| period two | ||
| Compressor Capacity Control | ||
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methods of capacity control, many of them function in a manner similar to the | |||
inlet vanes presented in this section of the clinic. | |||
| Inlet vanes “preswirl” the refrigerant before it enters the impeller. By | ||
| changing the refrigerant’s angle of entry, these vanes lessen the ability of the | ||
| impeller to take in the refrigerant. As a result, the compressor’s refrigerant- | ||
| pumping capacity decreases to balance with the evaporator load. | ||
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FDSDFLW\ | Figure 40 |
These curves represent the performance of a typical centrifugal compressor over a range of inlet vane positions. The pressure difference between the compressor inlet (evaporator) and outlet (condenser) is on the vertical axis and compressor capacity is on the horizontal axis. The surge region represents the conditions that cause unstable compressor operation.
As the load on the compressor decreases from the
Less refrigerant, and therefore less heat, are transferred to the condenser. Since the available heat rejection capacity of the condenser is now greater than required, the refrigerant condenses at a lower temperature and pressure. This reduces the pressure difference between the evaporator and the condenser. Continuing along the unloading line, the compressor remains within its stable operating range until it reaches C.
Inlet vanes on a centrifugal compressor allow it to unload over a broad capacity range while preventing the compressor from operating in the surge region.
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