Question

Air is to be cooled in the evaporator section of a refrigerator by passing it over...

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 0.8-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 9 m/s. The tubes are arranged in-line with longitudinal and transverse pitches of SL  =  ST  = 1.5 cm. There are 25 rows in the flow direction with 15 tubes in each row. Assume the mean temperature as −5°C and the properties of air at this temperature and 1 atm are (Table A-15) k = 0.02326 W/m⋅K, cp = 1.006 kJ/kg⋅K, ρ = 1.317 kg/m3, Pr = 0.7375, μ = 1.705 × 10−5 kg/m⋅s, and Prs = Pr@Ts = –20°C = 0.7408. Also, the density of air at the inlet temperature of 0°C (for use in the mass flow rate calculation at the inlet) is ρi = 1.292 kg/m3.

NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part.

Determine the refrigeration capacity of this system.

The refrigeration capacity of the system is  W.

Determine the pressure drop across the tube bank. (Round off  SLD/SLD  value to the nearest whole number.)

The pressure drop across the tube bank is  Pa.

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