Apparatus and method for determining refrigerant charge level
First Claim
1. A method of non-invasively determining a charge level (mtotal) of a refrigerant in a vapor-compression cycle system comprising a compressor, a condenser, an expansion device, an evaporator, a discharge line fluidically connecting the compressor to the condenser, a liquid line fluidically connecting the condenser to the expansion device, a distribution line fluidically connecting the expansion device to the evaporator, and a suction line fluidically connecting the evaporator to the compressor, the method comprising:
- monitoring the system while operating the system to ascertain that the system is operating at approximately steady-state;
determining the superheat (Tsh) and the subcooling (Tsc) of the system at the suction line and at the liquid line, respectively; and
calculating the refrigerant charge level (mtotal) based on the determined subcooling (Tsc), the determined superheat (Tsh), and rated operating conditions of the system including rated refrigerant charge level (mtotal,rated), rated liquid line subcooling (Tsc,rated), and rated suction line superheat (Tsh,rated) using the equation
(mtotal−
mtotal,rated)/mtotal,rated=(1/kch){(Tsc−
Tsc,rated)−
ksh/sc(Tsh−
Tsh,rated)}wherein kch is and empirical constant and ksh/sc is the slope of a straight line plot of (Tsc−
Tsc,rated) versus (Tsh−
Tsh,rated) for the rated rrefrigerant charge for the system; and
thenadjusting the charge level of the refrigerant in the system in response to the calculated refrigerant charge level of the system.
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Accused Products
Abstract
A method and apparatus for non-invasively determining a charge level of a refrigerant in a vapor-compression cycle system. The method and apparatus monitor the system while the system is operated to ascertain that the system is operating at approximately steady-state. The superheat and the subcooling of the system are then determined at the suction line and at the liquid line, respectively, and the refrigerant charge level is calculated based on the determined subcooling, the determined superheat, and rated operating conditions of the system, including rated refrigerant charge level, rated liquid line subcooling, and rated suction line superheat.
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Citations
14 Claims
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1. A method of non-invasively determining a charge level (mtotal) of a refrigerant in a vapor-compression cycle system comprising a compressor, a condenser, an expansion device, an evaporator, a discharge line fluidically connecting the compressor to the condenser, a liquid line fluidically connecting the condenser to the expansion device, a distribution line fluidically connecting the expansion device to the evaporator, and a suction line fluidically connecting the evaporator to the compressor, the method comprising:
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monitoring the system while operating the system to ascertain that the system is operating at approximately steady-state; determining the superheat (Tsh) and the subcooling (Tsc) of the system at the suction line and at the liquid line, respectively; and calculating the refrigerant charge level (mtotal) based on the determined subcooling (Tsc), the determined superheat (Tsh), and rated operating conditions of the system including rated refrigerant charge level (mtotal,rated), rated liquid line subcooling (Tsc,rated), and rated suction line superheat (Tsh,rated) using the equation
(mtotal−
mtotal,rated)/mtotal,rated=(1/kch){(Tsc−
Tsc,rated)−
ksh/sc(Tsh−
Tsh,rated)}wherein kch is and empirical constant and ksh/sc is the slope of a straight line plot of (Tsc−
Tsc,rated) versus (Tsh−
Tsh,rated) for the rated rrefrigerant charge for the system; and
thenadjusting the charge level of the refrigerant in the system in response to the calculated refrigerant charge level of the system. - View Dependent Claims (2, 3, 4, 5, 6, 7)
wherein α
hs,o,rated is the fraction of the rated refrigerant charge level (mtotal,rated) under which the refrigerant is saturated liquid at an exit of the liquid line under the rated operating conditions, and Xhigh,rated is the ratio of rated refrigerant charge level at a high side of the system over the rated refrigerant charge level (mtotal,rated) of the system.
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4. The method according to claim 1, wherein kch is about 50°
- C.
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5. The method according to claim 1, wherein ksh/sc is between about ¼
- to about ½
.
- to about ½
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6. The method according to claim 1, wherein ksh/sc is about 1/2.5.
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7. The method according to claim 1, wherein the determining and calculating steps are performed without training the system to develop a model correlating the subcooling and superheat of the system to refrigerant pressures in the system, and without empirical data regression.
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8. An apparatus for non-invasively determining a charge level (mtotal) of a refrigerant in a vapor-compression cycle system comprising a compressor, a condenser, an expansion device, an evaporator, a discharge line fluidically connecting the compressor to the condenser, a liquid line fluidically connecting the condenser to the expansion device, a distribution line fluidically connecting the expansion device to the evaporator, and a suction line fluidically connecting the evaporator to the compressor, the apparatus comprising:
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means for monitoring the system while operating the system to ascertain that the system is operating at approximately steady-state; means for determining the superheat (Tsh) and the subcooling (Tsc) of the system at the suction line and at the liquid line, respectively; and means for calculating the refrigerant charge level (mtotal) based on the determined subcooling (Tsc), the determined superheat (Tsh), and rated operating conditions of the system including rated refrigerant charge level (mtotal,rated), rated liquid line subcooling (Tsc,rated), and rated suction line superheat (Tsh,rated), the calculation means calculating the refrigerant charge level (mtotal) with the equation
(mtotal−
mtotal,rated)/mtotal,rated=(1/kch){(Tsc−
Tsc,rated)−
ksh/sc(Tsh−
Tsh,rated)}wherein kch is an empirical constant and ksh/sc is the slope of a straight line plot of (Tsc−
Tsc,rated) versus (Tsh−
Tsh,rated) for the rated refrigerant charge for the system.- View Dependent Claims (9, 10, 11, 12, 13, 14)
wherein α
hs,o,rated is the fraction of the rated refrigerant charge level (mtotal,rated) under which the refrigerant is saturated liquid at an exit of the liquid line under the rated operating conditions, and Xhigh,rated is the ratio of rated refrigerant charge level at a high side of the system over the rated refrigerant charge level (mtotal,rated) of the system.
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11. The apparatus according to claim 8, wherein kch is about 50°
- C.
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12. The apparatus according to claim 8, wherein ksh/sc is between about ¼
- to about ½
.
- to about ½
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13. The apparatus according to claim 8, wherein ksh/sc is about 1/2.5.
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14. The apparatus according to claim 8, wherein the determining means and calculating means operate without training the system to develop a model correlating the subcooling and superheat of the system to refrigerant pressures in the system, and without empirical data regression.
Specification