Last updated: 12/12/2018
The projects described here are each simple enough that they may be assigned to undergraduates taking a first heat transfer course. They may be implemented using MS Excel or some other user-friendly computational package. Thorough (4-6 pages) instructions for each of the first six were included in the first edition of Heat Transfer Tools and seven of the first eight have been assigned in MAE 314 - Heat and Mass Transfer.
1. One-dimensional, Steady-state Conduction in Composite Systems.
This project studies steady-state conduction in series/parallel configurations, such as are used in conventional stud-wall (balloon) residential construction. The discussion includes both the planar isotherm model and the straight-line heat flux model. A similar insulating arrangement is seen in this 1950’s photograph of a DC-6 aircraft interior.
involves a finite-difference calculation of transient conduction in a slab subject
to a time-varying convective boundary condition at one surface. In this case the slab corresponds to a wall
3. Sandwich Wall Construction.
A 21st century improvement on Monticello’s construction, the Insulated Concrete Form (ICF) house includes both thermal mass and thermal resistance. Polystyrene foam sheets about 3” thick are used as forms when the concrete is poured, but unlike conventional plywood or metal forms, are left in place permanently. Conventional wall finishes are used over the Styrofoamtm both outside and inside. This sandwich configuration yields both energy storage and thermal resistance in one package. Slightly under 2% of new homes built in the U.S. in 1998 used ICF construction.
4. Transient Conduction at the Interface between Two Materials.
In this project we model a finger touching a hot material as a, one-dimensional, transient conduction problem. We test flesh-soapstone, flesh-cast iron and flesh-Space Shuttle tile (shown at right) and compare and contrast the resulting behavior. The interface between the flesh and other material provides an interesting numerical challenge for students, as do the significantly different thermal properties of the three hot materials. (Write-up)
This problem is an embellishment of the common textbook problem of approximating a runner as a cylinder in cross-flow. We compute both the sensible and latent heat transfer as a function of the runner’s speed relative to the wind, ambient air temperature and relative humidity. The air and water property functions Excel/VBA workbook makes it a simple matter to test a wide range of parameters without having to look up all the needed properties (some 11 of them) manually.
6. Transmissivity of Glass.
Here we use tabulated spectral values to compute the total transmissivity of regular glass and “Low E” glass to both solar (short wavelength) and terrestrial radiation. The required integration is done using Simpson’s 1/3 Rule, and the resulting values are compared with values obtained using the tabulated blackbody radiation functions in conjunction with a simple “hat” approximation of the actual curves seen to the right.
7. Mr. Washington’s Dung Repository.
Here we provide some design
guidance for our first President by solving analytically the one-dimensional,
steady-state conduction equation with volumetric generation. The volumetric heat generation comes from the
composting of manure and other organic matter.
The actual structure at Mount Vernon,
8. Evaporative Cooling of Water in a Lister (or Lyster) Bag.
In this project we approximate the water-containing, semi-permeable, canvas bag as a “lumped capacitance” and use standard forced convection correlations for a cylinder in crossflow to find the sensible and latent heat transfer (the latter associated with evaporation from the outer surface to the bag). With this information we predict the temperature-time history of the water as a function of atmospheric conditions including wind speed, air temperature and relative humidity. This project makes extensive use of the air-water property spreadsheet in HTT.
9. Network analysis for steady-state and transient conduction and for radiative exchange.
This workbook allows the
user to draw resistors (and capacitors) for representing a thermal system and
then apply Excel’s equation solving features to the resulting equations and plot
the solution. The simple example
illustrated here is steady-state conduction in a Structural Insulated Panel
(SIPs) as used in residential construction.
The core is expanded polystyrene while the outer layers are oriented
strand board (OSB). A similar
construction using cement rather than OSB for the outer layers has been
proposed for use in earthquake-prone countries such as
10.Two-Dimensional Steady-State Conduction
Figure 1 Temperature Contours in a 2-D Fin
This spreadsheet is set up to go with the HTTtwodss.exe module. It includes instructions and space in which to do a step-by-step tutorial, a two-dimension fin problem (complete with data from a corresponding DC electrical analog of the problem) and another 2-D problem for the student to set up. The two-d module can be used to create computational art as well:
Click here to download workbook.