Refrigeration systems with two-stage compression are used for the generation of particularly low temperatures. At very low temperatures large pressure differences are required between the evaporator and condenser. In a compressor the volumetric efficiency drops significantly at high pressure ratios.
Therefore, two compressors are connected in series, with each compressor only having a relatively low pressure ratio. This makes a more favourable dimensioning of the low pressure stage compressor possible. Due to the large specific volume it requires a larger capacity at lower drive power.
In addition, intercooling between the low pressure compressor (LP) and the high pressure compressor (HP) reduces the outlet temperature of the HP compressor to harmless values and improves the efficiency of the compression.
Learning Objectives/Experiments
- Design and function of a refrigeration system with two-stage compression and injection intercooling
- Effect of the inlet temperature at the HP compressor on the efficiency of the compression
- With intercooling
- Without intercooling
- Effect of the additional refrigerant intercooling
- Distribution of the compressor pressure ratios
- Represent and understand the refrigeration cycle process in the log p-h diagram
Specification
- Refrigeration system with two-stage compression
- Hermetic low and high pressure compressors
- Adjustable intercooling via refrigerant injection
- Heat exchange for additional supercooling of the liquid refrigerant
- Closed refrigeration chamber contains evaporator with fan and adjustable electric heater as cooling load
- Digital display for temperatures, drive power of the compressors and cooling load power
- Real-time representation of the process in the log p-h diagram of the software
Technical Specification
- Low Pressure Compressor (LP)
- Power Consumption: 275W At -10/55°C
- Refrigeration Capacity: 583W At -10/55°C
- High Pressure Compressor (HP)
- Power Consumption: Aprrox. 841W At -25/55°C
- Refrigeration Capacity: 702W At -25/55°C
- Refrigerant
- R449A
- GWP: 1397
- Filling Volume: 1,29kg
- CO2-Equivalent: 1,8t
- Measuring Ranges
- Flow Rate: 2…29L/H, 4…40L/H
- Pressure: 1x -1…15bar, 2x -1…24bar
- Temperature: 8x -75…125°C
Power:
- 0…562W (Heater)
- 0…750W (LP Compressor)
- 0…2250W (HP Compressor)
- 230V, 50Hz, 1 Phase
- 230V, 60Hz, 1 Phase
- 230V, 60Hz, 3 phases
