KOK YIN HUI (MY)
LIM CHING HON (MY)
KR20010076425A | 2001-08-16 | |||
CN106016867A | 2016-10-12 | |||
CN107975988A | 2018-05-01 | |||
US20060137366A1 | 2006-06-29 |
CLAIMS 1. A system for determining refrigerant charge status of an air conditioner comprising a processor for executing operation of the system; and a determining module for determining the refrigerant charge status through a value obtained by comparing a measured saturated fluid property with a predicted saturated fluid property that is computed based on a measured indoor ambient temperature and a measured outdoor ambient temperature; wherein the refrigerant charge status is considered overcharged when the value exceeds a range of normal charge level, and the refrigeration charge status is considered undercharged when the value is less than the range of normal charge level. 2. The system according to claim 1, further comprising a measuring device for obtaining the measured indoor ambient temperature, measured outdoor ambient temperature and measured saturated fluid property. 3. The system according to claim 2, wherein the measuring device is any one or a combination of thermistor, pressure sensor, or humidity sensor. 4. The system according to any one of the preceding claims, further comprising a database for storing a set of precomputed predicted saturated fluid property data to obtain the predicted saturated fluid property to be compared with the measured saturated fluid property. 5. The system according to any one of the preceding claims, further comprising a predicting module for computing a predicted saturated fluid property by applying the measured indoor ambient temperature and outdoor ambient temperature into a predetermined equation. 6. The system according to any one of the preceding claims, further comprising an activation element for initiating process for determining the refrigerant charge status. 7. The system according to any one of the preceding claims, further comprising an indicator for presenting the determined refrigerant charge status. 8. The system according to any one of the preceding claims, wherein the fluid property is temperature or pressure. 9. The system according to any one of the preceding claims, wherein the measured indoor ambient temperature is indoor wet bulb temperature. 10. The system according to any one of the preceding claims, wherein the measured outdoor ambient temperature is outdoor dry bulb temperature. 11. The system according to any one of the preceding claims, wherein the saturated fluid property is evaporator inlet temperature, evaporator inlet pressure, evaporator outlet pressure or suction pressure. 12. The system according to any one of the preceding claims, wherein the air conditioner is an inverter air conditioner. 13. A method executed by a system having a processor for determining refrigerant charge status of an air conditioner, the method comprising the step of obtaining (170) a value through comparing a measured saturated fluid property with a predicted saturated fluid property that is computed based on a measured indoor ambient temperature and a measured outdoor ambient temperature; wherein the refrigerant charge status is determined as overcharged when the value exceeds a range of normal charge level, and the refrigeration charge status is determined as undercharged when the value is less than the range of normal charge level. 14. The method according to claim 13, further comprising the step of maintaining (130) any one or a combination of a compressor frequency, expansion valve opening dimension, indoor unit fan speed and outdoor unit fan speed at a constant value when the method is conducted. 15. The method according to claim 13 or 14, wherein the measured indoor ambient temperature, measured outdoor ambient temperature, and measured saturated fluid property are obtained (140) by a measuring device. 16. The method according to any one of claims 13 to 15, further comprising the step of obtaining (150) the predicted saturated fluid property from a set of precomputed predicted saturated fluid property data stored in a database prior to comparing the predicted saturated fluid property with the measured saturated fluid property. 17. The method according to any one of claims 13 to 16, wherein the predicted saturated fluid property is computed by applying the measured indoor ambient temperature and measured outdoor ambient temperature into a predetermined equation. 18. The method according to any one of claims 13 to 17, wherein the fluid property is temperature or pressure. 19. The method according to any one of claims 13 to 18, wherein the indoor ambient temperature is indoor wet bulb temperature. 20. The method according to any one of claims 13 to 19, wherein the outdoor ambient temperature is outdoor dry bulb temperature. 21. The method according to any one of claims 13 to 20, wherein the saturated fluid property is evaporator inlet temperature, evaporator inlet pressure, evaporator outlet pressure or suction pressure. 22. The method according to any one of claims 13 to 21, wherein the system is an inverter air conditioner. 23. The method according to any one of claims 13 to 22, further comprising the step of deactivating (120) inverter mode of the inverter air conditioner at the start of the method. |
FIELD OF INVENTION
This invention relates to a system and method for determining refrigerant charge status of an air conditioner. In particular, the invention is applied for conducting commissioning process of the air conditioner.
BACKGROUND OF THE INVENTION
Commissioning is a crucial process to assure operation requirement is met for an air conditioner. This process is needed for modelling, installation and maintenance of air conditioner. One of the items required for checking during the commissioning process is the refrigerant charge status to ensure the refrigerant is within a range of factory set level that allows the air conditioner to operate at a normal state. If the refrigerant amount exceeds the factory set level range, the air conditioner is deemed overcharged. Conversely, if the refrigerant amount is less than the factory set level range, the air conditioner is considered undercharged.
An overcharged air conditioner results in several issues including high head pressure that affects cooling performance as well as backflow of liquid refrigerant and oil dilution that can cause component failure, especially compressor damage. On the other hand, an undercharged air conditioner results in high superheat, low mass flow rate, low subcooling and overheating problems. The happening of high superheat causes water splitting whereas low mass flow rate is the reason for loss of cooling capacity. Noise is created by low subcooling and overheating damages components of the air conditioner. Commonly, to detect refrigerant charge level, subcooling or superheat measurements are applied with superheat indicating the amount of refrigerant in the evaporator and subcooling indicating the amount of refrigerant in the condenser. For example, US6571566B1 introduced a method for determining refrigerant charge level in a space temperature conditioning system. Both condenser subcooling and evaporator superheat parameters are measured for establishing a relationship with refrigerant charge level to determine an actual refrigerant charge level. Besides that, US5987903A discloses the use of a charge detection device for detecting a refrigerant charge in an air conditioner. The charge detection device determines difference between an actual subcooling value and a desirable sub cooling value during operation of the air conditioner. If the difference between the values is outside of an acceptable predetermined range, the air conditioner is concluded to be experiencing overcharged or undercharged problem.
However, accurate measurement of supercooling and superheat can be difficult, tedious and time consuming. In certain situations, subcooling and superheat are not able to be measured. Correct subcooling and superheat are difficult to be obtained during heating mode of the air conditioner as they do not provide an actual measurement that reflects the situation inside the coil. By simply checking subcooling or superheat alone, it is difficult to indicate whether the charge is set correctly due to lack of proper guidelines. It is thus important for the present invention to provide an alternative method for determining refrigerant charge status that solves the difficulties and limitations of the supercooling and superheat method.
SUMMARY OF INVENTION
One aspect of the present invention is to provide a system for determining refrigerant charge status of an air conditioner. The system comprises a processor for executing operation of the system; and a determining module for determining the refrigerant charge status through a value obtained by comparing a measured saturated fluid property with a predicted saturated fluid property that is computed based on a measured indoor ambient temperature and a measured outdoor ambient temperature; wherein the refrigerant charge status is considered overcharged when the value exceeds a range of normal charge level, and the refrigeration charge status is considered undercharged when the value is less than the range of normal charge level.
In a preferred embodiment, the system further comprises a measuring device for obtaining the measured indoor ambient temperature, measured outdoor ambient temperature, and measured saturated fluid property.
Preferably, the measuring device is any one or a combination of thermistor, pressure sensor, or humidity sensor.
The system is preferred to further comprise a database for storing a set of precomputed predicted saturated fluid property data to obtain the predicted saturated fluid property to be compared with the measured saturated fluid property.
According to the preferred embodiment, the system further comprises a predicting module for computing a predicted saturated fluid property by applying the measured indoor ambient temperature and outdoor ambient temperature into a predetermined equation.
It is preferred that the system further comprises an activation element for initiating process for determining the refrigerant charge status.
In addition, it is preferred that the system further comprises an indicator for presenting the determined refrigerant charge status. Based on the preferred embodiment, the fluid property is temperature or pressure.
Preferably, the measured indoor ambient temperature is indoor wet bulb temperature.
On the other hand, the measured outdoor ambient temperature is preferred to be outdoor dry bulb temperature.
Besides that, the saturated fluid property is preferred to be evaporator inlet temperature, evaporator inlet pressure, evaporator outlet pressure or suction pressure.
In accordance with the preferred embodiment, the air conditioner is an inverter air conditioner.
Another aspect of the present invention provides a method executed by a system having a processor for determining refrigerant charge status of an air conditioner. The method comprises the step of obtaining a value through comparing a measured saturated fluid property with a predicted saturated fluid property that is computed based on a measured indoor ambient temperature and a measured outdoor ambient temperature; wherein the refrigerant charge status is determined as overcharged when the value exceeds a range of normal charge level, and the refrigeration charge status is determined as undercharged when the value is less than the range of normal charge level.
Based on a preferred embodiment of the invention, the method further comprises the step of maintaining any one or a combination of a compressor frequency, expansion valve opening, indoor unit fan speed and outdoor unit fan speed at a constant value when the method is conducted.
Preferably, the measured indoor ambient temperature, measured outdoor ambient temperature and measured saturated fluid property are obtained by a measuring device.
It is preferred that the method further comprises the step of obtaining the predicted saturated fluid property from a set of precomputed predicted saturated fluid property data stored in a database prior to comparing the predicted saturated fluid property with the measured saturated fluid property.
The predicted saturated fluid property is preferred to be computed by applying the measured indoor ambient temperature and measured outdoor ambient temperature into a predetermined equation.
According to the preferred embodiment, the fluid property is temperature or pressure.
Preferably, the indoor ambient temperature is indoor wet bulb temperature.
On the other hand, the outdoor ambient temperature is preferred to be outdoor dry bulb temperature.
Further, the saturated fluid property is preferred to be evaporator inlet temperature, evaporator inlet pressure, evaporator outlet pressure or suction pressure.
In accordance with the preferred embodiment, the system is an inverter air conditioner.
It is preferred that the method further comprises the step of deactivating inverter mode of the inverter air conditioner at the start of the method.
Accordingly, the present invention provides a solution for determining refrigerant charge status of an air conditioner by the use of the system and method introduced herein during commissioning of the air conditioner. In particular, the invention is targeted for determining refrigerant charge status of an inverter air conditioner that regulates temperature by varying speed of the compressor motor. The system implements the method for determining refrigerant charge status that omits the need for subcooling and superheat measurements which are difficult, tedious and time consuming to be obtained. In addition, complications in obtaining accurate subcooling and superheat measurements can be solved as the present invention utilizes saturated fluid property such as saturated temperature or saturated pressure for determining refrigerant charge status in replace of subcooling and superheat measurements. Thus, measurements required for the present invention do not have to be carried out under restricted situations. Since the saturated fluid property is measured at the evaporator inlet, evaporator outlet or suction area, the measured saturated fluid property is able to provide an accurate reflection of the situation within the coils. The system and method introduced herein are simple, not tedious and less time consuming while providing accurate determination of the refrigerant charge status.
BRIEF DESCRIPTION OF THE DRAWINGS
This invention will now be described in greater detail with reference to the accompanying drawings.
Figure 1 shows a flowchart depicting the steps of the method executed by the system for determining refrigerant charge status.
DETAILED DESCRIPTION OF THE INVENTION
For a better understanding of the invention, preferred embodiments of the invention that are illustrated in the accompanying drawings will be described in detail. Disclosed herein is a system and method for determining refrigerant charge status of an air conditioner. The air conditioner is installed within an area that is capable of providing either or both cooling and heating mode. In particular, the system and method are especially targeted for determining refrigerant charge of inverted air conditioner that changes compressor speed for regulating temperature within the area. Thus, the air conditioner can be an inverter air conditioner which is usually a split air conditioner comprising an indoor unit and an outdoor unit. The indoor unit is installed within the area and produces conditioned air inside the area, whereas the outdoor unit is installed outside of the area. Therefore, in this disclosure, the term‘indoor’ refers to the area subject to conditioned air, whereas the term‘outdoor’ refers to space outside of the area that is not subject to conditioned air.
The system comprises a processor for executing operation of the system through controlling operation of components comprised in the system. The components include modules, devices, elements, database and indicator that are able to communicate with the processor for carrying out process of the method to determine the refrigerant charge status. A control unit exposed at the external of the air conditioner allows user to check the refrigerant charge status. Other than being in the form of a remote control that is separated from the air conditioner, the control unit can also be provided at the housing of the air conditioner, both of which are operable by the user.
An activation element provided by the system is available at the control unit for initiating (110) the method of the present invention to determine the refrigerant charge status, which is usually conducted during installation or maintenance of the air conditioner. The activation element can be a physical button that switches on a circuit for connecting the components of the system to conduct the method, or it can be a virtual button on a display available at the control unit. Upon initiating (110) the method through manipulating the activation element, the system enters a refrigerant charge determination mode. The next step of the method is to control factors that affect heat exchanger performance. It is understood that when there is a change in refrigerant charge, the overall pressure of the air conditioner will also change. Such pressure change will reflect on the saturated temperature. There are several factors that affect performance of heat exchanger which leads to pressure change including compressor frequency, expansion valve opening, indoor unit fan speed, outdoor unit fan speed, indoor ambient temperature and outdoor ambient temperature. The present invention adopts the method in utilising indoor ambient temperature and outdoor ambient temperature as parameters to determine refrigerant charge status. Therefore, the other remaining factors need to be maintained (130) at a constant value when the method is conducted. For inverter air conditioners, the processor deactivates (120) inverter mode of the inverter air conditioner at the start of the method, thereby turning the air conditioner into a non-inverter air conditioner whereby the speed of the air conditioner compressor remains constant and does not vary for regulating temperature.
Following the maintenance (130) of factors that are not intended for use as parameters in the present invention at constant values, measurement of the indoor ambient temperature and outdoor ambient temperature are obtained (140) using measuring devices of the system such as thermistor or humidity sensor. The indoor ambient temperature is indoor wet bulb temperature that can be measured by a humidity sensor. On the other hand, the outdoor ambient temperature is outdoor dry bulb temperature that can be measured by a thermistor. Further, measurement of a saturated fluid property being a saturated temperature or saturated pressure is obtained (140) as the present invention determines refrigerant charge status based on saturated fluid property. The term‘fluid property’ includes temperature and pressure. The saturated fluid property can be measured at the evaporator inlet, evaporator outlet or suction area of the air conditioner through the use of measuring device such as thermistor or pressure sensor. Therefore, the saturated temperature can be the evaporator inlet temperature, whereas the saturated pressure can be the evaporator inlet pressure, evaporator outlet pressure or suction pressure.
Measurements of the indoor ambient temperature being the measured indoor wet bulb temperature, and the outdoor ambient temperature being the measured outdoor dry bulb temperature are then sent to a predicting module of the system for computing a predicted saturated fluid property by applying the measured indoor ambient temperature and outdoor ambient temperature into a predetermined equation. To generate quick and accurate result of the predicted saturated fluid property, a set of precomputed predicted saturated fluid property data can be stored in a database of the system. The set of precomputed predicted saturated fluid property data are computed based on a range of temperature or pressure such that when the predicting module receives information of the measured indoor ambient temperature and the measured outdoor ambient temperature, the predicted saturated fluid property can be timely obtained (150) through retrieving the measurement from the precomputed predicted saturated fluid property data.
Information of the predicted saturated fluid property is then sent to a determining module for determining the refrigerant charge status through a value obtained (160) by comparing the measured saturated fluid property with the predicted saturated fluid property. If the value falls within a range of factory set level that defines a normal charge level, the refrigerant charge status is deemed good. However, if the value exceeds a range of normal charge level, the refrigerant charge status is considered overcharged, whereas if the value is less than the range of normal charge level, the refrigerant charge status is considered undercharged. Both overcharged and undercharged indicate abnormal refrigerant levels, and thus action needs to be taken to rectify the refrigerant charge level. In a preferred embodiment of the invention, the tolerance for the value for saturated temperature is ± 1°C, whereas the tolerance for the value for saturated pressure is ± 5 psi that is approximately equal to ± 6895 N/m. Thus, if the value falls within the tolerance, the refrigerant charge status is deemed within the range of normal charge level. It should be noted that if the measured saturated fluid property is pressure and the predicted saturated fluid property is temperature, the measured saturated pressure can be converted to temperature to be compared with the predicted saturated temperature. Optionally, the predicted saturated temperature can be converted to pressure to be compared with the measured saturated pressure. Conversely, if the measured saturated fluid property is temperature and the predicted saturated fluid property is pressure, the measured saturated temperature can be converted to pressure to be compared with the predicted saturated pressure. Alternatively, the predicted saturated pressure can be converted to temperature for comparing with the measured saturated temperature.
In another situation when the precomputed predicted saturated fluid property data is pressure based, the measured indoor ambient temperature and measured outdoor ambient temperature can be converted to pressure for obtaining the predicted saturated pressure from the precomputed predicted saturated pressure data.
When the refrigerant charge status is determined, the system provides an indication of the outcome through an indicator. The indicator presents (170) the determined refrigerant charge status in a form visually and/or audibly noticeable by the user of the system. In a preferred embodiment, the indicator is an LED light having blinking patterns to indicate the determined refrigerant charge status. Optionally, the indicator can be presented on a display at the control unit.
Although the description above contains many specifications, it is understood that the embodiments of the preferred form are not to be regarded as a departure from the invention and it may be modified within the scope of the appended claims.
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