Patent Description:
A transport climate control system can include, for example, a transport refrigeration system (TRS) and/or a heating, ventilation and air conditioning (HVAC) system. A TRS is generally used to control an environmental condition (e.g., temperature, humidity, air quality, and the like) within an internal space or cargo space of a transport unit (e.g., a truck, a container (such as a container on a flat car, an intermodal container, etc.), a box car, a semi-tractor, a bus, or other similar transport unit). The TRS can maintain environmental condition(s) of the internal space to maintain cargo (e.g., produce, frozen foods, pharmaceuticals, etc.) In some embodiments, the transport unit can include a HVAC system to control a climate within a passenger space of the vehicle.

<CIT> describes a transport temperature control apparatus which includes a refrigeration circuit and a heat exchanger having an air inlet and an air outlet in communication with a conditioned space.

This invention relates generally to a transport climate control system. More specifically, the invention relates to a system according to claim <NUM> and a method according to claim <NUM> for defrosting a transport climate control system having a transport climate control circuit that includes an evaporator.

The embodiments described herein can be used in a mechanically powered (e.g., prime mover powered), electrically powered (e.g., battery powered), or a hybrid powered (e.g., combination of mechanically and electrically powered) transport climate control systems where maximizing operation of the transport climate control system and minimizing energy (e.g., battery) usage while in transit can be important.

The embodiments described herein can remove frost buildup on a transport climate control system evaporator coil that can occur, for example, during hot and/or humid ambient conditions outside of a climate controlled space (e.g., an internal or cargo space of a transport unit, a passenger space of a vehicle, etc.) being conditioned by the transport climate control system. It will be appreciated that frost buildup on the evaporator coil that is not periodically removed can reduce the cooling capacity of the transport climate control system and can lead to damage to the transport climate control system and increased power consumption of the transport climate control system.

The embodiments of the invention disclosed herein use convection heat to defrost ice/frost formed on an evaporator coil of the evaporator in the transport climate control system by independently controlling at least two evaporator fans in the evaporator. Embodiments disclosed herein can provide a transport climate control circuit and a controller. The transport climate control system includes the transport climate control circuit that includes a compressor that compresses a working fluid passing through the transport climate control circuit, the evaporator that absorbs heat from a climate controlled space and evaporates the working fluid, and at least two evaporator fans that control air flow around the evaporator coil of the evaporator. The controller is configured to control the transport climate control circuit and to defrost the evaporator coil. When a defrost event is triggered (e.g., based on temperature, pressure, and/or humidity data in the evaporator or on door opening events), the controller instructs the transport climate control circuit to supply heat to or around one section of the evaporator coil, and independently controls the at least two fans to move the air around the evaporator coil in controlled directions (e.g. a respective controlled direction for each one of the at least two fans) so that heat from one section of the evaporator coil is used to convectively heat the inlet of the evaporator coil. In an embodiment, the evaporator further includes a damper to prevent the heated air from entering the climate controlled space. The damper can be a damper blade that uses a damper solenoid that when activated closes the damper blade or similar structure that is able to prevent the heated air from entering the climate controlled space or leaving the evaporator during defrost.

In another embodiment, a method for defrosting an evaporator of a transport climate control circuit of a transport climate control system that provides climate control to a climate controlled space of a transport unit is provided. The transport climate control circuit includes a compressor, an evaporator that includes an evaporator coil, and at least two fans. The method includes a controller of the transport climate control system detecting whether a defrost event condition occurs. The method further includes upon detecting the defrost event condition: supplying heat to or around one section of the evaporator coil; independently controlling a first fan of the at least two fans to move air around the evaporator coil in a first controlled direction so that heat from the one section of the evaporator coil is used to convectively heat a first side of the inlet of the evaporator coil, and independently controlling a second fan of the at least two fans to move air around the evaporator coil in a second controlled direction so that heat from the one section of the evaporator coil is used to convectively heat a second side of the inlet of the evaporator coil.

In some embodiments, the supply of heat is provided by an electric heating device (e.g., a device that includes an electrical resistor) that is provided adjacent to or on the evaporator coil, i.e., on a face of an evaporator coil. The at least two fans are then independently controlled to move the air around the evaporator coil in controlled directions (e.g., counterclockwise or clockwise direction) so that frost formed at the inlet of the evaporator coil can be defrosted. In other embodiments, the supply of heat is provided from the working fluid from the discharge of the compressor or from a thermal energy system.

Accordingly, in some embodiments, the heat supplied to the evaporator coil is not used to directly heat the frost formed on the evaporator coil, but is distributed around the evaporator coil for selective heating of different portions or sections of the evaporator coil. In some embodiments, since the frost is not directly heated, the frost does not sublimate to vapor, but instead is melted to water so that the water can be removed from the evaporator (e.g., via a drip line/pan and water outlet).

Additional features and aspects will become apparent by consideration of the following detailed description and accompanying drawings.

References are made to the accompanying drawings that form a part of this disclosure and which illustrate embodiments in which the systems and methods described in this specification can be practiced.

This disclosure relates generally to a transport climate control system. More specifically, the disclosure relates to methods and systems for providing energy efficient defrosting of a transport climate control system evaporator.

<FIG> depicts a temperature-controlled straight truck <NUM> that includes a climate controlled space <NUM> for carrying cargo and a transport climate control system <NUM> for providing climate control to the climate controlled space <NUM>. The transport climate control system <NUM> includes a transport climate control unit (TCCU) <NUM> that is mounted to a front wall <NUM> of the climate controlled space <NUM>. The TCCU <NUM> includes a transport climate control circuit that connects, for example, a compressor, a condenser, an evaporator, and an expansion valve, and includes at least two fans and a damper to provide conditioned air within the climate controlled space <NUM>.

The climate control system <NUM> also includes a programmable climate controller <NUM> and one or more sensors (not shown) that are configured to measure one or more parameters of the climate control system <NUM> and communicate parameter data to the climate controller <NUM>. The climate controller <NUM> may comprise a single integrated control unit or may comprise a distributed network of climate controller elements. The number of distributed control elements in a given network can depend upon the particular application of the principles described herein. The climate controller <NUM> is configured to control operation of the climate control system <NUM> including a transport climate control circuit.

The truck <NUM> further includes a vehicle power bay <NUM>, which houses a prime mover <NUM>, such as a combustion engine (e.g., diesel engine, etc.), an electric motor, etc. that provides power to move the truck <NUM> and to operate the TCCU <NUM>. In some embodiments, the prime mover <NUM> can work in combination with an optional machine <NUM> (e.g., an alternator) to operate the TCCU <NUM>. In some embodiments, the truck <NUM> can be a hybrid vehicle that is powered by the prime mover <NUM> in combination with a battery power source or can be an electrically driven truck in which the prime mover <NUM> is replaced with an electric power source (e.g., a battery power source). In some embodiments, the TCCU <NUM> can have its own independent power source (e.g., a TCCU prime mover, a TCCU alternator, a TCCU battery power source, etc.) that is separate from the prime mover <NUM> to provide power to and operate the TCCU <NUM>. A TCCU prime mover can power the TCCU <NUM> by itself or in combination with a TCCU alternator or the optional machine <NUM> or a TCCU battery power source. In some embodiments, the TCCU <NUM> can be powered by a TCCU electric power source (e.g., a battery power source) without the use of a prime mover (e.g., the prime mover <NUM>, a TCCU prime mover, etc.).

While <FIG> illustrates a temperature-controlled straight truck <NUM>, it will be appreciated that the embodiments described herein can also apply to any other type of transport unit (TU) including, but not limited to, a container (such as a container on a flat car, an intermodal container, etc.), a box car, or other similar transport unit. container, etc.), a box car, or other similar transport unit.

<FIG> illustrates one embodiment of a refrigerated transport unit <NUM> attached to a tractor <NUM>. The refrigerated transport unit <NUM> includes a transport climate control system <NUM> for a transport unit <NUM>. The tractor <NUM> is attached to and is configured to tow the transport unit <NUM>. The transport unit <NUM> shown in <FIG> is a trailer. It will be appreciated that the embodiments described herein are not limited to tractor and trailer units, but can apply to any type of transport unit (e.g., a container on a flat car, an intermodal container, etc.), a truck, a box car, or other similar transport unit. The transport unit <NUM> can include one or more doors (not shown) that are movable between an open position and a closed position to selectively allow access to a climate controlled space (e.g., internal or cargo space) <NUM>.

The transport climate control system <NUM> includes a climate control unit (CCU) <NUM> that provides environmental control (e.g. temperature, humidity, air quality, etc.) within the climate controlled space <NUM> of the transport unit <NUM>. The climate control system <NUM> also includes a programmable climate controller <NUM> and one or more sensors (not shown) that are configured to measure one or more parameters of the climate control system <NUM> and communicate parameter data to the climate controller <NUM>.

The CCU <NUM> is disposed on a front wall <NUM> of the transport unit <NUM>. In other embodiments, it will be appreciated that the CCU <NUM> can be disposed, for example, on a rooftop or another wall of the transport unit <NUM>. The CCU <NUM> includes a transport climate control circuit that connects, for example, a compressor, a condenser, an evaporator and an expansion valve and includes at least two fans and a damper to provide conditioned air within the climate controlled space <NUM>.

The climate controller <NUM> may comprise a single integrated control unit <NUM> or may comprise a distributed network of climate controller elements <NUM>, <NUM>, which includes the control unit. The number of distributed control elements in a given network can depend upon the particular application of the principles described herein. The climate controller <NUM> is configured to control operation of the climate control system <NUM> including the transport climate control circuit.

<FIG> illustrates one embodiment of a multi-zone transport climate control system (MCCS) <NUM> for a transport unit (TU) <NUM> that can be towed, for example, by a tractor (not shown). The MCCS <NUM> includes a transport climate control unit (TCCU) <NUM> that provides environmental control (e.g. temperature, humidity, air quality, etc.) within an internal climate controlled space <NUM> of the TU <NUM>. The MCCS <NUM> also includes a MCCS controller <NUM> and one or more sensors (e.g., Hall effect sensors, current transducers, etc.) that are configured to measure one or more parameters (e.g., ambient temperature, compressor suction pressure, compressor discharge pressure, supply air temperature, return air temperature, humidity, etc.) of the MCCS <NUM> and communicate parameter data to the MCCS controller <NUM>. The MCCS <NUM> is powered by a power module <NUM>. The TCCU <NUM> is disposed on a front wall <NUM> of the TU <NUM>. In other embodiments, it will be appreciated that the TCCU <NUM> can be disposed, for example, on a rooftop <NUM> or another wall of the TU <NUM>.

In some embodiments, the MCCS <NUM> can include an undermount unit <NUM>. In some embodiments, the undermount unit <NUM> can be a TCCU that can also provide environmental control (e.g. temperature, humidity, air quality, etc.) within the internal climate controlled space <NUM> of the TU <NUM>. The undermount unit <NUM> can work in combination with the TCCU <NUM> to provide redundancy or can replace the TCCU <NUM>. Also, in some embodiments, the undermount unit <NUM> can be a power module that includes, for example, a generator that can help power the TCCU <NUM>.

The programmable MCCS Controller <NUM> may comprise a single integrated control unit or may comprise a distributed network of control elements. The number of distributed control elements in a given network can depend upon the particular application of the principles described herein. The MCCS controller <NUM> is configured to control operation of the MCCS <NUM>.

As shown in <FIG>, the power module <NUM> is disposed in the TCCU <NUM>. In other embodiments, the power module <NUM> can be separate from the TCCU <NUM>. Also, in some embodiments, the power module <NUM> can include two or more different power sources disposed within or outside of the TCCU <NUM>. In some embodiments, the power module <NUM> can include one or more of a prime mover, a battery, an alternator, a generator, a solar panel, a fuel cell, etc. Also, the prime mover can be a combustion engine or a microturbine engine and can operate as a two speed prime mover, a variable speed prime mover, etc. The power module <NUM> can provide power to, for example, the MCCS Controller <NUM>, a compressor (not shown), a plurality of DC (Direct Current) components (not shown), a power management unit (not shown), etc. The DC components can be accessories or components of the MCCS <NUM> that require DC power to operate. Examples of the DC components can include, for example, DC fan motor(s) for a condenser fan or an evaporator blower (e.g., an Electrically Commutated Motor (ECM), a Brushless DC Motor (BLDC), etc.), a fuel pump, a drain tube heater, solenoid valves (e.g., controller pulsed control valves), etc..

The power module <NUM> can include a DC power source (not shown) for providing DC electrical power to the plurality of DC components (not shown), the power management unit (not shown), etc. The DC power source can receive mechanical and/or electrical power from, for example, a utility power source (e.g., Utility power, etc.), a prime mover (e.g., a combustion engine such as a diesel engine, etc.) coupled with a generator machine (e.g., a belt-driven alternator, a direct drive generator, etc.), a series of battery sources, etc. For example, in some embodiments, mechanical energy generated by a diesel engine is converted into electrical energy via a generator machine. The electrical energy generated via the belt driven alternator is then converted into DC electrical power via, for example, a bi-directional voltage converter. The bi-directional voltage converter can be a bi-directional multi-battery voltage converter.

The internal climate controlled space <NUM> can be divided into a plurality of zones <NUM>. The term "zone" means a part of an area of the internal climate controlled space <NUM> separated by walls <NUM>. It will be appreciated that the invention disclosed herein can also be used in a single zone TCCU.

The MCCS <NUM> for the TU <NUM> includes the TCCU <NUM> and a plurality of remote evaporator units <NUM>. In some embodiments, an HVAC system can be powered by an Auxiliary Power Unit. The APU can be operated when a main prime mover of the TU <NUM> is turned off such as, for example, when a driver parks the TU <NUM> for an extended period of time to rest. The APU can provide, for example, power to operate a secondary HVAC system to provide conditioned air to a cabin of the TU <NUM>. The APU can also provide power to operate cabin accessories within the cabin such as a television, a microwave, a coffee maker, a refrigerator, etc. The APU can be a mechanically driven APU (e.g., prime mover driven) or an electrically driven APU (e.g., battery driven).

The tractor includes a vehicle electrical system for supplying electrical power to the electrical loads of the tractor, the MCCS <NUM>, and/or the TU <NUM>. In some embodiments, the tractor can include a compressor that can compress air and store the compressed air in compressor tank(s).

<FIG> depicts a temperature-controlled van <NUM> that includes a climate controlled load space <NUM> (or internal space) for carrying cargo and a transport climate control system (TCCS) <NUM>. The TCCS <NUM> includes a transport climate control unit (TCCU) <NUM> that is mounted to a rooftop <NUM> of the climate controlled load space <NUM>. The TCCS <NUM> is controlled via a controller <NUM> to provide climate control within the climate controlled load space <NUM>. The van <NUM> further includes a vehicle power bay <NUM>, which houses a prime mover <NUM>, such as a combustion engine (e.g., diesel engine, etc.) or battery power source, that provides power to move the van <NUM> and to operate the TCCS <NUM>. In some embodiments, the prime mover <NUM> can work in combination with an optional machine <NUM> (e.g., an alternator) to operate the TCCU <NUM>. In one embodiment, the van <NUM> includes a vehicle electrical system. Also, in some embodiments, the van <NUM> can be a hybrid vehicle that is powered by the prime mover <NUM> in combination with a battery power source or can be an electrically driven truck in which the prime mover <NUM> is replaced with an electric power source (e.g., a battery power source).

<FIG> illustrates a block diagram of a transport climate control circuit <NUM>, according to one embodiment that can be used in any of the above transport climate control systems shown in <FIG>. The transport climate control circuit <NUM> can be, for example, a circuit that can be used to provide climate control within a passenger space of a vehicle (e.g., the climate controlled space <NUM> shown in <FIG>), a circuit that can be used to provide climate control within an internal space or cargo space that is a climate controlled space of a transport unit (e.g., the climate controlled space <NUM>, <NUM>, <NUM>, <NUM> shown in <FIG>), etc. A working fluid (e.g., a refrigerant) is configured to pass through components of the transport climate control circuit <NUM> to provide climate control within the internal space or cargo space.

The transport climate control circuit <NUM> includes at least a compressor <NUM>, a condenser <NUM>, an expansion device <NUM>, an evaporator <NUM>, and a heating device <NUM>.

The compressor <NUM> can be a digital scroll compressor, a reciprocating compressor, a screw compressor, a positive displacement compressor, a centrifugal compressor, or other suitable type of compressor for compressing a working fluid. A climate controller (e.g., the controller <NUM>, <NUM>, <NUM>, <NUM> shown in <FIG>, <FIG>, <FIG>, <FIG>) is configured to control the climate control circuit <NUM> to operate in a plurality of different operation modes including, for example, a continuous cooling mode, a start-stop cooling mode, a heating mode, a defrost mode, etc..

Of particular note, in the continuous cooling mode, the climate controller is configured to instruct the compressor <NUM> to continuously compress the working fluid until the temperature within the climate controlled space reaches a desired setpoint temperature. In the start-stop cooling mode, the climate controller is configured to instruct the compressor <NUM> to operate in a periodic cycle in which during each cycle the compressor <NUM> is configured to compress the working fluid for a first period of time and then the compressor <NUM> is configured to stop compressing the working fluid for a second period of time. The compressor <NUM> will continue to cycle between compressing the working fluid and not compressing the working fluid until the temperature within the climate controlled space reaches the desired setpoint temperature. In some embodiments, the compressor <NUM> is configured to compress the working fluid and direct the compressed working fluid from the compressor <NUM> to the condenser <NUM> during the start portion and configured to not compress working fluid during the stop portion. In some embodiments, during the stop portion of the start-stop cooling mode fan(s) of the condenser <NUM> and the evaporator <NUM> are turned off and are not operating.

The compressor <NUM> is configured to compress a working fluid (e.g., refrigerant) and direct the working fluid through the climate control circuit <NUM> in order to provide temperature control within a climate controlled space. In particular, the compressor <NUM> is configured to direct the compressed working fluid that is a gas to the condenser <NUM>.

The condenser <NUM> can include a condenser coil (not shown) and one or more condenser fans. The condenser <NUM> is configured to allow the working fluid, received from the compressor <NUM>, to transform from a gas to a liquid by releasing heat absorbed by the working fluid into the ambient environment outside of the climate controlled space. That is, the condenser <NUM> is configured to cool and condense the working fluid. The condenser <NUM> is configured to direct the liquid working fluid to the expansion device <NUM>.

The expansion device <NUM> is configured to receive the working fluid in the form of a liquid from the condenser <NUM> and is configured to restrict the flow of the working fluid in the form of a gas to the evaporator <NUM>. In some embodiments, the expansion device <NUM> can be an expansion valve. The gaseous working fluid is directed by the expansion device <NUM> to the evaporator <NUM>.

The evaporator <NUM> can include an evaporator coil and two or more evaporator fans (described in detail below). The evaporator <NUM> is configured to allow the working fluid, received from the expansion device <NUM>, to evaporate from a liquid to a gas by absorbing heat from the climate controlled space and thereby provide cooling to the climate controlled space.

The transport climate control circuit <NUM> can also include a heating device <NUM> that can provide thermal energy for defrosting the evaporator <NUM> or heat during the heating mode. This can allow for increased flexibility in defrost operation, such as, during frequent door openings of the climate controlled space (e.g., also referred to as door opening events). In some embodiments, the heating device <NUM> can be an electric heating device that uses heating coils or an electric heater having an electrical resistor that converts electricity to heat and/or an electric heating bar that is able to generate heat and/or includes a heating fin connected to the electric heating device, electric heater, or electric heating bar to conduct heat from the heating source to evenly distribute the supply of heat in the evaporator by having an increased area to increase the rate of heat transfer. In some embodiments, the heating device <NUM> can operate between <NUM> V DC and <NUM> V DC, and preferably, between <NUM> V to <NUM> V DC, and nominally at <NUM> V DC, but it is appreciated that the electric heating device can be operated based on AC or DC voltage based on the specific unit/design of the electric heating device and/or at the voltage range for the operation of the transport unit. Also, in some embodiments, the discharge from the compressor <NUM> having the compressed working fluid can be connected to the heating device <NUM> (and optionally also including an electric heating element) to provide thermal energy to the evaporator <NUM> in order to provide heating to the climate controlled space and/or the evaporator. It is appreciated that other heat sources can be used for providing heat to the heating device <NUM>, for example, a thermal storage system that uses brine or phase change material for capturing heat from the transport climate control circuit or other heating source from the transport unit, e.g., oil, exhaust, etc..

<FIG> and <FIG> illustrate the evaporator <NUM> in further detail, according to one embodiment. The evaporator <NUM> is used to absorb heat from the climate controlled space and evaporate the working fluid. The evaporator <NUM> includes at least one evaporator coil having an inlet and outlet for receiving and returning the working fluid, at least two evaporator fans that control air flow around the evaporator coil, and at least one damper that moves between at least an open position and a closed position to control an amount of the air flow between the evaporator and the climate controlled space. Optionally, the transport climate control circuit <NUM> can also include the heating device <NUM> to defrost the evaporator coil or provide heat during the heating mode and a controller to control the transport control circuit <NUM>, as necessary.

The at least two evaporator fans can include a roadside evaporator fan <NUM>, e.g., fan nearer the middle/inner side of the road on which the transport unit is driven, e.g., a first side, and a curbside evaporator fan <NUM>, e.g., fan nearer the curb or outer side of the road on which the transport unit is driven, e.g., a second side. The at least two evaporator fans are used to control the air flow around specific sections of the evaporator coil, as described below. Additional evaporator fans can be used to control the amount of air flow around the evaporator coil, where the amount of evaporator fans are not limited hereto, but can be provided as required to meet the operating conditions of the transport climate control system. For example, a third evaporator fan can be provided between the roadside evaporator fan and the curbside evaporator fan, where the third evaporator fan would be used to further selectively control the air flow around specific parts of the evaporator coil for controlled cooling and/or heating.

The at least one evaporator coil can be a single evaporator coil <NUM> that receives the working fluid from the expansion device at an inlet thereof, which is then evaporated by absorbing heat from the climate controlled space, and returns the working fluid to the compressor from the exit or outlet of the evaporator coil to continue the working fluid cycle. The at least one evaporator coil has sections or parts associated with the at least two evaporator fans for selective control of the air flow and can include at least a curbside section of the evaporator coil and at least a roadside section of the evaporator coil, which correspond to the same side as the roadside evaporator fan <NUM> and the curbside evaporator fan <NUM>, respectively. It is understood that the evaporator coil can be a single coil having an inlet(s) closest to the evaporator fans, multiple inlets along various sections of the evaporator coil, or the evaporator coil can be multiple separate evaporator coils connected along different flows paths in the evaporator with or without dividers, e.g., to provide different cooling profiles across the evaporator.

The heating device <NUM> can be controlled, for example, by the climate controller and can be connected to a high voltage power source, e.g., electric vehicle battery or battery charged from movement of a prime mover, or can be connected to another heat source, e.g., discharge outlet of the compressor or thermal storage system, for providing heat to the evaporator. The heating device can be heated, for example to have a surface temperature, between <NUM> (<NUM> °F) and <NUM> (<NUM> °F), and preferably between <NUM> (<NUM> °F) and <NUM> (<NUM> °F), and most preferably below <NUM> (<NUM> °F) or similar temperature range that is sufficient to defrost the evaporator coil.

Operation of the transport climate control circuit <NUM> is described below with respect to <FIG>.

<FIG> illustrates a flowchart for a method <NUM> for providing thermal energy to the evaporator <NUM> of the climate control circuit <NUM> shown in <FIG>, according to one embodiment.

The method <NUM> begins at <NUM> whereby a controller (e.g., the climate controller <NUM>, <NUM>, <NUM>, <NUM> shown in <FIG>) determines whether a defrost event condition is detected/occurs in the transport climate control circuit <NUM>. For example, the defrost event condition can be: a door opening event; a time condition, (e.g., every two minutes or every two hours, etc.); or based on pressure, temperature, and/or humidity data from sensors, or a combination thereof. When the controller determines that a defrost event is triggered in the transport climate control circuit <NUM>, the method <NUM> proceeds to <NUM>, which can be an automatic event to defrost the evaporator coil or require user selection of the defrost mode. When the controller determines that a defrost event is not triggered in the transport climate control circuit <NUM>, the method <NUM> continues to loop until a defrost event is triggered.

At <NUM>, the controller begins operating in a defrost mode and closes the damper <NUM> that separates the evaporator from the climate controlled space of a transport unit. In some embodiments, the controller can operate a solenoid coupled to the damper. Additionally, a valve (not shown in this embodiment) in the transport climate control circuit can be closed, preventing cold working fluid from flowing into the evaporator coil. The method <NUM> then proceeds to <NUM>.

At <NUM>, the controller can defrost the evaporator coil by instructing the transport climate control circuit to supply heat to or around at least one section of the evaporator coil based on, among other things, mass of the ice/frost, size of the coil, airflow, etc. For example, the controller can control the heating device, e.g., an electric heating device, to supply the marketing requested heat capacity for the heating device that is sufficient to perform defrost to heat around one section of the evaporator coil, e.g., by turning on the electric heating device to a specified temperature to generate heat, where the specified temperature is between <NUM> (<NUM> °F) and <NUM> (<NUM> °F), and preferably between <NUM> (<NUM> °F) to <NUM> (<NUM> °F), and most preferably at or below <NUM> (<NUM> °F). It is appreciated that other heating sources can be optionally used to supply heat for defrosting the evaporator coil. For example, since the discharge temperature of the working fluid of the compressor is typically between <NUM>-<NUM> (<NUM>-<NUM> °F) the discharge of the compressor can also be used as the heating source of the heating device, where the controller instructs the transport climate control circuit to supply heat to or around one section of the evaporator by instructing the transport climate control circuit to direct hot gas from the compressor to the evaporator coil. Similarly, a thermal energy storage system can be used as the heat source, since such system captures heat from the working fluid for later reuse. It is appreciated that during the defrosting, the heat can be supplied solely by the electric heating device, e.g., without using the hot gas from the compressor discharge during defrosting, or in conjunction with the hot gas from the compressor through the evaporator coil. The method <NUM> then proceeds to <NUM>.

At <NUM>, the controller independently controls two or more evaporator fans, e.g., evaporator fans <NUM>, <NUM> in <FIG>, of the climate control circuit <NUM> to convectively heat different portions or sections of the evaporator coil, i.e., so that heat from one section of the evaporator coil is used to heat and defrost the frost formed at a different portion or section of the evaporator coil. For example, as illustrated in <FIG> and <FIG>, the controller independently controls operation of the evaporator fan to move air around the evaporator coil in a first controlled direction A, e.g., clockwise direction, so that the air is moved from an inlet of the evaporator coil to an exit or outlet of the evaporator coil along different sections of the evaporator coil, e.g., so that heat from the one section of the evaporator coil is used to convectively defrost frost formed at the inlet of the evaporator coil. For example, <FIG> illustrates the operation of a first (or roadside) evaporator fan <NUM>, which draws air from the evaporator and forces the air across a first section (or roadside section) of the evaporator coil <NUM> at an inlet of the evaporator coil at the roadside section of the evaporator coil and then across the roadside section of the evaporator coil and the heating device <NUM>. The air is then moved from around the exit/outlet of the evaporator coil and heating device across a second section (or curbside section) of the evaporator coil at the curbside section of the evaporator coil towards the inlet of the evaporator coil at the curbside section. In so doing, frost formed at the inlet of the curbside section of the evaporator coil is defrosted by convection heating. It is appreciated that the evaporator fans can be controlled at various speeds depending on the conditions necessary for defrost. That is, the evaporator fans can be run at a low speed, middle speed, or high speed, or combinations thereof for defrosting the evaporator coil.

The controller can then stop the first evaporator fan <NUM> and start the second (or curbside) evaporator fan <NUM> as seen in <FIG>. The second evaporator fan <NUM> moves air around the evaporator coil in a second controlled direction B, e.g., counterclockwise direction, where air is moved from the inlet of the evaporator coil to the exit or outlet of the evaporator coil along different sections of the evaporator coil. For example, the second evaporator fan <NUM> draws air from the evaporator and moves the air across the second section of the evaporator coil <NUM> at the inlet of the evaporator coil at the curbside section of the evaporator coil and then across the curbside section of the evaporator coil and the heating device <NUM>. The air is then forced from the exit/outlet of the evaporator coil across the first section of the evaporator coil at roadside section of the evaporator coil towards the inlet of the evaporator coil at the roadside section. In so doing, frost formed at the inlet of the first section/roadside section of the evaporator coil is defrosted by convection heating.

It is appreciated that the controller can also control the evaporator fans in a positive air flow direction, where air is blown towards the evaporator coil, and in a negative air flow direction, where air is drawn from the evaporator coil to provide desired convection heating around the evaporator coil. In so doing, in one embodiment, during the defrost mode, the controller can control the operation of the curbside evaporator fan <NUM> nearer the curbside section of the evaporator coil so that air is first drawn across the heating device <NUM> and the exit/outlet of the evaporator coil at the curbside section of the evaporator coil so that the heated air is used to defrost the inlet of the evaporator coil at the curbside section of the evaporator coil, e.g., the evaporator coil on the same side as the evaporator fan.

It is further appreciated that while the controller controls one of the two or more evaporator fans and stops the second or other fans, so that less static pressure is built up in the evaporator, in some embodiments, both fans can be operated at the same time, but in opposite directions. For example, the first/roadside evaporator fan can be controlled to blow air in the positive air flow direction towards the roadside section of the evaporator coil, while the second/curbside evaporator fan is controlled in the negative air flow direction to draw air from curbside section of the evaporator coil. In this way, a greater air flow can be generated to convectively heat the evaporator. The method then optionally proceeds to <NUM>.

At <NUM>, the controller can optionally monitor parameters or conditions in the evaporator using sensors on or around the evaporator coil and/or in the climate controlled space to monitor at least one of temperature, pressure, or humidity, or combination thereof. In some embodiments, monitoring the evaporator coil can include monitoring a temperature difference across the evaporator coil. For example, in one embodiment, one or more temperature sensors can be provided on the evaporator coil that provide evaporator coil temperature data across the evaporator coil. In another embodiment, one or more pressure sensors can be provided for providing pressure data across the evaporator coil. In some embodiments, monitoring the climate controlled space can include monitoring door openings of doors that access the climate controlled space (also referred to as door opening events), monitoring a temperature within the climate controlled space, etc. The method then proceeds to <NUM>.

At <NUM>, the controller determines whether or not the evaporator coil is sufficiently defrosted, e.g., by using the above mentioned sensors as discussed with respect to optional <NUM>. It is appreciated that while the determination of whether or not the evaporator coil is sufficiently defrosted can be based on sensors indicating that frost is still formed on the evaporator coil, it is understood that the evaporator fans can be started based on monitored/detected events or a programmed time, e.g., every two hours, or manually operated. If the evaporator coil is not sufficiently defrosted, the method returns to <NUM> to independently control the two or more fans to continue the convection heating of the evaporator coil. Based on the conditions in the evaporator, the controller can then determine which of the evaporator fans should be running to defrost the evaporator coil, e.g., a temperature at the inlet of the roadside section of the evaporator coil is low, while the adjacent section of the evaporator coil at the curbside section of the evaporator coil does not indicate signs of frost formation, then the curbside evaporator would be run. When the evaporator coil is sufficiently defrosted, the method proceeds to <NUM>.

At <NUM>, the controller exits the defrost mode and proceeds to <NUM> to restart the previous operating mode (e.g., a continuous cooling mode, a start-stop cooling mode, a heating mode, etc.) and returns to <NUM> to wait for the next defrost event to occur.

Accordingly, the method <NUM> can provide heating energy that is efficient in defrosting the evaporator. Reducing total energy consumption and/or time by the transport climate control system can be important particularly for those transport climate control systems that rely on battery power for operations. This is because, for example, the energy storage can be expensive, heavy, and/or take valuable space of the transport vehicle. An advantage of these embodiments is that the transport climate control system can provide defrost to the evaporator coil without requiring additional energy to generate heat to remove any frost buildup.

It is appreciated that while the above disclosure is described with respect to the cooling mode being off, the defrosting mode can be used while the transport climate control system is providing cooling to improve cooling efficiency of the transport climate control system as a frosted evaporator coil can lower capacity and efficiency of the transport climate control system during cooling.

<FIG> illustrates a block diagram of a transport climate control circuit <NUM>, according to another embodiment of the invention, having similar elements to <FIG>, but where a heating device is not provided in the evaporator. Instead, hot gas from the compressor is used to defrost the evaporator. The transport climate control circuit <NUM> includes at least a compressor <NUM>, a condenser <NUM>, an expansion device <NUM>, and an evaporator <NUM>.

In this embodiment, during the defrost mode, the first valve <NUM> which is provided between the exit of the compressor <NUM> and the condenser <NUM> can be closed, either manually or automatically by the controller. The second valve <NUM> can then be opened to circulate the hot gas from the compressor discharge to the inlet of the evaporator coil of the evaporator <NUM>. It is appreciated that the hot gas can be provided at different sections of the evaporator coil, e.g., multiple or different inlets to the evaporator coil, along different sections of the evaporator coil using valves, or at the exit/outlet of the evaporator coil and/or the different sections of the evaporator can be divided using dividers. In so doing, the hot gas is not used to directly heat the frost formation on the evaporator coil, which typically occurs at the inlet of the evaporator coil, but can be used with the evaporator fans, as discussed above, so that convective heating of the evaporator can occur by the independent control of the evaporator fans to move the air around the evaporator coil in controlled directions (e.g. a respective controlled direction for each one of the fans) so that heat from one section of the evaporator coil is used to convectively defrost the frost formed on the evaporator coil.

The terminology used in this specification is intended to describe particular embodiments and is not intended to be limiting. The terms "a," "an," and "the" include the plural forms as well, unless clearly indicated otherwise. The terms "comprises" and/or "comprising," when used in this specification, indicate the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or components. The terms first, second, first side, second side, roadside, curbside, etc. are not intended to be limiting, but are only provided to give context of the relationship and understanding of the different features in the different embodiments of the invention.

Claim 1:
A transport climate control system (<NUM>, <NUM>, <NUM>, <NUM>) for providing climate control to a climate controlled space (<NUM>, <NUM>, <NUM>, <NUM>) of a transport unit (<NUM>, <NUM>), the transport climate control system comprising:
a transport climate control circuit (<NUM>) comprising:
a compressor (<NUM>) that compresses a working fluid passing through the transport climate control circuit,
an evaporator (<NUM>) that absorbs heat from the climate controlled space and evaporates the working fluid, said evaporator comprising:
an evaporator coil (<NUM>) having an inlet for receiving the working fluid and an outlet for returning the working fluid,
at least two fans (<NUM>, <NUM>) that control air flow around a first side of the evaporator coil (<NUM>) and a second side of the evaporator coil (<NUM>),
characterized in that the system comprises
an electric heating device (<NUM>) that is positioned at an outlet of the evaporator coil (<NUM>) and configured to generate heat, the electric heating device (<NUM>) extending across the evaporator coil (<NUM>) between the first side and the second side, and
a damper (<NUM>) that moves between at least an open position and a closed position to separate the evaporator from the climate controlled space and to control an amount of the air flow between the evaporator and the climate controlled space,
a controller (<NUM>, <NUM>, <NUM>, <NUM>) configured to control the transport climate control circuit and configured to defrost the evaporator coil (<NUM>) by:
closing the damper (<NUM>) when a defrost event is triggered to separate the evaporator from the climate controlled space,
instructing the transport climate control circuit to supply heat to or around one section of the evaporator coil (<NUM>) by turning on the electric heating device (<NUM>) to generate heat, and
independently controlling each of the at least two fans (<NUM>, <NUM>) to move the air around the evaporator coil (<NUM>) in a controlled direction so that heat from the one section of the evaporator coil (<NUM>) is used to convectively heat the inlet of the evaporator coil.