Bitzer ST-140-2 Mode D'emploi page 43

1 Introduction
In case of high thermal load of compressors, additional cooling is required. For screw compressors, oil cooling is of-
ten used for this purpose: The use of an external oil cooler is universally possible and allows operation with exten-
ded application limits and high efficiency. The following options are described in this document:
• air cooled external oil coolers
• water cooled external oil coolers
• refrigerant cooled external oil coolers (thermosiphon oil cooling)
[bar]
Condensation
Evaporation
Fig. 1: Influence of oil cooling on the discharge gas temperature in the log-p-h diagram. The discharge gas temperature can thus be reduced
e.g. from 140°C to 80°C.
As an alternative to oil cooling, liquid injection will be briefly mentioned. However, this technique is limited to a relat-
ively low refrigerating capacity due to the risk of oil dilution (see BITZER Software).
Also observe the following technical documents
• SB-100 : Operating instructions Semi-hermetic screw compressors HS.53 .. 74
• SB-110 : Operating instructions Semi-hermetic screw compressors HS.85 .. 95
• SB-160 : Operating instructions Semi-hermetic compact screw compressors with integrated frequency inverter
CSV.
• SB-170 : Operating instructions Semi-hermetic compact screw compressors CS.65 .. 105
• SB-500 : Operating instructions Open drive screw compressors OS.53 .. 74
• SB-510 : Operating instructions Open drive screw compressors OS.85
• SB-520 : Operating instructions Open drive screw compressors OS.85, OS.95, OS.105
• DB-510 : Operating Instructions Water-cooled oil coolers (OW401(B) .. 941(B))
• AT-640 : Use of ammonia (R717) in BITZER compressors
• ST-500 : BITZER refrigeration compressor oils for compact screw compressors CS., CSV.
• ST-610 : Economiser operation of screw compressors
ST-140-2 // PDF Download
Effect of
oil cooling
[kJ/kg]
43