In order to heat oil (cp = 1.8 kj/kg. k), a shell-and-tube heat exchanger with 1-shell pass and 6-tube passes is used. the oil enters the tube side at a rate of 10 kg/s at 22°c and exits at 48°c. heat is supplied by hot water (cp = 4.18 kj/kg. k) that enters the shell side at 80 °c at a rate of 5.1 kg/s. the overall heat transfer coefficient is estimated to be 975 w/m2 . k. determine the heat transfer surface area of the heat exchanger using lmtd method.

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

Refrigerant 134a enters an insulated compressor operating at steady state as saturated vapor at -26°c with a volumetric flow rate of 0.18 m3/s. refrigerant exits at 9 bar, 70°c. changes in kinetic and potential energy from inlet to exit can be ignored. determine the volumetric flow rate at the exit, in m3/s, and the compressor power, in kw.

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?