5. A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of
7. In a shell and tube heat exchanger for a given heat transfer surface area, smaller diameter tubes are favoured as compared to larger diameter ones ; because the smaller diameter tubes
Options
A. are easier to clean.
B. are less prone to fouling.
C. can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less.
9. In hydrostatic testing of welded pipe (for leakage, strength etc.) the ratio of minimum hydrostatic test pressure to internal design pressure is around
10. In a pressure vessel containing multiple openings of various dimensions at different parts, stress concentration at the edges of the opening is maximum which becomes negligibly small beyond the area covered by __________ times the hole diameter.