Determination of Sound Power Level for Volumetric Compressors According to GB4980-85
1. Introduction
The aim of this project is to study the determination of sound power level for volumetric compressors according to GB4980-85. Sound power level, which is a measure of acoustic power emitted by a sound source, is an important parameter for acoustics measurement, and sound power level measurement is a common practice for compressor evaluation. This project will discuss the details of the sound power level measurements of volumetric compressors.
2. Compressor classification
IC compressors, which are widely used in many industries for air conditioning and refrigeration, are classified into two types according to the method of delivery. The first involves volumetric compressors, in which the volume of the cold gas remains constant throughout the delivery stroke of the compressor. The second method involves fixed-volume, or displacement compressors, in which the entire delivery stroke of the compressor, variable or fixed, is devoted to delivering the cooling medium. Volumetric compressors, also referred to as dynamic compressors, are the most commonly used type and are therefore the focus of this project.
3. Sound power level measurement according to GB4980-85
The sound power level of volumetric compressors should be measured according to the standard GB4980-85. The standard specifies the test conditions for determining the sound power level and is applicable for the W12cm sheet, gasket and motor protection frames.
The test conditions specified by the standard include the following:
• Room size: The room size should be at least 5m × 5m × 3m (L × W × H), and all of the walls in the room should be covered with sound-absorbing material with a minimum sound absorption coefficient of 0.5.
• Sound source: The sound source should be the electric motor driving the volumetric compressor.
• Measurement sources: The measurement microphone should be located in the center of the room at the volume of the sound source.
• Sound pressure level: The sound pressure level in the room should be between 45dB and 80dB.
• Measurement time: The measurement time should be at least one minute.
4. Conclusion
In conclusion, the standard GB4980-85 provides the measurement procedure of sound power level for volumetric compressors. The standard requires the particular conditions of the test room, such as room size, sound source, measurement sources, sound pressure level and measurement time, so as to obtain accurate results of the sound power level from volumetric compressors.
