Sr. Thermal Systems Engineer

Senior Thermal Systems Engineer

At JetCool, a Flex company, we're at the forefront of liquid cooling innovation, delivering advanced solutions that empower our partners in AI and high-performance computing. United by a shared purpose, our teams are pushing the limits of what's possible and tackling complex challenges.

A career at JetCool offers the opportunity to make a real impact by helping build smarter, more sustainable data centers. Together, we're not just advancing technology we're redefining cooling standards to create a more sustainable tomorrow.

To support our extraordinary teams who build great products and contribute to our growth, we're looking to add a Senior Thermal Systems Engineer located in Littleton, MA.

Reporting to the Product Manager the Senior Thermal Systems Engineer will own the end-to-end architecture, analysis, validation, and deployment of direct-to-chip (D2C) cooling systems used to cool high-TDP CPUs/GPUs/accelerators. They will be the technical leader partnering with Product Management, Mechanical/Electrical Engineering, Manufacturing, Quality, Reliability, and key customers to deliver robust, scalable products that meet performance, reliability, and cost targets.

What a typical day looks like:

Own thermal architecture & modeling

• Define system-level thermal requirements (TDP range, ?T, coolant temperature, flow rate, pressure drop, acoustic & power budgets).
• Apply first principles in fluid dynamics and heat transfer to analyze design concept thermal performance
• Build and validate 1D/3D models (e.g., FloEFD, Icepak, MacroFlow, ANSYS Fluent, COMSOL) for cold plates, manifolds, quick-disconnects (QDs), pumps, and CDUs.
• Perform sensitivity trade-offs (flow distribution, fin geometry, microchannel optimization, TIM selection, manifold topology).

Design liquid cooling subsystems

• Specify and refine cold plates, CDUs, manifolds, hoses/QDs, reservoirs, filters, sensors, and controls.
• Collaborate with ME/EE on mechanical stack-up, materials, corrosion mitigation (galvanic compatibility), and leak risk reduction.
• Define DFX (DFM/DFA/DFT) and lead EVT/DVT/PVT from prototypes to mass production.

Validate and qualify

• Develop test plans for thermal performance, pressure integrity, leak detection, long-term reliability (HALT/HASS), and contamination control (particulates, biogrowth).
• Execute lab and rack-scale testing (pump curves, flow balance, ?P mapping, heat load emulation, transient behavior).
• Drive failure analysis and corrective actions (FMEAs, 8D/PPS).

Partner across the business

• Work with Product Management on PRDs, roadmaps, and business cases.
• Support manufacturing process development (leak/pressure test stations, purge and fill, cleanliness criteria) and supplier selection/qualification.
• Engage with customers: define requirements, run pilots, analyze fleet telemetry, and support deployment at scale.

The experience we're looking to add to our team:

• BS/MS in Mechanical Engineering or Aerospace Engineering or related field (PhD a plus).
• 5+ years experience in thermal design/validation for high-power electronics (preferably data center/server/HPC).
• Excellent first principles knowledge in fluid dynamics, thermodynamics, and heat transfer
• Proven expertise in liquid cooling, including CFD, pressure drop/flow modeling, and thermal metrology.
• Hands-on with lab instrumentation (flow meters, pressure transducers, thermocouples/RTDs, DAQ, leak detectors) and test automation (Python, LabVIEW, or similar).
• Experience bringing products from EVT ? DVT ? PVT ? ramp, including DFX and supplier engagement.
• Excellent technical communication and documentation skills.

What you'll receive for the great work you provide:

• Full range of medical, dental, and vision plans
• Life Insurance
• Short-term and Long-term Disability
• Matching 401(k) Contributions
• Vacation and Paid Sick Time
• Tuition Reimbursement

Job Category: Design, Process & Technology Engineering

Is Sponsorship Available? No

JetCool is an Equal Opportunity Employer and employment selection decisions are based on merit, qualifications, and abilities. We do not discriminate based on: age, race, religion, color, sex, national origin, marital status, sexual orientation, gender identity, veteran status, disability, pregnancy status, or any other status protected by law. We're happy to provide reasonable accommodations to those with a disability for assistance in the application process. To be considered for a position at JetCool, you must complete the application process first.