Exhaust Gas Heat Exchanger Control for Buffer Tank Stratification
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Solution Overview
Problem
Existing heating systems face inefficiencies in utilizing the calorific value and storing heat generated by heat generators, as they require a constantly regulated minimum return temperature and efficient use of heat transport and storage media, which is not optimally achieved by existing control systems.
Innovation Solution
A control system that uses separate control circuits for the exhaust gas temperature and the return flow increase, allowing for optimal setting of the heating medium quantity from the buffer storage tank, ensuring the exhaust gas heat exchanger receives a sufficient and cold heating medium to maximize latent heat utilization while minimizing the withdrawal of the coldest heating medium, thereby optimizing both heat utilization and storage efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the return temperature is increased to meet the heat generator's minimum requirement, then the reliability of the heat generator is improved, but the efficiency of calorific value utilization deteriorates because the return temperature exceeds the dew point
Solution Approach 1:
The patent segments the buffer tank water supply into two separate circuits: one circuit (first control circuit) supplies water to the exhaust gas heat exchanger to maximize calorific value utilization, while another circuit (second control circuit) supplies water to the heat generator return to ensure minimum temperature requirements. This segmentation allows each circuit to be optimized independently for its specific function.
Solution Approach 2:
The patent introduces a separate control circuit for the exhaust gas heat exchanger that acts as an intermediary between the buffer tank and the heat generator. This intermediary circuit provides cold water directly to the heat exchanger, enabling efficient heat recovery from exhaust gases without compromising the heat generator's minimum return temperature requirement.
2Loss of energy
If more cold water is withdrawn from the buffer tank to supply the exhaust gas heat exchanger, then the calorific value utilization is improved, but the heat storage efficiency deteriorates due to unnecessary withdrawal of cold heating medium
Solution Approach 1:
The patent implements feedback control in both circuits: the first control circuit monitors exhaust gas temperature or heat exchanger outlet water temperature to regulate water flow for optimal calorific value recovery, while the second control circuit monitors return temperature to regulate flow for minimum temperature maintenance. This feedback mechanism prevents excessive water withdrawal and optimizes heat storage efficiency.
Solution Approach 2:
The patent employs dynamically adjustable control valves in both circuits that can independently modulate water flow rates based on real-time temperature conditions. This dynamic control allows the system to adapt to varying heat demands and exhaust gas conditions, optimizing both calorific value utilization and heat storage efficiency under different operating scenarios.
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
This approach optimizes the use of calorific value and heat storage by ensuring precise control of the exhaust gas temperature and heating medium flow, reducing unnecessary withdrawals and maintaining stable temperature stratification in the buffer tank, leading to improved efficiency and reliability in heat transport and storage.
Implementation Method 1
the exhaust gas is routed through an exhaust gas heat exchanger
Implementation Method 2
water from a lowest connection of a buffer storage tank flows through a bottom exhaust gas heat exchanger
Implementation Method 3
the heat of condensation of the water vapor contained in the exhaust gases is used
Data Source
Figure 1a
Figure 1b
Figure 2a
AI summary
The method involves energizing an exhaust gas heat exchanger (6) of a buffer storage-cold connection (26) for exhaust gas of a heat generator (2). Exhaust gas heat exchanger-flow of a heat medium is fed over an exhaust gas heat exchanger-line (67) of an outlet flow (61) of the heat generator. Temperature of exhaust gas or heat medium from the exhaust gas heat exchanger is regulated and utilized as a correcting variable of the flow of the heat medium by an exhaust gas heat exchanger closed loop that is independent from a return flow increase closed loop. An independent claim is also included for a heating system comprising a heat generator.