Device for detecting formation of water ice on a substrate has a first permanent magnet and a second permanent magnet. The magnets are spaced apart and arranged with a north pole of one magnet opposed to a south pole of the other magnet. A container contains a body of water within the space between the permanent magnets. At least one of the magnets is movable in the container. A heat conductor arrangement conducts heat between the substrate and the body of water the container. As heat is conducted from the body of water in the container to the substrate and the temperature of the body of water decreases below the temperature at which the density of water is a maximum, the volume of the body of water increases which drives the first and second permanent magnets apart from each other.

Device for detecting formation of water ice on a substrate has a first permanent magnet and a second permanent magnet. The magnets are spaced apart and arranged with a north pole of one magnet opposed to a south pole of the other magnet. A container contains a body of water within the space between the permanent magnets. At least one of the magnets is movable in the container. A heat conductor arrangement conducts heat between the substrate and the body of water the container. As heat is conducted from the body of water in the container to the substrate and the temperature of the body of water decreases below the temperature at which the density of water is a maximum, the volume of the body of water increases which drives the first and second permanent magnets apart from each other.

A capacitance sensing system for sensing frost and ice accumulation. The capacitance sensing system comprises a first capacitor formed by a portion of a metal heat exchanger and a sensor electrode electrically isolated from the metal heat exchanger, a tank oscillator comprising a second capacitor and an inductor connected in parallel with each other and coupled in parallel with the first capacitor, and a circuit coupled to the tank oscillator. The circuit coupled to the tank oscillator is configured to determine a resonant frequency of the tank oscillator, determine a capacitance value based on the resonant frequency of the tank oscillator, determine that the capacitance value is greater than a predefined threshold, and transmit a heater activation command in response to determining the capacitance value is greater than the predefined threshold.

A capacitance sensing system for sensing frost and ice accumulation. The capacitance sensing system comprises a first capacitor formed by a portion of a metal heat exchanger and a sensor electrode electrically isolated from the metal heat exchanger, a tank oscillator comprising a second capacitor and an inductor connected in parallel with each other and coupled in parallel with the first capacitor, and a circuit coupled to the tank oscillator. The circuit coupled to the tank oscillator is configured to determine a resonant frequency of the tank oscillator, determine a capacitance value based on the resonant frequency of the tank oscillator, determine that the capacitance value is greater than a predefined threshold, and transmit a heater activation command in response to determining the capacitance value is greater than the predefined threshold.

A system and method of freeze protection for a chiller including a metering device in flow communication with a condenser, a controller in electrical communication with the metering device, wherein the controller is configured to determine whether the difference between the fluid characteristic of the first liquid and the fluid characteristic of the second liquid is greater than a freezing limit, and enter a freeze protection mode if the difference between the fluid characteristic of the first liquid and the fluid characteristic of the second liquid is greater than the freezing limit.

A system and method of freeze protection for a chiller including a metering device in flow communication with a condenser, a controller in electrical communication with the metering device, wherein the controller is configured to determine whether the difference between the fluid characteristic of the first liquid and the fluid characteristic of the second liquid is greater than a freezing limit, and enter a freeze protection mode if the difference between the fluid characteristic of the first liquid and the fluid characteristic of the second liquid is greater than the freezing limit.

A transport refrigeration unit (TRU) is provided. The TRU includes a housing defining a flow path from an intake to an outlet, a blower to drive air along the flow path from the intake to the outlet, coils disposed in the flow path between the intake and the outlet and over which the air driven by the blower flows, a defrost element to execute a defrost action with respect to the coils, sensing elements at the intake and the outlet to sense pressures of the air at the intake and the outlet and a controller. The controller is configured to control at least one of the blower and the defrost element in accordance with readings of the sensing elements.

The present disclosure relates to a refrigerator. The refrigerator according to an embodiment of the present disclosure includes: a compressor configured to compress a refrigerant; an evaporator configured to perform heat exchange using the refrigerant compressed by the compressor; an RF output device configured to output an RF signal to the evaporator for removing frost on the evaporator; and a controller configured to control the RF output device, wherein the controller is configured to: based on the RF signal, control the frost to phase change into a liquid by heat radiated from a plurality of metal fins of the evaporator; and after the phase change, control temperature of the phase changed liquid to increase by a water molecule movement based on the RF signal. Accordingly, defrosting may be performed using the RF signal.

The present disclosure relates to a refrigerator. The refrigerator according to an embodiment of the present disclosure includes: a compressor configured to compress a refrigerant; an evaporator configured to perform heat exchange using the refrigerant compressed by the compressor; an RF output device configured to output an RF signal to the evaporator for removing frost on the evaporator; and a controller configured to control the RF output device, wherein the controller is configured to: based on the RF signal, control the frost to phase change into a liquid by heat radiated from a plurality of metal fins of the evaporator; and after the phase change, control temperature of the phase changed liquid to increase by a water molecule movement based on the RF signal. Accordingly, defrosting may be performed using the RF signal.

A transport refrigeration unit (TRU) is provided. The TRU includes a housing defining a flow path from an intake to an outlet, a blower to drive air along the flow path from the intake to the outlet, coils disposed in the flow path between the intake and the outlet and over which the air driven by the blower flows, a defrost element to execute a defrost action with respect to the coils, sensing elements at the intake and the outlet to sense pressures of the air at the intake and the outlet and a controller. The controller is configured to control at least one of the blower and the defrost element in accordance with readings of the sensing elements.