terms of inlet volume flow rate under a specific set of operating conditions. 6.3.10 It is important to recognize that the volumetric efficiency of a given cylinder configuration (fixed diameter, stroke, speed, internal clearance volume) is not a constant parameter. a. Volumetric efficiency decreases with increasing pressure ratio across the cylinder. b. Volumetric efficiency decreases with increasing internal cylinder clearance volume. 6.3.11 The volumetric efficiency (hence, capacity) of a given cylinder configuration can be altered by varying the internal clearance within the cylinder control volume. 6.3.12 The internal clearance within the cylinder control volume can be varied through the use of fixed or variable volume clearance pockets which add internal clearance volume to the cylinder if manually or automatically actuated for capacity control.
PIP REEC001 COMPLETE REVISION Compressor Selection Guidelines April 2013 Process Industry Practices Page 36 of 44 6.3.13 The theoretical discharge temperature is given by: k 1 - k P P T = T s d s d k is the ratio of specific heats (C p /C v ) 6.3.14 Where temperatures and pressures are in absolute units. The compressor equipment manufacturers should be able to provide estimates of predicted discharge temperature and shaft power for given operating conditions. K is the ratio of specific heats. 7. Selection Considerations 7.1 Safety Safety attributes that should be considered in the selection of compressor systems include: a. Limiting gas properties (e.g., decomposition, flammability, toxicity). Normal compressor operation should not violate these limiting gas properties. b. Compatibility of process gas with materials of construction (e.g., H 2 S with copper, ethylene oxide with brass, oxygen) c. Containment, collection and disposal of seal and vent gases d. Over-pressure protection e. Process and economic issues listed below should also be evaluated for safety implications 7.2 Process 7.2.1 Key process variables which should be considered in the selection of compressor systems include: a. Mass flow rate b. Absolute suction pressure and absolute temperature c. Absolute discharge pressure and absolute temperature d. Gas physical properties (e.g., composition, molecular weight, ratio of specific heats, compressibility) e. Effects of process gas on the compressor system (e.g., corrosion, erosion, fouling, chemical reaction, coking, polymerization, temperature, condensation and liquid removal) f. Machinery interaction with the process gas (e.g., lubricants, buffer fluids, seal media) g. Solubility of the compressed gas in the lubricant in flooded screw applications.
PIP REEC001 COMPLETE REVISION Compressor Selection Guidelines April 2013 Process Industry Practices Page 37 of 44 h. Startup and shutdown process/mechanical conditions. These conditions can be very different than normal operating conditions and may significantly influence the selection process.
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- Summer '09
- ramana rao
- Thermodynamics, Gas compressor, compressor inlet