Homework 5
Complete the electrical problemsand the paint mixingproblem in the matrix template spreadsheet for practice (these will not be collected). From Chapter 5, do problems 2, 4, 7 and “9” (heat transfer problem below).
For problem 2, if a solution does not exist make a comment to that effect. Try to indicate why no solution is possible (eg., indicate which equations are not independent).
Problem 4 is a resistive circuit problem, similar to the one in the class exercise spreadsheet.
These problems (except 2) involve a physical situation which is best explained with a diagram – either a circuit diagram or a process flow diagram. You should use the simple drawing tools (shapes, lines and connectors) in Excel to create a sketch as part of the problem definition. Be sure to document the equations used (preferably using the equation editor) and to highlight and comment on results. Remember that each problem should also have a brief statement at the beginning stating the purpose of the problem, as discussed in class.
9 Heat Transfer Problem:
Heat transfer from a furnace to the surrounding air is modeled using a set of convection and conduction equations. For the case being considered, we wish to determine the rate of heat loss from a furnace which has walls made up of several layers – some structural and some designed for thermal insulation. The basic equation for convection (transfer of heat in a fluid, such as air) is:
Where q is the heat flux (heat flow per unit time, per unit area perpendicular to the direction of heat flow) with units such as calories per cm2 s. Thus the heat flux is proportional to the temperature difference at two points in the fluid. This might be the temperature at a window pane compared to the temperature of the outside air. The constant h is called a heat transfer coefficient and its value depends on the geometry, flow conditions and fluid properties.
Heat transfer by conduction is the flow of heat by molecule to…