Lucas built a model to show the effect of human population growth on an aquifer that supplies water for a growing city. Recent measurements show that the levels of water in the aquifer are dropping at a rate that correlates with population growth. Lucas placed a tub under a stream of water until the tub filled and began to overflow. Then he used a water pump to begin removing water from the tub. At first he pumped slowly, and the water still overflowed. Then he pumped harder until, eventually, the water level in the tub began to go down. What is represented by the pump in this model?

Acompressor receives the shaft work to decrease the pressure of the fluid. a)- true b)- false

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?

The thermal expansion or contraction of a given metal is a function of the f a)-density b)-initial temperature c)- temperature difference d)- linear coefficient of thermal expansion e)- final temperature f)- original length