Windows overall heat transfer coefficient

This type is selected in the top window shown in Figure 5.25 on the Specifications page tab. The overall heat transfer coefficient (U = 142 W K-1 m 2) and the coolant temperature (400 K) are specified. Clicking the Configuration page tab opens the window shown at the bottom of Figure 5.25. The number of tubes (250), their length (10 m), and their diameter (0.1 m) are specified. 

The first line calculates the heat-transfer rate from the fixed area (132.4m ), the fixed overall heat-transfer coefficient (0.00306GJh m °C ), and the current difference in temperature between the reflux dmm of the high-pressure column and the reboiler of low-pressure column. The second line equates the two heat duties with the appropriate change in sign. Right clicking the window and selecting Compile complete the operation. 

C Why are the windows considered in three regions when anolyzing heat transfer tlirough them Name those regions and explain how the overall LZ-value of the window is determined when the heal transfer coefficients for all three regions are known. 

Calculate (a) the overall coefficient U for heat transfer through a vertical glass window from a room at 70 T to still air at 0°F. Assume that a single pane of glass is 5 in. thick and 4 ft high, (b) Calculate U for a thermopane window with a -j-in. air space between the two panes. For this glass k = 0.4 Btu/h-ft-°F. 

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