How Is Heat Transferred During Gas Expansion in a Diesel Engine?

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SUMMARY

The discussion focuses on the thermodynamic principles governing heat transfer during gas expansion in a diesel engine. Specifically, it addresses a scenario involving 0.25 kg of combustion gas at an initial temperature of 727°C, expanding at constant pressure to a volume 1.8 times its original value. Key calculations include determining the final temperature after expansion, the heat transferred, and the work done using the specific gas constants R = 0.302 kJ/kgK and Cp = 1.09 kJ/kgK. The principles of Charles's Law and the definition of specific heat at constant pressure (C_p) are essential for solving these problems.

PREREQUISITES
  • Understanding of thermodynamic laws, particularly Charles's Law.
  • Familiarity with specific heat capacity (C_p) and gas constant (R) values.
  • Knowledge of work done by gases during expansion at constant pressure.
  • Basic principles of gas behavior under varying pressures and volumes.
NEXT STEPS
  • Study the application of Charles's Law in gas expansion scenarios.
  • Learn how to calculate heat transfer using the formula Q = m * C_p * ΔT.
  • Explore the work done by gases during expansion using W = P * ΔV.
  • Investigate the implications of specific heat and gas constants in different thermodynamic processes.
USEFUL FOR

Mechanical engineers, thermodynamics students, and professionals working with diesel engines or gas expansion processes will benefit from this discussion.

junec21
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i have problem with these 2 questions.i been cracking my head the whole day about this/ anyone please help. please write down the steps for me if possible. thanks a lot in advance.

1) 0.25 kg of combustion gas in a diesel engine cylinder is at temperature of 727°C. The gas expands at constant pressure until its volume is 1.8 times its original value. For the combustion gas, R = 0.302 kJ/kgK and Cp = 1.09 kJ/kgK. Find the following:
a) temperature of the gas after expansion
b) heat transferred
c) work transferred

2) A quantity of gas has an initial pressure and volume of 0.1 MN/m2 and 0.1 m3, respectively. It is compressed to a final pressure of 1.4 MN/m2 according to the law pV1'26 = constant. Determine the final volume of the gas.
 
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junec21 said:
i have problem with these 2 questions.i been cracking my head the whole day about this/ anyone please help. please write down the steps for me if possible. thanks a lot in advance.
Hi Junec & welcome to PF,

What have you attempted thus far?
 
junec21 said:
i have problem with these 2 questions.i been cracking my head the whole day about this/ anyone please help. please write down the steps for me if possible. thanks a lot in advance.

1) 0.25 kg of combustion gas in a diesel engine cylinder is at temperature of 727°C. The gas expands at constant pressure until its volume is 1.8 times its original value. For the combustion gas, R = 0.302 kJ/kgK and Cp = 1.09 kJ/kgK. Find the following:
a) temperature of the gas after expansion
b) heat transferred
c) work transferred

a)If you know it expands at constant pressure...What does that mean for Volume and Temperature? (Check what Charles's law says about it)
b)What is the definition of [itex]C_p[/itex]?
c) Do you know a formula for finding the Work done by a gas when it expands its volume at a constant pressure?
 

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