In a common refrigeration process, a refrigerant starts in the form of a vapor at or slightly above ambient temperature. This vapor enters a compressor and exits the compressor at a high temperature and high pressure. This vapor then travels under pressure through a condenser. The condenser comprises a series of tubes that are passively cooled by air, water, or glycol. By traveling through the condenser, the vapor is brought to a lower temperature, but remains at a high pressure. Because of this, the vapor becomes a liquid. When this liquid exits the condenser and passes through a type of restriction, the pressure suddenly decreases. The evaporation and expansion of the liquid causes a large decrease in temperature and pressure. This now cold vapor passes through the tubes of an evaporator. A fan blows ambient air over the cold tubes of the evaporator, which produces cooled air.
At the liquid outlet of the condenser, it is expected that only liquid refrigerant will be present. The number of degrees that the liquid temperature is cooler than the saturation temperature corresponding to the liquid pressure is called the liquid subcooling. The subcooling is a measure of the effectiveness of the condenser and relates to proper refrigerant charge.
At the outlet of the evaporator, it is expected that only vapor refrigerant will be present. The number of degrees that the vapor temperature is warmer than the saturation temperature corresponding to the vapor pressure is called the superheat. The superheat is a measure of the effectiveness of the evaporator and relates to the refrigerant charge.
The saturation temperature, as mentioned above, corresponds to a pressure of the refrigerant. If the pressure of the refrigerant and the type of refrigerant is known, the saturation temperature may be determined. Different refrigerants have different relationships between pressure and saturation temperature, but for a given refrigerant, a chart or formula may readily express the relationship.
Therefore, in order to calculate the superheat or subcooling of a refrigeration system, a user must first know the type of refrigerant and the pressure of the refrigerant in the refrigeration system. Then the user must determine the saturation temperature using the measured pressure and the chart or formula corresponding to the known refrigerant. Then the user must measure the actual temperature of the refrigerant and compare this value to the determined saturation temperature. To determine the subcooling, the user by subtract the actual refrigerant temperature from the saturation temperature, and to determine the superheat, the user would subtract the saturation temperature from the actual refrigerant temperature.
Refrigeration systems may be provided with service ports as a means to take these measurements. These service ports may be at one or more locations to provide the user access to both the refrigerant in the condenser and the evaporator.
Hand held refrigeration gauges are known to provide refrigeration details and information to a user such as disclosed by U.S. Pat. No. 6,898,979. However, not all the necessary features for accurate subcooling and superheat determination are disclosed. The gauge disclosed does not provide a temperature sensor, but only a pressure sensor. In addition, the gauge disclosed does not provide a user interface. Also, the gauge disclosed does not provide means by which a user may interact with the operations and calculations of the gauge.
The present inventor has recognized the need for a refrigeration gauge that may be held in the hand of a user.
The present inventor has further recognized the need for a refrigeration gauge that has an easy-to-use user interface.
The present inventor has further recognized the need for a refrigeration gauge that may measure both pressure and temperature.
The present inventor has further recognized the need for a refrigeration gauge that may, given the necessary data, calculate values for superheat and/or subcooling.
The present inventor has further recognized the need for a refrigeration gauge that may accept types of input from the user.
USPTO Backgrounds
USPTO Backgrounds