In the Figure below, the cover gate AB closesa circular opening 80 cm in diameter. The gate
is held closed by a 200-kg mass as shown.
Assume standard gravity at 20 °C. At what
water level (h) will the gate be dislodged?
Neglect the weight of the gate.
Specific weight of water 9790 N/m3​

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?