EIR Chiller Power calculation and its output performance

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Hi Everyone,

I'm currently doing a simulation and I find something strange with chiller

The chiller capacity is 1920000 Btu/hr, the rated EIR is 0.1722 and
considered the actual chiller curves from the chiller datasheet in the

In the image below, the data in white columns is from eQuest, and the grey
column is my calculations.
[image: image.png]

1) Refer to above screenshot, rated EIR considered by the software to
calculate the corrected EIR is 0.2190 (highlighted in Grey) however; I have
entered the rated EIR at chiller level as 0..1722. I think that the rated
EIR entered at the chiller lever should be the same as the rated EIR
considered by software to calculate the corrected EIR. Please find the
attached file of chiller datasheet.

When I consider the software default chiller curves, the entered rated EIR
at chiller level is the same as the rated EIR considered by the software to
calculate the corrected EIR.

Why is there discrepancy in the entered rate EIR and rated EIR considered
by software to calculate the corrected EIR when I enter chiller curves from
the manufacture datasheet?

2) It is difficult to understand that operating capacity indicated in
the cell G-15, G17 to G-20 is exceeding the rated chiller capacity. I know
that the formula to calculate the operating capacity is rated capacity
multiplied by Capacity-FT curve respect to LCHWT & ECWT. The value of
Capacity-FT curve at particular hours is totally based on the LCWT & ECWT,
I understand that the coefficients of Capacity-FT curve using raw data
points may be the reason for exceeding the operating capacity. Is there any
way to verify the coefficients that the eQuest software generates after
entering the raw data point for Capacity-FT curve or any manual calculation
to find these coefficients for the chiller curve?

3) To calculate the COP at a particular hour, reciprocal of the
corrected EIR is the right way or we need to consider the ratio of output
capacity to input chiller power. There are three capacities (highlighted in
Yellow in attached screenshot) provided in the hourly customized report.
Which capacity needs to be considered with input chiller power to calculate
the COP at a particular hour?

4) It was observed that the software considers the part load ratio as
EQload/operating capacity. The output of hourly report indicates that the
operating capacity is varying throughout the time however the part load
ratio provided in the manufacture datasheet is the current capacity to
rated capacity.

As per my understanding, the part load ratio should be current capacity to
rated capacity whereas the software part load ratio is EQload/operating
capacity. Please correct me if I am wrong and explain why the part load
ratio calculated by software is not in line with the standard part load
ratio provided by the manufacturer.
Anyone could help me with the above queries that will be grateful.

Nitin Harjai's picture
Joined: 2015-09-23
Reputation: 0