1. Field of the Invention
An air conditioning system for cooling the cabin of a vehicle.
2. Description of the Prior Art
Fuel efficiency in vehicles is enhanced by shutting off the gasoline engine during inefficient periods, such as when the vehicle is coasting or temporarily stopped. However, the compressor of a traditional air conditioning system runs off the crankshaft of the gasoline engine, and therefore, the gasoline engine continues to operate during those inefficient periods to prevent uncomfortable conditions for the passengers of the vehicle. It is desirable to have an air conditioning system that continues to operate when the engine is shut off, so that vehicles may shut off their gasoline engine during those inefficient periods.
U.S. Pat. No. 7,156,156, issued to Haller et al. on Jan. 2, 2007 (hereinafter referred to as Haller '156), provides one solution to the problem of the air conditioning system not functioning when the engine is not running. The Haller '156 patent shows an evaporator having a refrigerant flowing there-through for transferring heat from a flow of air to the refrigerant in a first operating mode with the engine of the vehicle running. The evaporator includes a manifold extending in a horizontal direction. At least one tube is in fluid communication with manifold and extends downward in a vertical direction away from the manifold. The evaporator defines at least one cavity, or phase change material (PCM) tank, for storing a phase change material to transfer heat from the phase change material to the refrigerant to cool and freeze the phase change material in the first operating mode with the engine of the vehicle running.
The cavities of the Haller '156 patent are disposed adjacent to and engaging the plurality of tubes. In a second operating mode with the engine of the vehicle dormant, heat is transferred directly from the flow of air to the phase change material in the cavities to cool the flow of air and to melt or warm the phase change material. There remains a continuing need for improved air conditioning systems that continue to operate during inefficient periods when the engine of the vehicle is shut off.