ETD 1kW Concept
Thermal Analysis Report

// Table of Contents

• 1  Introduction1
• 1.1 Report Structure
• 1.2 Unit Overview
• 1.2.1 Main Chassis · 1.2.2 Fan Assembly · 1.2.3 RF Modules
• 1.3 Simulation Model
• 1.4 Prerequisite Information
• 2  Simulation Overview10
• 2.1–2.4 Environment · Model · Domain
• 2.5 Simulation Parameters
• 2.6 Simulation Details
• 3  Simulation Deliverables15
• 3.1–3.2 Analysis Goals · Global Min-Max
• 3.3 Steady State Results
• 3.4 Fluid Dynamics Package
• 3.5 Transient Results
• 4  Conclusion21
• 4.1 Suggestions
• 5  Appendix23
• 5.1 Cooling System Specs · 5.2 Component Specs · 5.3 Material Data

// Section 1

1Introduction

1.1 Report Structure

Introduction — a brief outline of the unit under analysis, and a restatement of all prerequisite data provided to ETD, including significant definitions and final deliverables.
Simulation Overview — the raw data pertaining to the initialization and execution of the thermodynamic simulation(s).
Simulation Deliverables — a collection of the graphical/visual deliverables derived from the simulation.
Conclusion — a brief summary highlighting key results and insights, as well as suggestions for improving thermal performance.

1.2 Unit Overview

The goal of this report is to assess the thermal performance of the Kilowatt Concept enclosure and cooling system. The Kilowatt Concept is a modularized three part design. The unit features a main chassis which houses the power and control components. On the bottom of the main chassis are two docks, designed to receive the RF modules. These modules are left- and right-hand specific, each containing a 4-pipe heatpipe system with the capacity to transfer up to 440 W per module. The final assembly measures roughly 12.9" × 11.1" × 6.4" (32.8 × 28.2 × 16.5 cm) and weighs 21.3 lbs (9.65 kg). A Technical Explosion Animation is available as a visual aid.

The Kilowatt Concept cooling apparatus is a heat-pipe heat exchanger + forced-air system, referred to as the heatpipe system throughout this report. Eight partially embedded heatpipes draw up to 800 W of power from heat sources within the modules. The exposed end of each heatpipe features a 90° bend, creating a vertical section populated by 54 press-fit sheet fins acting as radiators. An additional heatsink sits on the top plane of the main chassis. Both the chassis heatsink and the heatpipe fins are cooled by a Sanyo Denki 9WL1424P1H001 fan located at the rear, set up as an outlet (pulling) fan providing ≈147 CFM.

REF · Full assembly render▸ Model

Main chassis (top), control panel (front), and RF module docks (bottom).

1.2.1 Main Chassis

The main chassis is the largest subassembly in the Kilowatt Concept. It consists of an interior cavity to house power and control hardware, a machined heatsink, and an interface plate. This report concentrates on the power cavity and its subsequent heatsink. Located within the power cavity are five individual power supply units (PSU #1–#5), mated to the surface opposite the main chassis heatsink.

1.2.1 · Main Chassis, Cutaway▸ Model

1.2.1.1 · Power Cavity▸ Model

Cross-sectional view of the empty power cavity.

1.2.1.2 · Power Supplies▸ Model

PSU #1–#5, within the power cavity.

1.2.1.3 · Main Chassis Heatsink▸ Model

Top-down view showing the main chassis heatsink.

1.2.2 Fan Assembly

The fan assembly is composed of the 9WL1424P1H001 Sanyo Denki fan and four sheet-metal brackets, located at the rear of the unit. The space between the main chassis and the fan assembly — where the heatpipe fins reside — is called the fan chamber. The San Ace 140W 9WL1424P1H001 is an IP-68 aluminum-framed fan.

1.2.2 · Fan Assembly▸ Model

1.2.2.1 · Fan Chamber▸ Model

Top-down view — the fan chamber / heatpipe fin area is highlighted.

1.2.3 RF Modules

The RF Modules are detachable subassemblies where the HEMTs (primary heat sources) live, and therefore house the heatpipe system. There is a left-hand module and a right-hand module — exact mirror images of each other — each containing two HEMTs (HEMT #1/#2 left, HEMT #3/#4 right).

1.2.3 · RF Modules▸ Model

1.2.3.1 · HEMTs▸ Model

Top-down view of the HEMT locations within the RF modules — HEMT #1/#2 (left module), HEMT #3/#4 (right module).

1.3 Simulation Model

The cooling system pulls air from the front of the unit, across the main chassis heatsink, through the fan chamber, and exhausts it out the rear. This configuration requires internal fluid-flow analysis, meaning the unit must be air-tight aside from the intake orifices. A "simulation-friendly" 3D model was therefore created prior to solving:

• Control Panel — removed entirely; the gap in the main chassis is filled to create a seamless power cavity, and top-plate fasteners are suppressed.
• Fan Assembly — sheet-metal brackets replaced with solid surfaces of equal size/shape; fan guard discarded; the Sanyo Denki fan replaced with a solid cylindrical placeholder.

1.3.1.1 Control Panel

True Model

Simulation Model

The control panel is completely removed and the gap in the main chassis is filled, creating a seamless power cavity.

1.3.1.2 Fan Assembly

True Model

Simulation Model

The sheet-metal brackets are replaced with solid surfaces; the fan guard is discarded and the Sanyo Denki fan is replaced with a solid, cylindrical place-holder.

1.4 Prerequisite Information

The following prerequisite information was defined and agreed upon by ETD and the customer prior to initialization.

// Section 2

2Simulation Overview

2.5 Simulation Parameters

// Section 3

3Simulation Deliverables

3.2 Global Min–Max Table

Full 27-row parameter table (density, vorticity, shear stress, enthalpy flux, etc.) retained from the source Flow Simulation export; abridged here to the parameters referenced in Section 4.

3.3 Steady State Results

3.3.1 Surface Temperatures (3D Heat Map)

3.3.2 Cut Temperatures (Cross-Sectional Heat Map)

3.3.3 Advanced Component Analysis — HEMT Junction to Unit Exterior

Temperature plotted as a function of displacement, starting at an HEMT junction (x = 0 mm, 184.18 °C) and following a linear path to the RF module exterior (x = 14.224 mm, 79.67 °C).

SOLVE · T(x) — Junction → Exterior▸ Analyzed

Typical HEMT, junction-to-exterior temperature vs. displacement.

Path of Displacement▸ Model

A cross-sectional plot through an HEMT, showing the path of displacement referred to in the graph above.

HEMT #1

HEMT #2

HEMT #3

HEMT #4

Per-device breakdown across all four GaN HEMTs (goal component group, Section 2.5.7).

3.4 Fluid Dynamics Package

3.4.1 Flow Trajectories

3.4.2 Pressure Gradients

3.4.3 Cooling System Performance — Fan Curve

The chart below shows the 9WL1424P1H001 fan curve (theoretical, no back pressure) against the derated operating curve. Equilibrium was reached at the steady-state operating point.

9WL1424P1H001 Outlet Fan▸ Operating Point

Result: airflow of 0.0495 m³/s at a back pressure of 172.57 Pa.

3.4.3.2 Heatpipe System Efficiency

Efficiency is assessed on a system level — heat load transported from the HEMTs, through the eight-heatpipe network, and released to ambient via the fins — rather than treating heatpipes as isolated entities. Heat load out was determined via a Flow Simulation surface parameter study on the heatpipe fins (convective heat transfer rate).

Surface Parameter Study — Fins▸ 600.622 W

Efficiency Calculation

3.5 Transient Results

3.5.1 Transient Surface Temperatures (Heat Flow Animations)

Simulation playback of surface temperature, captured across the 3-minute and 30-minute full-power transient runs.

3.5.2 Transient Cut Temperatures (Cross-Sectional Heat Flow Animations)

3.5.3 Transient Component Analysis — Temperature vs. Time

Component Temperature Rise — 3 Minutes▸ Analyzed

HEMTs settle within ~30 s owing to their low thermal mass.

Component Temperature Rise — 30 Minutes▸ Analyzed

Power supplies and heatpipe fins continue trending upward through the full 1800 s window, approaching but not reaching the steady-state solution.

// Section 4

4Conclusion

The purpose of this report is to provide a data-driven analysis of the thermal capabilities of the Kilowatt Concept housing and cooling system under a 1000 W thermal load. A series of thermodynamic simulations were conducted using SolidWorks Flow Simulation software.

The results reveal the cooling system successfully diffused the 1000 W heat load — all critical components reached steady-state without exceeding maximum operating temperatures. The GaN HEMTs, the highest and most dense heat source, reached a collective maximum junction temperature of 186.05 °C, comfortably within the 9WL1424P1H001 datasheet's maximum recommended junction temperature of 225 °C. The power supplies reached a collective maximum of 67.38 °C (PSU #3, center) — low enough to be a non-priority.

The heatpipe cooling system is the heart of the unit, cooling four 200 W HEMTs across only 0.5 in² of footprint each. Section 3.4.3.2 calculates an overall efficiency of 75.1% — over 600 W of heat load taken directly out of the HEMTs and dispersed to ambient — allowing the unit to remain within operating limits while retaining a compact, lightweight frame.

4.1 Suggestions

Any marginal improvement in thermal performance is most likely to come from adjusting parameters of the heatpipe system or elements directly related to it.

4.1.1 Adjusting the Profile of the Heatpipe Fins

The current profile features 54 fins at 0.06" thickness. Reducing thickness to 0.03" would allow doubling the fin count to 108 with no increase in fan back pressure — likely yielding a 5–10 °C drop in HEMT maximum temperature.

4.1.2 Increasing Airflow to the Heatpipe Fins

The pressure drop across the main chassis heatsink (~150 Pa) sits close to the fan's operating point (172.6 Pa). Creating a higher free-space ratio in the chassis heatsink profile (fewer fins, spaced further apart) would reduce back pressure, shift the operating point down the fan curve, and generate more airflow to the heatpipe fins — trading a rise in power-supply temperature (non-priority) for a drop in HEMT temperature.

Fan Curve / Operating Point

Pressure Gradient — Main Chassis Heatsink

4.1.3 D-Shaped Surface Heatpipes

Raising the heatpipes to the module surface and switching from circular to D-shaped cross-sections would let the HEMTs sit directly on the heatpipe, reducing heat slippage into the module base. Trade-offs: reduced manufacturability (custom D-shaped pipes) and reduced structural durability (partially vs. fully embedded).

// Section 5

5Appendix

5.1 Cooling System Specs

5.1.1 Heatpipe System

Eight heatpipes total, four per RF module, working fluid 70% water / 30% ammonia. Each pipe: 0.30" diameter, 5.50" horizontal evaporator section (heat in), 90° bend to a ~4.25" vertical condenser section (heat out). Conservatively rated at 110 W/pipe → 880 W system capacity.

5.1.1.1 · Transparent Heatpipe System▸ Model

Transparent view of the 4 heatpipes embedded within a single RF module, condenser sections rising to the fin stack.

Heatpipe Route — Depth

Heatpipe Route — Diameter

5.1.1.2 · Heatpipe + Fin Assembly▸ Model

5.1.2 Sanyo Denki 9WL1424P1H001 Fan

Datasheet: publish.sanyodenki.com — San Ace E, p.286

5.2 Component Specs

5.2.1 Wolf Speed CGHV96130F GaN HEMT

Datasheet: assets.wolfspeed.com/cghv96130f.pdf

5.3 Material Data

Temperature-dependent dynamic viscosity, specific heat, and thermal conductivity curves (−200 °C to 3000 °C) sourced from the Flow Simulation engineering database; see source datasheet for full curve data.