Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B49/00—Arrangement or mounting of control or safety devices
  • F25B49/005—Arrangement or mounting of control or safety devices of safety devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B49/00—Arrangement or mounting of control or safety devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2500/00—Problems to be solved
  • F25B2500/22—Preventing, detecting or repairing leaks of refrigeration fluids
  • F25B2500/222—Detecting refrigerant leaks

Definitions

• the invention relates to an automatic refrigerant leak detection system of indirect means designed to be used on air conditioning, cooling and refrigeration units installed on vehicles and other transportation means.
• air conditioning, cooling and refrigeration units will be referred to in the remaining text as cooling unit.
• the cooling units contain refrigerants under high pressure. Cooling units installed on vehicles and other transport means and in general all those located in mobile sites often have problems due to leakage of refrigerant.
• Leak check with the use of special dyes, either alone or in combination with special ultraviolet lamp. • Leak check with the use of mobile electronic leak detection equipment that have electronic sensors for detecting the presence of refrigerant (corona, heated diode, etc.).
• Cooling units are fitted with safety devices as well as control and monitoring systems for their operation. These include pressure switches or pressure sensors that are used in the low and high pressure branches to protect the compressor, and anti-frost thermostats to engage / disengage the compressor.
• the above control systems for car and other means of transportation cooling units control individual pressures and temperatures in different parts of the circuit. Their tasks are to protect the circuit from operating with very low refrigerant charge or to ensure proper operation of the cooling unit.
• These switches and sensors are usually installed in series. It is therefore obvious that these give independent output signals, which control the activation or de-activation of the unit either as direct switches or indirectly through an algorithm.
• the automatic refrigerant leak detection system of indirect means designed to be used on air conditioning, cooling and refrigeration units installed on vehicles and other transportation means refers to a device, which monitors the operating parameters of a cooling unit, and specifically monitors / controls the temperature and pressure conditions and revolutions of its parts, as described in detail below.
• the system estimates the amount of refrigerant within the cooling unit as a percentage of the optimum charging (specified by the manufacturer of the cooling unit) and produces a signal when the quantity is not within tolerance.
• the proposed system eliminates the problem of late diagnosis of leak as
• the attached schematic diagram shows a typical form of vehicle cooling unit.
• the refrigerant is compressed in the compressor (3) and then passes through the condenser (4) where it is cooled and condensed with or without the use of a fan (1) by the air of the environment (A).
• the refrigerant continues the cycle (flow in accordance with the arrows) passes through the receiver dryer (6) and then expands passing through the expansion valve (7).
• the heat exchanger 10 it evaporates absorbing heat from the recycled air (D) or the environment air (C) giving air conditioned air (E).
• cooling unit In this typical form of cooling unit are installed (or are utilized if available) some or all of the following sensors depending on the form and type of the cooling, refrigeration or air conditioning unit and its corresponding critical parameters as specified by the manufacturer:
• External / environment air temperature sensor This sensor is installed in the airflow before the condenser or condenser fan (1) and measures the temperature of the air supply to the condenser.
• the type of sensor and its mode of operation is not restrictive.
• a typical type is a sensor with resistance proportional to the temperature, either NTC or PTC .
• the sensor is used to measure the external temperature (A) and feed this information to the CPU. Usually such a sensor is available in vehicles and is used to inform the driver about the external temperature.
• Pressure sensor in high pressure branch This sensor is installed in the high pressure branch of the cooling unit preferably before the receiver dryer (6). (This is not always possible since in some late model cooling units the manufacturers use a receiver dryer built-into the condenser (4)).
• the type of the sensor and its mode of operation are not restrictive.
• the first type uses one earth cable, a 5V volt input and an output that is proportional to the pressure.
• the second type creates a pulse that has a frequency that is proportional to the pressure.
• the sensor is used to measure the pressure in the high pressure branch of the cooling unit and feed this information to the CPU.
• such a sensor is available and its primary function is to activate the condensing fan and compressor. If the sensor is present its output can be fed to the CPU.
• the pressure sensor In the rest of the vehicles that use a pressure switch (high / medium / low) the pressure sensor must be added. > (9) Evaporator temperature sensor.
• This sensor is installed in the flow of air from the evaporator (10).
• the type of sensor and its mode of operation is not restrictive.
• a typical type is a sensor with resistance proportional to the temperature, either NTC or PTC .
• the sensor is used to measure the temperature of the air leaving the evaporator (R) which is the temperature of evaporation and feeds this information to the CPU.
• R the temperature of the air leaving the evaporator
• PTC PTC
• Pressure sensor in the low pressure branch This sensor is installed in the low pressure branch of the cooling unit between the evaporator (10) and the compressor.
• the type and mode of operation is not restrictive.
• the second type creates a pulse that has a frequency that is proportional to the pressure.
• the sensor is used to measure, the pressure in the low- pressure branch of the cooling unit and feed this information to the CPU. Such a sensor is not integrated in typical cooling units.
• Temperature sensor for the monitoring of the temperature of the air conditioned space. This sensor is installed in the flow of air towards the evaporator (10).
• the type of sensor and its mode of operation is not restrictive. A typical type is a sensor with resistance proportional to the temperature, either NTC or PTC .
• the sensor is used to measure the temperature of the air entering the evaporator (E) and feed this information to the CPU. Usually such a sensor is available in vehicles and in refrigeration units and it is used for the recording of the temperature of the chamber (passenger cabin/ cold storage space).
• Engine speed sensor The sensor is used to measure the RPM of the engine and feed this information to the CPU. Such a sensor is available in vehicles and it is used to control the engine.
• These sensors (T), (5), (9), (11), (12) and (13) send signals to a central processing unit CPU (14).
• the CPU is integrated in the cooling unit and compares the measurements from the sensors (2), (5), (9), (11), (12) and
• Step one the critical operating parameters and their values are retrieved from the ROM of the CPU (time needed for the pressures to stabilize).
• the device verifies that the pressures of the cooling unit are balanced, as it is not possible to draw any conclusions at startup and before the pressures are balanced.
• the sensor (2) reads the ambient temperature and the remaining critical operating parameters (compressor activation rate from CPU (13), cooled space temperature from sensor (12), etc.). The data is stored in the CPU as a function of the condensation temperature. The values corresponding to the condensation temperature that was measured by the sensor (2), of the other critical operating parameters are recovered from the
• the high pressure measured by the pressure sensor (5) in the high pressure branch is compared to the stored data of the high pressure that corresponds to the condensation temperature measured.
• the high pressure measured is higher than normal it is not possible to have low charge and the only conclusions reached are auxiliary diagnostic conclusions as presented in the logical diagram. If the high pressure measured is normal or lower than normal, to determine whether there is insufficient refrigerant charge it is necessary to measure additional data that is then processed and compared with the stored specifications in step two.
• Step two of the algorithm is to compare the data measured by the pressure sensor (11) in the branch of low pressure with the low pressure stored on the CPU No (14) that corresponds to the high pressure. If the low pressure is higher than the normal it is not possible to have low charge and the only conclusions reached are auxiliary diagnostic conclusions as presented in the logical diagram.
• step three If the low pressure is normal or lower than normal not within the specifications range, it is necessary to measure additional data that is then processed and compared with the stored specifications in step three.
• Step three of the algorithm is to compare the data measured by the evaporation temperature sensor (9) with the evaporation temperature stored on the CPU No (14) that corresponds to the low pressure. If the measured evaporation temperature is higher then the specifications the filling of the unit is insufficient and therefore a leakage has occurred.
• the proposed leak detection system produces a signal which can be further processed to inform the user.
• This invention combines the use of a CPU in the memory of which are stored the critical operating parameters, and their values specified by manufacturer for the operating conditions (engine speed) and compares them with data measured from two pressure sensors and two temperature sensors in order to diagnose a leak at its inception.
• the application of this invention is possible without significant cost in modern cars which include both external temperature sensor and internal temperature sensor (evaporation temperature). Manny also include pressure sensor for the monitoring of the high pressure. Their use, however, is limited to the management of the air conditioner components only (activate fans (1) and (8) and compressor (3)). The data acquired by these sensors are neither processed further nor combined. IN most cases their use is limited once fed to the CPU of the vehicle to the operating speed of the fans and the activation of the compressor.
• the proposed automatic refrigerant leak detection method of indirect means designed to be used on air conditioning, cooling and refrigeration units installed on vehicles and other transportation means has a different set of parameters depending on the air conditioning unit in which it is integrated.
• the stored critical operating parameters such as type of refrigerant, engine revolutions in relation to compressor revolutions, refrigerant pressure in the high pressure branch, evaporator temperature, low pressure branch pressure, as a function of the condensing temperature, compressor activation rate for variable compressor etc are recovered and compared to the values of the critical operating parameters that are drawn from corresponding sensors during the unit's operation .
• the above example is not restrictive, since the algorithm can be operated with more data which need to be recorded as additional critical parameters. Other factors affecting the algorithm are the compression rate, the condensation rate, the type of refrigeration circuit/system, the type of compressor and the location of the sensors.
• the temperature of the air-conditioned space varies only by 10 0 C.
• the evaporation temperature varies greatly from the ambient temperature of the conditioned space. Therefore the ambient temperature is not a critical parameter.
• the temperature inside the refrigeration chamber varies a lot and the fluctuation could be in the range of 60 0 C.
• the ambient temperature inside the refrigeration chamber is very close to the evaporation temperature. This has a significant impact to the optimum operation conditions and therefore the refrigeration chamber ambient temperature is classified as a critical parameter.
• the ambient temperature data can be measured by the temperature recording device of the refrigeration chamber.
• the algorithm discussed and analyzed above is presented in detail in the attached flowchart.
• the sensors that were selected are of piezoelectric type, which have an output voltage proportional to the pressure of the refrigerant in the unit's branch. Sensors that operate with a pulse could also be used, as the type of sensor is not essential characteristic of the invention. As a result the type of sensors that can be used is not limited to the above mentioned types, since any type of data can be processed to monitor the pressure.
• the temperature sensors used are of variable resistance type with positive or negative response (PTC or NTC). The position that the sensors are installed for the of measuring of the condensation and evaporation temperature is not essential characteristic of the invention, neither is the type of sensors used limited in the above mentioned types, since any type of data can be processed to monitor the operating temperature.
• the data of the manufacturer's specifications and the critical operating parameters are stored sorted by condensation temperature.
• the data of the remaining values depend on the condensation temperature.
• the condensation temperature measured is related to the corresponding stored data. From the stored data for the specific temperature the values of the other parameters are drawn. These are compared to the values measured by the sensors. From this comparison the algorithm draws conclusions regarding the filling of the cooling unit with refrigerant and the percentage (%) off loss is estimated. Any conclusion of loss greater than the considered by the manufacturer as normal, for this cooling unit, is evaluated as leak and a signal is given out by the system. This signal can be further processed. (As an indication, depending on the size of the cooling unit and its use, it could be triggering an alarm, or activate a warning lamp, etc.).
• the proposed automatic leak detection system of indirect means in cooling unit may include a mechanism that activates the cooling unit at regular intervals, for the necessary time to balance the pressures and to take the necessary measurements. (The interval between two successive activations, the minimum operating time etc. data, is recorded in the database as critical factors of operation).
• the advantage of this invention is that it combines the data, which is available from the sensors with the cooling unit's manufacturer's specifications. Making comparisons the algorithm estimates the refrigerant charging, as a percentage of the optimum fill (specified). Based on the results it can diagnose a leakage and predict the complete deactivation of the cooling unit before it occurs.
• the automatic refrigerant leak detection method of indirect means applicable to air conditioning, cooling and refrigeration units installed on vehicles and other transportation means at the same time can serve as a device to verify the correct filling of the cooling unit with refrigerant during the periodic maintenance. In the case of improper filling, the craftsman will receive an error signal. He can then correct the problem immediately, and when used in this manner it can be considered as a diagnostic tool.
• a stand alone multy parameter automatic refrigerant leak detection device of indirect means for cooling units can serve as a repair and maintenance tool for cooling units. Used in cooling units that do not have it built in, it can diagnose problems, being a useful tool for repair and maintenance.
• This device would have to include two temperature sensors to be placed respectively in the flow of air into a condenser and the evaporator by the technician performing maintenance and two quick couplers to be connected to the low and high pressure charging ports. Fom the ports the pressure sensors will receive the information for the pressure in the high and low pressure branch of the cooling unit. It would also have to be connected to the central processing unit of the vehicle / transportation mean to receive data such as engine speed and the percentage (%) of activation of the compressor.
• Attached follows the logical diagram of the operation of the control algorithm of the stand alone multy parameter maintenance tool (Pg 4), the analysis of which is identical with that of the above indirect leak detection device with the only difference being the output of warning signs for any malfunction.
• the numbering of the parts relates to the schematic diagram (Pg 3).

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Examining Or Testing Airtightness (AREA)
• Air-Conditioning For Vehicles (AREA)

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Cited By (19)

Citations (6)

• 2008
  • 2008-07-14 GR GR20080100468A patent/GR1006642B/el not_active IP Right Cessation
• 2009
  • 2009-07-13 WO PCT/GR2009/000050 patent/WO2010007448A1/en active Application Filing

Patent Citations (6)

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