Positive-Displacement Compressors

Positive Displacement Compressors Positive displacement compressors are machines that are essentially constant volume machines with variable discharge pressures. These machines can be divided into two types ... 

The two principal elements of evaporator control are evaporation rate a.ndproduct concentration. Evaporation rate in single- and multiple-effect evaporators is usually achieved by steam-flow control. Conventional-control instrumentation is used (see Sec. 22), with the added precaution that pressure drop across meter and control valve, which reduces temperature difference available for heat transfer, not be excessive when maximum capacity is desired. Capacity control of thermocompression evaporators depends on the type of compressor positive-displacement compressors can utilize speed control or variations in operating pressure level. Centrifugal machines normally utihze adjustable inlet-guide vanes. Steam jets may have an adjustable spindle in the high-pressure orifice or be arranged as multiple jets that can individually be cut out of the system. 

Type Comparison. Reciprocating Compressors. Positive Displacement Rotary Compressors. Centrifugal Compressors. Axial Compressors. 

The general multistage compressor model may have several functions polytropic and isentropic compressor, positive displacement compressor, inter-cooler between stages, isentropic turbine. Single phase, as well as two- or three-phase calculations, is possible. 

Air blower and compressor (positive displacement type) are preferable with silencer-cum-filter, dampers for primary (atomising) air, primary and secondary air piping, manometer, pressure regulators for air supply at burner inlet. The positive displacement-type combustion air blowers shall also be able to atomise the oil or separate compressors for atomisation of oil shall be provided. 

---