Spring 1999, METBD452 - FEA Heat Transfer Applications

Prof. Dave Johnson, dhj1@psu.edu, Penn State - Erie, The Behrend College

Project Assignment 1

Concepts:

• Modeling:  2D cross-section, periodic symmetry (1^o sector)
• Conduction and Convection (no radiation)
• Multiple materials
• Surface Effect Finite Elements (for inner and outer convection)
• Steady-state, linear Thermal Analysis

A submarine is to be designed to provide a comfortable temperature for the crew of no less than 70 ^oF.  The structure can be idealized as a cylinder (above), 30 ft. O.D. and 200 ft. in length (ignoring heat flow from the end caps).  The wall of the submarine is a sandwich construction with a 0.75 inch thick outer layer of stainless steel, a 1.0 inch thick middle layer of fiberglass insulation, and a 0.25 inch thick inner layer of aluminum.  The average sea water temperature outside the submarine is 44.5 ^oF and the outside film coefficient for convection 80 BTU/hr-ft²-^oF.  Inside the submarine, the convection film coefficient to air is 2.5 BTU/hr-ft²-^oF.

Material Properties, thermal conductivity (in BTU/hr-ft-^oF):

    Stainless steel:  8.27,   Fiberglass insulation: 0.028,  Aluminum: 117.4

An appropriate model is shown above, a symmetric slice of the cylinder.  Use 2D solid elements for the metal and insulation layers.  Use surface effect finite elements for the inside and outside convection behavior.  Be very careful of UNITS !!

Determine:

1)    The temperature distribution through the wall of the submarine, illustrated with both a temperature contour plot and a temperature path plot.

2)    The total heat flow (Q) through the wall of the FEA model.

Report, should include:

• Plots showing the model geometry (with different materials) and boundary conditions
• Thermal results contour plot of the temperatures on the model.
• Thermal results path plot of temperature through the wall.
• Comment on the amount of heat dissipated through the model's walls:   what rating of heater (in W) could be required to maintain the inside temperature for the entire submarine (not just for the sector model) ?  Compare the model's total heat flow to a hand calculation of the total heat flow through the submarine wall.
• Hand calculation (thermal "electrical" circuit analogy) of temperature at each material interface.  Make a table comparing the temperatures you calculate, to the model solution at each material interface.
• Include the annotated log file, showing the model generation and solution.

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  Reminder: All project reports will be typed, and include:

• a cover page with course name, project name, your name, and date
• a brief objective statement (2-3 sentences, maximum)
• a summary of procedures (bulleted items: assumptions, data, analysis steps)
• a conclusion statement (what was learned, perhaps an evaluation of the design)
• a copy of the project statement (this web page) may be attached.

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