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All the nearby buildings' heating is provided by saturated steam generated at a nearby steam plant using natural gas boilers. On March 13th, 2019 (cycle weather bomb), the area experienced a cold front with outdoor air temperature equal to 39°F at 9 am. After heating all buildings in the area, water returns to the boiler as saturated liquid at 222°F. Water is then preheated and pressurized to 222°F and 180 psig (state before entering the boiler). Water leaves the boiler as saturated vapor at 322°F. For this date/time steam mass flow rate was 21,900 lbm/hr. Boiler combustion produces combustion gases at 3,000°F at 20psia, which leaves the boiler at 400°F 19.5psia. Determine: The pressure of the steam leaving the boiler and the oiler heat capacity (heat needed to produce steam at the given flowrate and temperature, MMBtu/h) Mass air flow rate (lbm/h) and he exergy destroyed (MMBtu/h) in the boiler Second law efficiency in the boiler

All the nearby buildings' heating is provided by saturated steam generated at a nearby steam plant using natural gas boilers. On March 13th, 2019 (cycle weather bomb), the area experienced a cold front with outdoor air temperature equal to 39°F at 9 am. After heating all buildings in the area, water returns to the boiler as saturated liquid at 222°F. Water is then preheated and pressurized to 222°F and 180 psig (state before entering the boiler). Water leaves the boiler as saturated vapor at 322°F. For this date/time steam mass flow rate was 21,900 lbm/hr. Boiler combustion produces combustion gases at 3,000°F at 20psia, which leaves the boiler at 400°F 19.5psia. Determine: The pressure of the steam leaving the boiler and the oiler heat capacity (heat needed to produce steam at the given flowrate and temperature, MMBtu/h) Mass air flow rate (lbm/h) and he exergy destroyed (MMBtu/h) in the boiler Second law efficiency in the boiler

Refrigeration and Air Conditioning Technology (MindTap Course List)
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
Chapter50: Commercial, Packaged Rooftop, Variable Refrigerant Flow, And Variable Air Volume Systems
Section: Chapter Questions
Problem 15RQ: Explain why the outside air damper is typically never completely closed, even when the outside air...
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All the nearby buildings' heating is provided by saturated steam generated at a nearby steam plant using natural gas boilers. On March 13th, 2019 (cycle weather bomb), the area experienced a cold front with outdoor air temperature equal to 39°F at 9 am. After heating all buildings in the area, water returns to the boiler as saturated liquid at 222°F. Water is then preheated and pressurized to 222°F and 180 psig (state before entering the boiler).

Water leaves the boiler as saturated vapor at 322°F. For this date/time steam mass flow rate was 21,900 lbm/hr.
Boiler combustion produces combustion gases at 3,000°F at 20psia, which leaves the boiler at 400°F 19.5psia.
Determine:

  • The pressure of the steam leaving the boiler and the oiler heat capacity (heat needed to produce steam at the given flowrate and temperature, MMBtu/h)
  • Mass air flow rate (lbm/h) and he exergy destroyed (MMBtu/h) in the boiler
  • Second law efficiency in the boiler

Assumptions:

  • Steady operating conditions exist and Kinetic and potential energy changes are negligible.
  • Combustion gases are assumed to be air and modeled as an ideal gas (you cannot use Cp or Cv).
  • You cannot assume pressure remains constant in the boiler.

The image below depicts a simplified model of the system, as well as an actual picture of the boiler at the time of this problem.

Fresh Air Dampe Combustion W Time since FR 40.7% . PV746 PS SP 75.0 PGI CV406% Damper stencer BPM Const 40.6% kader Stack Damper 100 Gegen Manu Press DMS Inte Warmup Control Enable Off Oran Leve PIT 350 Windbox BOILER #1 (BUZZ) OVERVIEW CA 200 Economizer B-1 BUZZ GAS Water 180 psia 222°F Drum 40.9 Gas Va of vave 20.3% OAT: 39 F STEAM HEADER FIT FEE HEADER PVP VDONE FLOW 215 P DA LEVEL: 41.9 Boter 1 Mun Hours: 201 Gas Flow 26.4 Kach DE FLOW GPM ER # SYSTEM IN MODE 6 9 Sat Steam 322°F
Transcribed Image Text:Fresh Air Dampe Combustion W Time since FR 40.7% . PV746 PS SP 75.0 PGI CV406% Damper stencer BPM Const 40.6% kader Stack Damper 100 Gegen Manu Press DMS Inte Warmup Control Enable Off Oran Leve PIT 350 Windbox BOILER #1 (BUZZ) OVERVIEW CA 200 Economizer B-1 BUZZ GAS Water 180 psia 222°F Drum 40.9 Gas Va of vave 20.3% OAT: 39 F STEAM HEADER FIT FEE HEADER PVP VDONE FLOW 215 P DA LEVEL: 41.9 Boter 1 Mun Hours: 201 Gas Flow 26.4 Kach DE FLOW GPM ER # SYSTEM IN MODE 6 9 Sat Steam 322°F
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