Patent Description:
Aircraft that fly at altitudes above that at which ambient air is suitable for the health and comfort of crew and passengers are often equipped with environmental air conditioning systems. Such systems provide pressurized conditioned air for cooling passengers, crew, and other aircraft systems and components. These air conditioning systems typically use high pressure air bled from a turbine engine or auxiliary power unit (APU). This high-pressure air is typically at a temperature and pressure far in excess of the temperature and pressure required for conditioned air to be supplied to the cockpit and passenger cabin, so it must be expanded and cooled by the air conditioning system before it can be discharged into the aircraft cabin as conditioned air.

The high-pressure air bled from a turbine engine or auxiliary power unit is typically cooled within the air conditioning system by rejecting heat therefrom directly to a ram air circuit. However, the use of engine bleed air increases the overall fuel burn of the system and ram air heat exchangers typically must be large to provide an acceptable heat sink for cooling the bleed air. <CIT> describes an aircraft air conditioning system. <CIT> describes an air cycle environmental control system. <CIT> describes a high efficiency air cycle air conditioning system. <CIT> describes a bootstrap air cycle with vapour power turbine.

An environmental control system of a vehicle according to independent claim <NUM> includes an inlet configured to receive a medium, a heat exchanger fluidly connected to the inlet to receive the medium, a water separator arranged directly downstream from the heat exchanger relative to a flow of the medium, and a ram air circuit including another inlet configured to receive ram air and including a ram air heat exchanger. A closed secondary fluid loop is operably coupled to the heat exchanger and to the ram air heat exchanger. The secondary fluid loop has a secondary fluid circulating therein that removes heat from the medium in the heat exchanger and that discharges heat to the ram air in the ram air heat exchanger.

In further embodiments the secondary fluid is a liquid, optionally.

In further embodiments the system comprises an expansion device, the expansion device being operably coupled to the heat exchanger and to the ram air circuit.

In further embodiments the expansion device further comprises a turbine and a fan operably coupled by a shaft, the turbine being arranged to receive the medium from the heat exchanger, and the fan being arranged within the ram air circuit.

In further embodiments the expansion device further comprises a pump mounted to the shaft, the pump being arranged within the secondary fluid loop, wherein work extracted by the turbine is transferred to the pump via the shaft.

In further embodiments the ram air is not arranged in a direct heat exchange relationship with the medium.

In further embodiments the medium is bleed air.

In further embodiments the vehicle is an aircraft.

A method of operating an environmental control system of a vehicle according to independent claim <NUM> includes receiving a medium at an inlet for delivery to one or more loads at a heat exchanger, the heat exchanger being directly downstream from the inlet and removing water from the medium within a water extractor located directly downstream from the heat exchanger relative to a flow of the medium, circulating a secondary fluid within a secondary fluid loop operably coupled to the heat exchanger and a ram air circuit, cooling the medium by removing heat from the medium via the secondary fluid at the heat exchanger, and discharging heat from the secondary fluid to a ram air within the ram air circuit.

In further embodiments the method comprises extracting energy from the medium and driving a pump using the energy extracted from the medium, the circulating of the secondary fluid being performed by the pump.

In further embodiments the method comprises extracting energy from the medium; and driving a fan arranged within the ram air circuit using the energy extracted from the medium.

In further embodiments the method comprises moving the ram air through the ram air circuit in response to driving the fan.

In further embodiments the secondary fluid is a liquid.

In further embodiments the secondary fluid is water.

With reference to the accompanying drawings, like elements are numbered alike:
The Figure is a schematic diagram of an environmental control system of a vehicle according to an embodiment.

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figure.

With reference now to the figure, a schematic diagram of an embodiment a portion of an environmental control system (ECS) <NUM>, such as an air conditioning unit or pack for example, is depicted according to a non-limiting embodiment. Although the environmental control system <NUM> is described with reference to an aircraft, alternative applications, such as another vehicle for example, are also within the scope of the disclosure. As shown, the ECS <NUM> may be configured to receive a medium A at an inlet <NUM> and provide a conditioned form of the medium A to one or more loads <NUM>. In embodiments where the ECS <NUM> is used in an aircraft application, the medium A may be bleed air, which is pressurized air originating from, i.e., being "bled" from, an engine or auxiliary power unit of the aircraft. It shall be understood that one or more of the temperature, humidity, and pressure of the bleed air can vary based upon the compressor stage and revolutions per minute of the engine or auxiliary power unit from which the air is drawn.

As shown, the environmental control system <NUM> may include a ram air circuit <NUM> including a shell or duct <NUM> within which one or more heat exchangers are located. The ram air duct <NUM> can receive a medium RA, such as ram air for example, at an inlet <NUM> and can direct the medium RA through a portion of the ECS <NUM>. The ram air RA may be ambient air from outside the aircraft. The one or more heat exchangers are devices built for efficient heat transfer from one medium to another. Examples of the type of heat exchangers that may be used, include, but are not limited to, double pipe, shell and tube, plate, plate and shell, adiabatic shell, plate fin, pillow plate, and fluid heat exchangers.

The one or more heat exchangers arranged within the ram air duct <NUM> may be referred to as ram heat exchangers. In the illustrated, non-limiting embodiment, the ram air circuit <NUM> includes a single heat exchanger <NUM>. However, embodiments having additional ram air heat exchangers are also contemplated herein. Within the ram air heat exchanger <NUM>, ram air RA, such as outside air for example, acts as a heat sink to cool another medium passing there through.

The ECS <NUM> additionally includes an expansion device <NUM>. The expansion device <NUM> of the ECS <NUM> is a mechanical device that includes components for performing thermodynamic work on one or more mediums (e.g., extracts work from or applies work to a medium A by raising and/or lowering pressure and by raising and/or lowering temperature). Examples of the expansion device <NUM> include, but are not limited to, an air cycle machine, such as a three-wheel or four-wheel air cycle machine. In the illustrated, non-limiting embodiment, the compression device is a simple cycle or two-wheel air cycle machine.

As shown, the expansion device <NUM> includes a turbine <NUM> and a fan <NUM> operably coupled to one another via a shaft <NUM>. The turbine <NUM> is a mechanical device that expands a medium and extracts work therefrom (also referred to as extracting energy). In the expansion device <NUM>, the turbine <NUM> drives the fan <NUM> via the shaft <NUM>. A fan <NUM> is a mechanical device that can force via push or pull methods air through the ram air duct <NUM>, across at least a portion of one or more ram air heat exchangers <NUM>. However, embodiments where the fan <NUM> is a component separate from the expansion device and is driven by any suitable means are also contemplated herein.

The ECS <NUM> additionally includes one or more heat exchangers or devices configured to provide efficient heat transfer from one medium to another. In the illustrated, non-limiting embodiment, the ECS <NUM> includes a single heat exchanger <NUM> arranged directly downstream from the inlet <NUM> of the medium A. However, embodiments including additional heat exchangers or other components at any suitable location relative to the flow of medium A or the flow of ram air RA are also within the scope of the disclosure.

In the illustrated, non-limiting embodiment, the ram air RA is not arranged in a direct heat exchange relationship with the medium A at either the heat exchanger <NUM> or the ram air heat exchanger <NUM>. Rather, the ECS <NUM> uses a secondary fluid W circulating through a closed secondary fluid loop <NUM> to condition both the medium A and the ram air RA. In an embodiment, the secondary fluid W is a liquid, such as water or another suitable liquid for example. A pump <NUM> may be used to circulate the secondary fluid W through the secondary fluid loop <NUM>. In an embodiment, the pump is <NUM> mounted to the shaft <NUM> of the expansion device <NUM> as a third wheel and is therefore driven by rotation of the shaft <NUM> resulting from work or energy extracted from the medium A within the turbine <NUM>.

The secondary fluid loop <NUM> is thermally coupled to both the heat exchanger <NUM> and the ram air heat exchanger <NUM>. In the illustrated, non-limiting embodiment, the heat exchanger <NUM> includes a secondary fluid inlet <NUM> and a secondary fluid outlet <NUM>. The secondary fluid inlet <NUM> may be connected to an outlet <NUM> of the pump <NUM> by a conduit <NUM>. Similarly, the ram air heat exchanger <NUM> includes a secondary fluid inlet <NUM> connected to the secondary fluid outlet <NUM> of the heat exchanger <NUM> by a conduit <NUM>. The secondary fluid outlet <NUM> of the ram air heat exchanger <NUM> is fluidly coupled to an inlet <NUM> of the pump <NUM> by a conduit <NUM>.

In operation, the medium A is provided to the ECS <NUM> via the inlet <NUM>. From the inlet <NUM>, the medium A is delivered to the heat exchanger <NUM>. Within the heat exchanger <NUM>, heat transfers from the medium A to the secondary fluid W. The resulting cooled medium A may then be provided to a downstream water separator or extractor <NUM>. In an embodiment, the heat exchanger <NUM> is configured as a condenser such that as the medium A cools therein, the water entrained within the medium A will condense. This condensed fluid may then be removed from the medium A within the water extractor <NUM>. The condensed fluid, for example water, removed from the medium A may be reused elsewhere on the aircraft. In the illustrated, non-limiting embodiment, the water is sprayed on the face of the ram air heat exchanger <NUM>.

From the water extractor <NUM>, the dry medium A is provided to an inlet of the turbine <NUM>. Within the turbine <NUM>, the medium A is expanded, and work is extracted therefrom which results in a cooling and depressurization of the medium A. The cooler and lower pressure medium A provided at an outlet of the turbine <NUM> may then be delivered to one or more loads of the vehicle.

The work extracted from the medium A within the turbine <NUM>, drives the pump <NUM> causing the secondary fluid W to circulate within the secondary fluid loop <NUM>. The work extracted form the medium A within the turbine <NUM> also drives rotation of the fan <NUM>. As a result of this rotation of the fan <NUM>, ram air RA from the inlet <NUM> moves through the ram air duct <NUM>, and specifically, across the ram air heat exchanger <NUM>. As previously noted, the heated secondary fluid W output from the heat exchanger <NUM> is provided to the secondary fluid inlet <NUM> of the ram air heat exchanger <NUM>. Accordingly, within the ram air heat exchanger <NUM>, heat from the secondary fluid W is transferred to the ram air RA. The heated ram air RA is then exhausted overboard from an outlet of the ram air duct <NUM>.

An environmental control system <NUM> as described herein relies on a secondary fluid to remove heat from the medium A and then discharge that heat to the flow of ram air RA. Because the ability to transfer heat is significantly increased in liquid-air heat exchangers compared to air-air heat exchangers, inclusion of the secondary fluid loop results not only in an improved ability to discharge heat to the ram air RA, but also the potential to achieve cooler air temperatures at the outlet of the heat exchanger <NUM>. Additionally, the energy required to increase a fluid's pressure via a pump is significantly less than required to increase the pressure of a gaseous medium (such as air) via a compressor which may allow for heat exchanger designs with more heat transfer surface area on the liquid sides relative to an air-air heat exchanger.

The terminology used herein is for the purpose of describing embodiments only and is not intended to be limiting of the present disclosure.

Claim 1:
An environmental control system of a vehicle comprising:
an inlet (<NUM>) configured to receive a medium;
a heat exchanger (<NUM>) fluidly connected directly to the inlet to receive the medium; and a water separator (<NUM>);
a ram air circuit (<NUM>) including another inlet (<NUM>) configured to receive ram air and including a ram air heat exchanger (<NUM>); and
a closed secondary fluid loop (<NUM>) operably coupled to the heat exchanger (<NUM>) and to the ram air heat exchanger (<NUM>), the secondary fluid loop having a secondary fluid circulating therein that removes heat from the medium in the heat exchanger (<NUM>) and that discharges heat to the ram air in the ram air heat exchanger (<NUM>), characterised in that the water separator is arranged directly downstream from the heat exchanger (<NUM>) relative to a flow of the medium.