The subject matter disclosed herein relates to refrigerated storage containers and, more particularly, to refrigerated storage container air passage designs, energy efficient refrigerated storage container operation and energy efficient coordination of refrigerated storage containers on cargo ships.
A refrigerated storage container or reefer is an intermodal container (i.e., a shipping container) that is used in intermodal freight transport and may be refrigerated for the transportation of temperature sensitive cargo. An intermodal container is a large standardized shipping container, designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport—from ship to rail to truck—without unloading and reloading their cargo. Intermodal containers are primarily used to store and transport materials and products efficiently and securely in the global containerized intermodal freight transport system, but smaller numbers are in regional use as well.
Other than the standard, general purpose containers, many variations of intermodal containers exist for use with different types of cargoes. The most prominent of these are refrigerated containers, such as containers with integrated refrigeration units (a.k.a. reefers) that are used in the transport of temperature sensitive goods.
According to one aspect of the disclosure, a refrigerated storage container is provided and includes a container housing defining an interior in which cargo is storable, a condenser configured to receive air to remove heat from a refrigerant passing through the condenser, a condenser air inlet receptive of the air, a condenser air outlet configured to direct air exhausted from the condenser away from the condenser air inlet and a reefer air outlet configured to direct conditioned air exhausted from the interior toward the condenser air inlet.
In accordance with additional or alternative embodiments, the condenser air inlet is configured to be receptive of the conditioned air from the reefer air outlet.
In accordance with additional or alternative embodiments, the condenser air inlet, the condenser air outlet and the reefer air outlet each include louvers.
In accordance with additional or alternative embodiments, a local or remote controller is disposed to dependently or independently control an angling of each of the louvers.
In accordance with additional or alternative embodiments, the louvers are movable relative to a plane of a wall of the container housing.
In accordance with additional or alternative embodiments, the condenser air inlet, the condenser air outlet and the reefer air outlet are disposed on an end wall of the container housing.
In accordance with additional or alternative embodiments, the condenser air outlet is in a central region of the wall, the condenser air inlet includes first and second condenser air inlets aside the central region and a third condenser air inlet below the central region and the reefer air outlet includes first and second reefer air outlets outside the first and second condenser air inlets and a third reefer air outlet below the third condenser air inlet.
In accordance with additional or alternative embodiments, the condenser air outlet includes louvers angled upwardly, the first and second condenser air inlets each include louvers angled outwardly, the third condenser air inlet includes louvers angled downwardly, the first and second reefer air outlets each include louvers angled inwardly and the third reefer air outlet includes louvers angled upwardly.
In accordance with additional or alternative embodiments, an attachment is removably attachable to the reefer air outlet and configured to constrain a flow of the conditioned air to remain in a flowpath directed toward the condenser air inlet.
According to another aspect of the disclosure, a refrigerated storage container is provided and includes a container housing, a condenser configured to receive air to remove heat from a refrigerant passing through the condenser, a condenser air inlet by which the air is received, a condenser air outlet and a reefer air outlet configured such that air exhausted from the condenser is directed away from the condenser air inlet and conditioned air exhausted from the interior is directed toward the condenser air inlet.
In accordance with additional or alternative embodiments, the condenser air inlet, the condenser air outlet and the reefer air outlet each include louvers.
In accordance with additional or alternative embodiments, a local or remote controller is disposed to dependently or independently control an angling of each of the louvers.
In accordance with additional or alternative embodiments, the louvers are movable relative to a plane of a wall of the container housing.
In accordance with additional or alternative embodiments, the condenser air inlet, the condenser air outlet, and the reefer air outlet are disposed on an end wall of the container housing.
In accordance with additional or alternative embodiments, the condenser air outlet is in a central region of the wall, the condenser air inlet includes first and second condenser air inlets aside the central region and a third condenser air inlet below the central region and the reefer air outlet includes first and second reefer air outlets outside the first and second condenser air inlets and a third reefer air outlet below the third condenser air inlet.
In accordance with additional or alternative embodiments, the condenser air outlet includes louvers angled upwardly, the first and second condenser air inlets each include louvers angled outwardly, the third condenser air inlet includes louvers angled downwardly, the first and second reefer air outlets each include louvers angled inwardly and the third reefer air outlet includes louvers angled upwardly.
In accordance with additional or alternative embodiments, an attachment is removably attachable to the reefer air outlet and configured to constrain a flow of the conditioned air to remain in a flowpath directed toward the condenser air inlet.
According to yet another aspect of the disclosure, a ship or yard is provided and includes first and second sets of one or more refrigerated storage containers respectively stackable to define a pathway. Each one of the first and second sets of the one or more refrigerated storage containers includes a container housing having an end wall facing the pathway, a condenser configured to receive air to remove heat from a refrigerant passing through the condenser and a condenser air inlet by which the air is received, a condenser air outlet and a reefer air outlet configured such that air exhausted from the condenser is directed away from the condenser air inlet and conditioned air exhausted from the interior is directed toward the condenser air inlet.
In accordance with additional or alternative embodiments, the condenser air inlet, the condenser air outlet and the reefer air outlet each include louvers.
In accordance with additional or alternative embodiments, a local or remote controller is disposed to dependently or independently control an angling of each of the louvers.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the disclosure, together with advantages and features, by way of example with reference to the drawings.
As will be described below, containers with refrigeration systems which are generally referred to as reefers, need to dissipate heat through condensers. Air-cooled reefers employ fans to extract ambient air from the reefer's surroundings, pass the extracted air through condensers and then discharge the resulting heated air back into the ambient air of the surroundings. On a container ship or in a container yard, reefers are stacked in rows separated by a narrow aisle, however, and therefore air exhaust from a condenser may impinge on containers across the aisle. Such impingement can lead to the heating of reefers across the aisle, increased condensing pressure and hence power consumption with elevated air temperatures with condenser air recirculation due to reflection and potential cargo degradation caused by system trip-offs with continuous increasing air temperature into condenser due to recirculated air.
As such, air openings are typically designed into reefers in order to alleviate the effects of recirculated heated air (condenser air recirculation due to reflection can also be reduced or avoided by increasing the distance between aisles, but space constraints on a ship or in a yard are frequently stringent). Such air openings can be more effective, however, with the addition of louvers with adjustable parallel blades that can direct air at an angle to reduce direct impingement and hence decrease air reflection. The blades can be set at an angle between 30-60 degrees relative to the horizontal so that air will be exhausted upward with buoyance or so that cool exhaust air from inside the reefer will be directed toward the condenser air inlets.
With reference to
With reference to
For the purposes of the present description, each refrigerated storage container 20 may have a substantially uniform structure and configuration. That is, each refrigerated storage container 20 may be provided as a substantially rectangular body 21 that is formed to define an interior 22 in which cargo is stored. The body 21 includes a bottom, sidewalls and a top that are provided to enclose the interior 22 and the sidewalls include an endwall 23 that faces the aisle 203. Each refrigerated storage container 20 may further include a condenser 24 of an air conditioning unit which is disposed within the interior 22 to condition the air in the interior 22 and sensors 25 (e.g., cargo space temperature sensors) to sense various operational parameters of the refrigerated storage container 20.
Various operations of the refrigerated storage containers 20 are controllable by one or more local controllers 30 and one or more supervisory controllers 40. The one or more local controllers 30 and the one or more supervisory controllers 40 may be stand-alone components or components of the above-mentioned operational computers.
In accordance with embodiments and, as shown in
With reference to
In accordance with embodiments, the condenser air outlet 241 may be located in a central, somewhat upper region of the end wall 23. In such cases, the first and second condenser air inlets 2401 and 2402 may be located proximate to opposite sides of the condenser air outlet 241 with the third condenser air inlet 2403 located just below the condenser air outlet 241. The condenser air outlet 241 may therefore be configured to direct the relatively high temperature air in an upward direction so as to avoid generating flows of air toward and over the first, second and third condenser air inlets 2401-3. In addition, the first and second reefer air outlets 2421 and 2422 may be located proximate to and outside of the first and second condenser air inlets 2401 and 2402, respectively, with the third reefer air outlet 2423 located just below the third condenser air inlet 2403.
Each one of the first, second and third condenser air inlets 2401-3 includes CAI louvers 501, 502 and 503, the condenser air outlet 241 includes CAO louvers 51 and each one of the first, second and third reefer air outlets 2421-3 includes RAO louvers 521, 522 and 523. The CAI louvers 501, 502 and 503, the CAO louvers 51 and the RAO louvers 521, 522 and 523 may all be independently or dependently controlled by the local controllers 30 and/or the supervisory controllers 40. Such independent or dependent controls generally relates to angling of respective louver blades and in some cases to positioning of the angled louver blades relative to the end wall 23.
In accordance with embodiments and, as shown in
With reference to
With reference to
In accordance with further embodiments, to the extent any of the blades of the RAO louvers 521, 522 or 523 protrude from the plane of the end wall 23 or to the extent that an attachment 60 is removably attached to the first, second and third reefer air outlets 2421-3, it is to be understood that the length of the protrusion or the width of the attachment 60 is substantially less than the width of the aisle 203. For example, if the aisle 203 is about 2 meters wide, the length of the protrusion or the width of the attachment 60 is on the order of only a few centimeters.
The above-described louvers will help reduce recirculation of heated air and direct impingement of heated air into and onto refrigerated storage containers 20 and will thereby improve energy efficiency and operation of the refrigerated storage containers 20. For refrigerated storage containers 20 with ventilation or air modification capabilities, cold air that is discharged from interiors 22 can be utilized to lower condenser air temperatures and therefore reduce energy consumption of the refrigeration system and improve operation to maintain cargo quality.
In accordance with another aspect and, with reference back to
Scheduling reefer operations to avoid re-ingestion of hot air typically relies on local feedback control where the refrigeration unit including the condenser 24 of each refrigerated storage container 20 is cycled on and off based primarily on the cargo temperature requirements of each particular refrigerated storage container 20 and without any information on the operation of adjacent refrigerated storage containers 20 and their exhaust air flow distributions. A decentralized control algorithm is provided, however, with low sensing and communication requirements in which each local controller 30 determines when to turn its corresponding refrigerated storage container 20 on and off within a given time window in order to minimize waste heat ingestion from neighboring refrigerated storage containers 20.
Using the control algorithm, ambient air temperature and condenser inlet air temperature are measured and the difference between them (ΔT) is utilized as a pseudo-data element for potential exhaust air ingestion. The algorithm further includes on-off control logic that minimizes interactions between adjacent refrigerated storage containers 20 and enables higher system operation efficiency by running the refrigerated storage containers when ΔT is sufficiently small. The time window for the on-off decision making depends on cargo space temperature performance information and allowable temperature variability (Thigh, Tlow) around given set-point (Tsp).
In greater detail and, with reference to
The local controller 30 derives a value of the waste heat ingestion from a difference between periodically measured ambient and condenser inlet air temperatures and is configured to limit a number of cycles within the time window, implement an override command to force the air conditioner to cycle in an event a temperature within the interior reaches a limit and potentially override a cycling command issued by a supervisory controller (generally, if a supervisory controller is present, it is to be understood that a default condition could be that the supervisory controller would have priority to override local level decisions except in critical situations or for safety reasons).
Thus, for the example of
With reference to
The autonomous reefer schedule logic based on the quality of air at the unit's condenser inlet, in addition to the cargo space temperature, minimizes potential waste heat ingestion and thereby reduces energy usage for refrigeration. The decentralized control logic only requires one additional sensor for condenser inlet temperature, rendering the solution practical with low implementation cost. The control logic can be easily integrated with the individual unit legacy controller or implemented as a stand-alone local controller for each reefer.
In accordance with still further aspects, overall electrical energy consumption related to operations of the refrigerated storage containers 20 is controlled through coordination of multiple refrigerated storage containers 20 and the local controllers 30 by the supervisory controller 40. The supervisory controller 40 (e.g., the reefer coordinator) receives condenser inlet temperate measurements and operational parameters from the local controllers 30 and uses the data to learn or identify (online) correlations between the total electric power consumption of each of the refrigerated storage containers 20 and their respective operations and thus determines an optimal on-off control strategy that satisfies cargo space temperature requirements and minimizes power consumption and short cycling.
As shown in
With reference to
In accordance with embodiments, the determining may be further based on at least one or more of a learned time constant of one or more of the refrigerated storage containers, a time constant associated with an interaction of a group of the refrigerated storage containers and knowledge of expected environmental conditions. That is, if over time one of the refrigerated storage containers 20 (or a group of refrigerated storage containers 20) is/are found to respond more quickly to controls executed by its/their local controller 30 while another refrigerated storage container 20 responds slowly, the supervisory controller 40 can derive a learned time constant for each refrigerated storage container 20. This learned time constant can thereafter be updated periodically and used in concert with knowledge of future or expected environmental conditions (e.g., weather, on-board and off-board temperatures, transport time, etc.) to modulate the determining of the on-off control strategy.
The method further includes issuing control commands based on the optimal on-off control strategy for each refrigerated storage container to the local controllers (block 1205). These control commands can be overridden in some cases by the local controllers 30 if they are in conflict with control algorithms resident in the local controllers 30 individually. For example, if the control algorithm of the embodiments of
When additional data related to, for example, diesel generator(s) and fuel efficiencies are available, the supervisory controller 40 may also optimize generator fuel consumption while guaranteeing cargo reliability based on a holistic view of on-board electrical systems. Such energy aware scheduling systems may achieve fuel savings by reducing generator(s) operation at inefficient part-load conditions, generator (and reefer) cycling rates and hot air re-ingestion.
The supervisory controller 40 serves to minimize total electrical energy usage while maintaining cargo space temperatures within acceptable ranges by coordination of multiple refrigerated storage containers 20 to prevent unwanted waste heat re-ingestion. Also, the solution guarantees dynamic optimal performance by learning system behaviors online and adapting to operational and ambient changes.
While the disclosure is provided in detail in connection with only a limited number of embodiments, it should be readily understood that the disclosure is not limited to such disclosed embodiments. Rather, the disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that the exemplary embodiment(s) may include only some of the described exemplary aspects. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Filing Document | Filing Date | Country | Kind |
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PCT/US17/56304 | 10/12/2017 | WO | 00 |
Number | Date | Country | |
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62407250 | Oct 2016 | US |