###### Thermodynamics and Heat Power

251 SOLVED PROBLEMS

Question: 11.21

## A bare steel pipe of outside diameter 3.50 in. runs through a room whose walls are at 70°F. Determine the heat loss by radiation from 5 ft. of the pipe if its outside temperature is 120°F. ...

From Table 11.4, case 2,$F_{A}$ = 1, ...
Question: 11.30

## To increase the heat transfer rate from the box in Illustrative Problem 11.17, a vertical fin is added to each of the four sides (see Figure 11.36). The fins are aluminum, 15 cm high and 0.15 cm thick, and protrude 3 cm from the box. Find the new heat loss rate. ...

The fins are vertical plates with the same charact...
Question: 11.29

## A heat exchanger has one shell pass and two tube passes similar to Figure 11.27c. Oil flows in the tube side and is cooled from 280°F to 140°F. On the shell side, water is heated from 85°F to 115°F. Determine the true mean temperature difference. ...

In order to use Figure 11.32, which is applicable ...
Question: 11.28

## Using Table 11.6 for the appropriate fouling factors, calculate the surface required for Illustrative Problem 11.27. ...

For the oil side, a resistance (fouling factor) of...
Question: 11.27

## If the best exchanger in Illustrative Problem 11.26 is operated in parallel flow, determine the outside tube surface required. ...

From Figure 11.31,$\theta_{A}$ = 215 ...
Question: 11.26

## A counterflow heat exchanger is used to cool a flow of 400 lb./min of lubricating oil. Hot oil enters at 215°F and leaves at 125°F. The specific heat of the oil is 0.85 Btu/lb.·°F, and the overall coefficient of heat transfer of the unit ...

From Figure 11.30, $\theta_{A}$ = 215...
Question: 11.25

## A steel pipe, k = 26 Btu/(h·ft.·°F), having an outside diameter of 3.5 in. and an inside diameter of 3.00 in., and 5 ft. long, is covered with 1 in. of mineral wool, k = 0.026 Btu/ (h·ft.·°F). ...

Because the same amount of heat traverses each of ...
Question: 11.24

## Determine the overall heat-transfer coefficient for the composite wall of Illustrative Problem 11.4 if h on the hot side is 0.9 Btu/(h·ft .^2·°F) and h on the cold side is 1.5 Btu/(h·ft .^2·°F). ...

For a plane wall, the areas are all the same, and ...
Question: 11.23