Hot Water Storage Charging Layout for Legionella-Safe Circulation
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Solution Overview
Problem
Existing water heating systems face challenges in preventing the growth of legionella and inefficient utilization of thermal energy, particularly due to direct integration of the hot water tank into the circulation circuit, leading to continuous mixing with cooler water and energy loss.
Innovation Solution
A water heating system with a primary heating water circuit and a secondary drinking water circuit, featuring a heat exchanger system with a control unit and mass flow control to regulate the heating water return temperature, ensuring effective heat exchange and preventing legionella growth by maintaining optimal temperatures and reducing energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the hot water tank is integrated directly into the hot water circulation circuit, then hot water can be continuously supplied to and removed from the tank, but this causes currents in the tank and mixing of hot water with cooler water, leading to temperature drop and legionella growth
Solution Approach 1:
The system separates the hot water storage function from the circulation function by placing the tank outside the circulation circuit and using a dedicated charging pump and heat exchanger for storage, while the circulation circuit operates independently to maintain temperature without mixing
Solution Approach 2:
A heat exchanger is introduced as an intermediary between the heating water circuit and the drinking water storage tank, allowing heat transfer without direct water mixing, thus preventing temperature drop and legionella growth in the circulation circuit
2Reliability
If the first heat exchanger is operated continuously due to circulation in the hot water circulation circuit, then hot water can be maintained in the circuit, but the heat energy in the district heating circuit is only used to a small extent
Solution Approach 1:
The system enables continuous useful action by directing heating water through the second heat exchanger to charge the storage tank, ensuring that heat energy is continuously transferred to drinking water for storage, maximizing energy utilization while maintaining circulation reliability
Solution Approach 2:
The control unit adjusts the mass flow of drinking water through the second heat exchanger based on the heating water return temperature, optimizing heat transfer parameters to maximize energy utilization while maintaining adequate circulation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively prevents legionella growth and optimizes thermal energy utilization by controlling the mass flow and temperature in the drinking water circuit, reducing energy losses and maintaining safe temperatures, thereby enhancing energy efficiency and safety.
Implementation Method 1
a first heat exchanger (26), which enables heat exchange between the primary heating water circuit (12) and the hot water circulation circuit (36)
Implementation Method 2
a second heat exchanger (28), which is arranged in the heating water circuit in the return of the first heat exchanger (26) and in the storage loading system (42) of the drinking water circuit in the course of the first heat exchanger (26) and enables a heat exchange between the primary heating water circuit (12) and a charging supply line (44)
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A water heating system (10) comprises a primary heating water circuit (12) and a secondary drinking water circuit (14), which is coupled to the heating water circuit (12) via a heat exchanger system (16) and a hot water circulation circuit (36), one outside of the hot water circulation circuit (36) arranged and with the hot water circulation circuit (36) coupled hot water tank (40) and with the heat exchanger system (16) connected memory loading system (42). The heat exchanger system (16) has a first heat exchanger (26) and a second heat exchanger (28), which is located in the heating water circuit (12) in the return of the first heat exchanger (26) and in the storage charging system (42) of the drinking water circuit (14) in the supply of the first heat exchanger (26) is arranged. A control unit (60), which in the heating water circuit (12) includes a heating water temperature sensor (30) in the return of the second heat exchanger (28) and a mass flow control unit (48) in the storage charging system (42), enables the heating water return temperature in the return of the second heat exchanger (28 ) by controlling the mass flow of drinking water through the second heat exchanger (28) in the drinking water circuit (14).