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Part load ratio performance coefficients for chiller and unitary DX system

asked 2020-04-24 01:58:26 -0500

VS gravatar image

updated 2020-04-24 08:20:30 -0500

I am trying to calculate part load ratio performance coefficients for water cooled chiller and unitary system. For Water cooled chiller, EIRfPLR curve coefficients can be get from Energy Plus curve fit tool(excel sheet) in quadratic form? And for unitary DX system, Part load fraction correlation curve was available in Energy Plus - Engineering Reference document (pg no. 818) PLR=0.85+0.15(PLR), can I use this same correlation values for simulation?

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answered 2020-04-24 12:53:31 -0500

The DX coil part load fraction correlation curve PLR=0.85+0.15(PLR) should be used for simulation.The 0.85 in this correlation represents high efficiency DX equipment. Low efficiency DX equipment would use 0.75 to 0.80 (but I have no reference for this).

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Thank you for your answer. Any idea about EIRfPLR (Energy Input Ratio function of Part load Ratio) curve coefficients for water cooled chiller. Whether that can obtained from Energy Plus curve fit tool excel by using quadratic form. Are any other way to find this coefficients?

VS gravatar image VS  ( 2020-04-25 06:48:25 -0500 )edit

Yes the tool can be used for water-cooled chillers. Just input water temps instead of air temps.

rraustad gravatar image rraustad  ( 2020-04-27 05:45:21 -0500 )edit

In order to calculate EIR as a function of PLR, you wouldn't you need to have PLR (Flow Fraction) as the independent variable? And further, to control for temperature on a quadratic curve, wouldn't the temperatures (Evaporator and Condenser Entering Temperatures) have to be held constant for the range of data?

Ski90Moo gravatar image Ski90Moo  ( 2020-05-20 13:00:51 -0500 )edit

The chiller EIRfPLR can't be calculated using the CurveFitTool provided with E+. But it's really only a power fraction curve that roughly goes from 0 at PLR=0 to 1 at PLR=1. I did say "roughly" so bear in mind there is a little bit of a bend to this curve. Plot a chiller curve and you will see.

rraustad gravatar image rraustad  ( 2020-05-20 15:34:34 -0500 )edit

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Asked: 2020-04-24 01:58:26 -0500

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Last updated: Apr 24 '20