Development of a 1D Simulation Model for BEV Thermal Management Systems
-(Part 2) Modeling of Oil Behavior in the Refrigeration Cycle-

Yu Yamashita･Yosuke Yasuda･Yusuke Sato･Tomohiro Sudo (DENSO)

Thermal management systems for BEVs have seen increasing diversification of operating modes, raising the demands placed on the refrigeration cycle that lies at their core. The compressor, in particular, is lubricated by oil dissolved in the refrigerant, making it essential to achieve both adequate lubrication and high efficiency. In this report, we present an original model that predicts oil behavior within the cycle based on the underlying physical phenomena, and demonstrate that it reproduces measured values from actual equipment with high accuracy.

Study on Thermal Management System utilizing Next-Generation Refrigerant for future xEV

Ryo Michikawauchi･Hiroyuki Sugihara･Atsuharu Ota (Toyota Motor)･Yuichi Kami (DENSO)

Considering the European PFAS regulatory landscape, thermal management system for xEVs was investigated using propane refrigerant as a non-PFAS alternative with superior cabin comfort energy efficiency and battery thermal control performance. To enhance safety, refrigerant circulation is restricted outside the cabin by adopting a coolant-based secondary loop with newly integrated chiller and cooler core components. While this architecture may increase system complexity, a simplified thermal circuit with reduced refrigerant charge was designed. Feasibility was confirmed through analytical evaluation.

Formulation design for long-life low-conductivity battery coolants

Yasuaki Kodama (Toyota Motor)･Ryo Karasawa･Takumi Otsubo (Japan Chemical Industries)

In battery electric vehicles (BEVs), battery cooling system safety and reliability are critical under high-load and high-temperature conditions such as rapid charging and high-power driving. Low-electrical-conductivity coolants reduce the risk of abnormal heating due to leakage; however, conductivity increases over time because of ethylene glycol oxidation and ion dissolution from components. This study identified flux-derived ions from aluminum brazing as a key factor. The use of optimized aluminum corrosion inhibitors effectively suppressed ion dissolution and stabilized conductivity during long-term circulation. The developed coolant formulation extends service life and has been applied to battery cooling systems since 2025, ensuring electrical safety and durability.

Thermal-Flow Stabilization Design of a Coolant Heater for Electric Vehicles

Daeseong Han･Jung Han Kim･Dae Nyeon Kim (Gyeongbuk Institute of IT Convergence Industry Technology)･Il Hwan Yi (Kumoh National Institute of Technology)･Jaehwan Jeong (DHG)

This study analyzed the outlet coolant temperature characteristics according to the flow channel design of a coolant heater. CFD simulations were conducted under conditions of 8 kW heating power and 10 L/min flow rate to evaluate the outlet coolant temperature and derive an optimal flow channel design. The results confirmed that the flow channel structure attached to the heating plate was effective in improving heat transfer performance and generating coolant turbulence.