Senior Mechanical Engineer - Thermal & Fluids Systems

MaC VC; Hawthorne (CA); On-site; USD 140,000 - 200,000; Full time

Benefits offered by this job

Equity options

Customer medical coverage 100%

Dental and vision coverage

Daily catered lunch

Team building outings

Job summary

Critical Energy is hiring a Senior Mechanical Engineer to lead thermal and fluid dynamics efforts for our geothermal power generation systems. You will own system-level modeling, 1D simulations, and integration of heat exchangers, turbines, pumps, and cooling loops.

Collaborate across Turbomachinery, Manufacturing, and Field Ops to optimize performance and reliability. Ideal candidates have 5+ years designing complex systems from concept to realization, strong fundamentals in thermodynamics, and

Qualifications

• Bachelor's degree in mechanical engineering or related field.
• 5+ years designing and building complex systems from 0 to 1.
• Strong fundamentals in fluid mechanics, thermodynamics, and materials.
• Experience with CAD and Siemens NX.
• Proven cross-functional collaboration across disciplines.

Responsibilities

• Define system requirements, interfaces, and performance budgets for thermal and fluid subsystems.
• Own system PFD and P&ID.
• Develop 1D models of thermo-fluid systems using commercial software or Python.
• Support system trade studies evaluating performance, efficiency, and cost impacts.
• Perform hand calculations to size components and estimate flow rates.
• Conduct CFD and thermal analyses to evaluate heat transfer and losses.
• Assist in test plan development and instrumentation strategies.
• Analyze experimental data to refine models and improve design.
• Support development of control strategies for thermal/fluid systems.
• Prepare design documentation and vendor relation materials.
• Collaborate with Field Ops for design feedback post-delivery.

Skills

Thermal modeling

CFD analysis

Python programming

Cross-functional collaboration

Education

Bachelor's degree in mechanical engineering

Tools

Siemens NX

Aspen

Dymola

ANSYS Fluent

Job description

Company Description:

Critical Energy is an innovative, early-stage, venture-backed cleantech company on a mission to accelerate the global energy transition through abundant, low-cost clean energy. Founded by an ex-SpaceX engineer, Critical Energy designs and manufactures factory-built, modular power plants. These rapidly deployable systems convert heat into electricity using a closed-loop thermodynamic cycle and can be installed in just weeks.

Critical Energy’s technology delivers high-efficiency, 24/7 power for geothermal applications and waste heat recovery (including from data center gas turbines), making clean energy practical and cost-effective for demanding sectors like AI hyperscalers and data centers. Backed by top climate and technology investors, Critical Energy is scaling rapidly.

Our Mission:

To build an abundant, low-cost, 100% clean energy future through groundbreaking geothermal innovation.

We are a team of passionate engineers, designers, and visionaries building cutting-edge solutions to meet the world’s energy needs with 100% clean energy. We are in the initial stages of development and building our team. This is your chance to join on the ground floor of something big! If you are ready to work at a fun, fast-paced, groundbreaking organization that is positioned to revolutionize geothermal energy.

About the Role:

We are seeking a versatile Senior Mechanical Engineer with experience in thermal and fluid dynamics to support the design, development, testing, and optimization of clean energy power generation systems. Collaborating with engineers across the company, this Mechanical Engineer will take ownership from cradle to grave and help drive the project through completion. This role focuses on system-level modeling, thermal management, and fluid flow analysis, primarily at the 1D level, across components such as heat exchangers, turbines, pumps, cooling & lubrication loops, and other balance-of-plant subsystems.

The ideal candidate will bridge system architecture, physics-based modeling, and product development, ensuring industry-leading performance, reliability, and integration of complex energy systems.

Responsibilities:

• Define system requirements, interfaces, and performance budgets for thermal and fluid subsystems

• Own system PFD and P&ID

• Develop sub-system and system-level models to calculate steady, transient, and off-design thermal and fluid behavior using commercial analysis tools or in-house tools (e.g., Python code)

• Support system trade studies evaluating performance, efficiency, and cost impacts

• Support the integration of components including heat exchangers, pumps, fluid management systems, piping networks, and other auxiliary and support systems

• Perform hand calculations using first principles to size components, determine flow rates, estimate component and system efficiency, etc.

• Perform CFD and thermal analysis to evaluate heat transfer, pressure losses, flow distribution, and efficiency

• Identify, outline, and support component-level and sub-system testing required for risk mitigation

• Assist in the development of test plans and instrumentation strategies to validate thermo-fluid performance

• Analyze experimental data to refine models and improve system design

• Support development of control strategies related to thermal and fluid system performance

• Generate technical documentation including system specifications, modeling reports, design trade studies, test analysis reports

• Develop and manage relationships with third-party vendors

• Support Field Ops teams with technical expertise and advice after product delivery and accept feedback on possible design improvements

• Other related tasks as defined by your supervisor that add value to the design needs

Required Qualifications:

• Bachelor's degree in mechanical engineering or related field, or equivalent experience

• 5+ years of proven experience designing and building complex systems from 0 ->1 with a strong portfolio of projects involving diverse and integrated machinery

• A solid understanding of and the ability to apply first principles of core mechanical engineering principles, including fluid mechanics, thermodynamics, and material science as it pertains to system sizing and modeling

• Experience with a modern CAD package and a willingness to immediately self-teach proficiency in Siemens NX

• Excellent analytical and critical thinking skills

• Working cross-functionally with Turbomachinery, Supply Chain, Manufacturing, Field Ops, and others.

Basic Experience:

• Experience with components and sub-systems common to power generation or process plants, like heat exchangers, pumps, turbines, valves, piping, fittings, sensors, and fluid management systems

• Understanding of thermodynamic cycles (e.g., Rankine, Brayton)

• Experience generating 3D models and managing assemblies in CAD while ensuring proper fit and function

• Building 1D models of thermo-fluid systems using commercial software (e.g., Aspen, Dymola)

• Proven experience using Python or another coding language to build thermal and/or fluid models

• In-depth knowledge of the design and operation of heat exchangers and how to select the appropriate type for a given application

• Understanding of the applicable codes, compliance, and regulations pertaining to development, deployment, and commissioning processing or power generation hardware

• Experience with computational fluid dynamics (CFD) using commercial software (e.g., ANSYS CFX, ANSYS Fluent, Numeca)

• You have worked with other engineering disciplines (such as Aerodynamics, Turbomachinery, Dev Test, Materials, and Manufacturing) to optimize designs for performance, reliability, and manufacturability

• You are effective and respectful in communicating with other engineers even when it is controversial or regarding errors that you have observed or have been observed in your work

• Experience creating and maintaining comprehensive design documentation including design reviews and component and system specifications

Bonus Experience:

• Experience specifically with power generation or process plant systems is not a requirement but is a significant bonus.

• Proven expertise in Siemens NX / Teamcenter environment

• Experience with finite element analysis (FEA) for static structural, vibration, and fatigue using commercial software (e.g., ANSYS Mechanical, NASTRAN, Catia)

• Hands-on experience with product development, such as resolving manufacturing issues and analyzing test data to inform design modifications

Compensation:

• Base salary ranges from $140-200k per annum

• Equity options

• 100% company-covered Platinum or HD/HSA (with company contribution) medical

• 100% company-covered dental and vision

• Daily catered lunch

• Several annual social and team building outings

Actual base salary offered will be determined by: experience, skills, and work location. This range is for base salary, our total compensation includes equity and benefits.

Critical Energy is committed to creating a diverse environment and is proud to be an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, gender, gender identity or expression, sexual orientation, national origin, genetics, disability, age, or veteran status.

Critical Energy is committed to providing reasonable accommodations for qualified individuals with disabilities in our job application procedures and throughout employment. If you need assistance or any accommodation, please let us know.