Hi Everyone,

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

performance:

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

model.

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 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.