Heat Transfer Practice Test 10

1. The heat loss from unpainted aluminum side of a house has been calculated on the presumption that overall coefficient of heat transfer is 5 W/m ² K. Later, it was discovered that the air pollution levels are such that fouling factor on this side is of the order of 0.0005 m² K/W. Find overall heat transfer coefficient of dirty side

2. Which one is having highest value of overall heat transfer coefficient?

3. Which one is having the lowest value of specific heat?

4. Which one is having the highest value of solar absorptivity?

5. A copper pipe (k = 350 W/m K) having inner diameter of 1.75 cm and 2.0 cm outside diameter conveys water and the oil flows through the annular passage between this pipe and a steel pipe. On the water side, the film coefficient is 4600 W/m² K and the fouling factor is 0.00034 m² K/W. The corresponding values for the oil side are 1200 W/m² K and 0.00086 m² K/W. Estimate the overall heat transfer coefficient between the oil and water

6. Shear stress at the middle of the plate is given by

7. Which parameter is responsible for the commencement of the turbulent flow?

8. For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference for parallel flow is

9. Which one is having highest value of overall heat transfer coefficient?

10. In a counter flow heat exchanger, water flowing through a tube of 10 cm inner diameter is heated by steam condensing on the outside of the tube. The convective film coefficient on the water and steam side are estimated to be 12000 and 20000 k J/m² hr degree. Neglecting tube thickness and its resistance to heat flow, workout the overall heat transfer coefficient for the heat exchanger