Abstract: A computer-implemented method for designing a built-in test is described. The method includes receiving, via a processor, a subsystem model including system parameters for a heat exchanger, wherein each of the system parameters includes a sensor variance; determining, via the processor, a test design vector based on one or more of the system parameters; and designing, via the processor, the built-in test based on the test design vector.

Abstract: A defrost cycle time of an aircraft vapor cycle refrigeration system is adaptively controlled. A pressure of refrigerant at an inlet of a compressor of the vapor cycle refrigeration system is sensed. A defrost cycle of the vapor cycle refrigeration system is initiated in response to the sensed pressure being less than a threshold pressure. The defrost cycle is terminated upon expiration of the defrost cycle time. The defrost cycle time is based upon a time duration of the cooling cycle.

Abstract: Operational parameters of an aircraft vapor cycle refrigeration system are measured via a plurality of sensors while the vapor cycle refrigeration system is operating. The measured operational parameters are transmitted to a computer system. The computer system generates, using a first reduced order model corresponding to an unclogged state of a filter of the vapor cycle refrigeration system, a first predicted discharge pressure of a compressor based on the measured operational parameters. The computer system generates, using a second reduced order model that corresponds to a clogged state of the filter, a second predicted discharge pressure of the compressor based on the measured operational parameters. The computer system determines a remaining useful life of the filter based on the first predicted discharge pressure, the second predicted discharge pressure, and a measured discharge pressure of the compressor. The computer system outputs an indication of the remaining useful life of the filter.

Abstract: A computer-implemented method for designing a built-in test is described. The method includes receiving, via a processor, a subsystem model including system parameters for a heat exchanger, wherein each of the system parameters includes a sensor variance; determining, via the processor, a test design vector based on one or more of the system parameters; and designing, via the processor, the built-in test based on the test design vector.

Abstract: Embodiments relate to adjusting cabin pressure based on ambient conditions to achieve a target aircraft inflow. An aspect includes receiving a number of occupants on an aircraft. The ambient conditions on the aircraft are monitored and an occupant threshold limit is determined for the aircraft based on the ambient conditions. If it is determined that the number of occupants exceeds the occupant threshold limit, the cabin pressure is reduced in the aircraft according to embodiments. The cabin pressure in the aircraft is reset in response to the occupant threshold limit being increased due to changing ambient conditions.

Abstract: An environmental control system having parallel compressors includes a first compressor driven by a first motor, the first compressor being operable for fluidly directing a first flow at a first flow rate through the first compressor. Also included is a second compressor driven by a second motor, the second compressor being operable for fluidly directing a second flow at a second flow rate through the second compressor. Further included is a monitoring component configured to compare the first flow rate to the second flow rate.

Abstract: Embodiments relate to adjusting cabin pressure based on ambient conditions to achieve a target aircraft inflow. An aspect includes receiving a number of occupants on an aircraft. The ambient conditions on the aircraft are monitored and an occupant threshold limit is determined for the aircraft based on the ambient conditions. If it is determined that the number of occupants exceeds the occupant threshold limit, the cabin pressure is reduced in the aircraft according to embodiments. The cabin pressure in the aircraft is reset in response to the occupant threshold limit being increased due to changing ambient conditions.

Abstract: An environmental control system having parallel compressors includes a first compressor driven by a first motor, the first compressor being operable for fluidly directing a first flow at a first flow rate through the first compressor. Also included is a second compressor driven by a second motor, the second compressor being operable for fluidly directing a second flow at a second flow rate through the second compressor. Further included is a monitoring component configured to compare the first flow rate to the second flow rate.

Abstract: A vapor cycle system comprises a compressor for compressing a coolant to form a superheated vapor, a de-superheater for cooling the superheated vapor to form a reduced temperature vapor by exchanging heat with a cooling fluid flow, a condenser for condensing the reduced temperature vapor to form a condensed liquid by exchanging heat with the cooling fluid flow, and an evaporator for evaporating the condensed liquid. The de-superheater is located downstream of the condenser in the cooling fluid flow, and a temperature of the cooling fluid flow is higher at the de-superheater than at the condenser.

Abstract: A cooling system includes a compressor for compressing a refrigerant from a subcritical state to a supercritical state, a cooler for transferring heat from the refrigerant, an expander for expanding the refrigerant in the supercritical state, an expansion valve for expanding the refrigerant from the supercritical state to the subcritical state and an evaporator for transferring heat from a cooling fluid to the refrigerant in the subcritical state. Work extracted by the expander provides power to the compressor. A method for cooling a vehicle includes compressing a refrigerant from a subcritical state to a supercritical state, cooling the refrigerant, expanding the refrigerant in the supercritical state where work produced by expanding the refrigerant is used to compress the refrigerant, expanding the refrigerant from the supercritical state to the subcritical state, cooling a cooling fluid with the refrigerant in the subcritical state and cooling vehicle components with the cooling fluid.

Abstract: A multi-pass heat exchanger having a return manifold with a partition, a front wall, and a rear wall is provided. The partition separates the return manifold into a collection chamber and a distribution chamber. The front and rear walls define a fluid channel. The front wall has a plurality of perforations placing the fluid channel in separate fluid communication with the collection chamber and the distribution chamber.

Abstract: An inlet header of a microchannel heat exchanger is provided with a first insert disposed within the inlet header and extending substantially the length thereof, and having a plurality of openings for the flow of refrigerant into the internal confines of the inlet header and then to the channels. A second insert, disposed within the first insert, extends substantially the length of the first insert and is of increasing cross sectional area toward its downstream end such that annular cavity is formed between the first and second insert. The annular cavity of decreasing cross sectional area provides for the maintenance of a substantially constant mass flux of the refrigerant along the length of the annulus so as to thereby maintain an annular flow regime of the liquid and thereby promote uniform flow distribution to the channels.

Abstract: A microchannel heat exchanger includes for each channel, a serpentine shaped tube for providing a plurality of parallel flow passes for successively conducting fluid flow therethrough, and being fluidly interconnected between an inlet and an outlet manifold. Multiple circuits are obtained by the individual serpentine shaped tubes. Various methods are provided for forming the serpentine shaped tubes.

Abstract: A cooling system includes a compressor for compressing a refrigerant from a subcritical state to a supercritical state, a cooler for transferring heat from the refrigerant, an expander for expanding the refrigerant in the supercritical state, an expansion valve for expanding the refrigerant from the supercritical state to the subcritical state and an evaporator for transferring heat from a cooling fluid to the refrigerant in the subcritical state. Work extracted by the expander provides power to the compressor. A method for cooling a vehicle includes compressing a refrigerant from a subcritical state to a supercritical state, cooling the refrigerant, expanding the refrigerant in the supercritical state where work produced by expanding the refrigerant is used to compress the refrigerant, expanding the refrigerant from the supercritical state to the subcritical state, cooling a cooling fluid with the refrigerant in the subcritical state and cooling vehicle components with the cooling fluid.

Abstract: An inlet header of a microchannel heat exchanger is provided with a first insert disposed within the inlet header and extending substantially the length thereof, and having a plurality of openings for the flow of refrigerant into the internal confines of the inlet header and then to the channels. A second insert, disposed within the first insert, extends substantially the length of the first insert and is of increasing cross sectional area toward its downstream end such that annular cavity is formed between the first and second insert. The annular cavity of decreasing cross sectional area provides for the maintenance of a substantially constant mass flux of the refrigerant along the length of the annulus so as to thereby maintain an annular flow regime of the liquid and thereby promote uniform flow distribution to the channels.

Abstract: A heat exchanger for a fluid having a vapor-phase and a liquid-phase is provided. The heat exchanger includes a first manifold, a second manifold, a plurality of parallel channels, a mixing device, and one or more baffles. The parallel channels are in fluid communication with the first and second manifolds. The mixing device mixes the fluid flowing into the first manifold so that the fluid is a substantially homogeneous two-phase mixture of the vapor and liquid phases. The baffles are within the first manifold and ensure that the fluid enters the parallel channels as the substantially homogeneous two-phase mixture.

Abstract: A multi-pass heat exchanger having a return manifold with a partition, a front wall, and a rear wall is provided. The partition separates the return manifold into a collection chamber and a distribution chamber. The front and rear walls define a fluid channel. The front wall has a plurality of perforations placing the fluid channel in separate fluid communication with the collection chamber and the distribution chamber.

Abstract: A mini-channel heat exchanger or a micro-channel heat exchanger includes an insert (140, 240, 340, 440, 540, 640, 4, 940, 1040) having a volume. The insert is within a gap between a plurality of tubes (130, 230, 330, 430, 530, 630, 1, 930, 1030) of the mini-channel heat exchanger or the micro-channel heat exchanger and a manifold inner wall of a manifold (120, 220, 320, 420, 520, 620, 2, 920, 1020).

Abstract: A refrigerant cycle is provided with a control for an expansion device to achieve a desired compressor discharge pressure. The system operates transcritically, such that greater freedom over compressor discharge pressure is provided. The system's efficiency is optimized by selecting an optimum discharge pressure. The optimum discharge pressure is selected based upon sensed environmental conditions, and the expansion device is adjusted to achieve the desired compressor discharge pressure. A feedback loop may be provided to sense the actual compressor discharge pressure and adjust the actual compressor discharge pressure by further refining the expansion device. The system is disclosed providing heated water based upon a demand for a particular hot water temperature.

Abstract: The expansion of a high pressure or intermediate pressure refrigerant in an expansion device in a transcritical vapor compression system converts the potential energy into usable kinetic energy. The kinetic energy provides work which is employed to fully or partially drive an expansion motor unit which is coupled to rotating auxiliary machinery. By providing work to the rotating auxiliary machinery, system efficiency is improved. The auxiliary rotating machinery can be an evaporator fan or a gas cooler fan to pull the refrigerant through the evaporator and gas cooler, respectively. Alternatively, the auxiliary rotating machinery can be a water pump or an oil pump.