Research

Research Fields

AI Semiconductor Cooling

Connecting bubble dynamics and surface structure to cooling limits.

Two-phase immersion cooling removes chip heat through boiling in a dielectric fluid. We study how surface structure and orientation affect bubble dynamics and critical heat flux (CHF).

Two-phase immersion coolingStudying boiling heat removal and chip cooling limits.
Boiling and rewetting on a chipStudying bubble growth, departure and liquid replenishment to understand cooling limits.

From test facilities to bubbles and surfaces

Pool boiling facility
Pool boiling facility

Measuring boiling performance under changing heat loads

Dielectric-fluid test section
Dielectric-fluid test section

Observing the heated surface and bubbles

Surface microstructure
Surface microstructure

Relating surface structure to boiling behaviour

Copper foam specimens
Copper foam specimens

Comparing pore structure and surface wettability

Bubble dynamics
Bubble dynamics

High-speed imaging of growth and departure

Boiling performance and cooling limits
Boiling performance and cooling limits

Evaluating heat flux against wall superheat

How It Works

  1. Fluid Submersion

    Servers submerged in dielectric fluid

  2. Two-Phase Boiling

    Fluid boils, absorbing massive heat via latent heat

  3. Condense & Recirculate

    Vapor condenses, natural circulation loop

Research activities

  • EV Battery Immersion Cooling via Boiling

    We study boiling in dielectric fluids for battery cooling. Tests evaluate heat removal and temperature uniformity.

    Inha University · 2025
  • Metal Foam-Enhanced Boiling Heat Transfer

    We compare boiling across copper foam pore sizes, thicknesses, and orientations. Tests evaluate heat transfer coefficients and critical heat flux.

    3 related papers
  • CHF Dependence on Surface Orientation

    We examine how surface orientation and bubble dynamics affect critical heat flux on silicon and silicon dioxide.

    1 related paper
  • Gas-Liquid Flow Path Separation Patent

    The patented design separates gas and liquid flow paths. It aims to reduce bubble interference during battery immersion cooling.

    KR 10-2855737

Thermal Energy Storage

Understanding heat recovery from the storage material to the tube.

We develop charging and discharging solutions for thermal energy storage systems using sand, molten salt and other media. Experiments and system analysis evaluate heat transfer and heat exchange across materials and operating conditions.

Heat recovery from sand storageEvaluating steam production through in-tube evaporation and heat transfer.
Molten-salt heat storageStoring heat and delivering it when needed.

Sand storage · apparatus and system design

Thermal storage prototype
Thermal storage prototype

A storage unit connected to piping and a water bath

Heat exchanger configurations
Heat exchanger configurations

Comparing straight, U-shaped, and helical tubes

Thermal storage system model
Thermal storage system model

Analysing tube and system response with MARS-KS

Storage temperature measurements
Storage temperature measurements

Temperature changes across locations and time

Other storage media · PCM and molten salt

PCM studies examine melting and solidification. Molten-salt simulations examine natural convection. These are separate from the sand system.

PCM test section
PCM test section

Direct-contact tests with PCM and heat transfer fluid

Molten-salt convection
Molten-salt convection

Temperature and flow fields during charging and discharge

Energy Conversion Process

  1. Excess Renewable

    Solar / Wind surplus

  2. Store as Heat

    High-temp thermal tank

  3. Heat → Electricity

    Heat engine cycle

  4. Stable Power

    24/7 data center supply

Research activities

  • Direct-Contact Latent Heat Storage System

    We study heat exchange through direct contact between PCM and heat transfer fluid. Experiments track melting and solidification during charging and discharge.

    National Research Foundation of Korea · 2023–2025
  • Sand Battery Thermal Energy Storage

    We study sand as a high-temperature storage medium. Tube design and system analysis connect heat storage to steam production.

    KR 10-2906225
  • Sustainable Energy Process Innovation

    The convergence graduate programme trains researchers in thermal storage and digital energy process analysis.

    KETEP · 2023–2027
  • Lab-to-Startup TES Development

    Prototype development and performance tests evaluate the commercial potential of laboratory thermal storage technology.

    Ministry of Science and ICT · 2025

Small Modular Reactors

Identifying when flow and pressure begin to oscillate.

We study two-phase flow instabilities in SMR steam generators and natural circulation systems. Experiments and one-dimensional system analysis evaluate how flow and pressure oscillations affect heat transfer and system stability.

SMR thermal-hydraulic systemsStudying system responses to changes in steam-generator flow.
Flow instability between channelsUnderstanding why parallel flows diverge and oscillate.

The test loop and flow oscillations

Two-phase flow instability facility
Two-phase flow instability facility

Measuring responses to heating and flow conditions

Thermal-hydraulic test loop
Thermal-hydraulic test loop

Connecting the test section to pressure, temperature, and flow measurements

Pressure and flow oscillations
Pressure and flow oscillations

Analysing delays and interactions between flow channels

Density-wave oscillations
Density-wave oscillations

Flow oscillations under different operating conditions

From local phenomena to the system

  1. Locate boiling

    Density and pressure-drop changes on the secondary side

  2. Measure oscillations

    Delays between flow, pressure, and temperature responses

  3. Analyse the system

    Evaluate operating stability with a one-dimensional code

Research activities

  • Core Safety Validation for Multiple-Failure Accidents

    Validating core safety against strengthened technical criteria and improving safety in multiple-failure accidents. A long-term project covering natural circulation cooling, two-phase flow instability, and accident progression.

    National Research Foundation of Korea · 2022–2029
  • Next-Gen SMR Safety Enhancement Design

    An international programme training specialists in passive safety systems, helical steam generators, and containment cooling.

    KETEP · 2024–2025
  • Containment Condensation Heat Transfer

    Measuring how noncondensable gases in steam-air mixtures degrade condensation heat transfer and stratify inside the containment.

    3 related papers
  • External Reactor Vessel Cooling (ERVC)

    Simulating external vessel cooling in high-power reactors. A CFD-aided natural circulation estimate quantifies the ERVC coolability limit.

    2 related papers

Methods

EXPERIMENTS

Two-Phase Flow Instability · Pool Boiling Heat Transfer · Flow Boiling Heat Transfer · Thermal Margin Test · Dielectric Fluid · Leidenfrost Effect · Wettability · Condensation

COMPUTATIONAL ANALYSIS

Nuclear Safety · NSK System · Code Coupling · OpenFOAM · MARS-KS · CUPID · GAMMA+ · ANSYS CFD · Fluent · STAR-CCM+

Collaborators

INTERNATIONAL

NTNU · HZDR · UPC · Kyushu Univ.

INSTITUTES

KAERI · KIER

INDUSTRY

HD Hyundai Heavy Industries · Hyundai E&C · LG Electronics · Buildersgate

UNIVERSITIES

Seoul Nat'l Univ. · Kyung Hee Univ.