Answer:
Step-by-step explanation:
In this context, we are dealing with the cooling of hot air as it flows through tubes exposed to atmospheric air. Based on this, we can make the following statements:
a. Heat transfer coefficient inside the tube will be higher - This statement is false. As the hot air flows through the tube and comes into contact with the cooler atmospheric air outside the tube, heat transfer occurs between the two fluids. In this process, the temperature difference between the two fluids drives the heat transfer. Therefore, the heat transfer coefficient inside the tube will be lower because the hot air will have a higher temperature than the atmospheric air, and the temperature difference will be smaller.
b. Heat transfer coefficient inside the tube will be lower - This statement is true, as explained in the previous statement.
c. Fins should be attached to the outside of the tube - This statement is true. Fins are used to increase the surface area of the tube, which in turn increases the rate of heat transfer between the hot air inside the tube and the atmospheric air outside. Attaching fins to the outside of the tube will increase the surface area exposed to the atmospheric air, facilitating faster cooling of the hot air.
d. Fins should be attached to the inside of the tube - This statement is false. Attaching fins to the inside of the tube will actually reduce the effective cross-sectional area of the tube, restricting the flow of air and hindering the heat transfer process. Therefore, fins should be attached to the outside of the tube to maximize the surface area and facilitate efficient heat transfer.