The most conducive surface for dropwise condensation to occur is the ________ surface?

A mercury (specific gravity = 13.6) manometer connected across an orificemeter fitted in a pipe shows a manometer reading of 2 cms. If the manometer liquid is changed to carbon tetrachloride (specific gravity = 1.6), then for the same flow rate of water the new manometer reading will be ________ cms?

Compressibility factor of a gas is________?

Plastics are________?

Filter medium resistance is that offered by the________?

Hydraulic diameter for non-circular ducts is equal to ________ times the area of flow divided by the perimeter?