A boiler plant, see Fig. 8.19 (p. 254), incorporates an economizer and an air pre-heater, and generates steam at 40 bar and 300°C with fuel of calorific value 33000 kJ/kg burned at a rate of 500 kg/h. The temperature of the feedwater is raised from 40 to 125°C in the economizer, and the flue gases are cooled at the same time from 395 to 225 °C. The flue gases then enter the air pre-heater in which the temperature of the combustion air is raised by 75 K. A forced-draught fan delivers the air to the pre-heater at a pressure of 1.02 bar and a temperature of 16°C with a pressure rise across the fan of 180 mm of Urheberrechtlich geschütztes Materia Reforences water. The power input to the fan is 5 kW and it has a mechanical efficiency of 78%. Neglecting heat losses, and taking ce, as 1.01 kJ/kg K for the flue gases, calculate: (i) the mass flow rate of air; (ii) the temperature of the flue gases leaving the plant; (ii) the mass flow rate of steam; (iv) the efficiency of the boiler. The power required to drive the fan is given by hp.gV where h is the pressure rise across the fan expressed as a head of water, p, the density of water, g the acceleration due to gravity, V the volume flow rate of air, and ŋm is the mechanical efficiency of the fan.
A boiler plant, see Fig. 8.19 (p. 254), incorporates an economizer and an air pre-heater, and generates steam at 40 bar and 300°C with fuel of calorific value 33000 kJ/kg burned at a rate of 500 kg/h. The temperature of the feedwater is raised from 40 to 125°C in the economizer, and the flue gases are cooled at the same time from 395 to 225 °C. The flue gases then enter the air pre-heater in which the temperature of the combustion air is raised by 75 K. A forced-draught fan delivers the air to the pre-heater at a pressure of 1.02 bar and a temperature of 16°C with a pressure rise across the fan of 180 mm of Urheberrechtlich geschütztes Materia Reforences water. The power input to the fan is 5 kW and it has a mechanical efficiency of 78%. Neglecting heat losses, and taking ce, as 1.01 kJ/kg K for the flue gases, calculate: (i) the mass flow rate of air; (ii) the temperature of the flue gases leaving the plant; (ii) the mass flow rate of steam; (iv) the efficiency of the boiler. The power required to drive the fan is given by hp.gV where h is the pressure rise across the fan expressed as a head of water, p, the density of water, g the acceleration due to gravity, V the volume flow rate of air, and ŋm is the mechanical efficiency of the fan.
Refrigeration and Air Conditioning Technology (MindTap Course List)
8th Edition
ISBN:9781305578296
Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson
Publisher:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson
Chapter45: Domestic Refrigerators And Freezers
Section: Chapter Questions
Problem 12RQ: Refrigerators currently being manufactured in the United States are using______as their refrigerant.
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