Patent Description:
The present disclosure is directed generally to aircraft environmental control systems and, more particularly, to a vapor cycle liquid cabin cooling system. Vapor cycle systems (VCSs) have been used for aircraft environmental control systems for cabin and avionic cooling. A typical VCS is a closed loop system that includes a compressor, condenser, expansion device, and evaporator with a refrigerant that continuously circulates through the components. The refrigerant enters the compressor as a vapor and is compressed, increasing a temperature and pressure of the refrigerant. The refrigerant is cooled to a liquid phase in the condenser and heat is rejected (typically to ambient air). The refrigerant is expanded through the expansion device reducing a pressure of the refrigerant, thereby forming a saturated liquid/vapor mixture at a lower temperature, which enters the evaporator. The refrigerant is expanded in the evaporator, changing form a liquid to vapor phase and absorbing heat from cooling fluid (e.g., air in a cabin to be cooled). Although VCSs can provide improved efficiency over traditional air cycle machines and are more compatible with modern electrical aircraft, VCSs introduce reliability issues in aerospace applications. Because VCSs are capable of producing more cooling capacity than needed, cooling demand is typically met by intermittent operation of the VCSs (i.e. turning VCSs off and on) or by varying a speed of a compressor of the VCSs. Start and stop cycles can wear out mechanical components of the compressor. Lowering a speed of the compressor can result in loss of lubrication to the compressor. Environmental control systems are disclosed in <CIT>, <CIT> and <CIT>. <CIT>, according to its abstract, describes a method for operating an aircraft cooling system comprising the steps of guiding a cooling medium through a cooling circuit which is coupled to a refrigerating machine and to at least one cooling energy consumer in order to supply cooling medium cooled by the refrigerating machine to the cooling energy consumer, and controlling the operation of the refrigerating machine by a control unit, such that coolant medium cooled by the refrigerating machine to a predetermined cooling medium flow temperature is supplied to the cooling energy consumer. The operation of the refrigerating machine is controlled by the control unit in such a way that cooling medium which is guided through the cooling circuit is cooled to a cooling medium flow temperature which is adapted to a cooling energy requirement of the cooling energy consumer.

More reliable systems incorporating VCSs into aircraft environmental control systems are desired.

In one aspect, a vapor cycle liquid cooling system for an aircraft is provided as defined by claim <NUM>.

In another aspect, a method for providing cooling in an aircraft environmental control system is provided as defined by claim <NUM>.

The present summary is provided only by way of example, and not limitation. Other aspects of the present disclosure will be appreciated in view of the entirety of the present disclosure, including the entire text, claims and accompanying figures.

While the above-identified figures set forth embodiments of the present invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation.

The figures may not be drawn to scale, and applications and embodiments of the present invention may include features, steps and/or components not specifically shown in the drawings.

A vapor cycle liquid cooling system including one or more vapor cycle systems (VCSs) and a liquid loop in thermal communication with the one or more VCSs can be used for cabin and avionic cooling of an aircraft. The disclosed vapor cycle liquid cooling system can be designed to maintain constant load or operating point (constant compressor speed) on the one or more VCSs and minimize the need for heat sink cooling flow. By maintaining a constant operating point, the disclosed system can provide efficient cooling with improved reliability. Controlled delivery of waste heat generated by the constant operation of the one or more VCSs to thermal loads can prevent overcooling of the aircraft.

In the present disclosure, a VCS is in thermal communication with a closed loop liquid cooling system including cooling liquid conduits with cooling liquid received from the VCS, heating liquid conduits with heating liquid received from the VCS, and mixed heating/cooling liquid conduits with mixed heating/cooling liquid, which is delivered back to the VCS where a portion of the mixed heating/cooling liquid is heated and a portion is cooled by the VCS. All cooling liquid is delivered via the cooling liquid conduits to a thermal load (e.g. aircraft cabin) during operation of the VCS. Because the VCS is run at a constant operating point (constant compressor speed), overcooling can occur with constant delivery of the cooling liquid. To prevent overcooling, the heating liquid delivered via the heating liquid conduits can be mixed with the cooling liquid at the thermal load to modulate a temperature of the cooling liquid to meet a cooling or heating demand. The mixed heating/cooling liquid can be returned to the VCS via the mixed heating/cooling liquid conduits. Excess heat can be rejected to a heat sink (e.g., ram air) via a heat exchanger before the mixed heating/cooling liquid is returned to the VCS. The temperature of the heating and cooling liquid entering the VCS can be regulated to maintain a constant fluid temperature at a VCS inlet.

<FIG> are discussed together. <FIG> is a schematized view of cooling system <NUM> for an environmental control system of aircraft <NUM>. <FIG> shows VCSs 14A-14D; closed heating and cooling liquid loop <NUM> with cooling liquid conduits <NUM> (shown as dotted lines), cooling liquid outlets 20A-20D, heating liquid conduits <NUM> (shown as solid lines), heating liquid outlets 24A-24D, mixed heating/cooling liquid conduits <NUM> (shown as dashed lines), and mixed heating/cooling liquid inlets <NUM>/29A-<NUM>/29D (arrows indicate the direction of liquid flow); zone load coolers 30A-30D in cabin zones 32A-32D, and zone load cooler 30E in flight deck 32E; fresh air supply As; recirculating air supply AR; cabin zone air supply AC; electrical load coolers (avionic coolers) 34A, 34B; heat exchangers 36A, 36B; and cooling pumps 38A, 38B.

<FIG> is schematized view of a single zone load cooler 30A-30E. <FIG> shows zone load cooler 30A, cooling liquid conduit <NUM>, heating liquid conduit <NUM>, mixed heating/cooling liquid conduit <NUM>, liquid temperature control valve <NUM>, fan <NUM>, heat exchanger <NUM>, fresh air supply AS, recirculating air supply AR, cabin zone air supply AC, and air temperature sensor <NUM>. <FIG> is a schematized view of a single VCSs 14A-14D.

<FIG> shows VCS 14A, compressor <NUM>, condenser <NUM>, flash tank <NUM>, expansion valve <NUM>, evaporator <NUM>, cooling liquid outlet 20A, heating liquid outlet 24A, mixed heating/cooling liquid inlets 28A and 29A, and temperature sensor <NUM> of mixed heating/cooling liquid conduit <NUM>. VCS 14A includes multiple valves, pressure sensors, temperature sensors, and bypass conduits, and other conventional components shown but not labeled.

<FIG> shows an aircraft divided into four cabin zones 32A-32D, each having a separate zone load cooler 30A-30D for heating and cooling. It will be understood by one of ordinary skill in the art that the disclosed vapor cycle liquid cabin cooling system can be adapted for use with any number of zone load coolers and cabin zones and is not limited to any particular type or size of aircraft. Furthermore, the number of VCSs can be adapted to accommodate varying cooling demands.

Each VCS 14A-14D functions as a liquid heating and cooling unit configured to reject heat to and absorb heat from a fluid contained in closed heating and cooling liquid loop <NUM>, which is used to cool thermal loads of aircraft <NUM>, including cabin zones 32A-32D, flight deck 32E, and electrical load coolers 34A and 34B. As illustrated in <FIG>, VCS 14A has a conventional design including compressor <NUM>, condenser <NUM>, flash tank <NUM>, expansion valve <NUM>, and evaporator <NUM> with a refrigerant that continuously circulates through the components. The refrigerant enters compressor <NUM> as a vapor and is compressed increasing a temperature and pressure of the refrigerant. The refrigerant is cooled to a liquid phase in condenser <NUM> and heat is rejected to heating liquid in heating and cooling liquid loop <NUM>, which is in thermal communication with condenser <NUM>. Heating liquid enters VCS 14A in heating and cooling liquid loop <NUM> via mixed heating/cooling liquid conduit <NUM> at mixed heating cooling inlet <NUM> and is discharged from VCS 14A at heating liquid outlet 24A. The refrigerant is collected in flash tank <NUM> and expanded through expansion valve <NUM> reducing a pressure of the refrigerant forming a saturated liquid/vapor mixture at a lower temperature, which enters evaporator <NUM>. The refrigerant is expanded in evaporator <NUM>, changing form a liquid to vapor phase and absorbing heat from cooling liquid in heating and cooling liquid loop <NUM>, which is in thermal communication with evaporator <NUM>. Heating/cooling fluid enters VCS 14A via mixed heating/cooling liquid conduit <NUM> at mixed heating/cooling inlet <NUM> and is discharged from VCS 14A at cooling liquid outlet 20A.

VCS <NUM> can include multiple valves, pressure sensors, temperature sensors, and bypass conduits, and other components shown but not labeled for the functioning of VCS 14A as known in the art.

As will be described further herein, a temperature of heating/cooling liquid entering VCS 14A via mixed heating/cooling inlets <NUM> and <NUM> can be kept constant during operation of VCS <NUM> as measured by temperature sensor <NUM>.

Refrigerant can be any refrigerant known in the art suitable for aircraft cooling applications, including, for example, R134a, R1234yf, R1234ze. The refrigerant loop is confined in VCS <NUM> and used only for indirect cooling of cabin zones 32A-32D, flight deck 32E, and electrical load coolers 34A and 34B (i.e., the refrigerant does not directly cool cabin air supply AC or electronic components). VCSs 14A-14D can be operated at a constant operating point (constant compressor speed) during operation of aircraft <NUM>. The operation of VCSs 14A-14D is independent of the aircraft cooling demand and the speed of compressor <NUM> is maintained regardless of changes in cooling demand during flight. As such, VCSs 14A-14D can be operated with limited control.

Heating and cooling liquid loop <NUM> is in thermal communication with VCSs 14A-14D and thermal loads requiring cooling-in this case, zone load coolers 30A-30E and electrical load coolers 34A and 34B. Heating and cooling liquid loop <NUM> is a closed loop system with a recirculating heating/cooling liquid. The heating/cooling liquid can be, for example, an antifreeze water mixture including, for example, ethylene glycol water or propylene glycol water, or fluid capable of remaining in a liquid phase at ambient temperatures of aircraft operation. Heating and cooling liquid loop <NUM> can be formed of solid metallic tubes or flexible plastic tubing.

Heating and cooling liquid loop <NUM> includes cooling liquid conduits <NUM>, heating liquid conduits <NUM>, and mixed heating/cooling liquid conduits <NUM>. Cooling liquid conduits are in fluid communication with cooling liquid outlets 20A-20D and are configured to carry cooling liquid discharged from cooling liquid outlets 20A-20D of VCSs 14A-14D. Heating liquid conduits <NUM> are in fluid communication with heating liquid outlets 24A-24D and are configured to carry heating liquid discharged from VCSs 14A-14D from heating liquid outlets 24A-24D. Mixed heating/cooling liquid conduits <NUM> are in fluid communication with mixed heating/cooling inlets 28A/29A-28D-29D and are configured to carry a mixture of cooling liquid and heating liquid or cooling liquid that has absorbed heat from thermal loads (e.g., at zone load coolers 30A-30E).

Vapor cycle liquid cooling system <NUM> is configured to deliver all cooling capacity (i.e., all cooling liquid discharged from VCSs 14A-14D) to each thermal load at all times of operation. As illustrated in <FIG>, all cooling liquid discharged from VCSs 14A-14D is delivered to zone load coolers 30A-30E via cooling liquid conduits <NUM>, which extend from VCSs 14A-14D to zone load coolers 30A-30E. Because operation of VCSs 14A-14D can maintained at a steady state with a constant temperature of mixed heating/cooling liquid at mixed heating/cooling inlets 28A/29A-28D-29D, cooling liquid can be maintained at a constant temperature at cooling liquid outlets 20A-20D.

Cooling liquid conduits <NUM> can be arranged and/or combined in any configuration. As illustrated in <FIG>. Cooling liquid outlets 20A and 20B can feed a first leg of cooling liquid conduit <NUM>, while cooling liquid outlets 20C and 20D can feed a second leg of cooling liquid conduit <NUM>. The first and second legs of cooling liquid conduit <NUM> can be combined upstream of zone load coolers 30A-30E before branching into separate conduits to feed each zone load cooler 30A-30E. Arrows indicate the direction of cooling liquid flow from VCSs 14A-14D to zone load coolers 30A-30E.

Vapor cycle liquid cooling system <NUM> is configured to modulate a flow of heating liquid to zone load coolers 30A-30D. Heating liquid can be delivered to zone load coolers 30A-30D (or other thermal loads) via heating liquid conduit <NUM> to adjust a temperature of the cooling liquid at the thermal load as needed to prevent overcooling. Heating liquid is discharged from VCSs 14A-14D via heating liquid outlets 24A-24D. Because operation of VCSs 14A-14D can maintained at a steady state with a constant temperature of mixed heating/cooling liquid at mixed heating/cooling inlets 28A/29A-28D-29D, heating liquid can be maintained at a constant temperature at heating liquid outlets 24A-24D.

As illustrated in <FIG>, heating liquid conduits <NUM> can be arranged in a similar configuration as cooling liquid conduits <NUM>, with heating liquid outlets 24A and 24B feeding a first leg of heating liquid conduit <NUM> and heating liquid outlets 24C and 24D feeding a second leg of heating liquid conduits <NUM>. The first and second legs of heating liquid conduits <NUM> can be combined upstream of zone load coolers 30A-30E before branching into separate conduits to feed each zone load cooler 30A-30E. As illustrated in <FIG> and discussed further herein, heating liquid conduits <NUM> can be in valved or interruptible fluid communication with cooling liquid conduits <NUM>. Heating liquid conduits <NUM> can include liquid temperature control valve <NUM>, which can control a flow of heating liquid into cooling liquid conduit <NUM> at each zone load cooler 30A-30E.

VCSs 14A-14D produce more heating capacity than needed. Excess heating liquid can be delivered to heat exchanger 36A and 36B to be cooled. For example, excess heating liquid can be cooled by ram air at heat exchangers. As illustrated, heating liquid conduits <NUM> extend both from VCSs 14A-14D to zone load coolers 30A-30E and from VCSs 14A-14D to mixed heating/cooling liquid conduits <NUM> upstream of heat exchangers 36A and 36B. Arrows indicate the direction of flow of heating liquid from VCSs 14A-14D to zone load coolers 30A-30E and heat exchangers 36A and 36B.

Mixed heating/cooling liquid conduits <NUM> can carry cooling liquid that has absorbed heat from cabin zones 32A-32D and flight deck 32E in zone load coolers 30A-30E and any additional heating liquid that has been supplied to zone load coolers 30A-30E. In other words mixed heating/cooling liquid is produced by mixing heating liquid with cooling liquid at zone load coolers 30A-30E and/or by heating cooling liquid with, for example, an air-to-liquid heat exchanger of zone load coolers 30A-30E. Mixed heating/cooling liquid is discharged from zone load coolers 30A-30E.

Mixed heating/cooling liquid can be used to cool electrical loads. Mixed heating/cooling liquid conduits <NUM> can be combined in a single mixed heating/cooling liquid conduit <NUM> upstream of electrical load coolers 34A and 34B before branching to be delivered to each of electrical load coolers 34A and 34B in separate mixed heating/cooling liquid conduits <NUM>. Heating/cooling liquid can be used to cool electrical components, for example, by an air-to-liquid heat exchanger or by any heat exchange means known in the art. Mixed heating/cooling liquid leaving electrical load coolers 34A and 34B can be directed to heat exchangers 36A and 36B before being returned to VCSs 14A-14D. Arrows indicate the direction of mixed heating/cooling liquid flow. As illustrated in <FIG>, excess heating liquid in heating liquid conduit <NUM> can be combined with mixed heating/cooling liquid downstream of electrical load coolers 34A and 34B relative to a flow of the mixed heating/cooling liquid.

Heat exchangers 36A and 36B can be, for example, ram air heat exchangers configured to exchange heat between ram air flow and the mixed heating/cooling liquid, which includes excess heating liquid from heating liquid conduit <NUM>. Heat exchangers 36A and 36B can have any air-to-liquid heat exchange configuration known in the art. All or a portion of the mixed heating/cooling liquid can be cooled by ram air in heat exchangers 36A and 36B depending on a temperature of the mixed heating/cooling liquid and ram air temperature. Vapor cycle liquid cooling system <NUM> can be configured to maintain a constant mixed heating/cooling liquid temperature at inlets 28A-28D and 29A-29D of VCSs 14A-14D. Mixed heating/cooling liquid conduits <NUM> can include bypass valves 62A and 62B to allow all or a portion of the mixed heating/cooling liquid to bypass heat exchangers 36A and 36B to prevent overcooling of the mixed heating/cooling liquid. Temperature sensor <NUM> (<FIG>) can detect a temperature of the mixed heating/cooling liquid entering VCSs 14A-14D and can trigger the opening or closing of valves 62A and 62B to modulate the cooling of the mixed heating/cooling liquid in mixed heating/cooling liquid conduits <NUM>.

As illustrated in <FIG>, the branches of mixed heating/cooling liquid conduits <NUM> received at electrical load coolers 34A and 34B can remain separate and feed different subsets of VCSs 14A-14D. The portion of the mixed heating/cooling liquid used to cool electrical load cooler 34A can be delivered to heat exchanger 36A before being returned to VCSs 14A and 14B, while the portion of the mixed heating/cooling liquid leaving electrical load cooler 34B can be delivered to heat exchanger 36B before being returned to VCSs 14C and 14D. As illustrated in <FIG>, the mixed heating/cooling liquid can be further divided into separate mixed heating/cooling liquid conduits <NUM> at VCSs 14A-14D, where a portion of the mixed heating/cooling liquid can be delivered to VCSs 14A-14D via inlet 28A-28D to be heated and discharged via heating liquid outlets 24A-24D and a portion can be delivered to VCSs 14A-14D via inlet 29A-29D to be cooled and discharged via cooling liquid outlets 20A-20D.

It will be understood by one of ordinary skill in the art that alternative routing configurations and combinations of cooling liquid conduits <NUM>, heating liquid conduits <NUM>, and mixed heating/cooling liquid conduits <NUM> fall within the scope of the present disclosure and can be optimized to accommodate cooling demand and varying numbers and arrangements of VCSs and thermal loads.

Cooling pumps 38A and 38B maintain circulation of the cooling liquid, heating liquid, and mixed heating/cooling liquid through cooling liquid conduits <NUM>, heating liquid conduits <NUM>, and mixed heating/cooling liquid conduits <NUM>, respectively. Cooling pumps can be any type of liquid pump known in the art and suitable for pumping antifreeze or other suitable liquid.

<FIG> further illustrates the control of cooling and heating liquid to zone load coolers 30A-30E. Zone load cooler 30A in cabin zone 32A is shown as an example. Each zone load cooler 30A-30E can have the same configuration. Zone load cooler 30A can be an air handling unit including air-to-liquid heat exchanger <NUM>, fan <NUM>, liquid temperature control valve <NUM>, and air temperature sensor <NUM>. Fan <NUM> can recirculate air AR from cabin zone 32A or circulate a thermal load across heat exchanger <NUM> to provide heating/cooling to cabin zone 32A. Both a fresh air supply As and a recirculating air supply AR can be delivered to heat exchanger <NUM>. As illustrated and previously described, all cooling liquid is delivered heat exchanger <NUM> of zone load cooler 30A via cooling liquid conduit <NUM> during aircraft operation regardless of cooling demand. Air temperature sensor <NUM> can measure a temperature of cabin air AC, which can vary between flights and in-flight due to variations in heat sources (e.g., number of people, in-flight entertainment, personal computers, etc.) Typically, zone load coolers are configured to maintain a cabin temperature between <NUM> °F (<NUM>) and <NUM> °F (<NUM>) in each cabin zone. When the temperature of cabin air AC falls below a preset temperature (e.g., below <NUM> °F (<NUM>) ), air temperature sensor <NUM> can trigger the opening of liquid temperature control valve <NUM> to mix heating liquid from heating liquid conduit <NUM> discharged from VCSs 14A-14D with cooling liquid to achieve a desired cabin air temperature. Once the desired cabin air temperature is reached, air temperature sensor <NUM> can trigger liquid temperature control valve <NUM> to close. As previously described, VCSs 14A-14D create more heating capacity than needed. Excess heating liquid can be delivered to heat exchangers 36A and 36B via mixed heating/cooling liquid conduit <NUM> to be cooled before being returned to VCSs 14A-14D.

The disclosed vapor cycle liquid cabin cooling system can be used for efficient cabin and avionic cooling of an aircraft with improved reliability. Each VCS can be run at a constant operating point during operation of aircraft <NUM> and, as such, can be operated with limited control. Control of cooling capacity can be achieved by modulating the mixing of heating liquid discharged from the VCS with cooling liquid discharged from the VCS in the closed heating and cooling liquid loop at the location of the thermal load (e.g., cabin zone). All mixed heating/cooling liquid can be returned to the VCS at a constant temperature maintained by modulation of flow of mixed heating/cooling liquid through an air-to-liquid heat exchanger (e.g., ram air heat exchanger).

It will be understood by one of ordinary skill in the art that the number of VCSs, thermal load coolers, types of air-to-liquid heat exchangers, and heating and cooling liquid loop configurations can be varied without departing from the scope of the present disclosure.

Any relative terms or terms of degree used herein, such as "substantially", "essentially", "generally", "approximately" and the like, should be interpreted in accordance with and subject to any applicable definitions or limits expressly stated herein. In all instances, any relative terms or terms of degree used herein should be interpreted to broadly encompass any relevant disclosed embodiments as well as such ranges or variations as would be understood by a person of ordinary skill in the art in view of the entirety of the present disclosure, such as to encompass ordinary manufacturing tolerance variations, incidental alignment variations, transient alignment or shape variations induced by thermal, rotational or vibrational operational conditions, and the like. Moreover, any relative terms or terms of degree used herein should be interpreted to encompass a range that expressly includes the designated quality, characteristic, parameter or value, without variation, as if no qualifying relative term or term of degree were utilized in the given disclosure or recitation.

While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made without departing from the scope of the invention as defined by the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from said scope.

Claim 1:
A vapor cycle liquid cooling system for an aircraft comprises:
a vapor cycle system (14A-14D) comprising:
a closed refrigerant loop;
a cooling liquid outlet (<NUM>);
and a heating liquid outlet (24A);
an air handling unit (30A); and
a closed liquid loop (<NUM>) comprising the cooling liquid outlet (<NUM>) and the heating liquid outlet (24A), the closed liquid loop in thermal communication with the closed refrigerant loop and the air handling unit;
wherein the cooling liquid outlet is configured to deliver a cooling liquid in the liquid loop and the heating liquid outlet is configured to deliver a heating liquid in the liquid loop; and
wherein the vapor cycle liquid cooling system is configured to deliver the cooling liquid to the air handling unit and is configured to modulate a flow of the heating liquid to the air handling unit.