Components of kW/Ton 2

[javier83]

I am trying to figure out the optimum production cost of the overall cooling process (water cooled chilled water system)0. I would like to know what components are included in the kW per Ton value provided by the manufacturer. I am using the kW from the compressor, fan, and cooling tower and total cooling load and total cooling load capacity (from mechanical plans), but am unable to match the kW per ton value.

Any help would be appreciated

 

[KiwiMace]

You don't mention chilled water and condenser water pump power. Less important is ancilliary power from oil pumps etc.

Are any of the pumps, compressors, CT fans variable speed?

 

[ChrisConley]

Generally manufacturer listed efficiencies are for the chiller only: kW of electricity consumed by the chiller to create x tons of cooling.

The condenser and evaporator pumps, as well as the tower fan motor would all add to the total kW required to produce cooling.

One item to watch would be part load production. Many chiller are sold on full load kW/ton, but studying the efficiency of the plant at part load (depending on your process) may tell a better story.

 

[HVAC68]

If you know the load pattern of your process and the ambient temperature profile for the year (24 hours x 365 days), you can work out the power consumption for your specific installation with a greater level of accuracy than the standard NPLV number or full load IKW/TR numbers.

You should then compare this for various manufacturers to arrive at a more realistic way of comparison.

The components to be added are the compressor power, the chilled water pump power (primary and secondary) condenser water pump power and cooling tower fan motor power (assuming a water-cooled system). If the applcationis for air-conditioning, then add the AHU fan motors, FCU fan motors as well.

HVAC68

 

[sterl]

I believe the key to your question is the units: They are really KW-Hr per TR-Hour.

The only way you can get to TR-Hr is to detail-model the duty cycle. Lots of them have been done for Air Conditioning type operating conditions and "normal" occupancy; Carrier has "bin-method" software that will help identify the conditions and durations of concern, but if a lot of your heat load is process-oriented, its not going to do a very good job estimating heat load or duration; especially if there are some batch processes involved.

(KW per TR) fills in the gap from total cooling
requirement to cost of power; and will depend on the load on the plant as a proportion of peak capacity and on the specific management of compressor capacity, fans and the like.