Optimizing Low-Temperature Three-Circuit Evaporative Cooling System for an Electric Motor by Using Refrigerants

Dmytro Konovalov (), Ignat Tolstorebrov, Yuhiro Iwamoto, Halina Kobalava, Jacob Joseph Lamb and Trygve Magne Eikevik
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Dmytro Konovalov: Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 1, 7034 Trondheim, Norway
Ignat Tolstorebrov: Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 1, 7034 Trondheim, Norway
Yuhiro Iwamoto: Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Aichi, Japan
Halina Kobalava: Heat Engineering Department, Kherson Educational-Scientific Institute, Admiral Makarov National, University of Shipbuilding, 44 Ushakov Av., 73003 Kherson, Ukraine
Jacob Joseph Lamb: Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 1, 7034 Trondheim, Norway
Trygve Magne Eikevik: Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 1, 7034 Trondheim, Norway

Energies, 2024, vol. 17, issue 16, 1-28

Abstract: This article presents modeling results and a comprehensive analysis of evaporative cooling systems designed for electric motors using the refrigerants R744 (trans-critical), R134a, R600a, and R290. This study aims to determine the most suitable refrigerant for use in a cooling system, optimize the system design, and calculate the maximum achievable motor power while adhering to specified temperature constraints. The modeling was validated by an experimental setup, which had the cooling system’s configuration featuring three circuits for motor housing, stator, and rotor cooling, respectively. The modeling of an evaporative system was used to present the cooling efficiency under varying loads and external temperature conditions. Mathematical modeling encompasses complex algorithms to simulate heat transfer phenomena, accounting for fluid dynamics and refrigeration cycle dynamics. The analyses revealed trends in winding temperature, rotor temperature, air temperature inside the motor, heat transfer coefficient, coefficient of performance (COP), and motor power across different operating conditions while using different cooling refrigerants. The maximal heat transfer coefficients were calculated for all the refrigerants for winding temperatures in the range from 32 to 82 °C, while air temperature and rotor temperatures were between 42 and 105 °C and 76 and 185 °C, respectively. Lowering the evaporation temperature of the coolant to −35 °C resulted in a significant decrease in the winding temperature to 15 °C, air temperature to 38 °C, and maximum rotor temperature to 118 °C at a motor power of 90 kW. Refrigerant R744 emerged as a promising option, offering high heat transfer coefficients and achieving high motor power within temperature limits. At the same time, the COP was lower when compared with other working fluids because of the high ambient temperature on the gas cooler side.

Keywords: electric motor; cooling system; vehicle; coolant; power-to-dimension ratio; refrigerant; CO 2 (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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