ExxonMobil Technology and Engineering

A heat transfer fluid for electric vehicle applications, wherein the heat transfer fluid is a dielectric fluid configured to transfer heat in direct contact with live parts, the heat transfer fluid comprises at least 20 wt% of a first component based on the total weight of the heat transfer fluid, and at least 1 wt% and up to 80 wt% of a second component based on the total weight of the heat transfer fluid, wherein the first component has a kinematic viscosity KV 20 ≤ 50.0mm<2>/s, a kinematic viscosity KV 100 ≤ 10.0mm<2>/s, and an initial boiling point (IBP) ≥ 150 °C, and the second component has a kinematic viscosity KV 20 ≤ 1.0 mm<2>/s,, wherein the KV 20 of the first component is higher than the KV 20 of the second component and a final boiling point (FBP) ≤ 100 °C,. A method for operating a thermal management arrangement (1) for electric components (2) in electric vehicles comprises the step of providing the thermal management arrangement (1). The thermal management arrangement (1) includes a heat source in the form of an electric component (2) which is arranged in a housing (3), a cooling circuit (5) comprising an encircling fluid line (6) which is thermally coupled to the electric component (2) and a heat exchanger (7) arranged in the fluid line (6). The thermal management arrangement (1) further comprises a heat transfer fluid disposed in the fluid line (6) and a pump (8) configured for transporting the heat transfer fluid through the fluid line (6). The heat transfer fluid comprises at least 20 wt% of a first component based on the total weight of the heat transfer fluid, and at least 1 wt% and up to 80 wt% of a second component based on the total weight of the heat transfer fluid. The first component has a kinematic viscosity KV 20 ≤ 50.0 mm<2>/s, a kinematic viscosity KV 100 ≤ 10.0mm<2>/s, and an initial boiling point (IBP) ≥ 150 °C. The second component has a kinematic viscosity KV 20 ≤ 1.0 mm<2>/s, , wherein the KV 20 of the first component is higher than the KV 20 of the second component and a final boiling point (FBP) ≤ 100 °C, preferably ≤ 80 °C. The method further comprises the step of pumping the heat transfer fluid through the fluid line (6) thereby generating a mass flow (m) of the heat transfer fluid. The heat transfer fluid enters the housing (3) of the electric component (2) at a first fluid temperature (T1 ) and exits the housing (3) of the electric component at a second fluid temperature (T2 ) which is higher than the first fluid temperature thereby absorbing a heat flow (Q) from the electric component (2) and lowering a component temperature (TC) of the electric component (2). The method further comprises the step of regulating the mass flow (m) of the heat transfer fluid depending on the difference between the second temperature (T2 ) and the first temperature (T1 ) and a predefined heat flow (Q) to be absorbed from the electric component (2) according to the following equation: m ˙ = Q ˙ c p T 2 − T 1 <img class="EMIRef" id="486420af-fabe-48b8-8d5c-ad2dffc9bee7-ia01" /> wherein m is the fluid mass flow, Q is the absorbed heat flow, cp is the heat capacity of the heat transfer fluid, T1 is the temperature of the heat transfer fluid entering the housing (3) of the electric component (2) and T2 is the temperature of the heat transfer fluid exiting the housing (3) of the electric component (2); The first temperature (T1 ) of the heat transfer fluid is lower than a temperature required for vaporizing the second component in the heat transfer fluid and wherein the component temperature (TC) of the electric component (2) when being operated is higher than the temperature required for vaporizing the second component in the heat transfer fluid. The second component of the heat transfer fluid vaporizes when the heat transfer fluid absorbs the heat flow (Q̇) from the electric component (2).

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