jberrio
Mechanical
- May 10, 2001
- 3
I am trying to find the time upon a loss of cooling water to reach a high temperature condition.
I have a typical lube oil system for a pump which has a pump take a suction on a sump, pump it through a lube oil cooler, and then supply the oil to the bearings which gravity drains back to the sump.
I need to estimate the time upon a loss of cooling water to the cooler until I damage my bearings. There are alot of assumptions I will make since I dont know how to calculate the individual bearing heat inputs.
But...
I am assuming that: 1. The system is initially at steady state. 2. All the heat inputted into the bearing is what is taken out of the cooler(qin=qout). The sump temperature is constant.
Now it is a problem of finding at what l.o. inlet temp I will cause damage. I am going to assume 150 F. (My bearings are typical lead/tin babbit material)
So, if I know the mass flow rate of my oil into the sump and the capacity of the sump, an initial lube oil sump temp, and the qin to the oil from the bearings, how do I find time. I will assume complete mixing in the sump but dont know an equation with time, given an inlet flowrate and temp whose temp will also increase with time.
Also, with regard to accuracies, do I really need to deal with bulk stream temperatures or can I take my measurements for initial data using a contact pyrometer to get inlet and outlet temperatures. I know these will lead to inaccuracies but are they negligible.
I have a typical lube oil system for a pump which has a pump take a suction on a sump, pump it through a lube oil cooler, and then supply the oil to the bearings which gravity drains back to the sump.
I need to estimate the time upon a loss of cooling water to the cooler until I damage my bearings. There are alot of assumptions I will make since I dont know how to calculate the individual bearing heat inputs.
But...
I am assuming that: 1. The system is initially at steady state. 2. All the heat inputted into the bearing is what is taken out of the cooler(qin=qout). The sump temperature is constant.
Now it is a problem of finding at what l.o. inlet temp I will cause damage. I am going to assume 150 F. (My bearings are typical lead/tin babbit material)
So, if I know the mass flow rate of my oil into the sump and the capacity of the sump, an initial lube oil sump temp, and the qin to the oil from the bearings, how do I find time. I will assume complete mixing in the sump but dont know an equation with time, given an inlet flowrate and temp whose temp will also increase with time.
Also, with regard to accuracies, do I really need to deal with bulk stream temperatures or can I take my measurements for initial data using a contact pyrometer to get inlet and outlet temperatures. I know these will lead to inaccuracies but are they negligible.
