Bitzer ST-140-3 Manuel D'utilisation page 45

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-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
2 Safety
Authorized staff
All work done on the products and the systems in which they are or will be installed may only be performed by
qualified and authorised staff who have been trained and instructed in all work. The qualification and competence
of the qualified staff must correspond to the local regulations and guidelines.
ST-140-3 // PDF Download
Effect of
oil cooling
[kJ/kg]
45