Sr. 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.

Job Summary

Job Description

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 leads thermal-fluid architecture, product requirements, advanced modeling, and performance optimization across multiple liquid-cooling programs. This individual serves as a system-level subject-matter expert and provides technical direction to other thermal engineers.

What a Typical Day Looks Like

• Lead thermal-fluid architecture and system-performance development across multiple programs.
• Own thermal, hydraulic, environmental, controls, and operating requirements.
• Maintain system specifications, interface requirements, and requirements traceability.
• Develop and review 1D models using MacroFlow and 3D CFD and conjugate heat-transfer models using Cadence Celsius EC.
• Model flow distribution, pressure drop, pump operating points, heat rejection, and component temperatures.
• Lead component sizing and selection for pumps, radiators, heat exchangers, manifolds, tubing, and related hardware.
• Define operating envelopes, design margins, controls requirements, and acceptance criteria.
• Establish model-to-test correlation strategies and resolve discrepancies between predicted and measured performance.
• Lead thermal-fluid risk-retirement activities and support prototype testing and troubleshooting.
• Participate in architecture reviews, PDRs, CDRs, FDRs, and production-readiness reviews.
• Communicate assumptions, uncertainty, limitations, and residual risks to leadership.
• Mentor thermal engineers and support customer, supplier, and manufacturing activities.
  
  

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

• Bachelor’s degree in engineering or equivalent practical experience.
• Typically 8 years of thermal-fluid analysis and hardware-development experience.
• Advanced knowledge of thermodynamics, fluid mechanics, heat transfer, pumps, and heat exchangers.
• Strong experience with 1D system modeling, CFD, conjugate heat transfer, and test correlation.
• Experience developing product requirements, system architectures, and operating envelopes.
• Strong hands-on testing, instrumentation, and troubleshooting capability.
• MacroFlow, Cadence Celsius EC, datacenter, or liquid-cooling experience strongly preferred.
• System architectures meet requirements with appropriate design margin.
• Models effectively guide architecture, component selection, and controls.
• Predictions correlate with physical testing.
• Thermal risks are identified and retired early.
• Technical mentorship improves the team’s overall systems capability.
  
  

BO18

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
  
  

Application Deadline

Applications for this job position will be accepted for at least five days following the job posting start date below and continuing until the end date below or until the position is filled. This posting may close sooner due to application volume.

Job Posting Start Date 09-18-2026 Job Posting End Date 11-27-2026

The base pay range for this position is provided below. The final base rate offered will be determined using job-related, non-discriminatory criteria, including but not limited to experience, qualifications, geographic location, education, external market data, and internal equity.

$126,500.00 USD - $173,900.00 USD Annual

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. Please email accessibility@flex.com and we'll discuss your specific situation and next steps (NOTE: this email does not accept or consider resumes or applications. This is only for disability assistance. To be considered for a position at JetCool, you must complete the application process first).