Improving Winter Driving Range of EVs with a Desiccant Device: Ceramic Humidity Regulator (CHR)

Hirotaka Saito･Yukio Ihara･Hajime Ota･Naoki Sakai (NGK INSULATORS)

One major challenge for electric vehicles (EVs) in winter is reduced driving range due to heating demands. Heat loss from ventilation for window defogging is a key factor. To address this, we developed the Ceramic Humidity Regulator (CHR), a desiccant device combining a moisture-adsorbent material with a ceramic PTC heater. This integrated system controls humidity while providing efficient heating. Vehicle tests showed that, compared to conventional automatic air-conditioning, CHR reduced heating power consumption by about 25%. This improvement is expected to enhance EV driving range under cold-weather conditions.

Holistic Evaluation of Electric Vehicle Efficiency: Benchmark Study of R-474A, R-1234yf, and R-744 using Digital Twin Simulation

Christian Macri･Alvaro de Leon･Felix Flohr (Daikin Chemical Europe GmbH)

The transition to battery electric vehicles (BEVs) comes with several challenges such as energy efficiency and the resulting driving range. The thermal management systems play a pivotal role ensuring optimal energy efficiency and passenger comfort. Refrigerants play a crucial role, as their properties impact heat exchange efficiency and overall energy consumption. This study presents a comprehensive benchmarking of the new refrigerant R-474A against R-1234yf and R-744 in a BEV thermal management system. A simulation has been conducted, beginning at system level, progressing to vehicle level, and concluding with evaluations under transient driving conditions across various driving patterns and temperature profiles.

Experimental study on the performance of a heat pump system with novel low-GWP R474A for new energy vehicles

Binbin YU･Yunlong zhang (Shanghai Jiao Tong University)･Hao Nie･Yasutaka NEGISHI･Shohei AJlOKA･Asuka Bunno･Kei Yamamoto (Daikin Industries, Ltd.)

This study investigates the cycle performance and system behavior of a novel refrigerant, R474A in the heat pump for new energy vehicles. Results show under both cooling and heating conditions, R474A demonstrated strong performance: a COP up to 3.67 under light-load conditions, a maximum cooling capacity of 7004.5 W, and a maximum heating capacity of 6044.5 W. Comparative analysis revealed that R474A outperforms R134a and R290 in terms of cooling and heating capacity across conventional and extreme operating conditions, while maintaining a higher COP than R290. Notably, R474A overcame the operational limitations of R134a at extreme low temperatures and exhibited minimal temperature non-uniformity from glide effects, ensuring satisfactory thermal comfort. These findings highlight R474A's significant potential as a sustainable alternative refrigerant for NEV heat pump applications.

Testing of novel refrigerants in an indirect automotive heat pump module

Tomas Mrkvica･Jan Tuhovcak･Milos Fojtlin (SATTELO)

Driven by electric mobility and mobile machinery needs, the market demands efficient thermal management with refrigerants that work across climates, meet low-GWP and PFAS-free requirements, and require minimal system changes. This study evaluates two novel blends, R474B and R491A, as drop-in candidates versus common automotive refrigerants. Laboratory tests under heating, cooling, and high-load conditions show performance can be limited by existing equipment and safety constraints, though cooling and dehumidification needs were met. Overall, the results show the new refrigerants are technically viable and offer a promising path for future EV thermal management.

Development of a System Simulation Model for Estimating Short-Circuit Discharge Energy of an Automotive Electric Compressor

Kengo Nagai･Ryoto Nakayama･Itsuki Masuda (Nagoya University)･Yasutaka Negishi･Asuka Bunno･Takashi Usui (Daikin Industries, LTD.)･Koichi Shigematsu･Jun Imaoka･Masayoshi Yamamoto (Nagoya University)

In recent years, hydrofluoroolefin (HFO) refrigerants have gained attention for their high cooling performance and low global warming potential (GWP). However, if a short-circuit discharge occurs inside an in-vehicle electric compressor and the refrigerant absorbs the discharge energy, it may undergo combustion or thermal decomposition. To assess this risk, short-circuit tests were performed on an actual compressor to measure discharge waveforms and energy. Using circuit parameters obtained from these tests and from compressor teardown analysis, a system simulation model was developed to estimate discharge energy, incorporating overcurrent protection and output-control functions.

An Experimental Method for the Development of Vehicle Thermal Management Systems using Transient Thermal Control Devices: Second Report

Jun Hatakeyama･Hirotaka Iseki･Toshiyuki Michikita･Seiji Hirai･Prasad Shiv Rohit (HORIBA)

This paper presents a follow-up to the experimental apparatus for vehicle thermal management systems reported at the 2025 Spring Meeting. Transient heat generated by the battery and eAxle during vehicle operation was reproduced on a bench, and the temperature, flow, and pressure responses of an actual thermal management system sample were measured and organized.