Principal Mechanical Engineer - Liquid Cooling

Job Posting Start Date 09-12-2025 Job Posting End Date

Flex is the diversified manufacturing partner of choice that helps market-leading brands design, build and deliver innovative products that improve the world.

A career at Flex offers the opportunity to make a difference and invest in your growth in a respectful, inclusive, and collaborative environment. If you are excited about a role but don't meet every bullet point, we encourage you to apply and join us to create the extraordinary.

Job Summary

JETCOOL Technologies, a Flex company, is seeking a Principal Mechanical Engineer to add to our team in Littleton, MA . Join us in shaping the future of data centers while making a significant impact on sustainability. Apply now to be part of our dedicated team of engineers and thinkers!

JetCool has a mission to continuously innovate next-generation cooling solutions to enable the devices that fuel a more sustainable tomorrow. JetCool designs and delivers microconvective cooling® technology for high-power electronics, enabling our customers to achieve unprecedented performance and unrivaled sustainability improvements. Our technology creates a ripple effect, enabling the businesses we serve to become more sustainable, profitable, and efficient. Join us to be part of some of today's fastest growing industries, while having a positive impact on society through technology.

What a typical day looks like:

• Lead the initial design, analysis, and optimization of complex fluid systems, including pumps, fluids, tubing, and heat exchangers, for the latest computer processing chipsets.
• Collaborate with customer and partner teams to integrate fluid systems into overall product designs.
• Conduct fluid flow simulations, analyses, and tests to ensure efficient and reliable performance of fluid systems under various operating conditions.
• Perform detailed calculations and analysis of fluid dynamics, pressure drops, thermal performance, and material compatibility.
• Develop and review engineering specifications and documentation for fluid system and heat transfer components and assemblies, ensuring compliance with industry standards and regulatory requirements.
• Assist in maintaining a strong best practice culture, driving additional foundational knowledge and IP through research.
• Identify technical gaps to advocate for research & development and lead research projects, maximizing product impact and benefit.
• Provide technical guidance and mentorship to junior engineers, fostering a culture of continuous learning and development.
• Participate in design reviews, presenting technical findings and recommendations to internal and external stakeholders.
• Contribute to the development of new product concepts and innovations in fluid system design, keeping abreast of industry trends and emerging technologies.
• Support the resolution of technical challenges and issues related to fluid systems throughout the product lifecycle.

• Bachelor of Science degree in Mechanical Engineering or related field.
• Minimum of 7 to 10 years of post-collegiate experience, with 4+ years in designing and engineering fluid systems, preferably within the data center thermal management/cooling, automotive, medical, or nuclear industries. Minimum of 3 years working at senior or principal engineer level.
• Profound expertise in fluid dynamics, thermodynamics, and heat transfer, with a strong foundation in engineering principles.
• Ability to independently develop product concepts, performance analysis and design experiments. Track record of new product development, preferably thermal fluid products.
• Strong analytical and problem-solving skills, with the ability to effectively troubleshoot and optimize fluid system performance.
• Excellent communication and documentation skills to convey complex technical concepts to both technical and non-technical audiences.

• 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