Acounter-flow, double-tube (shell-and-tube) heat exchanger is used to cool the lubricating oil for large industrial gas turbine engine by cooling water which enters the heat exchanger at 30°c the copper inner tubes have a diameter of 2 cm and negligible thickness, while the inner diameter of the outer annulus (the shell) is 4 cm. water flows through the tube at a rate of 0.18 kg/s, and the oil through the shell at a rate of 0.12 kg/s. the inlet and outlet temperatures of oil are 95°c and 65°c, respectively. assume the tube wall resistance, fouling factors and heat loss to the surroundings are negligible. design the heat exchanger.

The y form of iron is known as: a) ferrite b) cementite c) perlite d) austenite

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?

Different types of steels contain different elements that alter the characteristics of the steel. for each of the following elements, explain what the element does when alloyed with steel.