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Most impactful VRF object inputs

asked 2023-12-24 16:53:33 -0500

willyJohan's avatar

Of all the various performance curve inputs for the EnergyPlus AirConditioner:VariableRefrigerantFlow object, which can one expect to have the most impact on overall energy use?

I am trying to develop a generic set of VRF object inputs that will be representative of current VRF equipment and I'd like to prioritize any curve development effort based on impact (i.e., if i only have time to develop a few novel curves based on published equipment performance data, which should i start with?).

As a reminder here are the different curve inputs (ignoring heating vs cooling):

  • Capacity Ratio Boundary Curve Name
  • Capacity Ratio Modifier Function of High Temperature Curve Name
  • Capacity Ratio Modifier Function of Low Temperature Curve Name
  • Combination Ratio Correction Factor Curve Name
  • Defrost Energy Input Ratio Modifier Function of Temperature Curve Name
  • Energy Input Ratio Boundary Curve Name
  • Energy Input Ratio Modifier Function of High Part-Load Ratio Curve Name
  • Energy Input Ratio Modifier Function of High Temperature Curve Name
  • Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name
  • Energy Input Ratio Modifier Function of Low Temperature Curve Name
  • Heat Recovery Capacity Modifier Curve Name
  • Heat Recovery Energy Modifier Curve Name
  • Part-Load Fraction Correlation Curve Name
  • Piping Correction Factor for Length in Mode Curve Name

For bonus points, what of the non-performance curve inputs would one prioritize?

Thanks in advance.

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answered 2023-12-24 19:52:42 -0500

Keigo's avatar

Please do not list out all the curves. It is as if you are not even familiar with what each curve means.

Among curves, Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve would be the most imactful.

The second would be Energy Input Ratio Modifier Function of High/Low Temperature Curves, but I think it does not change that much from product to product.

In my experience, Minimum Heat Pump Part-Load Ratio is even more important than the above. When the heat pump operates at a PLR below this value, the heat pump’s compressor will cycle to meet the cooling or heating demand, which means that the all the Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve values below the Minimum Heat Pump Part-Load Ratio are ignored and the Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve value at the Minimum Heat Pump Part-Load Ratio is used. The larger Minimum Heat Pump Part-Load Ratio will increase the part load efficiency a lot. It's 0.15 by default, 0.1 or less in recent products, and the old value of 0.25 is often used in poorly researched papers.

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Thanks for the detailed answer. Happy to edit my question if you’d like me to remove the list of curves. And you are correct, I pretty much don’t know what any thing means, I just put in different values until I get the answer I’m hoping to get, isn’t that how everyone does it?

willyJohan's avatar willyJohan  ( 2023-12-27 16:38:00 -0500 )edit

I just guess the skill level of contributors from the year of registration, and I expect them to do the least they can before posting such as referring to Input/Output Reference unless they are not complete beginners. I thought you weren't a beginner, but it seems I was wrong. Sorry for the misunderstanding.

Keigo's avatar Keigo  ( 2023-12-27 22:03:08 -0500 )edit

Sorry, poor attempt at humour. I do appreciate the response.

willyJohan's avatar willyJohan  ( 2023-12-27 22:46:55 -0500 )edit

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Asked: 2023-12-24 16:53:33 -0500

Seen: 135 times

Last updated: Dec 27 '23