessments for any cooling system change that could impact live IT load
• Cross-Functional Collaboration & Documentation:
• Partner with capacity planners, rack design teams, site operations, facilities engineering, and procurement to ensure alignment between cooling design, deployment plans, and SLAs
• Ensure air-to-liquid decisions are integrated into forecast models and program timelines
• Produce and maintain design guides, reference one-lines, piping schematics, and airflow diagrams for baseline data halls and high-density deployments
• Contribute mechanical content to internal standards and playbooks covering cooling topology design rules, CFD methodologies, and failure simulation procedures

Required Qualifications:

• Bachelor's degree in Mechanical Engineering or a closely related engineering discipline
• 6+ years of experience in data center mechanical engineering, mission-critical HVAC design, or thermal systems engineering
• Demonstrated deep understanding of data center cooling topologies including air-cooled and liquid-cooled architectures
• Hands-on experience performing and interpreting CFD analysis for data