Thermodynamics rigid tank, determine electrical energy supplied to air

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Discussion Overview

The discussion revolves around determining the electrical energy supplied to air in an insulated rigid tank during a process where air escapes, leading to a drop in pressure while maintaining constant temperature. The focus includes thermodynamic principles, equations, and methods relevant to this scenario.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant describes the scenario of an insulated 8-m3 rigid tank containing air at specific pressure and temperature, seeking to determine the electrical energy supplied during the process.
  • Another participant questions the volume of air remaining after it escapes, given that the tank is rigid.
  • Several participants suggest using equations related to entropy changes at constant temperature, noting that the volume remains constant due to the tank's rigidity.
  • There are references to the relationship between pressure and temperature at constant volume and how to calculate heat transfer without needing temperature change values.
  • One participant expresses intent to solve the problem later and share their findings.

Areas of Agreement / Disagreement

Participants appear to agree on the use of constant temperature and the rigidity of the tank, but there are multiple approaches suggested for solving the problem, indicating that the discussion remains unresolved.

Contextual Notes

Participants mention the need for specific equations and relationships involving entropy, pressure, and temperature, but do not provide a complete set of assumptions or mathematical steps necessary for a full solution.

Who May Find This Useful

This discussion may be useful for students or practitioners interested in thermodynamics, particularly those dealing with energy transfer in rigid systems and the application of entropy in thermodynamic processes.

getfreshcrue
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An insulated 8-m^3 rigid tank contains air at 600 kPa and 400 K. A valve connected to the tank is now opened, and air is allowed to escape until the pressure inside drops to 200 kPa. The air temperature during the process is maintained constant by an electric resistance heater placed in the tank. Determine the electrical energy supplied to air during this process.

HELP!
 
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So if in the process the temperature is kept constant, what the volume after the air escapes?
 
Equations to help with this?
 
try change in entropy(at constant temp, the volume remains const as this is a rigid tank)= change in heat transfer/temperature(constant) & you get, the change in heat transfer as the rate of Electrical energy supplied by the electrical resistance placed..
 
getfreshcrue said:
Equations to help with this?

You should know how pressure relates to temperature at constant volume and how to find heat transfer at a given temperature difference.


I think this should give you the same value as the entropy method.
 
yep..there is.. but try relating entropy changes.. there are change in entropy relations with volume, pressure & temp..no need to go for ΔT values as Temperature is made constant by electric resistance heater... i ll try to solve it when i find time & post them..
 

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