Mechanical Engineering Placement Thermodynamics Problem

In summary, the conversation discusses a problem involving a pump compressing hydrogen from a low pressure to a high pressure tank, and finding the compressor outlet temperature using the first law of thermodynamics and the ideal gas law. The conversation also mentions the use of an adiabatic and polytropic process and suggests seeking help in a related thread in the Homework Help section.
  • #1
bianca1992
7
0
Hi all I am struggling with this classs example

A pump compressing hydrogen from a low pressure to a high pressure tank where the tanks pressure is constant and H2 is an ideal gas.
Hydrogen: (H2: MW = 2, Cv = 10 kJ/kgK)
Low pressure tank: (P = 4 bar, T = 30oC)
High pressure tank: (P = 100 bar).

1) Apply the first law of thermodynamics eliminating terms not needed
2) Find the compressor outlet temp when the compression goes along an adiabatic and polytrophic process
 
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  • #2
Since you stated this is a homework problem, what formulas are you using and what have you attempted so far?
 
  • #3
Hi,

For the first law I have used Q-W = difference in energy and attempted to find the temp via finding the internal energy and enthalpy using deltau = cv x delta T and delta h = cp x delta T where I got 8520 KJ and 12063 KJ but now I am not sure how if I should integrate and remove pressure from the first law and find the temp now.
 
  • #4
The problem states that Hydrogen can be considered an ideal gas, so it seems to me that all you really need to do is apply the ideal gas law using pressure and temperature at the input, and pressure at the output. Adiabatic means there is no heat entering or leaving the system during the process, so the gas is not cooled or heated by any other process.

As for the polytropic process, that will take a bit of fitting work to figure out what the polytropic index and constant is. Are you familiar with a polytropic process's form?
 
  • #5
firstly for the first law does one simply remove pressure from the closed loop first law of thermodynamics?
 

FAQ: Mechanical Engineering Placement Thermodynamics Problem

What is the purpose of a mechanical engineering placement thermodynamics problem?

The purpose of a mechanical engineering placement thermodynamics problem is to test the understanding and application of thermodynamics principles in real-world scenarios. It allows students to demonstrate their problem-solving skills and critical thinking abilities.

What are some common types of mechanical engineering placement thermodynamics problems?

Some common types of mechanical engineering placement thermodynamics problems include heat transfer, energy conversion, power cycles, and gas laws. These problems often involve calculations and analysis of thermodynamic properties such as temperature, pressure, and volume.

How can one approach solving a mechanical engineering placement thermodynamics problem?

The first step in solving a mechanical engineering placement thermodynamics problem is to clearly understand the given information and identify what is being asked. Then, apply the relevant thermodynamics principles and equations to solve for the unknown variables. It is important to keep track of units and use the correct equations for the given scenario.

What are some common mistakes students make when solving mechanical engineering placement thermodynamics problems?

Some common mistakes students make when solving mechanical engineering placement thermodynamics problems include not carefully reading and understanding the problem, using incorrect equations or not using them correctly, and not paying attention to units and conversions. It is also important to check the final answer to ensure it is reasonable and makes sense in the given context.

How can one prepare for a mechanical engineering placement thermodynamics problem?

To prepare for a mechanical engineering placement thermodynamics problem, one should review the fundamental principles and equations of thermodynamics. Practice solving different types of thermodynamics problems and familiarize yourself with commonly used equations and their applications. It is also helpful to work on sample problems and past placement tests to get a feel for the level of difficulty and types of problems that may be encountered.

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