Introduction

In case of high thermal load of compressors, additional cooling is required. For screw compressors, oil cooling is often used for this purpose: The use of an external oil cooler is universally possible and allows operation with extended 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)

Zoom

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 relatively low refrigerating capacity due to the risk of oil dilution (see BITZER SOFTWARE).

Also observe the following technical documents

SB-110: Operating instructions Semi-hermetic screw compressors HS.53 .. 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))
DB-530: Operating instructions Water cooled oil coolers (OWD)
AT-640: Use of ammonia (R717) in Bitzer compressors
ST-500: Bitzer refrigeration compressor oils for compact screw compressors CS., CSV.
ST-600: Integration of screw compressors into the refrigerant circuit
ST-610: Economiser operation of screw compressors