Chiller Capacity and System Heat Generation
Chiller Capacity and System Heat Generation
(OP)
I am trying to use a chiller to cool a hydraulic system, and am trying to verify if I have enough cooling capacity in my chiller. The stated maximum cooling capacity is 10.5KW.
My system starts with a 50HP motor (~37KW), and my first question is how much of that in worst case scenario can become heat? As for my system, the motor drives a pump, which runs a hydraulic motor, which runs a generator. This is a test setup and I realize highly inefficient, but are these inefficiencies translating to heat in my hydraulic oil? If I load my generator I can get say 10KW - does that mean that the remaining 27 KW would be heat? What about when there is no load on the generator - is it all heat? It is likely safe to assume that the pump swashplate is fully stroked for this application.
My initial instinct and testing is telling me that the 10.5KW chiller is not adequate, but I do not want to oversize the chiller. Any help for a worst case cooling scenario?
SMR
My system starts with a 50HP motor (~37KW), and my first question is how much of that in worst case scenario can become heat? As for my system, the motor drives a pump, which runs a hydraulic motor, which runs a generator. This is a test setup and I realize highly inefficient, but are these inefficiencies translating to heat in my hydraulic oil? If I load my generator I can get say 10KW - does that mean that the remaining 27 KW would be heat? What about when there is no load on the generator - is it all heat? It is likely safe to assume that the pump swashplate is fully stroked for this application.
My initial instinct and testing is telling me that the 10.5KW chiller is not adequate, but I do not want to oversize the chiller. Any help for a worst case cooling scenario?
SMR





RE: Chiller Capacity and System Heat Generation
RE: Chiller Capacity and System Heat Generation
I would use a heat exchanger ( radiator like in a car ) and a fan. Is a lot cheaper than using a chiller.
RE: Chiller Capacity and System Heat Generation
Just because you have a 50 HP motor doesn't mean that it producing 50 HP.
Beyond that, what are you trying to cool, or what are you trying to accomplish by cooling?
RE: Chiller Capacity and System Heat Generation
As for the electric motor and pump efficiencies, the motor is ~94% and the pump ~85%. The energy in the pressurized fluid is approximately 29kW. So the 37kW (50HP) is already ~29kW by the time it is in the form of pressurized fluid.
Does this help any? Am I looking at a worst case of needing to remove 29kW of heat?
Steve
RE: Chiller Capacity and System Heat Generation
RE: Chiller Capacity and System Heat Generation
When? Before it enters the pump, or after it leaves the pump?
What is the goal? What temperature decrease do you need to achieve, or what is the maximum allowed temperature at the exit of the cooler?
Ross is correct that all of the energy input will eventually leave the hydraulic system as heat - but you don't have to remove all of it with the chiller. Lots of it will leave all by itself.
You will lose heat in the piping. You will lose heat in the devices. You will lose heat to doing work (which will eventually become heat in whatever room the work is done).
Your cooler needs to be sized to match fluid flow x fluid heat capacity x required temperature drop.
RE: Chiller Capacity and System Heat Generation
MintJulep - I agree/understand that I have to remove less heat from the fluid when doing work , as this heat leaves the system as power from my hydraulic drive generator to an external load bank. However when there is no load on my alternator this pressurized fluid generates heat thru a pressure drop on a compensated control. How much of the loss due to inefficiencies (8kW from the 94% & 85%) end up as heat in the hydraulic fluid (that I have to remove), and how much ends going into the environment which I do not need to remove from the fluid?
The 29kW is a number I can arrive at two ways which gives some confidence:
1. 37kW (50HP) *.94(motor)*.85(pump) = ~29kW
2. The result of system gives me ~22GPM @ 3000 PSI. 3000*22/1714 = 38.5HP 38.5/1.341 = ~29kW
This makes sense that all of my inital power, minus inefficiencies to pressurize the fluid, ends up as energy in the pressurized fluid. If no work is done valves/fittings/motor heats up as well as the hydraulic oil... less when doing work as mentioned. I need to remove it from the hydraulic oil, but not the heat that hot valves/fittings give off to the environment. As mentioned, some of the 8kW efficiency loss is given to the environment which I do not need to remove.
Does this help? As for temperature ranges, I am trying to keep it 110-130F. When I run it now I have my chiller on and go right past 130F and need to shut down prior to reaching 150.