Principal Thermal Mechanical Engineer

Flex•Littleton, MA

18h

About The Position

JetCool, a Flex company, develops liquid cooling solutions for AI and high-performance computing. The Principal Thermal Mechanical Engineer will be based in Littleton, Massachusetts, and will contribute to early product development and guide products through maturation. The role supports more sustainable data center infrastructure by enabling higher coolant temperatures and more complete heat capture. The engineer will provide technical leadership, mentorship, and hands-on expertise in mechanical design, fluid dynamics, and heat transfer. They will also work directly with customers to explain JetCool technology and build technical relationships. The role owns fluid and mechanical system work from concept through production, partnering with internal teams and external collaborators to deliver solutions that meet performance, reliability, manufacturability, and compliance needs.

Requirements

At least 7 years of experience designing and engineering fluid systems in data center thermal management and cooling, automotive, medical, or nuclear industries.
At least 3 years of direct experience with Coolant Distribution Units (CDUs).
Deep expertise in fluid dynamics, thermodynamics, and heat transfer, with strong application of first-principles engineering.
Proven new product development experience in thermal or fluid systems, including concept development, performance analysis, validation testing, and experimental design.
Strong analytical and problem-solving capabilities, including troubleshooting and optimizing complex fluid systems across development and production.
Demonstrated technical leadership in a structured product development environment, with ownership of mechanical design deliverables from concept through release.
Experience leading and mentoring development teams, setting technical direction, coordinating cross-functional efforts, and aligning work to product requirements and schedules.
Accountability for product-level mechanical execution, including leading design reviews, resolving technical risks, and ensuring performance, reliability, manufacturability, and compliance.
Strong communication and technical documentation skills, including the ability to explain complex concepts to technical teams and senior stakeholders.

Responsibilities

Lead the architecture, design, analysis, and optimization of fluid and thermal systems, including pumps, fluids, tubing, heat exchangers, and related components.
Own mechanical and fluid system deliverables from concept through production, ensuring performance, reliability, manufacturability, and compliance.
Partner with customers and external collaborators on system-level integration of fluid solutions into broader product architectures.
Lead simulation, analysis, and testing to validate fluid flow, pressure drop, thermal performance, and material compatibility across operating conditions.
Develop, review, and approve engineering requirements, specifications, and technical documentation in accordance with industry standards and regulatory expectations.
Lead and influence design reviews, presenting technical tradeoffs, risks, and recommendations to cross-functional teams, customers, and senior stakeholders.
Identify technical gaps and emerging challenges, advocate for research and development, and lead exploratory work that builds foundational knowledge and intellectual property.
Establish and promote best practices in fluid system design, analysis, and documentation, supporting continuous improvement and a strong engineering culture.
Mentor and guide engineers across experience levels and support their professional development.
Evaluate emerging technologies, industry trends, and alternative architectures to develop differentiated fluid system solutions.
Resolve complex technical issues through development, qualification, production, and field support as needed.