Engineering Answers

11. A 100 BHP diesel engine has a brake thermal efficiency of 30% and jacket water loss of 34%. The engine is to be cooled by means of a cooling tower having a range of 27oC. Find the mass of water leaving the tower.

10. Air enters the tower at the rate of 60 kg/s. The entrance enthalpy is 86 KJ/kg and exit enthalpy of 53 KJ/kg. Find the temperature range of the tower if mass flow rate of water is 30 kg/s.

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32. An air-conditioning system is used to maintain a house at 65oF when the temperature outside is 85oF. The house is gaining heat through the walls and windows at a rate of 1250 Btu/min, and the heat generation rate within the house from people, lights, and appliances amounts to 350 Btu/min. Determine the minimum power input required for this air-conditioning system. A

31. A pressure difference of 500 Pa is available to force 20oC air through a circular sheet-metal duct 450 mm in diameter and 30 m long. At 20oC, p = 1.204 kg/m3 and take friction factor, f = 0.016. Determine the velocity.

30. Compute the pressure drop of 35oC air flowing with a mean velocity of 7 m/s in a circular sheet-metal duct 450 mm in diameter and 25 m long. Use a friction factor, f = 0.04, and Pair = 1.3799 kg/m3.

29. A coil has an inlet temperature of 70oF and outlet of 80oF. If the mean temperature of the coil is 120oF, find the bypass factor of the coil.

28. Compute the specific volume of an air-vapor mixture in cubic meters pre kilogram of dry air when the following conditions prevail : t = 45oC, w = 0.015 kg/kg, and Pt = 100 kPa.