The corps of engineers is building a large dam in a remote location and convinced the cement manufacturer to produce only type iv cement during this period. your company needs to build a large bridge and the concrete requires high early strength. write a short memo describing the potential challenges of using type iv cement and how you will solve the problem.

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?

Afluid flows with a velocity field given by v=(x/t)i.. determine the local and convective accelerations when x=3 and t=1.

Along 8-cm diameter steam pipe whose external surface temperature is 90°c connects two buildings. the pipe is exposed to ambient air at 70c with a wind speed of 50 km/hr blowing across the pipe. determine the heat loss from the pipe per unit length. (b) air at 50°c enters a section of a rectangular duct (15 cm x 20 cm) at an average velocity of 7 m/s. if the walls of the duct are maintained at 10°c, determine (i) the length of the tube for an exit temperature of air to be 40 °c (ii) the rate of heat transfer from the air and (iii) the fan power needed to overcome the pressure drop in this section of the duct.