Help with charts

[jroyce]

OK guys... (and gals)

I was working on brushing up my thermo skills because the thermo and HVAC killed me on the first test. Chapter 27 of the MERM and problem 1-almost all of them. They all say that you need to use the Mollier chart in order to find the one value (h2 I think).

How the hell do you read the Mollier chart because I tried numerous ways that I thought was right but couldn't get to the answer that they said.

Thanks in advance. I also have lots of problems with the psych charts but we will wait for those until I get to that chapter.

 

[Sschell]

I dont have the MERM questions infront of me, so I cant address them directly... but, In general, you are given two properties to specify an initial condition. find where the lines cross on the chart. Lets call this state one.

The process specified will typically keep one of the properties shown on the graph constant (isentropic, isobaric, isothermal etc.) They may not always tell you directly which property is constant, for example they will state that it is a throttling process, which (from page 25-2 in MERM) is a constant enthalpy process.

Follow the line for the constant property (i.e. for isentropic you move vertically along the chart) until you reach the characteristic theat specifies state two. Once you find the place on the graph, you can read all the corresponding properties.

Hope this helps, It would be easier to explain with a visual aid!