System separation
The system separation in warm- and hot water boiler systems serves to decouple heat generation, either fully or partially, from the heat consumers; in other words, there are two completely separate water circuits. This separation prevents contamination and stabilises the pressure and temperature conditions within the system. The following section describes the fundamental aspects and methods of system separation.
Heat exchangers are used for this purpose. Plate-type heat exchangers and pipe heat exchangers are used. Both variants are used in industry for heat transfer between two liquids, but differ in several key respects.
The plate-type heat exchanger consists of many thin, flat plates stacked on top of one another, creating a large heat transfer surface area within a small space. This design enables efficient heat transfer, particularly in applications with smaller temperature differences. Furthermore, plate-type heat exchangers are generally more compact and lighter, making them ideal for applications where space is limited. Cleaning and maintenance are also simpler, as the plates can be effortlessly dismantled and cleaned, which helps to maintain heat transfer efficiency.
In contrast, the pipe heat exchanger consists of a series of tubes arranged within a housing. One liquid flows through the pipes, whilst the other flows through the space around them. This design generally results in a smaller heat transfer area per volume unit compared to plate-type heat exchangers, which may reduce efficiency at lower temperature differences. Pipe heat exchangers are often larger and heavier, which means they take up more space. Cleaning may be more difficult, as deposits in the pipes often have to be removed using chemicals or the pipes have to be taken out.
In terms of applications, plate-type heat exchangers are commonly found in the food and beverage industry and in heating and cooling systems, whereas pipe heat exchangers are primarily used in the petrochemical industry and in power stations, where higher pressure and temperature requirements apply. In summary, the choice between these two types of heat exchanger depends on the specific requirements of the application, including space requirements, efficiency, ease of maintenance and the physical properties of the liquids to be used.
There are several reasons why it makes sense to separate the systems:- Protection against soiling: Separating heating circuits prevents dirt, rust or limescale from one circuit entering another.
- Use of corrective chemicals on the consumer side that are not compatible with the heat generators.
- Use of antifreeze on the consumer side.
- Pressure differences: Different heating circuits may have different pressure levels. A separation protects against unwanted pressure.
- Safety considerations: Separation reduces the risk of leaks or other problems that could affect the entire system.
Methods of system separation
A heat exchanger enables heat to be transferred between two water circuits without the media mixing.
- Plate-type heat exchanger: Consists of several thin plates through which hot and cold water flows, transferring heat.
- Pipe heat exchanger: Consists of a bundle of tubes through which one medium flows, whilst another medium flows around the tubes.
Safety and control components
In addition, the following components are important for system separation:
- Safety valves: Protection against overpressure in both circuits.
- Purging valves: Remove air from the circuits to improve efficiency and prevent corrosion.
- Pressure expansion vessels: Compensate for volume fluctuations caused by temperature changes.
- Temperature and pressure sensors: Monitor and regulate the operating conditions in the separate circuits.
Practical implementation
When implementing system separation, the following steps should be followed:
- Planning and dimensioning: Determining the necessary separation points and selecting suitable heat exchangers based on the system requirements.
- Installation: Professional installation of the separation components and the necessary control and safety devices.
- Commissioning: Careful commissioning, including tests to verify the functionality and efficiency of the system separation.
- Maintenance: Regular maintenance and inspection of the separation components to ensure reliable and efficient operation in the long term.