Super Efficient Chillers

[simple911]

Just looking for some experienced feedback. Have you ever heard of a 500 ton chiller running at an efficiency of .15kw/ton? And theoretically, under what conditions would this be possible?

 

[quark]

You must be seriously joking. That gives a COP of about 23.4 and I have never heard of such a beast.

May be you are talking of a vapor absorption system. Still, it is a wrong notion to consider only the absorber, refrigerant and vacuum pump power inputs for calculation COP.

If it is a vapor compression machine, check the capacity of motor. If it is provided with 75kW motor then make a detailed and flawless agreement with the vendor for performace.

If everything turns to be OK (with a probability of few zeros after decimal point, at this juncture), post us back. This is high time for salary increment here

PS: 0.15kW/ton is not efficiency but is called as specific power consumption.

 

[simple911]

This does sound like big business. I'm more familiar with kW/ton to be around 0.5.

A project is claiming that given the geographical location (sf), the chiller never sees condenser ARI conditions 85 deg entering and 95 deg leaving. The project also claims an average condenser supply temperature of 57 deg F.

Now I'm familiar with floating head pressures, where compressor consumption is reduced with increased fan speed and lower entering condenser temperatures, but is the above possible at even 0.25kW/ton?

 

[simple911]

Hi, let me add another piece of information.

It's a vsd chiller.

 

[quark]

Theoretically, there is not much difference. I am getting a power reduction of about 18% incase of R134a. When the refrigerant is pressurised, the compressor power is being imparted to the fluid and thus the enthalpy of the fluid increases. As the mass flowrate is constant, the change in power consumption will be proportional to the enthalpy difference of refrigerant between discharge and suction conditions.

How is the manufacturer showing it on paper? Did you have a look into the calculations?

 

[simple911]

I have been reviewing some case studies, where projects have claimed that vsd chillers actually run more efficiently at lower capacities. Also considering sf weather data, wet-bulbs are low enough for condensing water temperature to reach 57 deg.

I was just put onto this project and the nameplate provided was actually just for the vsd, so I don't have the manufacturers interpretations of performance.

Company 'x' monitored the data and came up with 'beast' like numbers. My feelings are that the numbers should be adjusted, but with time restraints on the project, I am unable to spend the time to remodel the facility.

 

[dcasto]

You can get a chiller to do .01 KW/ton, it all depends on the temperature of the chilling system. It would be impossible to geta chiller cycle to do .15KW/ton at a -40C. In order to quantify your effiency, what is the temperature of the chiller and what refrigerant are you using?

Also, what type of compressor, reciprocating, screw, centifical... can make a difference on whether the VSD is worth the extra cost. for example, valve unloaders are excellent ways to unload PD compresors.