Transformer Oil Air Coolers

Renzmann Transformer Oil Air Coolers

Leading Technologies and Individual Solutions

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Transformer oil air coolers can be supplied in different mounting variants. The standard air cooler version is designed for direct mounting on the transformer boiler. In addition, our range of products comprises free-standing transformer oil coolers designed to customer specifications.

  • Transformer Oil Air Cooler system
    Transformer Oil Air Cooler system
  • Transformer Oil Air Cooler pivoting ventilators
    Transformer Oil Air Cooler pivoting ventilators
  • Mobile Transformer Oil Air Cooler
    Mobile Transformer Oil Air Cooler

Transformer oil air coolers are available in different material versions.

  • Galvanized Steel Version
    For more than 80 years, we have manufactured transformer oil air coolers of galvanized steel construction. The key component of this cooler type is the proven elliptical finned tube.
  • Copper / Aluminum Version
    Our coolers featuring aluminum or copper finplates in conjunction with copper tubes are a low-priced alternative to the galvanized steel cooler.
  • Aluminum Version
    This type of cooler is made entirely of aluminum.

Details for different material versions

The advantages of the elliptical finned tube are:

  • Low air-side pressure loss
  • Compact construction
  • Excellent corrosion protection due to hot-dip galvanized coating
  • Long service life
  • Durable bond between the fin and core tube
  • Easy to clean thanks to robust, hot-dip galvanized steel fins
  • Gasketless and thus environmentally compatible construction


The key component of the galvanized steel version is the high-performance finned tube. Rectangular steel fins are pushed on to the elliptical steel tube. As the finned tubes are hot-dip galvanized, good metallic contact is ensured between the core tube and the wide fin collar. The fins will not come off under thermal or mechanical stress. Thus perfect heat transfer is ensured even after many years for service.

The finned tubes are welded into the tubesheet using two weld passes, which ensures high mechanical strength as well as a durable bond that stays oil-tight for years. The elliptical core tube has the advantage of an aerodynamically efficient profile. This allows high cooling efficiency to be achieved, while keeping the pressure drop at a minimum. Small pressure drops bring down fan operating costs, as the drive motor power consumption is lower. Moreover, low-noise fans can be used. The robust construction of the galvanized finned tube offers also significant advantages when it comes to cooler cleaning. The rectangular steel fins with their relatively low height provide essentially higher mechanical strength compared to coolers with aluminum fins.

Cooling capacities range from 100 to 2,500 kW in non-sound-insulated and sound-insulated designs. Depending on our customers’ noise control specifications, sound insulating elements are provided on the suction and/or discharge side.

In this type of cooler, cost-optimized copper/aluminum compact systems are used. The transformer oil flows through round copper tubes. Air-side heat transfer is ensured by aluminum or copper finplates. The bond between the core tube and the finplates is obtained by mechanical expansion. The copper tubes proper are rolled into the tubesheets. Due to the use of proven series production processes, the manufacturing costs of these coolers are moderate, so that they can be offered at favorable prices. Copper/aluminum systems offer advantages in particular in clean and non-corrosive environments.

We supply these transformer oil coolers in capacities from 100 kW to 400 kW.

In today’s economy, the weight of capital goods is a factor of ever increasing significance. In light of rising transportation and handling costs, transformer oil air coolers of aluminum construction are an attractive alternative. Their cooling element is an aluminum block made with a specially developed brazing process. This technology, which is known from the auto industry, benefits from the excellent heat transfer properties and the low weight of aluminum.

These transformer oil air coolers are especially suited for mobile applications. In the case of transformers whose original cooling systems - after having been in operation for years - are no longer capable of providing the required cooling efficiency, an additional mobile air cooler may bring down oil temperatures again and thus extend the transformer service life.

The aluminum transformer oil air coolers are currently available in capacities of up to 150 kW.

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