Determine operating tonnage on existing CHW System

[hvacman]

I am looking for help in determining the cooling load on an existing chiller. We want to generate a profile over a 24 hour period. I've been told to take temperature readings influent and effluent the chiller and the pressure drop would be part of the equation. I am looking for a recommendation/considerations that would help on this effort. I also need a recomemdation on metering equipment that can be used to take automatic readings over a 24 hour period. Any help is appreciated.
Thanks

 

[ChasBean1]

hvacman,

Is the flow constant (e.g., do you have a primary and secondary loop)? Assuming the flow is constant, measure dT (chilled water in/chilled water out) for the evaporator. Use anything to datalog this, such as a Hobo logger sensing element in direct contact with the pipe surface. Hobo logger info can be found at:

http://www.onsetcomp.com/Products/3654_temp.html

With the known flow, use Q = m Cp dT to figure out the varying load (Q). Once you collect the dT data, you can plug and chug in an Excel sheet with columns like:

Time Tout Tin Tin-Tout Flow Cp Q
14:35 42 55 =c2-b2 600 1.00 =e2*f2*d2

If the primary chiller flow varies, this becomes more involved as you should use a data logging flow meter (e.g., ultrasonic, clamp-on flow meter).

Best regards, -CB