Disclosed herein is a method for failure prediction in an Air Cycle Machine (ACM). The method includes calculating a change in energy of an ACM airflow passing from an inlet of the ACM compressor to an outlet of the ACM compressor. The method may also include calculating a kinetic energy of the ACM compressor based on calculating the work of the ACM compressor on the ACM airflow as the ACM airflow passes through the ACM compressor, calculating the work of the ACM compressor based on the inlet temperature of the ACM airflow at the inlet of the ACM compressor, compressor pressure ratio of the ACM compressor, and a fluid property of the ACM airflow at the inlet of the ACM compressor. Additionally, the method can include calculating an ACM compressor efficiency as a ratio of the change in energy of the ACM airflow across the ACM compressor to the kinetic energy of the compressor. The method may further include predicting a failure state of the ACM compressor.

A compressor frequency regulation method includes acquiring a first exhaust temperature of a compressor operating at a first operating frequency; determining that the first exhaust temperature is greater than or equal to a first preset temperature; controlling the compressor to perform frequency reduction processing, the frequency reduction processing reducing the first operating frequency to a second operating frequency, such that a second exhaust temperature of the compressor operating at the second operating frequency is less than the first preset temperature; and controlling the compressor to operate at the second operating frequency.

An example system for measuring emissions from a building includes a housing, a plurality of sensors arranged in the housing to detect concentrations of gas constituents in gas exiting the building, a gas flow sensor to detect a gas flow rate of the gas exiting the building, and a computing device to perform functions of calculating a total emissions of the particular gas constituent being tracked from a concentration of the particular gas constituent detected by the plurality of sensors and the gas flow rate, calculating an emission rate of the particular gas constituent being tracking, determining whether the total emissions and the emission rate of the particular gas constituent are within acceptable ranges, and based on the total emissions and the emission rate of the particular gas constituent being outside the acceptable ranges, outputting a prompt to a building computer system or operator indicating an alert.

In a calculation process, a control unit calculates a feature quantity from a physical quantity obtained from a device within a predetermined period. In an estimation process, the control unit estimates the state of the device, based on the feature quantity calculated by the calculation process. In a restriction process, the control unit restricts the estimation process when an estimation restriction condition is satisfied, maintains restriction of the estimation process until a standby release condition is satisfied when a restriction release condition is satisfied, and releases the restriction of the estimation process after the standby release condition is satisfied. The estimation restriction condition is a condition in which there is a possibility of occurrence of erroneous estimation in the estimation process. The restriction release condition is a condition in which the erroneous estimation in the estimation process is suppressed.

A method of operating a refrigerator appliance includes operating a compressor within a sealed cooling system for a first portion of a period of time and deactivating the compressor for a second portion of the period of time. The method also includes measuring a temperature at an evaporator of the sealed system while operating the compressor for the first portion of the period of time. The method further includes determining an actual duty cycle of the compressor based on a ratio of the first portion of the period of time to the period of time. The method also includes determining an optimal duty cycle of the compressor based on the measured temperature at the evaporator and comparing the actual duty cycle of the compressor to the optimal duty cycle. Based on the comparison of the actual duty cycle to the optimal duty cycle, the speed of the compressor is adjusted.

A vapor compression system includes a compressor, a condenser, an expansion device, and an evaporator fluidly connected to form a closed fluid loop having a working fluid circulating therethrough. A thermal storage device includes a storage material and the thermal storage device is thermally coupled to the closed fluid loop downstream from the expansion device relative to a flow of the working fluid. The vapor compression system is controllable such that the thermal storage device is operable to both store heat and release heat as the working fluid circulates through the closed fluid loop in a given direction.

An air conditioner may include: a compressor; a flow path switching valve; a first flow path connecting an outlet of the compressor to the flow path switching valve; a first heat exchanger; a second flow path connecting the first heat exchanger to the flow path switching valve; a first refrigerant port fluidly connected to an indoor unit; a third flow path extending from the first heat exchanger to the first refrigerant port; a sub-cooler provided on the third flow path; a first expansion valve provided between the first heat exchanger and the sub-cooler on the third flow path; a second expansion valve provided between the sub-cooler and the first refrigerant port on the third flow path; a fourth flow path branched from a branch point of the third flow path, passing through the sub-cooler, and extending to an inlet of the compressor; a third expansion valve provided between the sub-cooler and the branch point on the fourth flow path; a second refrigerant port fluidly connected to the indoor unit; a fifth flow path connecting the second refrigerant port to the flow path switching valve; and a sixth flow path connecting the flow path switching valve to an intake port of the compressor.