| Air travel passengers are all too familiar with the thermal discomforts of summer travel–the baking jetway and long wait while an aircraft is filled to capacity. They fan themselves with boarding passes in a vain attempt at personal cooling while the last oversized garment bag is stowed. Our DC-10 model examines these few miserable minutes and provides insight to thermal management techniques that could be employed.
This sample model highlights the transient analysis and environmental loading analysis capabilities of RadTherm. The sample DC-10 airplane is parked on the Phoenix International Airport runway during passenger boarding on a hot summer day in Arizona. The ambient temperature during the day ranges from 26°C to 39°C with solar flux reaching 1000 W/m^2. Weather data was adapted from TMY2 (Typical Meteorological Year, Series 2) measurements.
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Metabolic Loads from Boarding Passengers in Jetway and Cabin
The aircraft model includes transparent glass windows to capture the greenhouse effect of solar loads through the windows. Human metabolic loads were defined using a power curve that varies with the estimated head count in each zone as a function of time. First the jetway is loaded, and then the crowd slowly disperses to the assigned aircraft seating. The curves assume 100 W of metabolic load per passenger.
The jetway air node was flushed with 1000 liters per minute of ambient air.
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| Transient Power curve representing the metabolic loads to the air in a jetway as passengers cue up. (click to enlarge). |
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The power load inside the cabin does not decay as it does in the jetway.
Two analyses were performed. One fixed the interior air temperature to 20°C by using a large in flow of 20°C source air. This kept the cabin air temperature within a few fractions of a degree to 20°C. A second run was performed without air conditioning of the cabin. This resulted in very high cabin temperatures. See plots below for results.
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| Transient Power curve representing the metabolic loads to the air inside the airline cabin as (click to enlarge). |
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Mesh Geometry
DC-10 STL surfaces were imported into Eclectic and meshed. Interior seats, structure, bulkheads, and the terminal building with airport tarmac were created in Rhinoceros. These surfaces were meshed and exported into RadTherm. The model was parted out very carefully and materials, surface conditions, and glass windows were defined.
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RadTherm's Settings to Reduce Model File Size
To reduce the overall size of the model, RadTherm allows only surface geometry thermal nodes to be saved. This eliminates the storage of the interior nodes of the large terrain used in this model. Terrain parts have many vertical thermal nodes - 12-20 nodes. Storage of these values for every terrain element can create very large file sizes with transient environmental models. Where desired, all thermal nodes for selected elements can be defined. Furthermore, a Write Frequency Curve was employed on this model to record results only every two hours for the acclimation period leading up to the 12:00 PM Pre-Boarding Time. During the period of interest 12:00-1:00, results were stored every time step (5 minutes).
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| A write frequency curve for saving results primarily during the one-hour period of interest. Curve start time was assigned to 12:00PM (our arbitrary boarding time). (click to enlarge). |
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Thermal Results
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Airliner Cabin and Jetway air temperatures displayed, with and without air conditioning in the cabin.
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| The model's predicted temperature of seats indicates that the south side seats above the wing would be the least comfortable, whereas the center row of seats would be most comfortable. Even the diffuse solar loading through the north side windows causes those seats to be warmer than the center bank of seats. The seats were modeled as cotton over foam, with a simple convection coefficient of H=3 connecting them to the cabin air node, which was held at 20°C for this run. |
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Seat temperatures predicted by the model using a simple convection coefficient of H=3.
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