System and method for dynamically determining refrigerant film thickness and dynamically controlling refrigerant film thickness at rolling-element bearing of an oil free chiller
Methods are directed towards dynamically determining refrigerant film thickness at the rolling-element bearing and for dynamically controlling refrigerant film thickness at the rolling-element bearing. Further, an oil free chiller system is configured for dynamically determining refrigerant film thickness at the rolling-element bearing of the oil free chiller system, wherein the oil free chiller system is also configured for dynamically controlling refrigerant film thickness at the rolling-element bearing of the oil free chiller system.
1. A computerized controller device for an oil free chiller configured for dynamically determining an actual refrigerant film thickness at a bearing of the oil free chiller during operation of the oil free chiller, and for controlling other components of the oil free chiller to change a refrigerant film thickness at the bearing or an operation of the oil free chiller, when the actual refrigerant film thickness is different from a threshold refrigerant film thickness,
wherein the computerized controller device determines the actual refrigerant film thickness at the bearing of the oil free chiller during operation of the oil free chiller based only on temperature and rotation speed of the bearing.
2. The computerized controller device as in claim 1 , wherein the computerized controller device controls the other components of the oil free chiller so that the change of the refrigerant film thickness at the bearing is an increase of the refrigerant film thickness, when the actual refrigerant film thickness is below the threshold refrigerant film thickness.
3. The computerized controller device as in claim 1 , wherein the threshold refrigerant film thickness is a predetermined minimum refrigerant film thickness.
4. A computerized controller device for an oil free chiller configured for dynamically determining an actual refrigerant film thickness at a bearing of the oil free chiller during operation of the oil free chiller, and for controlling other components of the oil free chiller to change a refrigerant film thickness at the bearing or an operation of the oil free chiller, when the actual refrigerant film thickness is different from a threshold refrigerant film thickness, wherein the computerized controller device applies Formula 1 transformed to a computerized instruction set for performing a specialized function of determining the actual refrigerant film thickness (h actual):
h
actual
=
AR
(
1
-
e
Bk
)
[
Nv
ER
r
]
C
(
α
E
)
D
(
F
ER
r
2
)
G
Formula
1
wherein:
A, B, C, D, and G are constants;
e is the Euler's constant;
R r is a curvature radius of an inner bearing race;
R is a speed of rotation;
k is the Boltzmann constant;
E is a Young's Modulus;
F is a load parameter;
N is a dynamic viscosity;
v is a mean rolling velocity of a ball and the inner bearing race; and
αa is a pressure viscosity.
5. A computerized controller device for an oil free chiller configured for dynamically determining an actual refrigerant film thickness at a bearing of the oil free chiller during operation of the oil free chiller, and for controlling other components of the oil free chiller to change a refrigerant film thickness at the bearing or an operation of the oil free chiller, when the actual refrigerant film thickness is different from a threshold refrigerant film thickness, wherein the computerized controller device applies Formula 2 transformed to a computerized instruction set for performing a specialized function of determining the actual refrigerant film thickness (h actual ):
h
actual
=
HR
[
Nv
ER
r
]
I
[
F
ER
r
2
]
J
Formula
2
wherein:
H, I, and J are constants;
e is the Euler's constant;
R r is a curvature radius of an inner bearing race;
R is a speed of rotation;
E is a Young's Modulus;
F is a load parameter;
N is a dynamic viscosity; and
v is a mean rolling velocity of a ball and the inner bearing race.
6. An oil free chiller system, comprising the computerized controller device according to claim 1 , wherein the computerized controller device controls an operation of a motor of the oil free chiller system and/or operation of a refrigerant liquid temperature affecting device.
7. The oil free chiller system as in claim 6 , further comprising:
a sensor configured for measuring the capacitance of the refrigerant fluid, wherein the capacitance is communicated to the computerized controller device; and
the computerized controller device configured for determining a dynamic actual film thickness of the refrigerant fluid at the bearing based on the capacitance.
8. A method for controlling a lubricant film thickness at a bearing of a motor, comprising:
a computerized controller device determining a refrigerant fluid temperature at a bearing of a chiller;
the computerized controller device determining a rotational speed of the bearing;
the computerized controller device of the chiller determining an actual lubricant film thickness (h actual ) based on the refrigerant fluid temperature and the rotational speed by applying Formula 1 or Formula 2:
h
actual
=
AR
(
1
-
e
Bk
)
[
Nv
ER
r
]
C
(
α
E
)
D
(
F
ER
r
2
)
G
Formula
1
wherein:
A, B, C, D, and G are constants,
e is the Euler's constant,
R r is a curvature radius of an inner bearing race,
R is a speed of rotation,
k is the Boltzmann constant,
E is a Young's Modulus,
F is a load parameter,
N is a dynamic viscosity,
v is a mean rolling velocity of a ball and the inner bearing race, and
αis a pressure viscosity;
h
actual
=
HR
[
Nv
ER
r
]
I
[
F
ER
r
2
]
J
Formula
2
wherein:
H, I, and J are constants,
e is the Euler's constant,
R r is the curvature radius of the inner bearing race,
R is the speed of rotation,
E is the Young's Modulus,
F is the load parameter,
N is the dynamic viscosity, and
v is the mean rolling velocity of the ball and the inner bearing race;
the computerized controller device having a threshold lubricant film thickness information in a non-transitory computer-readable medium; and
the computerized controller device comparing the threshold lubricant film thickness to the actual lubricant film thickness (h actual ),
wherein when the actual lubricant film thickness (h actual ) is different from the threshold lubricant film thickness, the computerized controller device takes an action on the chiller to change the actual lubricant film thickness (h actual ).
9. The method as in claim 8 , wherein the threshold lubricant film thickness is a minimum lubricant film thickness (h min ).
10. The method as in claim 9 , wherein when h actual <h min , the computerized controller device takes an action on the chiller to increase the actual lubricant film thickness (h actual ).
11. The method as in claim 8 , wherein the action comprises increasing the rotation speed of the bearing of the chiller.
12. The method as in claims 8 , wherein the action comprises lowering the refrigerant fluid temperature.
13. The method as in claim 8 , wherein the action comprises changing a phase of a refrigerant fluid.
14. The method as in claim 13 , further comprising:
repeating the action on the chiller to increase h actual until h actual ≥h min .
15. The method as in claim 14 , further comprising:
after the computerized controller device has taken the action on the chiller to increase h actual , the computerized controller device determining that h actual <h min condition has lasted a predetermined amount of time.
16. The method as in claim 15 , further comprising:
after the computerized controller device has determined that h actual <h min condition has lasted the predetermined amount of time, the computerized controller device shutting down the chiller.