Claims:WE CLAIM:
1. A system for filling refrigerant into a refrigeration system, the system comprising:
a weighing scale for monitoring weight of a gas cylinder containing the refrigerant, the gas cylinder connected with charging ports of the refrigeration system;
a first temperature sensor and a second temperature sensor provided at inlet and outlet of compressor to determine temperature at inlet and outlet of the compressor;
a third temperature sensor and a fourth temperature sensor provided at inlet and outlet of condenser to determine temperature at inlet and outlet of the condenser;
a fifth temperature sensor provided at inlet of an expansion valve to determine temperature at inlet of the expansion valve; and
a sixth temperature sensor provided at outlet of evaporator to determine temperature at outlet of the evaporator;
a first pressure sensor provided at inlet of compressor to determine suction pressure;
a second pressure sensor provided at outlet of compressor to determine discharge pressure; and
a control unit configured to:
receive temperature information from the temperature sensors;
receive pressure information from the pressure sensors;
determine a sub-cool value or a superheat value based on temperature information and pressure information;
determine required quantity of refrigerant to be filled in the refrigeration system based upon the sub-cool value or the superheat value; and
operate the gas cylinder to release the required quantity of refrigerant to the refrigeration system.
2. The system as claimed in claim 1, wherein the temperature sensor is a thermocouple.
3. The system as claimed in claim 1, wherein the method comprising the step of comparing the sub-cool value or the superheat value with preset values.
4. A method for filling refrigerant into a refrigeration system, the method comprising the steps of:
monitoring weight of a gas cylinder containing the refrigerant, the gas cylinder connected with charging ports of the refrigeration system;
obtaining by temperature sensors temperature at inlet and outlet of condenser, temperature at inlet and outlet of compressor, temperature at inlet of expansion valve, and temperature at outlet of evaporator;
obtaining by pressure sensors pressure suction pressure and discharge pressure of the compressor; and
receiving at a control unit weight information of the gas cylinder, temperature information from the temperature sensors, and pressure information from the pressure sensors;
determining a sub-cool value or superheat value based on temperature information and pressure information;
determining required quantity of refrigerant to be filled in the refrigeration system based upon the sub-cool value or the superheat value; and
operating the gas cylinder to release the required quantity of refrigerant to the refrigeration system.
5. The method as claimed in claim 4, wherein the method comprising the step of comparing the sub-cool value or the superheat value with preset values.
6. The method as claimed in claim 4, wherein the gas cylinder is operated for a pre-determined amount of time such that a pre-determined quantity of gas is released.
, Description:FIELD OF THE INVENTION
[001] The invention relates to method and system for filling refrigerant into a refrigeration system.

BACKGROUND OF THE INVENTION
[002] Optimum level of refrigerant flowing through a refrigeration system is essential for efficient operation of the refrigerant system. Fluctuation in refrigerant quantity or filling improper quantity of refrigerant causes several problems – over charge of refrigerant causes compressor flooding, and low charge causes thermal over-load of the compressor, which also causes failure of other components of the refrigeration system.
[003] Currently, refrigerant systems are manually charged, whereby the quantity of refrigerant to be filled is manually controlled. Thus, there is a likelihood of improper quantity being filled, which is not desirable.
[004] In view of the above, there is a need in the art for addressing at-least the aforementioned problems.

SUMMARY OF THE INVENTION
[005] Accordingly, the present invention in one aspect provides a system for filling refrigerant into a refrigeration system, the system comprising a weighing scale for monitoring weight of a gas cylinder containing the refrigerant, the gas cylinder connected with charging ports of the refrigeration system; a first temperature sensor and a second temperature sensor provided at inlet and outlet of compressor to determine temperature at inlet and outlet of the compressor; a third temperature sensor and a fourth temperature sensor provided at inlet and outlet of condenser to determine temperature at inlet and outlet of the condenser; a fifth temperature sensor provided at inlet of an expansion valve to determine temperature at inlet of the expansion valve; and a sixth temperature sensor provided at outlet of the evaporator to determine temperature at outlet of the evaporator; a first pressure sensor provided at inlet of compressor to determine suction pressure; a second pressure sensor provided at outlet of compressor to determine discharge pressure; and a control unit configured to receive temperature information from the temperature sensors; receive pressure information from the pressure sensors; determine a sub-cool value or a superheat value based on temperature information and pressure information;
determine required quantity of refrigerant to be filled in the refrigeration system based upon the sub-cool value or the superheat value; and operate the gas cylinder to release the required quantity of refrigerant to the refrigeration system.

[006] In another aspect, the present invention provides a method for filling refrigerant into a refrigeration system, the method comprising the steps of monitoring weight of a gas cylinder containing the refrigerant, the gas cylinder connected with charging ports of the refrigeration system; obtaining by temperature sensors temperature at inlet and outlet of condenser, temperature at inlet and outlet of compressor, temperature at inlet of expansion valve, and temperature at outlet of evaporator; obtaining by pressure sensors pressure suction pressure and discharge pressure of the compressor; and receiving at a control unit weight information of the gas cylinder, temperature information from the temperature sensors, and pressure information from the pressure sensors; determining a sub-cool value or superheat value based on temperature information and pressure information; determining required quantity of refrigerant to be filled in the refrigeration system based upon the sub-cool value or the superheat value; and operating the gas cylinder to release the required quantity of refrigerant to the refrigeration system.

BRIEF DESCRIPTION OF THE DRAWINGS
[007] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 shows a system for filling refrigerant into a refrigeration system in accordance with an embodiment of the invention.
Figure 2 shows a flow diagram of a method for filling refrigerant into a refrigeration system in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[008] The present invention is directed towards filling refrigerant into a refrigeration system whereby an optimum amount of refrigerant is introduced/filled into the refrigerant system.
[009] Figure 1 shows a system 100 for filling refrigerant into a refrigeration system 10. The refrigeration system comprises of a compressor, a condenser, an expansion device and an evaporator coil connected in serial refrigerant flow relationship. The system of the present invention comprises a weighing scale 110, plurality of temperature sensors 120, plurality of pressure sensors 130, and a control unit 140.
[010] The refrigerant to be filled in the refrigeration system is contained in a gas cylinder X. The gas cylinder is connected with charging ports of the refrigeration system, and placed on the weighing scale. The weighing scale monitors the weight of the gas cylinder, and provides the information to the control unit.
[011] The temperature sensors include a first temperature sensor provided at inlet of the compressor, a second temperature sensor provided at outlet of the compressor, a third temperature sensor provided at inlet of the condenser, a fourth temperature sensor provided at outlet of the condenser, a fifth temperature sensor provided at inlet of the expansion valve, and a sixth temperature sensor provided at outlet of the evaporator. The temperature sensors are thermocouples, thermistors or the like, and the temperature measured by the temperature sensors are provided to the control unit.
[012] The pressure sensors include a first pressure sensor provided at inlet of compressor to determine suction pressure, and a second pressure sensor provided at outlet of compressor to determine discharge pressure of the compressor, and the pressure measured is provided to the control unit.
[013] The control unit is configured to receive weight information of the gas cylinder, temperature information from the temperature sensors, and pressure information from the pressure sensors, and is configured to determine a sub-cool value or a superheat value. The sub-cool value is determined based upon temperature at condenser current/Instantaneous temperature at the condenser outlet, and liquid saturation temperature at high pressure at the condenser. The superheat value is determined based upon current/instantaneous temperature at the compressor inlet and vapour saturation temperature at the compressor.
[014] Once the sub-cool value or the superheat value is obtained, the quantity of required refrigerant to be filled based on the sub-cool value or the superheat value is determined. In this regard, it may be noted that high sub-cool value means that there is excess refrigerant being held in the condenser whereas low sub-cool value means less refrigerant is held in the condenser. With regard to superheat value, high superheat value means system is running low on refrigerant, and high superheat value means system is overcharged with refrigerant. Accordingly, based on the sub-cool value or the superheat value amount of refrigerant in the refrigeration system can be determined. In an embodiment, the system has a preset sub-cool value and a preset superheat value. The sub-cool value or the superheat value determined by the system is compared with the preset values to check if there is any deviation from such pre-set values. Any deviation in the pre-set values indicates that the system is overcharged with refrigerant or is running low in refrigerant.
[015] Thereafter, the control unit operates the gas cylinder to fill the required refrigerant or stop flow of refrigerant depending upon the super-heat or subcool values. In this regard, a valve of the gas cylinder is operated for a pre-determined amount of time such that a pre-determined quantity of gas is released such that the refrigerant system reaches the pre-set sub-cool value and/or the pre-set superheat value. The weighing scale at this instant continues to monitor the weight of the cylinder and provide weight information to the control unit so as to track the amount of gas being released.
[016] Further, the system comprises of a display 150 for displaying all parameters measured by the system.

[017] Figure 2 shows a flow diagram of a method for filling refrigerant into a refrigeration system. The method at step 2A, monitors weight of a gas cylinder connected with refrigerant ports of the refrigeration system. Thereafter, at step 2B, temperature sensors measure/obtain temperature at inlet and outlet of condenser, temperature at inlet and outlet of compressor, and temperature at inlet of expansion valve, and temperature at outlet of evaporator. At step 2C, pressure sensor obtains suction pressure and discharge pressure of the compressor. Once, all aforementioned parameters are obtained, at step 2D, a control unit determines a sub-cool value or a superheat value, and determines at step 2E the quantity of required refrigerant to be filled based on the sub-cool value or the superheat value. The sub-cool value is determined based upon temperature at condenser current/Instantaneous temperature at the condenser outlet, and liquid saturation temperature at the same high pressure at the condenser. The superheat value is determined based upon current/instantaneous temperature at the compressor inlet and vapour saturation temperature at the compressor.
[018] Once the sub-cool value or the superheat value is obtained, the quantity of required refrigerant to be filled based on the sub-cool value or the superheat value is determined. In this regard, it may be noted that high sub-cool value means that there is excess refrigerant being held in the condenser whereas low sub-cool value means less refrigerant is held in the condenser.
[019] With regard to superheat value, high superheat value means system is running low in refrigerant, and high superheat value means system is overcharges with refrigerant. Accordingly, based on the sub-cool value or the superheat value amount of refrigerant in the refrigeration system can be determined. In an embodiment, the method has a preset sub-cool value and a preset superheat value. The sub-cool value or the superheat value determined by the method is compared with the preset values to check if there is any deviation from such pre-set values. Any deviation in the pre-set values indicates that the system is overcharged with refrigerant or is running low in refrigerant.
[020] Thereafter, the control unit at step 2F operates the gas cylinder to fill the required refrigerant or stop flow of refrigerant depending upon the super-heat or subcool values. In this regard, a valve of the gas cylinder is operated for a pre-determined amount of time such that a pre-determined quantity of gas is released such that the refrigerant system reaches the pre-set sub-cool value and/or the pre-set superheat value. The weighing scale at this instant continues to monitor the weight of the cylinder and provide weight information to the control unit so as to track the amount of gas being released.
[021] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.