【Q&A Question 120】April 30, 2018

The higher the compression ratio, the greater the load on the compressor, and the exhaust temperature will rise, which can cause damage to the compressor valves. Excessive load can have an impact on the motor.

Dangers of excessive pressure ratio: 1. It leads to a decrease in volumetric efficiency; when this decrease reaches a certain level, the compressor’s gas delivery coefficient becomes 0, and the compressor can hardly draw in refrigerant vapor, thereby losing its cooling capacity. 2. It causes the actual compression process to deviate more from the ideal condition, resulting in increased actual power consumption of the refrigeration compressor, reduced efficiency, and a lower coefficient of performance. 3. This inevitably leads to an increase in the exhaust temperature of the refrigeration compressor, sometimes even exceeding the allowable limit for that temperature. At the same time, excessively high exhaust temperature can also affect the proper operation of the refrigeration cycle. 4. Generally, the pressure ratio n for compressors in use is ≤8; for piston-type refrigeration compressors using Freon refrigerants, this ratio is ≤10. For centrifugal refrigeration compressors, the maximum achievable pressure ratio is ≤4. For these reasons, at a condensation temperature of 35°C, the lowest evaporation temperatures that can be achieved with different refrigerants are as follows: R717 = -22°C, R12 = -33°C, R22 = -34°C, R134A = -37°C. In summary, in some refrigeration systems, Freon-based single-stage systems can operate at medium temperature levels, whereas ammonia-based systems require a two-stage system to achieve better performance. It is also for this reason that some customers choose Freon systems: in certain compressors with advanced technology, such as those from Bitzer, single-stage systems are used to handle low-temperature conditions, and they can also be utilized for high-temperature conditions as well (but only in companies with advanced technical capabilities). Additionally, using supplementary liquid spraying can also meet the requirements for lower temperatures (for certain types of refrigeration screw units). If the compression ratio is too low, it’s simply like using a powerful engine for a small task, which results in wasted electrical energy.

⑴An excessively high compression ratio can cause the compressor’s terminal temperature to rise, leading to a decrease in the viscosity of the lubricating oil, coking, and softening of the packing. ⑵The relative volume of the cylinder decreases, while the volume occupied by the high-pressure residual gas inside the cylinder during expansion increases relatively. ⑶It has higher power consumption compared to multi-stage compression under the same pressure. ⑷The crankshaft experiences large fluctuations in load, frequent vibrations, and high levels of shock. ⑸If the compression ratio is too low, the number of compression cycles increases and the structure becomes more complex

⑴An excessively high compression ratio can cause the compressor’s terminal temperature to rise, leading to a decrease in the viscosity of the lubricating oil, coking, and softening of the packing. ⑵The relative volume of the cylinder decreases, while the volume occupied by the high-pressure residual gas inside the cylinder during expansion increases relatively. ⑶It has higher power consumption compared to multi-stage compression under the same pressure. ⑷The crankshaft experiences large fluctuations in load, frequent vibrations, and high levels of shock. ⑸If the compression ratio is too low, the number of compression cycles increases and the structure becomes more complex

⑴An excessively high compression ratio can cause the compressor’s terminal temperature to rise, leading to a decrease in the viscosity of the lubricating oil, coking, and softening of the packing. ⑵The relative volume of the cylinder decreases, and the high-pressure residual gas inside the cylinder occupies more space during expansion.

⑴An excessively high compression ratio can cause the compressor’s terminal temperature to rise, leading to a decrease in the viscosity of the lubricating oil, coking, and softening of the packing. ⑵The relative volume of the cylinder decreases, while the volume occupied by the high-pressure residual gas inside the cylinder during expansion increases relatively. ⑶It has higher power consumption compared to multi-stage compression under the same pressure. ⑷The crankshaft experiences large fluctuations in load, frequent vibrations, and high levels of shock. ⑸If the compression ratio is too low, the number of compression cycles increases and the structure becomes more complex.

The higher the compression ratio, the greater the load on the compressor, and the exhaust temperature will rise, which can cause damage to the compressor valves. Excessive load can have an impact on the motor.

⑴An excessively high compression ratio can cause the compressor’s terminal temperature to rise, leading to a decrease in the viscosity of the lubricating oil, coking, and softening of the packing. ⑵The relative volume of the cylinder decreases, while the volume occupied by the high-pressure residual gas inside the cylinder during expansion increases relatively. ⑶It has higher power consumption compared to multi-stage compression under the same pressure. ⑷The crankshaft experiences large fluctuations in load, frequent vibrations, and high levels of shock. ⑸If the compression ratio is too low, the number of compression cycles increases and the structure becomes more complex.

⑴An excessively high compression ratio can cause the compressor’s terminal temperature to rise, leading to a decrease in the viscosity of the lubricating oil, coking, and softening of the packing. ⑵The relative volume of the cylinder decreases, while the volume occupied by the high-pressure residual gas inside the cylinder during expansion increases relatively. ⑶It has higher power consumption compared to multi-stage compression under the same pressure. ⑷The crankshaft experiences large fluctuations in load, frequent vibrations, and high levels of shock. ⑸If the compression ratio is too low, the number of compression cycles increases and the structure becomes more complex.

The higher the compression ratio, the greater the load on the compressor, and the exhaust temperature will rise, which can cause damage to the compressor valves. Excessive load can have an impact on the motor.