Old Details New Model Old New Part III Dr. Scott R. Runnels Version 2010-02-24a Copyright 2010 RSI-AAR Tank Car Safety Research Project
Old Details New Model Old New Old Details 2
Old Model Details Old Details New Model Old New The old thermal protection system () model database can be accessed through the main menu. You can establish a database of setups that may then be referenced by name when setting up an analysis, e.g., Bare Tank and Example 1. Edit Window, next slide 3
Old Model Details Old Details New Model Old New In the Bare option, heat is conducted through the bare metal tank using the conductivity of the metal and, in the vapor space, a convective heat transfer coefficient. Bare metal tank Tank Adjacent to Vapor (Uniform Temperature) Vapor Well-Mixed Liquid Tank Adjacent to Liquid (Uniform Temperature) 4
Old Model Details Old Details New Model Old New The FRA Standard option is just like Bare, except that the conductivity is a hard-coded value. Material not specified. A hardcoded value for conductivity is used. Tank Adjacent to Vapor (Uniform Temperature) Vapor Well-Mixed Liquid Tank Adjacent to Liquid (Uniform Temperature) 5
Old Model Details Old Details New Model Old New With any of the insulation options, a liner can be added. The liner adds another layer of resistance to heat conduction. It linearly deteriorate over time, eventually disappearing completely. Tank Adjacent to Vapor (Uniform Temperature) Tank Wall Well-Mixed Vapor (Uniform temperature) Well-Mixed Liquid (Uniform temperature) (Different from vapor) Tank Adjacent to Liquid (Uniform Temperature) 6
Old Model Details Old Details New Model Old New Conduction through one layer Q D Q Heat Flux k D Material conductivity T L T R T L T R Thickness Conduction through two layers Q D 1 D 2 1 2 Q k D 12 T L T R T L T R Multiple layers, in series, have a composite resistance. k D 12 k D 1 k D 1 k D 2 k D 2 7
Old Model Details Old Details New Model Old New Conduction through multiple layers D 1 D 2 D 3 1 2 3 Q T Q L T R T L T R k D 123 The resistance is cumulative and can be computed using a hierarchical harmonic sum. k D 123 k D k D 12 12 k D 3 k D 3 8
Old Model Details Old Details New Model Old New Conduction through multiple layers D 1 D 2 D 3 1 2 3 Q T Q L TR T L T R k D 123 film Resistance due to a convective film layer is included as an additional layer. k D 123 film k D k D 123 123 h h film film 9
Old Model Details Old Details New Model Old New In the vapor region, there is an additional resistance to heat transfer due to convection. In the liquid, there is such excellent contact that the interior tank temperature equals the lading temperature. Three Layers: (1) Bare Tank (2) Liner (3) Convective Film Two Layers: (1) Bare Tank (2) Liner Tank Adjacent to Vapor (Uniform Temperature) Well-Mixed Vapor Well-Mixed Liquid Tank Adjacent to Liquid (Uniform Temperature) 10
{ Old Model Details Old Details New Model Old New Jacket Radiation { Insulation Tank Wall Liner In the Steel Jacketed option, conduction through multiple layers is combined with radiative exchange with the steel jacket. Flame Conduction Lading 11
Old Model Details Old Details New Model Old New When there is partial coverage of insulation as established as part of the Analysis setup, there are two radiation paths. Jacket Insulation Tank Wall Liner Flame Lading Two radiation paths. 12
Flame Old Model Details Old Details New Model Old New Insulation Tank Wall Liner Insulation Tank Wall Liner Insulation Tank Wall Liner Flame Lading Flame Lading Lading Example combinations: In each combination, the ability to model the liner and insulation is limited. 13
Old Model Details Old Details New Model Old New Examples of Insulation and Liner Models in Old : Deterioration time Initial conductance Final conductance Quadratic temperature-dependent model These limitations are what motivated the new model. 14
Old Details New Model Old New 15
Tutorial 10 Setup Old Details New Model Old New Infinite strength (cannot burst) 100% Full of liquid 100% Exposed to pool fire No PRV This tutorial uses a 100% full tank heated with a 1500 deg-f flame, but an insulation that deteriorates with time. Well-Mixed Liquid (Uniform temperature) 16
Tutorial 10: Full Tank and Deteriorating Old Details New Model Old New Copy and paste Tutorial 9. Name the new analysis T10: Full Tank- Deteriorating. Edit as follows and run it. Note you ll need to create a deteriorating insulation as shown here. Decaying Insulation 4 1 2 3 17
Tutorial 10: Full Tank and Deteriorating Old Details New Model Old New Results for deteriorating. 18
Old Details New Model Old New New Model 19
New Model Old Details New Model Old New Problems with the old insulation model 1. Time-based deterioration is unphysical. 2. Temperature-based conductivity may be more complex than linear or simple polynomial. 3. Multiple layers are needed for designing new cars. So, while the original insulation model (with partial coverage) is still present, a new general thermal protection system () model was developed and implemented. Now in Beta testing. 20
New Model Old Details New Model Old New Requirements Have Been Accommodate an arbitrary number of layers Store layer materials in a database Store the combinations of these layers, which form a specific (thermal protection system) in a database Each layer shall: 1. Accommodate tables for all thermal properties 2. Each table shall be associated with a temperature history. As a layer experiences a temperature history, its property values may migrate from one table to another to represent degradation or melting. The user shall be able to designate one layer or a group of layers as exhibiting partial coverage that is a function of angle on the tank. 21
New Model Old Details New Model Old New Arbitrary number of layers Jacket An arbitrary number of layers is accommodated. Jacket, tank wall, and liners are also treated as layers. Any layer may exhibit partial coverage. Air 22
New Model Old Details New Model Old New Material G For jacketed systems, the outermost layer would be the jacket, and that would be part of the database Material F Material E Material D Material C Material B Layers can be named separately and saved in a database. Composite systems can be assembled from named layers, and also saved in a database. Material A Innermost layer may be tank wall or liner. 23
New Model Old Details New Model Old New Thermal Protection System Model Material Database Conductivity, heat capacity, emissivity, and percent coverage as a function of time and temperature history for Jacket Spray-On B Spray-On A Fiberglass B Fiberglass A Steel Lining 1 2 3 User selects materials in order. Steel-Jacketed with Lining User assigns thickness and initial coverage. 100% coverage for all layers, thin lining, thick insulation User gives the composite system a name Ready for use in an analysis referred to by name. 24
New Model Old Details New Model Old New T l2 T r2 The new model is very general. Each layer has its own material properties. Each layer can have an individual value for partial coverage. Voids permit radiative and convective exchange with non-adjacent layers. The voids are modeled as being randomly distributed. Multiple interface temperatures are involved. T 2 T 2 25
New Model Old Details New Model Old New Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 The shapes of the voids are not specified by the user. They are assumed to be randomly distributed. Heat can be radiated and convected through voids in adjacent layers. 26
New Model Old Details New Model Old New Fractional coverage is modeled as a uniform distribution of voids that vary with angle. Settled insulation Each layer can have its own partial coverage vary with angle. 27
New Model Old Details New Model Old New T l2 These areas on Layer 2 can radiate because they are not covered by Layer 3. T 2 28
New Model Old Details New Model Old New Heat Balances: Conduction path (T 2 ) T l2 Radiation/convection path due to view ports in adjacent layer (T l2 ). 3xN simultaneous nonlinear algebraic equations. Expanded existing Newton-Raphson and linear solvers. T 2 29
New Model Old Details New Model Old New Settled insulation Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 c 1 c 2 c 3 c 4 c 5 Fraction of total area covered by layer. 30
New Model Old Details New Model Old New T flame T inner-wall Conducted Heat In Convected & Radiated Conducted Heat In T lading T flame 31
New Model Old Details New Model Old New 32
New Model Old Details New Model Old New 1 Define bulk materials 2 Use bulk materials to define 3 (no geometry) layers (add geometry and surface treatment) Define a TP system by assembling layers. 33
Old Details New Model Old New 34
Tutorial 11 Setup Old Details New Model Old New Infinite strength (cannot burst) 100% Full of liquid 100% Exposed to pool fire No PRV Imaginary No tank wall or jacket. Well-Mixed Liquid (Uniform temperature) 35
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New Enter Imaginary and click Add. Then highlight it in the list. 36
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New Enter a constant value of 5 and then click OK. Enter -10 in this box and click Add. Doing so adds it to the list. Double click the -10 in the list. 37
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New At this point, the bulk material Imaginary has a thermal conductivity of 5 for all temperatures. Now suppose that at 500 deg-f this material undergoes a phase change that causes it to turn into a perfect insulator. 38
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New To model that, add 500 to the list. Double click it and set it to all zeros. This second function will take over permanently once the material reaches 500 deg-f. 39
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New This k=k(t) becomes effective at -10 deg-f. This k=k(t) becomes effective at 500 deg-f. This is an unrealistic material used for demonstration only. At 500 deg-f, it becomes a perfect insulator. 40
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New A component (layer) is added using the text box under the list and the associated Add button. Here, the same word Imaginary_Layer is used for simplicity. It is composed of the Imaginary bulk material. But a component also has inner and outer surface emissivities, a width, and defect information.
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New A bulk material is then chosen using the Assign button.
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New A is added using the same procedure (entry + Add button). It is comprised of layers assembled in order. Here, Imaginary_ is entered. It will only consist of one layer, that layer being named Imaginary_Layer.
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New A layer is added by using one of the Add buttons. Click Done (write to file) when finished.
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New Now define a new analysis in the Main Window ( T11: Imaginary Run ) using the Copy-Paste Procedure. Edit the windows as follows. An imaginary new is used. A onelayer system that becomes a perfect insulator at 500 deg-f.
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New The execution time is much longer when using the new model. This execution takes approximately 10 seconds.
Tutorial 11: Modeling Insulation Changes Old Details New Model Old New Here we see that the lading temperature increases until the average temperature of the single layer reaches 500 deg-f, at which time it becomes a perfect insulator. Note that the average temperature of each layer is used to determine its thermal conductivity look-up temperature. Imaginary_Layer @ 100% coverage Phase Transition Temperature: 500 deg-f The inner surface of the Imaginary_Layer layer is just under 400 deg-f, but the outer surface is hotter.
Old Details New Model Old New 48
Tutorial 12 Setup Old Details New Model Old New Infinite strength (cannot burst) 100% Full of liquid 100% Exposed to pool fire No PRV Imaginary insulation: Starts as good conductor. With heat, becomes perfect insulator. Well-Mixed Liquid (Uniform temperature) 49
Tutorial 12: Multi-Layer Old Details New Model Old New In this tutorial, we will define a fictitious multi-layer thermal protection system (). Instructions are on the next slide. Here is an overview: We start by defining a perfect insulation bulk material named Perfect. It has only one k = k(t) function, wherein it has perfect insulation properties. Next, we define a layer called Perfect_Layer. See middle section. Third, we define a named 3_Layer_Perfect.
Tutorial 12: Multi-Layer Old Details New Model Old New Under Thermal Protection Systems 1. Enter Perfect in the text box and click Add under it. Under Conductivity Tables 1. Enter -10 in the text box and click Add under it. 2. Double-click on -10 in the list. 3. Enter all zeros. Click OK. Under Components 1. Enter Perfect_Layer in the text box then click Add under it. 2. Highlight Perfect_Layer in the list. 3. Highlight Perfect in the Material Name list. 4. Click Assign. Under Thermal Protection Systems 1. Enter 3_Layer_Perfect in the text box and click Add under it. Continue on next slide.
Tutorial 12: Multi-Layer Old Details New Model Old New Thermal Protection Systems Components 1. Highlight 3_Layer_Perfect under Thermal Protection Systems. 2. Highlight TankWall under _Components. 3. Click Add between these two lists. Now, repeat for two more layers: 4. Highlight 3_Layer_Perfect under Thermal Protection Systems. 5. Highlight Perfect under _Components. 6. Click Add After between these two lists. Now repeat for one more layer: 7. Highlight 3_Layer_Perfect under Thermal Protection Systems. 8. Highlight Jacket under _Components. 9. Click Add After between these two lists. Click Done (write to file) when finished.
Tutorial 12: Multi-Layer Old Details New Model Old New This screen shot illustrates the interplay of names. 1. Steel is a bulk material. 2. The Jacket layer is made from Steel and is 2 inches thick. 3. The 3_Layer_Perfect is comprised of a TankWall layer, a Perfect_Layer, and a Jacket layer. 1 2 3
Tutorial 12: Multi-Layer Old Details New Model Old New Create a new simulation, call it T12: Multi-Layer and edit it as follows. Then run it. Here the new 3 layer is selected.
Tutorial 11: Multi-Layer Insulation Old Details New Model Old New The results are as expected, basically no temperature change. 3-Layer Perfect @ 100% coverage Now, we will repeat the study, changing the coverage of the perfect insulating layer (next slide).
Tutorial 11: Multi-Layer Insulation Old Details New Model Old New 1. In the Main Window, edit the General database. 6. Click the blue button. 5. Highlight the T12: Multi_Layer analysis. 2. In the middle section, highlight Perfect_Layer, then doubleclick the Coverage table. 4. Click either Done button. 3. Change coverage to 10 (%).
Tutorial 11: Multi-Layer Insulation Old Details New Model Old New 3-Layer Perfect @ 100% coverage 3-Layer Perfect @ 50% coverage 3-Layer Perfect @ 10% coverage Less coverage of the perfect insulation enables radiative and convective heat exchange between the bounding layers, which are the TankWall and the Jacket.
Old Details New Model Old New 58
Entering Lading Properties Old Details New Model Old New 1. Navigate the menu to edit the ladings database. 2. Highlight a lading, e.g., Butane. Then click Edit. 3. Specify if it is a solution or pure substance, enter a molecular weight, and click Edit Table to specify the property as a function of temperature.
Entering Lading Properties Old Details New Model Old New Unchecking Depends on Temp replaces the Edit Table button with a single text entry box wherein you can enter a constant value.
Entering Lading Properties Old Details New Model Old New When the lading is a solution, each property has to be entered twice, once for a low concentration value and again for a high concentration value.
of Lading Properties Old Details New Model Old New Relates the change in internal energy to a temperature change. AFFTAC calculates the amount of heat flowing into the lading. This parameter is used to calculate the corresponding temperature change. This is the inverse of density. It is used to compute mass from volume, e.g., when a volumetric flow rate is computed using a PRV flow model, this term is used to determine how much mass actually escaped.
of Lading Properties Old Details New Model Old New Used to compute the heat lost from the liquid lading when it evaporates. This value is the pressure at which the vapor phase will exist in equilibrium with the liquid phase.
of Lading Properties Old Details New Model Old New Used in the choked flow model for the PRV, when venting vapor. Ratio of specific heat at constant pressure to specific heat at constant volume. Also used in the choked flow model for the PRV.
Old Details New Model Old New AFFTAC 65
AFFTAC Old Details New Model Old New.db.db Insulations.db (old model).db (new) User Input lading data file Output files Computational Module