Patent Application
20100175406
The present invention relates generally to a heating, ventilation and air conditioning (HVAC) system and a battery cooling system for a vehicle.
In order to improve the fuel economy of automotive vehicles, new types of powertrains that employ battery packs are being used in these vehicles. The use of a battery pack may necessitate cooling of the battery to maximize battery life and charging capacity. Any cooling system for the battery pack may offset the intended gains in fuel economy. Accordingly, it is desirable to maximize the efficiency with which the battery pack is cooled.
An embodiment contemplates a HVAC and battery cooling system for use in a vehicle that may include a HVAC system, a battery cooling system and a pre-cooling heat exchanger. The HVAC system may include an evaporator and a drain configured to receive condensate from the evaporator. The battery cooling system may include a main battery cooling subsystem configured to cool a cooling fluid that flows through a battery pack. The pre-cooling heat exchanger is configured to receive a flow of the cooling fluid therethrough and a flow of the condensate therethrough, whereby the condensate absorbs heat from the cooling fluid as the condensate flows through the pre-cooling heat exchanger.
An embodiment contemplates a method of cooling a battery pack in a vehicle, the method comprising the steps of: directing a cooling fluid in a battery cooling system through a pre-cooling heat exchanger; directing a condensate from an evaporator in a HVAC system through the pre-cooling heat exchanger to thereby cause the condensate to absorb heat from the pre-cooling heat exchanger; directing the cooling fluid in the battery cooling system from the pre-cooling heat exchanger through a main battery cooling subsystem; and directing the cooling fluid from the main battery cooling subsystem through the battery pack to thereby absorb heat from the battery pack.
An advantage of an embodiment is that the capacity of the main battery cooling system may be reduced due to the increased cooling capacity obtained by employing the evaporator condensate. If a chiller with refrigerant is being used for the main battery cooling system, then the compressor operation may be reduced. Use of the condensate, then, may improve overall fuel economy of the vehicle. The use of the condensate may also allow for faster battery pack cool down in a hot ambient environment.
The HVAC system 22 may also include a condensate bottle 34, which is preferably insulated to keep any condensate in the bottle 34 cold. The condensate bottle 34 has an inlet 35 that receives condensate from a drain 37 under the evaporator 30. A control valve 36 has an inlet 38 connected to an outlet 40 of the condensate bottle 34. The control valve 36 has two outlets, an outlet to atmosphere 42 and an outlet 44 that connects to a condensate pump 46. The condensate pump 46 has an outlet 48 through which the condensate may be pumped into a pre-cooling heat exchanger 50, with the heat exchanger 50 including a condensate outlet 52 to atmosphere.
The pre-cooling heat exchanger 50 is also part of the battery cooling system 24 and includes a coolant outlet 54 that connects to a main battery cooling subsystem 56. The main battery cooling subsystem 56 may employ cooled refrigerant and heat exchangers or other means for cooling the fluid flowing through the battery cooling system 24. The fluid flowing through the battery cooling system 24 may be a coolant, such as, for example, ethylene glycol—although, other types of coolant may be employed instead, if so desired. An outlet 58 from the main battery cooling subsystem 56 connects to a battery pack 60, with the cooling fluid directed through the battery pack 60 to cool it. A battery cooling pump 62 receives the fluid from the battery pack 60 and directs it to an inlet 64 to the pre-cooling heat exchanger 50. The cooling fluid is pumped through the battery cooling system 24 by the battery cooling pump 62.
A controller 66 (which may be made up of a single controller or several discrete controllers in communication with one another) may control the activation of the battery cooling pump 62 as well as controlling the condensate pump 46 and the control valve 36. The communication between the controller 66 and the components is indicated by dashed lines in
The operation of the HVAC and battery cooling system 20 will now be discussed. When operating a vehicle in hot ambient conditions, the refrigerant portion 32 of the HVAC system 22 is used to cool a passenger compartment of the vehicle, while the main battery cooling subsystem 56 is activated to cool the battery pack 60. As the air flows through the evaporator 30, the air temperature is lowered below its dew point, causing moisture in the air to condense out. This condensate is collected and directed from the drain 37 into the condensate bottle 34. The insulation around the condensate bottle 34 keeps the condensate cold.
After the condensate volume in the condensate bottle 34 reaches a minimum threshold, the control valve is actuated to direct the condensate toward the condensate pump 46, which is also activated to pump the condensate through the pre-cooling heat exchanger 50. As the condensate flows through the pre-cooling heat exchanger 50, it absorbs heat from the battery cooling system fluid flowing in the pre-cooling heat exchanger 50 before the condensate is discharged to atmosphere (i.e., allowed to flow out onto the ground).
The cooling fluid flowing through the battery cooling system 24, consequently, is cooled before it enters the main battery cooling subsystem 56 for further cooling—thus auxiliary cooling of the cooling fluid is achieved before the main battery cooling subsystem 56 further cools the fluid. This cooled fluid is then directed through the battery pack 60 to absorb heat from the batteries, with the battery cooling pump 62 pumping the fluid through this system. With the addition of the pre-cooling heat exchanger 50, the overall effectiveness of the battery cooling system 24 is improved.
Under operating conditions where there is already stored cold condensate in the condensate bottle 34, the control valve 36 and condensate pump 46 may be activated immediately upon activation of the battery cooling system 24, whether or not the refrigerant portion 32 of the HVAC system is activated 22. Also, should a situation arise where it is not desirable to direct the condensate through the pre-cooling heat exchanger 50, the control valve 36 may be actuated to direct the condensate from the condensate bottle 34 directly to atmosphere. The situation may arise depending upon various factors such as, for example, ambient air temperature, battery cooling fluid temperature and air conditioning system state.
The battery cooling system 124 can be essentially the same as the first embodiment, if so desired, with the battery cooling pump 162 pumping a coolant through the pre-cooling heat exchanger 150, main battery cooling subsystem 156, and battery pack 160. Also, the HVAC module 126, including the blower 128, evaporator 130 and refrigerant system 132, may be the same as in the first embodiment, if so desired. In this embodiment, however, the condensate flow is a passive rather than a controlled flow. That is, the condensate flowing from the evaporator drain 137 is always directed to an inlet 168 to the pre-cooling heat exchanger 150, and then from an outlet 152 from the heat exchanger 150 to atmosphere. Thus, the condensate always flows through the pre-cooling heat exchanger 150 at the rate at which the condensate is produced by the operation of the evaporator 130. The flow of the condensate can be achieved via gravity to eliminate a need for a condensate pump, in addition to the elimination of a control valve. Moreover, a condensate bottle may also be eliminated.
While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.
