(Parte 1 de 9 problem.1, known: Thermal conductivity, thickness and temperature difference across a sheet of rigid extruded insulation.
Analysis: From Fouriers law, if and k are each constant it is evident that the gradient, xq xdTdxqk, is a constant, and hence the temperature distribution is linear.
T qk, since the heat flux is uniform over the surface, the heat loss (rate) is q qxA q 2800 W/m2 3m2 comments: A linear temperature distribution exists in the glass for the prescribed conditions.
Comments: Without steady-state conditions and constant k, the temperature distribution in a plane wall would not be muhammad bin qasim pdf linear.Assumptions: (1) One-dimensional conduction in the x-direction, (2) Steady-state conditions, (3) Constant properties.Problem.2, k nown: Inner surface temperature and thermal conductivity of a concrete wall.Representative winter surface temperatures of single ane and air space.(1) and (2 the heat rate neither a hawk nor a dove book qx can be determined for the range of outer surface temperature, -15 T2 38C, with different wall thermal conductivities,.The magnitude of the heat rate increases ith increasing thermal conductivity.(2) The direction of heat flow is from hot to cold.Schematic: A ssumptions: (1) Steady state, (2) One-dimensional conduction, (3) Constant properties.F IND: Daily cost of heat loss.Schematic: qcond A 4 m2 x L 20 m, t1T2 10C qcond.Schematic: assumptions: (1) One-dimensional conduction in the x-direction, (2) Steady-state conditions, (3) Constant properties.Outside surface, heat loss, qx (W wall thermal conductivity,.25 W/m.K k 1 W/m.K, concrete wall.75 W/m.K.Problem.6 known: Width, height, thickness and thermal conductivity of a single pane window and the air space of a double pane window.(3) Note that a temperature difference may be expressed in kelvins or degrees Celsius.P F IND: Heat loss through single and double pane windows.Comments: (1) Be sure to keep in mind the important distinction between the heat flux (W/m2) and the heat rate (W).The daily cost of natural gas that must be combusted to compensate for the heat loss.The heat flux and heat rate when the outside wall temperature is T2 -15C x 25 C 15 Cdq k k 1W m K 133.3W m dx.30m.
Heat loss, qx (W wall thermal conductivity,.25 W/m.K k 1 W/m.K, concrete wall.75 W/m.K.