Which of the following best describes what happens when ice is placed in a warm glass of water?
a. the ice floats to the top, but small pieces break off and are suspended in the liquid to cool it through convection
b. heat from the glass moves through the liquid to melt the ice through radiation
c. the heat from the surrounding liquid is transferred to the ice through conduction
d. the ice transfers the cold temperature to the surrounding water through convection

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?