Design, Integration, and Multiphase Modeling of Phase Change Material (PCM) for Thermal Management of BEV Inverter

Abstract

With the rapid advancement of electromobility sector, the power density and heat generation of electronic chips is significantly rising. Due to its higher load and lower thermal mass, electronics chips in BEV inverters, such as MOSFETs, are increasingly susceptible to rapid temperature rises. Through the utilization of latent heat absorption, Phase Change Material (PCM) offers a promising passive cooling solution for sudden temperature spikes, while eliminating the requirement of continuous coolant flow for BEV inverter cooling. This paper aims to evaluate the effect of PCM integration on thermal performance by investigating the effect of heat sink designs, PCM materials, PCM coverage strategies, and metal foam porosity on MOSFET temperature.

Based on the results, Design 3 and Design 5 demonstrated the best performance in dissipating heat into the PCM domain due to their high effective mean thermal conductivity. However, the influence of porosity on thermal performance proved to be complex and highly dependent on the overall heat sink design. This trade-off is more noticeable in Design 3, where the thermal conductivity and latent heat capacity are properly balanced. Additionally, the choice of PCM material strongly influenced the timing and effectiveness of flattening temperature. Highmelting-point PCM tends to delay melting, while low-melting-point PCM often leads to premature melting. In this case, RT64HC offered the best balance in promoting thermal buffering effect. The PCM coverage strategy also affected thermal performance significantly. Partial coverage was ineffective due to insufficient PCM volume, while full x-axis coverage outperformed y-axis coverage by allowing more uniform and direct heat exposure.

The two best configurations in this study were full y-axis with RT64HC at P0.2 and full x-axis with RT64HC at P0.3, where both configurations promoted flattening temperature during second acceleration cycle. However, the x-axis configuration is preferred for its greater potential for future improvement.

Popular Abstract

Thermal management in BEV inverter systems play crucial role in maintaining the car’s performance and reliability. But as inverter chipset technology develops, they will get hot
faster, especially when we accelerate our car. In most cars, continuous coolant flow has been used for decades to keep inverter temperature below its safety level. However, is that really the best way? How can we cool it down in a more effective and efficient way?

When coolant circulates continuously in BEV, it leads to unnecessary energy consumption due to pumping work and pressure drop. Moreover, during acceleration, there is a short delay between the time inverter chipsets generate heat until the coolant starts absorbing those heat. This delay causes a sudden temperature spike despite a high coolant flow rate. To mitigate this problem, one strategy investigated in this thesis is using Phase Change Material (PCM) to reduce or even eliminate sudden temperature spikes during acceleration. Imagine PCM works just like paraffin in candles, where it changes into liquid when exposed to heat and back to solid when it is cooled down. In scientific words, PCM absorbs heat by using latent heat capacity, where temperature is relatively constant during this heat absorption process. If this works in inverter chipsets, it will be really cool since we don’t need to use coolant flow all the time! Instead, just wait until PCM absorbs those sudden heat for some time, then start to introduce the coolant flow once it fully melts.

This study aims to evaluate the effect of PCM integration on thermal performance by investigating the effect of inverter heat sink designs, PCM materials, PCM coverage strategies, and metal foam porosity on chipsets temperature. The result showed that PCM really works! Instead of generating sudden temperature spikes, the chipsets temperature is flattened out when PCM melts. But this only works under certain conditions. Firstly, the heat sink must be able to contain enough PCM while conducting heat quickly at the same time. Secondly, when should the PCM melt? Is it 57℃, 64℃, 70℃, or 77℃? The melting point should precisely match the temperature spike and based on this study: the best was 64℃!

How about the PCM coverage? Previously, placing PCM only below the chipsets didn’t work – there simply wasn’t enough material to handle the heat. So, the question becomes: if we want to improve it, should we spread the PCM wider across the heat sink, or stretch it longer along the coolant flow direction? Apparently, the second solution wins! Lastly, the effect of metal foam porosity… this isn’t very straightforward. It really depends on how the whole heat sink is designed. The better design we have, the more noticeable it will be! Curious how the best configuration looks like and how it affects thermal performance? Check out the complete report for more detailed analysis and design insights.

• author: Hudoyo, Henry
• supervisor: Lei Wang
• organization: Department of Energy Sciences
• course: MVKM05 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: BEV inverter, flattening temperature, latent heat absorption, PCM, thermal conductivity
• report number: ISRN LUTMDN/TMPH-25/5627-SE
• ISSN: 0282-1990
• language: English
• id: 9192436
• date added to LUP: 2025-06-05 09:22:41
• date last changed: 2025-06-05 09:22:41