Integrated environmental control systems and methods for controlling environmental temperature of an enclosed space
Environmental control systems and methods to control environmental temperature of an enclosed space by integrating a passive heat exchange subsystem (e.g., a loop heat pipe (LHP) heat exchange subsystem) having a closed loop heat exchange fluid circuit in heat-exchange relationship with the enclosed space for providing environmental temperature control therewithin, a RAM-air subsystem having a RAM-air circuit for circulating RAM cooling air, and a vapor compression cycle machine (VCM) subsystem having a VCM fluid circuit having a compressor, an evaporator, a condenser and an expansion valve.
1. An aircraft which comprises an environmental control system for controlling environmental temperature of an enclosed space of the aircraft, wherein the environmental control systems comprises:
a passive phase change heat exchange subsystem having a closed loop heat pipe (LHP) circuit for circulating a heat exchange fluid and a LHP evaporator for receiving the heat exchange fluid in heat-exchange relationship with the enclosed space for providing environmental temperature control therewithin;
a RAM-air subsystem which includes an air duct defined by duct walls having an inlet comprised of a NACA duct RAM-air intake and an outlet to allow ambient air to flow into and out of the air duct and to thereby define an air circuit for circulation of cooling air between the inlet and outlet, and an internal embedded skin heat exchanger (SHX) which is operatively affixed to the air duct to receive RAM-air, the internal embedded SHX comprising a plurality of fins oriented so as to face an internal side of a duct wall of the air duct; and
a vapor closed loop compression cycle machine (VCM) subsystem having a VCM fluid circuit comprising a VCM compressor, a primary VCM condenser in heat exchange relationship with the air circuit of the RAM-air subsystem, a secondary VCM condenser in the VCM fluid circuit positioned upstream or downstream of the primary VCM condenser, a VCM bypass line to bypass the secondary VCM condenser, a VCM expansion valve, a VCM evaporator and a VCM condenser bypass valve to selectively establish fluid communication between the primary VCM condenser and either the secondary VCM condenser or the VCM bypass line, wherein
the LHP circuit comprises:
(i) a first branch which includes a primary LHP condenser so as to receive the heat exchange fluid from the LHP evaporator and direct the heat exchange fluid into heat exchange relationship with the VCM evaporator of the VCM subsystem,
(ii) a second branch which includes a LHP SHX condenser for receiving the heat exchange fluid from the LHP evaporator,
(iii) a third branch which directs the heat exchange fluid from the LHP evaporator to the internal embedded SHX operatively affixed to the air duct to cool the heat exchange fluid in the RAM-air subsystem and direct cooled heat exchange fluid back to the LHP evaporator, and
(iv) a LHP control valve for directing the LHP circuit heat exchange fluid between one of the first, second and third branches thereof, and wherein
the system further comprises an on-board controller operatively connected to the VCM condenser bypass valve for operatively selecting fluid communication between either the secondary VCM condenser or the VCM bypass line, and the LHP control valve for operatively selecting heat exchange fluid flow through either the LHP SHX condenser or the LHP condenser into heat exchange relationship with the VCM evaporator or the SHX affixed to the air duct in the RAM-air subsystem, wherein during in-flight operation, the on-board controller is configured to:
(i) operatively activate the LHP control valve at an altitude of the aircraft having a temperature below standard to allow heat exchange fluid to flow only through the LHP SHX condenser in the absence of on-board power consumption by the system, or
(ii) operatively activate the LHP control valve at an altitude of the aircraft having a temperature above standard to allow heat exchange fluid to flow only through the LHP condenser with the VCM compressor being the only on-board power consumption by the system.
2. The aircraft according to claim 1 , wherein the air circuit of the RAM-air subsystem includes an inlet control door for controlling air flow into the inlet of the duct, and a cooling fan for drawing air into the inlet and through the duct.
3. The aircraft according to claim 1 , wherein the secondary VCM condenser is a compact heat exchanger in operative heat-sink relationship with at least one on-board fluid selected from the group consisting of on-board fuel and cabin air.
4. The aircraft according to claim 3 , wherein the on-board fluid with which the secondary VCM condenser is in operative heat exchange relationship is on-board fuel.
5. The aircraft according to claim 3 , wherein the on-board fluid with which the secondary VCM condenser is in operative heat exchange relationship is aircraft cabin air.