Patent Description:
Products may be shipped or stored within a conditioned space, such as a container, truck or trailer. These conditioned spaces utilize a refrigeration unit that circulates cooled air inside the interior volume. In many cases, the refrigeration unit uses a refrigeration cycle to cool the air. Refrigerant from the refrigeration unit may leak inside the conditioned space.

<CIT> discloses a refrigeration system according to the preamble of claim <NUM> having a plurality of conditioned spaces each having a refrigerant leakage sensor, wherein the supply of refrigerant to each conditioned space can be individually controlled and, in the event of a detected leak, cut off.

According to the invention a refrigeration system according to claim <NUM> is provided. The refrigeration system includes a compressor, a condenser, an evaporator, a leak sensor, and a controller. The compressor is driven by a power source and has a compressor outlet and a compressor inlet. The condenser has a condenser inlet fluidly connected to the compressor outlet and a condenser outlet. The evaporator has an evaporator inlet fluidly connected to the condenser outlet through a first valve movable between an open position and a closed position, and an evaporator outlet fluidly connected to the compressor inlet. The leak sensor is arranged to provide a signal indicative of a refrigerant. The controller is in communication with the first valve and the compressor. The controller is arranged to receive the signal and is programmed to command the first valve to move towards the closed position, responsive to the signal being indicative of the refrigerant. The refrigeration system includes a second valve fluidly connecting the evaporator outlet and the compressor inlet, the second valve being movable between an open position and a closed position. The controller is further programmed to operate the compressor such that refrigerant within the evaporator is directed towards the compressor until a suction pressure measurement proximate an inlet of the compressor is less than an ambient pressure. The controller is further programmed to command the second valve to move towards the closed position when the suction pressure measurement proximate an inlet of the compressor is less than an ambient pressure.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the controller is further programmed to output for display an indicator.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the controller is further programmed to operate the compressor such that refrigerant within the evaporator is directed towards the compressor.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the controller is further programmed to command the compressor to stop operating, responsive to a fluid pressure between the evaporator outlet and the compressor outlet being less than a threshold pressure.

In addition to one or more of the features described above, or as an alternative, further embodiments may include a receiver having a receiver inlet fluidly connected to the condenser outlet, wherein the receiver is arranged to receive the refrigerant from the condenser.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the controller is arranged to receive the signal and programmed to command the first valve to move towards the closed position, responsive to the signal being indicative of a selected concentration of the refrigerant.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the controller is further programmed to operate an evaporator fan when refrigerant is detected.

In addition to one or more of the features described above, or as an alternative, further embodiments may include a main heat valve fluidly connecting the compressor outlet and the condenser inlet, the main heat valve being movable between an open position and a closed position, wherein the controller is programed to command the main heat valve to move to the open position.

In addition to one or more of the features described above, or as an alternative, further embodiments may include a hot gas valve fluidly connecting the compressor and the evaporator inlet, the hot gas valve being movable between an open position and a closed position, and wherein the controller is programed to command the hot gas valve to move to the closed position prior to commanding the first valve to move towards the closed position.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the evaporator and the leak sensor are located within a conditioned space of the refrigeration system, and wherein the first valve and the second valve are located outside of the conditioned space.

According to the invention a method of mitigating refrigerant leaks within a refrigeration system according to claim <NUM> is provided. The method includes: detecting a leak of a refrigerant from a refrigeration system; closing a first valve to inhibit a fluid flow of the refrigerant between an evaporator and a condenser fluidly connected to the evaporator; operating a compressor to direct another fluid flow of the refrigerant from the evaporator to the compressor; operating the compressor to direct another fluid flow of the refrigerant from the evaporator to the compressor until a suction pressure measurement proximate an inlet of the compressor is less than an ambient pressure; and closing a second valve when the suction pressure measurement proximate an inlet of the compressor is less than an ambient pressure, the second valve fluidly connecting the evaporator outlet and the compressor inlet.

In addition to one or more of the features described above, or as an alternative, further embodiments may include directing the fluid flow of the refrigerant from the compressor to a receiver.

In addition to one or more of the features described above, or as an alternative, further embodiments may include operating an evaporator fan that is disposed proximate the evaporator.

In addition to one or more of the features described above, or as an alternative, further embodiments may include stopping operation of the compressor, responsive to an evaporator pressure being less than a threshold pressure.

In addition to one or more of the features described above, or as an alternative, further embodiments may include closing a second valve to inhibit a fluid flow of the refrigerant between the receiver and the condenser.

According to the invention the refrigeration system and the method includes closing a second valve to inhibit a fluid flow of the refrigerant between the evaporator and the compressor.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the method further includes: opening a main heat valve to allow a fluid flow of the refrigerant between the compressor and the condenser; and closing a hot gas valve to inhibit a fluid flow of the refrigerant between the compressor and the evaporator.

Referring to <FIG>, a transport system <NUM> is illustrated. In the illustrated embodiment, the transport systems <NUM> may include a tractor or vehicle <NUM>, a conditioned space <NUM>, <NUM>, and a refrigeration system <NUM>, <NUM>. The conditioned space <NUM>, <NUM> may be pulled by a vehicle <NUM>. It is understood that embodiments described herein may be applied to conditioned space that are shipped by rail, sea, air, or any other suitable container, thus the vehicle may be a truck, train, boat, airplane, helicopter, etc..

The vehicle <NUM> may include an operator's compartment or cab <NUM> and a vehicle motor <NUM>. The vehicle <NUM> may be driven by a driver located within the cab, driven by a driver remotely, driven autonomously, driven semi-autonomously, or any combination thereof. The vehicle motor <NUM> may be an electric or combustion engine powered by a combustible fuel. The vehicle motor <NUM> may also be part of the power train or drive system of the trailer system (i.e., conditioned space <NUM>, <NUM>), thus the vehicle motor <NUM> is configured to propel the wheels of the vehicle <NUM> and/or the wheels of the conditioned space <NUM>, <NUM>. The vehicle motor <NUM> may be mechanically connected to the wheels of the vehicle <NUM> and/or the wheels of the conditioned space <NUM>, <NUM>.

The conditioned space <NUM>, <NUM> may be coupled to the vehicle <NUM> and is thus pulled or propelled to desired destinations. The conditioned space <NUM>, <NUM> may include a top wall <NUM>, a bottom wall <NUM> opposed to and spaced from the top wall <NUM>, two side walls <NUM> spaced from and opposed to one-another, and opposing front and rear walls <NUM>, <NUM> with the front wall <NUM> being closest to the vehicle <NUM>. The conditioned space <NUM>, <NUM> may further include doors (not shown) at the rear wall <NUM>, or any other wall. The walls <NUM>, <NUM>, <NUM>, <NUM>, <NUM> together define the boundaries of a refrigerated interior volume <NUM>, <NUM>. Typically, transport systems <NUM> are used to transport and distribute cargo, such as, for example perishable goods and environmentally sensitive goods (herein referred to as perishable goods). The perishable goods may include but are not limited to fruits, vegetables, grains, beans, nuts, eggs, dairy, seed, flowers, meat, poultry, fish, ice, blood, pharmaceuticals, or any other suitable cargo requiring cold chain transport. In the illustrated embodiment, the refrigeration system <NUM>, <NUM> is associated with a conditioned space <NUM>, <NUM> to provide desired environmental parameters, such as, for example temperature, pressure, humidity, carbon dioxide, ethylene, ozone, light exposure, vibration exposure, and other conditions to the refrigerated interior volume <NUM>, <NUM>. In further embodiments, the refrigeration system <NUM>, <NUM> is a refrigeration system capable of providing a desired temperature and humidity range.

Referring to <FIG>, a conditioned space <NUM> may be provided with a refrigeration system <NUM> that provides conditioned air or cooled air to an interior volume <NUM> of the conditioned space <NUM>. The conditioned space <NUM> may include but is not limited to a refrigerated trailer, a refrigerated truck, a refrigerated space, or a refrigerated container. The refrigeration system <NUM> may be adapted to operate using a refrigerant such as a low global warming potential refrigerant including A1, A2, A2L, A3, etc. In some cases, the refrigerant may leak into the interior volume <NUM> and may present a hazard should the concentration of the leaked refrigerant within the interior volume <NUM> exceed a threshold level. The threshold level may be a lower flammability limit of the refrigerant. The evaporator <NUM>, a portion of a refrigerant line <NUM> proximate an evaporator outlet <NUM>, and a portion of a refrigerant line 64a proximate an evaporator inlet <NUM> may be located within the interior volume <NUM> of the conditioned space <NUM> and thus may be a potential source of a refrigerant leak into the interior volume <NUM>.

The refrigeration system <NUM> may be a transport refrigeration system such as a transportation refrigeration unit. The refrigeration system <NUM> includes a compressor <NUM>, a condenser <NUM>, an evaporator <NUM>, and a leak detection system <NUM> that is arranged to detect and mitigate the presence of refrigerant within an interior volume <NUM>.

The compressor <NUM> is powered by or driven by a power source <NUM>. The power source <NUM> may be an internal combustion engine that drives a generator that is arranged to provide power to the compressor through a belt or otherwise provide power to the compressor <NUM> and other components of the refrigeration system <NUM>.

The compressor <NUM> is arranged to receive refrigerant through a compressor inlet <NUM> from the evaporator <NUM>. The compressor <NUM> is arranged to discharge refrigerant through a compressor outlet <NUM> to the condenser <NUM> through a receiver <NUM>.

The condenser <NUM> is arranged to receive a fluid flow of refrigerant from the compressor <NUM> through a condenser inlet <NUM> and is arranged to discharge a fluid flow of refrigerant through a condenser outlet <NUM> to the receiver <NUM>. The condenser inlet <NUM> is fluidly connected to the compressor outlet <NUM> through a refrigerant line <NUM>.

A fan such as a condenser fan <NUM> may be associated with the condenser <NUM>. The condenser fan <NUM> is disposed proximate the condenser <NUM>.

The evaporator <NUM> is arranged to receive a fluid flow of refrigerant from the condenser <NUM> through an evaporator inlet <NUM> and is arranged to discharge a fluid flow of refrigerant to the compressor <NUM> through an evaporator outlet <NUM>. The evaporator inlet <NUM> is fluidly connected to the condenser outlet <NUM> through the receiver <NUM> via a refrigerant line 64a, b through a first valve <NUM> and/or a second valve <NUM> that is disposed on an opposite side of the receiver <NUM> than the first valve <NUM>. The evaporator outlet <NUM> is fluidly connected to the compressor inlet <NUM> through a refrigerant line <NUM>.

The first valve <NUM> may be an expansion valve such as an electronic expansion valve, a movable valve, or a thermal expansion valve. The first valve <NUM> is movable between an open position and a closed position to selectively inhibit and facilitate a fluid flow of refrigerant between the evaporator <NUM> and at least one of the condenser <NUM> and the receiver <NUM>. The open position facilitates a fluid flow of refrigerant between the evaporator inlet <NUM> and the condenser outlet <NUM> through the receiver <NUM>. The closed position inhibits a fluid flow of refrigerant between the evaporator inlet <NUM> and the condenser outlet <NUM> through the receiver <NUM> as well as inhibits a fluid flow of refrigerant between the receiver <NUM> and the evaporator inlet <NUM>.

A fan such as an evaporator fan <NUM> may be associated with the evaporator <NUM>. The evaporator fan <NUM> is disposed proximate the evaporator <NUM>.

The receiver <NUM> is fluidly connected to the condenser <NUM> and the evaporator <NUM> and is arranged to receive and store refrigerant based on a position of at least one of the first valve <NUM> and/or the second valve <NUM>. The receiver <NUM> is arranged to receive refrigerant from the condenser outlet <NUM> through a first receiver inlet <NUM> via the refrigerant line 64b. In at least one embodiment, the second valve <NUM> is arranged to selectively facilitate a fluid flow between the condenser outlet <NUM> and the first receiver inlet <NUM>. The second valve <NUM> may be a movable valve, a solenoid valve, a liquid service valve, a thermal expansion valve, or an electronic expansion valve. The second valve <NUM> is movable between an open position and a closed position. The open position facilitates a fluid flow of refrigerant between the condenser outlet <NUM> and the first receiver inlet <NUM>. The closed position inhibits a fluid flow of refrigerant between the condenser outlet <NUM> and the first receiver inlet <NUM>. The receiver <NUM> is arranged to discharge or provide a fluid flow of refrigerant through a receiver outlet <NUM> to the evaporator inlet <NUM> via the first valve <NUM> through the refrigerant line 64a.

A third valve <NUM> may be arranged to selectively facilitate a fluid flow between the compressor outlet <NUM> and the condenser inlet <NUM>. The third valve <NUM> may be a movable valve, check valve, a liquid service valve, a thermal expansion valve, or an electronic expansion valve. The third valve <NUM> is movable between an open position and a closed position. The open position facilitates a fluid flow of refrigerant between the compressor outlet <NUM> and the condenser inlet <NUM>. The closed position inhibits a fluid flow of refrigerant between the compressor outlet <NUM> and the condenser inlet <NUM>. Alternatively, the third valve <NUM> may be interposed in refrigerant line <NUM>.

A fourth valve <NUM> may be arranged to selectively facilitate a fluid flow between the evaporator outlet <NUM> and the compressor inlet <NUM>. The fourth valve <NUM> may be a movable valve, check valve, a liquid service valve, a thermal expansion valve, or an electronic expansion valve. The fourth valve <NUM> is movable between an open position and a closed position. The open position facilitates a fluid flow of refrigerant between the evaporator outlet <NUM> and the compressor inlet <NUM>. The closed position inhibits a fluid flow of refrigerant between the evaporator outlet <NUM> and the compressor inlet <NUM>.

In an embodiment, the first valve <NUM>, the second valve <NUM>, the third valve <NUM>, and the fourth valve <NUM> may be located outside of the conditioned space <NUM>.

As stated previously, the open position of the first valve <NUM> facilitates a fluid flow of refrigerant between the receiver outlet <NUM> and the evaporator inlet <NUM>. The closed position of the first valve <NUM> inhibits a fluid flow of refrigerant between the receiver outlet <NUM> and the evaporator inlet <NUM>.

The leak detection system <NUM> includes a controller <NUM> and a leak sensor <NUM>. The leak sensor <NUM> may be configured to detect refrigerant, detect a selected concentration of the refrigerant, and/or calculate a concentration of refrigerant. The controller <NUM> may be a controller that is provided with the transport refrigeration unit or may be a separately provided controller.

The controller <NUM> is provided with input communication channels that are arranged to receive information, data, or signals from, for example, the compressor <NUM>, the power source <NUM>, the condenser fan <NUM>, the first valve <NUM>, the evaporator fan <NUM>, the second valve <NUM>, a pressure sensor <NUM>, a compressor discharge pressure sensor <NUM>, and the leak sensor <NUM>. The controller <NUM> is provided with output communication channels that are arranged to provide commands, signals, or data to, for example, the compressor <NUM>, the power source <NUM>, the condenser fan <NUM>, the first valve <NUM>, the evaporator fan <NUM>, and the second valve <NUM>. The controller <NUM> is provided with at least one processor that is programmed to execute a leak detection and/or leak mitigation strategy based on information, data, or signals provided via the input communication channels and output commands via the output communication channels.

The leak sensor <NUM> is arranged to provide a signal indicative of a concentration, an amount, or the presence of refrigerant within the interior volume <NUM> to the controller <NUM>. The leak sensor <NUM> may be disposed proximate the evaporator <NUM> and/or may be disposed proximate the refrigerant line <NUM> or any other refrigerant line or component that could leak refrigerant into the conditioned space <NUM>. The leak sensor <NUM> may also be located near a likely location where refrigerant may collect, such as near a floor of the container <NUM>.

Responsive to the signal from the leak sensor <NUM> being indicative of a concentration of refrigerant greater than a threshold concentration or the signal being indicative of the presence of refrigerant within the interior volume <NUM>, the controller <NUM> may perform leak mitigation as illustrated by the flow chart in <FIG>.

Referring to <FIG>, with continued references to <FIG>, a method <NUM> of leak detection in a refrigeration system <NUM> is illustrated in accordance with an embodiment of the present invention. In an embodiment, the method <NUM> may be performed by the controller <NUM>. At block <NUM>, should the leak sensor <NUM> not detect the presence of refrigerant or the concentration of refrigerant greater than a threshold concentration, the method may end and/or continuously check for refrigerant leaks on a recurring basis. If the leak sensor <NUM> detects the presence of refrigerant or detects the concentration of refrigerant greater than a threshold concentration, the method <NUM> may continue to block <NUM>. At block <NUM>, the controller <NUM> may record the leak and the entrance of the leak mitigation strategy into memory. At block <NUM>, the controller <NUM> is programmed to output for display an indicator. The indicator may be an auditory indicator, a visual indicator, or the like. In at least one embodiment, the controller <NUM> may transmit information or data indicative of the leak to a driver, operator, remote computing system, a remote monitoring system, or a display.

The controller <NUM> may assess the operational state of various components of the refrigeration system <NUM>, in parallel, substantially simultaneously, or sequentially. At block <NUM>, the controller <NUM> may assess whether the compressor <NUM> is on and operational (e.g. running). At block <NUM>, the controller <NUM> may assess whether the evaporator fan <NUM> is on and operational (e.g. running). At block <NUM>, the controller <NUM> may assess the position of the first valve <NUM>.

Should the compressor <NUM> not be running at block <NUM>, the controller <NUM> may command that the compressor <NUM> to operate, at block <NUM>. If the compressor is running at block <NUM>, the method <NUM> may continue to block <NUM>.

Should the evaporator fan <NUM> not be running at block <NUM>, the controller <NUM> may command that the evaporator fan <NUM> operate at block <NUM>. The operation of the evaporator fan <NUM> may facilitate the disbursement or dilution of refrigerant proximate the evaporator <NUM>. The operation of the evaporator fan <NUM> may facilitate the releasing or venting of refrigerant from within the interior volume <NUM> towards an external environment. In at least one embodiment, should the evaporator fan <NUM> not be running at block <NUM>, the controller <NUM> may inhibit the evaporator fan <NUM> from operating. The inhibition of operation of the evaporator fan <NUM> may prevent refrigerant from being released or vented into an external environment. If the evaporator fan <NUM> is running at block <NUM>, the method <NUM> may continue to block <NUM>.

Should the first valve <NUM> be open at block <NUM>, the controller <NUM> may command that the first valve <NUM> move towards the closed position, at block <NUM>. The closing of the first valve <NUM> inhibits a fluid flow of refrigerant between the receiver outlet <NUM> and the evaporator inlet <NUM>. The closing of the first valve <NUM> essentially inhibits the delivery of refrigerant to the evaporator <NUM> that may be the source of the refrigerant leak into the interior volume <NUM>. If at least the first valve <NUM> is in a closed position, the method may contain the block <NUM>.

The closing of the first valve <NUM> enables the compressor <NUM> to evacuate or pump down the evaporator <NUM> to slow or stop the refrigerant leak into the interior volume <NUM>. The compressor <NUM> is operated while the first valve <NUM> is closed such that a fluid flow of refrigerant from the evaporator <NUM> is directed through the evaporator outlet <NUM> via the refrigerant line <NUM> towards the compressor inlet <NUM>. The removal of refrigerant from the evaporator <NUM> may be referred to as a pump down of the evaporator <NUM>. The compressor <NUM> directs the fluid flow of refrigerant from the evaporator <NUM>, through the compressor outlet <NUM>, and into the receiver <NUM> through the condenser inlet <NUM> and out of the condenser outlet <NUM> towards the first receiver inlet <NUM> such that the refrigerant is stored within the receiver <NUM>. The closing of the first valve <NUM> inhibits the refrigerant that is present within the receiver <NUM> from being delivered to the evaporator <NUM>. In at least one embodiment, should the second valve <NUM> be closed, the compressor <NUM> may pump down the evaporator <NUM> and direct the fluid flow of refrigerant from the evaporator <NUM> through the compressor <NUM> and towards the condenser <NUM>. The flow of refrigerant is directed into the condenser <NUM> through the condenser inlet <NUM> and is inhibited from flowing towards the receiver <NUM> by the second valve <NUM> being in the closed position. The compressor <NUM> may be provided with an anti-backflow valve such that refrigerant received by the condenser <NUM> is retained or is received within the condenser <NUM> and/or between the compressor <NUM> is unable to flow back through the compressor outlet <NUM> towards the compressor inlet <NUM>.

The method <NUM> may move onto block <NUM> or <NUM>. At block <NUM>, the method <NUM> may assess whether there is suction, such as a suction pressure less than an ambient pressure, within the refrigerant line <NUM> that extends between the evaporator <NUM> and the compressor <NUM>. In such an embodiment, a pressure sensor <NUM> is configured to detect pressure within the refrigerant line <NUM> and communicate the detected pressure to the controller <NUM>. At block <NUM>, the method may alternatively assess a fluid pressure within the evaporator <NUM> (e.g. evaporator pressure) and determine whether the fluid pressure within the evaporator <NUM> is less than a threshold pressure. In such an embodiment, the pressure sensor <NUM> is disposed within or proximate the evaporator <NUM>. Should the suction pressure be less than the ambient pressure or the evaporator pressure be less than a threshold pressure, the method <NUM> may continue to block <NUM>. If the suction pressure is greater than the ambient pressure or the pressure within the evaporator <NUM> is greater than a threshold pressure, the method may return to block <NUM>, block <NUM>, and/or block <NUM>.

Alternatively, the method may move to block <NUM> if a compressor discharge pressure is utilized rather than a suction pressure. For example, a compressor discharge pressure may be utilized if the fourth valve <NUM> is not present in the refrigeration system <NUM>. At block <NUM>, the method <NUM> may assess whether there is a discharge pressure at a compressor outlet <NUM> greater than a selected pressure, within the refrigerant line <NUM> that extends between the compressor <NUM> and the condenser <NUM>. In such an embodiment, a compressor discharge pressure sensor <NUM> is configured to detect pressure within the refrigerant line <NUM> and communicate the detected pressure to the controller <NUM>. Should the compressor discharge pressure be greater than the selected pressure, the method <NUM> may continue to block <NUM>. If the compressor discharge pressure is not greater than the selected pressure, the method may return to block <NUM>, block <NUM>, and/or block <NUM>.

At block <NUM>, should the second valve <NUM> be in an open position, the controller <NUM> may command the second valve <NUM> to close such that the refrigerant within the receiver <NUM> is inhibited from escaping the receiver <NUM> and flowing toward either the evaporator <NUM> and/or the condenser <NUM>. At block <NUM>, the refrigeration system <NUM> is shut down.

The leak mitigation strategy utilizing the pump down process greatly reduces the risk of the refrigerant reaching the lower flammability limit by removing and storing refrigerant from the evaporator <NUM> within at least one of the receiver <NUM> or the condenser <NUM> outside of the interior volume <NUM>. The leak mitigation strategy may also dilute or disperse refrigerant that may be present within the interior volume <NUM> of the conditioned space <NUM>. If a refrigerant leak is in an area that is not exposed to the interior volume <NUM> than the refrigerant may dissipate on its own. Additionally, the operation of the condenser fan <NUM> may facilitate the disbursement or dilution of refrigerant proximate the condenser <NUM> and may be utilized at any time during the method <NUM>.

Referring to <FIG>, a refrigeration system <NUM> having a heat line <NUM> for hot gas by-pass is illustrated, in accordance with an embodiment of the present invention. A conditioned space <NUM> that provides conditioned air or cooled air to an interior volume <NUM> of the conditioned space <NUM> is illustrated in <FIG>. The conditioned space <NUM> may include but is not limited to a refrigerated trailer, a refrigerated truck, a refrigerated space, or a refrigerated container. The refrigeration system <NUM> may be adapted to operate using a refrigerant such as a low global warming potential refrigerant including A1, A2, A2L, A3, etc. In some case the refrigerant may leak into the interior volume <NUM> and may present a hazard should the concentration of the leaked refrigerant within the interior volume <NUM> exceed a threshold level. The threshold level may be a lower flammability limit of the refrigerant. The evaporator <NUM>, a portion of a refrigerant line <NUM> proximate an evaporator outlet <NUM>, and a portion of a refrigerant line <NUM> proximate an evaporator inlet <NUM> may be located within the interior volume <NUM> of the conditioned space <NUM> and thus may be a potential source of a refrigerant leak into the interior volume <NUM>.

The compressor <NUM> is powered by or driven by a power source <NUM>. The power source <NUM> may be an internal combustion engine that drives a generator that is arranged to provide power to the compressor <NUM> and other components of the refrigeration system <NUM>.

The compressor <NUM> is arranged to receive refrigerant through a compressor inlet <NUM> from the evaporator <NUM>. The compressor <NUM> is arranged to discharge refrigerant through a compressor outlet <NUM> to the condenser <NUM>.

The condenser <NUM> is arranged to receive a fluid flow of refrigerant from the compressor <NUM> through a condenser inlet <NUM> and is arranged to discharge a fluid flow of refrigerant through a condenser outlet <NUM> to the evaporator <NUM>. The condenser inlet <NUM> is fluidly connected to the compressor outlet <NUM> through a refrigerant line <NUM>.

An oil separator <NUM> may be located within the refrigerant line <NUM> between the compressor <NUM> and the condenser <NUM> to remove oil from refrigerant leaving the compressor outlet <NUM> and direct the oil back to rotary components of the compressor <NUM>.

The evaporator <NUM> is arranged to receive a fluid flow of refrigerant from the condenser <NUM> through an evaporator inlet <NUM> and is arranged to discharge a fluid flow of refrigerant to the compressor <NUM> through an evaporator outlet <NUM>. The evaporator inlet <NUM> is fluidly connected to the condenser outlet <NUM> through a refrigerant line <NUM>. The evaporator outlet <NUM> is fluidly connected to the compressor inlet <NUM> through a refrigerant line <NUM>.

A first valve <NUM> may be located within the refrigerant line <NUM> between the condenser <NUM> and the evaporator <NUM>. In at least one embodiment, the first valve <NUM> is arranged to selectively facilitate a fluid flow between the condenser outlet <NUM> and the evaporator inlet <NUM>. The first valve <NUM> may be an expansion valve such as an electronic expansion valve, a movable valve, a solenoid valve, or a thermal expansion valve. The first valve <NUM> is movable between an open position and a closed position to selectively inhibit and facilitate a fluid flow of refrigerant between the evaporator <NUM> and the condenser <NUM>. The open position facilitates a fluid flow of refrigerant between the condenser outlet <NUM> and the evaporator inlet <NUM>. The closed position inhibits a fluid flow of refrigerant between the condenser outlet <NUM> and the evaporator inlet <NUM> through the refrigerant line <NUM>.

A second valve <NUM> may be located within the refrigerant line <NUM> between the evaporator <NUM> and the compressor <NUM>. In at least one embodiment, the second valve <NUM> is arranged to selectively facilitate a fluid flow between the evaporator outlet <NUM> and the compressor inlet <NUM>. The second valve <NUM> may be a movable valve, solenoid valve, check valve, a liquid service valve, a thermal expansion valve, or an electronic expansion valve. The second valve <NUM> is movable between an open position and a closed position. The open position facilitates a fluid flow of refrigerant between the evaporator outlet <NUM> and the compressor inlet <NUM>. The closed position inhibits a fluid flow of refrigerant between the evaporator outlet <NUM> and the compressor inlet <NUM>.

In an embodiment, the first valve <NUM> and the second valve <NUM> may be located outside of the conditioned space <NUM>.

A main heating valve <NUM> may be located within the refrigerant line <NUM> between the compressor <NUM> and the condenser <NUM>. In at least one embodiment, the main heating valve <NUM> is arranged to selectively facilitate a fluid flow between the compressor outlet <NUM> and the condenser inlet <NUM>. The main heating valve <NUM> may be a movable valve, a liquid service valve, a thermal expansion valve, or an electronic expansion valve. The main heating valve <NUM> is movable between an open position and a closed position. The open position facilitates a fluid flow of refrigerant between the compressor outlet <NUM> and the condenser inlet <NUM>. The closed position inhibits a fluid flow of refrigerant between the compressor outlet <NUM> and the condenser inlet <NUM>.

A heat line <NUM> may fluidly connect the compressor <NUM> and the refrigerant line <NUM> proximate the evaporator inlet <NUM>. During a heating mode of the refrigeration system <NUM>, the heat line <NUM> may deliver hot gas from the compressor <NUM> to the evaporator inlet <NUM>, which may help defrost the evaporator and/or heat up the interior volume <NUM>.

A hot gas valve <NUM> may be located within the heat line <NUM> between the compressor <NUM> and the evaporator <NUM>. In at least one embodiment, the hot gas valve <NUM> is arranged to selectively facilitate a fluid flow between the compressor outlet <NUM> and the evaporator inlet <NUM>. The hot gas valve <NUM> may be a movable valve, a liquid service valve, a thermal expansion valve, or an electronic expansion valve. The hot gas valve <NUM> is movable between an open position and a closed position. The open position facilitates a fluid flow of hot gas refrigerant between the compressor outlet <NUM> and the evaporator inlet <NUM>. The closed position inhibits a fluid flow of hot gas refrigerant between the compressor outlet <NUM> and the evaporator inlet <NUM>.

The refrigeration system <NUM> may include a check valve <NUM> located within the refrigerant line <NUM> between the first valve <NUM> and the evaporator <NUM>, as shown in <FIG>. The refrigeration system <NUM> may also include an expansion valve <NUM> located within the refrigerant line <NUM> between the check valve <NUM> and the evaporator <NUM>, as shown in <FIG>. The refrigeration system <NUM> may additionally include a pressure sensor <NUM> located within the refrigerant line <NUM> interposed between the evaporator <NUM> and the compressor inlet <NUM>.

The leak detection system <NUM> includes a controller <NUM> and a leak sensor <NUM>. The leak sensor <NUM> may be configured to detect refrigerant, detect a selected concentration of the refrigerant, and/or calculate a concentration of refrigerant. The leak sensor <NUM> may be located within the conditioned space <NUM>. The controller <NUM> may be a controller that is provided with the transport refrigeration unit or may be a separately provided controller.

The controller <NUM> is provided with input communication channels that are arranged to receive information, data, or signals from, for example, at least one of the compressor <NUM>, the power source <NUM>, the condenser fan <NUM>, the first valve <NUM>, the evaporator fan <NUM>, the second valve <NUM>, and the leak sensor <NUM>. The controller <NUM> is provided with output communication channels that are arranged to provide commands, signals, or data, for example, to the compressor <NUM>, the power source <NUM>, the condenser fan <NUM>, the first valve <NUM>, the evaporator fan <NUM>, the pressure sensor <NUM>, and the second valve <NUM>. The controller <NUM> is provided with at least one processor that is programmed to execute a leak detection and/or leak mitigation strategy based on information, data, or signals provided via the input communication channels and output commands via the output communication channels.

The leak sensor <NUM> is arranged to provide a signal indicative of a concentration, an amount or the presence of refrigerant within the interior volume <NUM> to the controller <NUM>. The leak sensor <NUM> may be disposed proximate the evaporator <NUM> and/or may be disposed proximate the refrigerant line <NUM> or any other refrigerant line or component that could leak refrigerant into the conditioned space <NUM>. The leak sensor <NUM> may also be located near a likely location where refrigerant may collect such as near a floor of the conditioned space <NUM>.

Referring to <FIG>, with continued references to <FIG>, a method <NUM> of leak detection in a refrigeration system <NUM> is illustrated in accordance with an embodiment of the present invention. In an embodiment, the method <NUM> may be performed by the controller <NUM>. At block <NUM>, should the leak sensor <NUM> not detect the presence of refrigerant or the concentration of refrigerant greater than a threshold concentration, the method <NUM> may end and/or continuously check for refrigerant leaks on a recurring basis. If the leak sensor <NUM> detects the presence of refrigerant or detects the concentration of refrigerant greater than a threshold concentration, the method <NUM> may continue to block <NUM>. At block <NUM>, the controller <NUM> may record the leak and the entrance of the leak mitigation strategy into memory. At block <NUM>, the controller <NUM> is programmed to output for display an indicator. The indicator may be an auditory indicator, a visual indicator, or the like. In at least one embodiment, the controller <NUM> may transmit information or data indicative of the leak to a driver, operator, remote computing system, a remote monitoring system, or a display.

The controller <NUM> may assess the operational state of various components of the refrigeration system <NUM>, in parallel, substantially simultaneously, or sequentially. At block <NUM>, the controller <NUM> may assess whether the main heating valve <NUM> is open. At block <NUM>, if the main heating valve <NUM> is not open then the controller <NUM> will open the main heating valve <NUM> at block <NUM>. At block <NUM>, the controller <NUM> may assess whether the hot gas valve <NUM> is open. At block <NUM>, if the hot gas valve <NUM> is open then the controller <NUM> will close the hot gas valve <NUM> at block <NUM>. At block <NUM>, the controller <NUM> may assess whether the condenser fan <NUM> is on and operation (e.g., running). At block <NUM>, if the condenser fan <NUM> is not running then the controller <NUM> may command the condenser fan <NUM> to run at block <NUM>. The operation of the condenser fan <NUM> may facilitate the disbursement or dilution of refrigerant proximate the condenser <NUM> if a leak occurs on a condenser side of the refrigeration system <NUM>. At block <NUM>, the controller <NUM> may assess whether the evaporator fan <NUM> is on and in operation (e.g., running). At block <NUM>, if the evaporator fan <NUM> is not running then the controller <NUM> may command the evaporator fan <NUM> to run at block <NUM>. The operation of the evaporator fan <NUM> may facilitate the disbursement or dilution of refrigerant proximate the evaporator <NUM>. At block <NUM>, the controller <NUM> may assess whether the first valve <NUM> is open. At block <NUM>, if the first valve <NUM> is open then the controller <NUM> will close the first valve <NUM> at block <NUM>. At block <NUM>, the controller <NUM> may assess whether the second valve <NUM> is open. At block <NUM>, if the second valve <NUM> is closed then the controller <NUM> will open the second valve <NUM> at block <NUM>.

At block <NUM>, the controller <NUM> may assess whether the compressor <NUM> is on and operational (e.g. running). At block <NUM>, if the compressor <NUM> is not on and operational then the controller <NUM> will run the compressor <NUM> before moving onto block <NUM>. At block <NUM>, the controller <NUM> may assess whether there is a suction pressure, such as a suction pressure less than an ambient pressure, within the refrigerant line <NUM> that extends between the evaporator <NUM> and the compressor <NUM>. In such an embodiment, a pressure sensor <NUM> is configured to detect pressure within the refrigerant line <NUM> and communicate the detected pressure to the controller <NUM>. At block <NUM>, the method may alternatively assess a fluid pressure within the evaporator <NUM> (e.g. evaporator pressure) and determine whether the fluid pressure within the evaporator <NUM> is less than a threshold pressure. In such an embodiment, the pressure sensor <NUM> is disposed within or proximate the evaporator <NUM>. Should the suction pressure be less than the ambient pressure or the evaporator pressure be less than a threshold pressure, the method <NUM> may continue to block <NUM>. If the suction pressure is greater than the ambient pressure or the pressure within the evaporator <NUM> is greater than a threshold pressure, the method <NUM> may return to block <NUM>.

At block <NUM>, the controller <NUM> may assess whether the second valve <NUM> is open. At block <NUM>, if the second valve <NUM> is open then the controller <NUM> will close the second valve <NUM> at block <NUM> before moving onto block <NUM>. At block <NUM>, the refrigeration system <NUM> is shut down. The leak mitigation strategy utilizing the pump down process greatly reduces the risk of the refrigerant reaching the lower flammability limit by removing and storing refrigerant from the evaporator <NUM> within the condenser <NUM>. The leak mitigation strategy may also dilute or disperse refrigerant that may be present within the interior volume <NUM> of the conditioned space <NUM>. If a refrigerant leak is in an area that is not exposed to the interior volume <NUM> than the refrigerant may dissipate on its own or with the aid of a condenser fan.

Claim 1:
A refrigeration system (<NUM>; <NUM>), comprising:
a compressor (<NUM>; <NUM>) driven by a power source (<NUM>; <NUM>), the compressor having a compressor outlet (<NUM>; <NUM>) and a compressor inlet (<NUM>; <NUM>);
a condenser (<NUM>; <NUM>) having a condenser inlet (<NUM>; <NUM>), fluidly connected to the compressor outlet, and a condenser outlet (<NUM>; <NUM>);
an evaporator (<NUM>; <NUM>) having an evaporator inlet (<NUM>; <NUM>), fluidly connected to the condenser outlet through a first valve (<NUM>; <NUM>) movable between an open position and a closed position, and a evaporator outlet (<NUM>; <NUM>) fluidly connected to the compressor inlet (<NUM>; <NUM>);
a leak sensor (<NUM>; <NUM>) arranged to provide a signal indicative of a refrigerant;
a controller (<NUM>) in communication with the first valve (<NUM>; <NUM>) and the compressor (<NUM>), the controller being arranged to receive the signal and programmed to command the first valve (<NUM>;<NUM>) to move towards the closed position, responsive to the signal being indicative of the refrigerant; and
a second valve (<NUM>; <NUM>) fluidly connecting the evaporator outlet (<NUM>; <NUM>) and the compressor inlet (<NUM>; <NUM>), the second valve (<NUM>; <NUM>) being moveable between an open position and a closed position;
wherein the controller (<NUM>) is further programmed to operate the compressor (<NUM>) such that refrigerant within the evaporator (<NUM>) is directed towards the compressor until a suction pressure measurement proximate an inlet (<NUM>) of the compressor is less than an ambient pressure;
characterized in that
the controller (<NUM>; <NUM>) is further programmed to command the second valve (<NUM>; <NUM>) to move towards the closed position when the suction pressure measurement proximate an inlet (<NUM>; <NUM>) of the compressor is less than an ambient pressure.