Chef
30-08-2008, 12:03 PM
The basics of the program have been resolved and tested in a limited way and the results are promising.:D
As the only system I have that has schreader valves is an R134a units running at 0.001Kg/s and Dx=8Bar Sx=1bar and a subcool of 5C I can only test the code against one known cap tube length. It was very close so it is a good confirmation of the base priciples but I need other examples to correlate against. Only R134a at the moment though please.
Then I can find out which part of the code is sensitive and try to smooth it out.
It must be a running system where you know the following:
Cap tube ID, Cap tube length, Discharge pressure (absolute or gauge) and temperature and evap P or T plus the mass flow rate.
Compressor volume and RPM would suffice if you dont have the mass flow.
Really - no guesses as it is the physical reality that proves the maths!
If any one has them please let me have them. Thanks.
______________________________________
The other items that would be very useful are:-
Viscosity data versus temp for fluid and gas states in saturated region.
Hf and Hfg for the saturated part versus temp
Any R134a tables
---------------------------------------------------
To date both EES and Refprop dont provide this data and so I have had to generate an equation of state parametric table for R134a and there seems to be a few areas where it seems to be not quite right and some correlation to another source would be useful.
What would be really cool is a table with P, T, H, Hf, Hfg, Hg, viscosity f, viscisty g, spec vol g, spec vol f, and of course quality! (A Christmas wish list?)
If any one knows what are the standard P and T values for h=0 for R134a it would also help immensely as that means I can develop the equations of state from principles.
Ice - The term for static head is actually quite small and as most systems have the tube running horizontally or close to it. Its not often one see's a cap tube fridge unit where the compressor and condensor is downstairs and the evaporator is upstairs? So for this cut it is not included but it can be added if want me to.
Your comment about entry and exit losses from the tube are relevant but the results shows them to be very small for the inlet and for the outlet it is equivalent to adding just 4mm of tube length. This seems too small to consider at the moment. (But I can add it in if you want me too)
Peter - The actual negative tube length does occur in this model as well as Stoecker's but it is when it actually reaches sonic velocities of 170m/s. This seems reasonable as the speed of sound I calculated is close to this. I think the Stoecker model omits acceleration Pressure drop at its peril but the momentum part was useful. Thanks for that.
Us Iceman - So far its up to 320 equations so the solver could not make it with just 50 but maybe later we can look at it.
The input module and output module I have worked up for the solver defeats its 'save' and 'load' and 'output' functions so does mean it is useable by anyone. If anyone needs it please send a PM.
Bottom line - it works.
Chef
As the only system I have that has schreader valves is an R134a units running at 0.001Kg/s and Dx=8Bar Sx=1bar and a subcool of 5C I can only test the code against one known cap tube length. It was very close so it is a good confirmation of the base priciples but I need other examples to correlate against. Only R134a at the moment though please.
Then I can find out which part of the code is sensitive and try to smooth it out.
It must be a running system where you know the following:
Cap tube ID, Cap tube length, Discharge pressure (absolute or gauge) and temperature and evap P or T plus the mass flow rate.
Compressor volume and RPM would suffice if you dont have the mass flow.
Really - no guesses as it is the physical reality that proves the maths!
If any one has them please let me have them. Thanks.
______________________________________
The other items that would be very useful are:-
Viscosity data versus temp for fluid and gas states in saturated region.
Hf and Hfg for the saturated part versus temp
Any R134a tables
---------------------------------------------------
To date both EES and Refprop dont provide this data and so I have had to generate an equation of state parametric table for R134a and there seems to be a few areas where it seems to be not quite right and some correlation to another source would be useful.
What would be really cool is a table with P, T, H, Hf, Hfg, Hg, viscosity f, viscisty g, spec vol g, spec vol f, and of course quality! (A Christmas wish list?)
If any one knows what are the standard P and T values for h=0 for R134a it would also help immensely as that means I can develop the equations of state from principles.
Ice - The term for static head is actually quite small and as most systems have the tube running horizontally or close to it. Its not often one see's a cap tube fridge unit where the compressor and condensor is downstairs and the evaporator is upstairs? So for this cut it is not included but it can be added if want me to.
Your comment about entry and exit losses from the tube are relevant but the results shows them to be very small for the inlet and for the outlet it is equivalent to adding just 4mm of tube length. This seems too small to consider at the moment. (But I can add it in if you want me too)
Peter - The actual negative tube length does occur in this model as well as Stoecker's but it is when it actually reaches sonic velocities of 170m/s. This seems reasonable as the speed of sound I calculated is close to this. I think the Stoecker model omits acceleration Pressure drop at its peril but the momentum part was useful. Thanks for that.
Us Iceman - So far its up to 320 equations so the solver could not make it with just 50 but maybe later we can look at it.
The input module and output module I have worked up for the solver defeats its 'save' and 'load' and 'output' functions so does mean it is useable by anyone. If anyone needs it please send a PM.
Bottom line - it works.
Chef