Dear Reader,

With our last newsletter, we explained how to save a lot of money by using a heat recovery system. Today we would like to give you more detailed information, which types of heat exchangers are commonly used.

Depending on the required heat output, media used, temperatures and respective framework conditions, we have developed a few different types of heat exchangers.

Heat Exchanger Types Tube Bundle Heat Exchanger

The first one would be the classical tube bundle Heat exchanger which is used primarily for the recovery of waste heat from small and medium sized engines or other exhaust gases of relatively small quantity. In this apparatus, the flue gases are collected in an inlet chamber and flow through the heat transfer tubes in the outlet chamber.

The colder heat transfer medium is guided around the tubes. The heating surface system is installed in a shell tube. Baffle plates are guiding the medium in the shell side around the tubes. The pipes are accessible from the exhaust side by removable endplates. For critical applications, a version as a tube-in-tube safety heat exchanger is possible. Here, tubes and tube sheets are used double, so that the resulting gap can be monitored. This ensures extremely high security against leaking or mixing of the media.

These devices are available in horizontal or vertical version.

Steam generators

The principle of the steam generators is more or less the same as of a shell and tube heat exchanger. The hot gases are passing through the tubes, while the steam is inside the shell (in this case we call it drum). As you can see on the pictures, the heat transfer tubes do not cover the complete diameter of the drum. The “empty” space above the heat transfer tubes is required to allow the steam to separate from water. Several inbuild items are designed to increase the steam quality (reducing quantity of drops in the steam). In order to increase the efficiency, we often combine the steam generators with an economizer to use the remaining heat from the exhaust gas and to pre-heat the feed water. Due to the fact that steam generators need a vapor room to allow the steam to separate form water, our standard types are only available in horizontal execution (for special requirements we can offer also vertical types). The instrumentation of steam generators is relatively cost intensive, if several hot gas streams are to be used (e.g. from more than one engines), our steam generators can be equipped with several parallel hot gas passages.

Tube Bottom Registers

In addition to the previously mentioned shell and tube design, we also produce the so-called tube bottom register, which is suitable for exhaust gases, for example; from gas turbines, cement plants, steel production, or other hot gas streams with large volume flows.

Depending on the cleanliness of the gases and temperatures, the surface of the heat exchanger tubes can be finned, which multiplies the surface and increases the heat transfer on the gas side.

The liquid or vaporous heat transfer medium flows through the pipes and can be deflected several times in the collection chambers according to the thermodynamic requirements.

The finished registers are arranged in series or parallel. This way, very large capacities can be transferred. In the housing, shut-off and bypass flap systems can be integrated, as well as different surface cleaning devices, dust discharge and inlet and outlet cones.

Exhaust Gas Heat Exchangers with concentrical pipe coils

For the exhaust gases of large engines, or high temperature gases, especially when using organic heat transfer media (e.g. Thermal Oil), we offer exhaust gas heat exchangers made of concentrically arranged pipe cylinders. The hot flue gases flow through the space between the tube cylinders, while the heat transfer medium flows through the pipes.

This design offers a safe control of the permissible medium temperature in all areas and is simultaneously insensitive to vibrations. Various accessories are available, such as pumps, shut-off, bypass and control valves. We also offer automatic cleaning systems for heating surfaces. On the gas side, we can supply shut-off and control dampers, required measuring and control technology, and not to forget complete bypass systems.

For each type of heat exchanger, we supply individually optimized cleaning systems, for all appliances, which ensure long-lasting, efficient operation.

Further, we offer the control and safety equipment for water, steam and organic heat transfer media. Heating surfaces and housings of our heat exchanger can be supplied in carbon and stainless steel. Special materials are also available upon request.

Application examples

All applications require heat exchangers, that exchange the heat from the flue gas in a heat transfer medium, such as water, thermal oil or steam.
Exhaust gas heat exchanger for combustion engines The use of exhaust heat from combustion engines has been practiced for decades and is applicable in many areas. To give you a few examples: in motor vehicles, the exhaust heat is often used to heat the passenger compartment; while in marine engines it is used to heat the tanks, the ship, the ships kitchen and also for thermal water treatment. In land-based power generation units with combustion engines, the waste heat can be used to heat industrial processes, for water treatment or seawater desalination, but also to produce chilled water with absorption refrigeration.

Depending on the nature of the media, our exhaust gas heat exchangers, can be made of carbon steel or stainless steel. In optimized systems, in which heat from the engine cooling is used additionally to the exhaust gas heat, the energy, contained in the fuel can be utilized to more than 90%.

Exhaust gas heat exchanger for biogas engines

For biogas applications, the exhaust gas temperature must not fall below the condensation point, so that the combination of condensate and sulfur from the exhaust gas does not lead to corrosion of the metal. Nevertheless, experience from many realized installation shows, that carbon steel is not suitable at all for biogas. Even though the temperature is maintained above dew point, stainless steel withstands the conditions much better than C-steel.