Sven-Olaf Klüe has been working in the field of design, manufacture and applications of pillow plate heat exchangers worldwide for 27 years. For the past 15 years, he has focused specifically on the process-related applications of pillow plate heat exchangers in industrial applications.
Heat recovery from shower wastewater
Heat recovery from shower waste water with the aid of a BUCO falling film chiller
The BUCO falling film chiller is an unbeatable alternative in heat recovery. Heating oil and gas consumption can be reduced by 50 % by installing the falling film chiller to heat the shower water. High performance due to the high heat transfer coefficients (up to 2000 W/m² K). Easy to clean thanks to smooth stainless steel surfaces, a possibility of cleaning during operation without loss of performance. Made entirely of stainless steel, the dimensions can be adapted to the respective space conditions on site in terms of length, width and height.
The starting position from waste water heat recovery
In public swimming pools, large amounts of hot water are used for showers and at the same time the same amount of hot wastewater is produced. This wastewater is extremely polluted by soap, hair, etc.
The majority of hot water consumption is required for personal hygiene. When showering, there is a simultaneous flow of warm wastewater and the withdrawal of cold water for water heating. In falling-film chiller, the outgoing wastewater is cooled and the incoming cold water is heated. The preheated cold water then continues to the hot water heater, requiring up to 35% less energy to be heated to 60˚C. Usually, the temperature of the mixed wastewater is so low that the thermal energy contained in it can only be used with heat pumps (see wastewater heat recovery). Heat exchangers for locations where sufficient hot water is generated (shower) are still relatively uncommon, although they are currently economically viable. An interesting development is shower cabins, shower trays, and falling-film chillers, in which the cold water is preheated with the wastewater. As a result, the cold water is pre-warmed and can be used directly or fed into the hot water heater. In conclusion, there is a significant reduction in the required energy consumption for hot water.
What is a Waste Water Heat Recovery System? What has been done so far concerning heat exchange?
In the past, hot shower wastewater was mostly discharged into the public sewer systems. At the same time, expensive heating oil or gas 15 was burned to heat the same amount of water used.
So, what is a Waste Water Heat Recovery System? Why use a falling film water chiller now for the heat exchange?
The waste water produced has a temperature of between 25 and 30 °C. The cold fresh water with an incoming temperature of 10 - 12 °C is pumped into an installed falling film chiller unit and, depending on the design and size, heated to 20 - 28 °C by warm water flowing down the outside of the heat exchange plate systems. The Buco falling film chiller unit is made entirely of stainless steel (AISI 316 Ti) and offers few points of attack for contamination due to its smooth surface. Periodic cleaning is very easy. The wall thicknesses of the heat exchanger plates are designed according to the water pressures. If required, corrosion enhancement up to a wall thickness of 3 mm is possible.
The following aspects are decisive for the selection of these falling film chillers as evaporators for heat recovery from shower water:
- flexibility in the heat load capacity of the heat exchanger , both in terms of temperatures and the volumetric water flows of heat recovery
- high robustness of the systems (if extreme climatic conditions or conditions far from the design conditions that are far from the design, the units will not be destroyed, as they are not they will not be destroyed because they are open systems)
- good cleanability of the open surfaces and distribution trough, even during water operation
- low control effort of this heat exchange system for shower waste water
- Heat exchange system with low cost per kWh and minimal refrigerant used ideal for use of heat recovery of shower waste water
- High efficiency heat recovery with optimal heat transfer, low pressure drop of these heat exchange systems
- Easy access to the open systems of these heat recovery heat recovery
- Easy to clean heat exchange systems ideal for use of heat recovery
- Cleaning during operation possible with these heat exchange systems
- Low tendency to fouling for this heat exchange system ideal for use of heat recovery systems
- No seals in this heat exchange systems for shower waste water
- No destruction of the apparatus in case of ice formation of this heat exchange system
- Simplicity of control of these heat exchange system for shower waste water
- Heat exchange completely made of stainless steel, also for salt water
- Special and customized heat exchanger system design possible
How effective is a Waste Water Heat Recovery System for this heat exchange process?
Conclusion to use heat exchange with shower water
Heating oil and gas energy consumption costs can be reduced by 50 % saving by installation of BUCO heat exchanger systems to heat the shower water. Amortisation due to this heat recovery efficiency in the shortest possible time is guaranteed.