Hybrid charge air cooler
Methods and systems are provided for cooling charge air in a hybrid engine. In one example, a method may include cooling charge air by a combination of air-to-air and air-to-coolant heat transfer with assistance from a chiller arranged in the coolant circuit. The coolant circuit includes an insert coupled to a charge air cooler allowing heat exchange via conduction and convection.
1. A method, comprising:
during first conditions, cooling charge air from a compressor via air-to-air conductive cooling and air-coolant conductive cooling at a hybrid charge air cooler (HCAC);
during second conditions, cooling charge air from the compressor via the air-to-air conductive cooling and via air-to-coolant convective cooling at the HCAC; and
during third conditions, cooling charge air from the compressor via the air-to-air conductive cooling and via chiller-assisted air-to-coolant convective cooling at the HCAC, wherein cooling tubes respectively containing the cooling charge air, air-to-coolant coolant, and chiller-assisted air-to-coolant coolant are vertically stacked within the HCAC via an insert positioned within the HCAC, with tubes for the chiller-assisted air-to-coolant coolant vertically between pairs of cooling tubes containing the cooling charge air and the air-to-coolant coolant.
2. The method of claim 1 , wherein cooling the charge air from the compressor via air-to-air conductive cooling at the HCAC comprises flowing the charge air through a plurality of heat exchange channels of the HCAC, the plurality of heat exchange channels each having at least one surface over which ram air is configured to flow during vehicle operation, wherein the first, second, and third conditions are non-overlapping and different from one another.
3. The method of claim 2 , wherein cooling charge air from the compressor via the air-to-air conductive cooling and via the air-to-coolant convective cooling at the HCAC comprises flowing the charge air through the plurality of heat exchange channels and activating a coolant pump to circulate coolant through the insert of the HCAC.
4. The method of claim 3 , wherein activating the coolant pump to circulate coolant through the insert of the HCAC comprises activating the coolant pump to circulate coolant through a plurality of the cooling tubes of the insert, each cooling tube positioned between respective two adjacent heat exchange channels of the plurality of heat exchange channels.
5. The method of claim 4 , further comprising, during the first conditions, maintaining the coolant pump in a deactivated state throughout the first conditions.
6. The method of claim 3 , wherein cooling charge air from the compressor via the air-to-air conductive cooling and via the chiller-assisted air-to-coolant convective cooling at the HCAC comprises activating a chiller to cool the coolant circulating through the insert of the HCAC.
7. The method of claim 1 , wherein the first conditions comprise vehicle operation with a temperature of coolant at an outlet of the insert of the HCAC being less than a first threshold temperature, wherein the second conditions comprise vehicle operation with the temperature of coolant at the outlet of the insert of the HCAC being equal to or greater than the first threshold temperature but less than a second threshold temperature, and wherein the third conditions comprise vehicle operation with the temperature of coolant at the outlet of the insert of the HCAC being equal to or greater than the second threshold temperature, the method including operating at each of the conditions sequentially and/or non-sequentially.
8. The method of claim 1 , further comprising adjusting grille shutters positioned in front of the HCAC with the insert.