Heat medium circulation structure and hot water temperature control method for micro combined heat and power generator
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Solution Overview
Problem
In micro-CHP generators, the returning heat medium's high temperature reduces electricity production and causes frequent operation stops and resumptions of the stirling engine, leading to durability deterioration.
Innovation Solution
A heat medium circulation structure with a return line heat exchanger that allows the heat medium to undergo heat exchange with low-temperature direct water before returning to the stirling engine, combined with a circulation pump to adjust the flow rate and a hot water temperature control method using predetermined temperature thresholds to manage stirling engine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the heat medium returns directly to the stirling engine without heat exchange with direct water, then the system structure is simple, but the returning heat medium's high temperature reduces electricity production and causes frequent operation stops
Solution Approach 1:
The heat medium circulation path is segmented into two separate lines: a direct water line for hot water supply and a return line heat exchanger for heat exchange. This segmentation allows the heat medium to cool down through heat exchange with direct water before returning to the stirling engine, reducing its temperature and improving electricity production efficiency without significantly complicating the overall system structure.
Solution Approach 2:
The return line heat exchanger acts as an intermediary device between the heat medium and the stirling engine. It facilitates heat exchange between the high-temperature heat medium and the direct water, allowing the heat medium to cool down before returning to the engine. This intermediary component resolves the contradiction by enabling temperature reduction without requiring direct mixing or complex cooling systems.
2Reliability
If the heat medium temperature is reduced through heat exchange, then electricity production efficiency is improved, but the system requires additional heat exchange components and control mechanisms
Solution Approach 1:
The return line heat exchanger serves multiple functions: it cools down the heat medium before it returns to the stirling engine, preheats the direct water that will be supplied to users, and maintains stable operation conditions for the stirling engine. This multi-functionality improves reliability while minimizing the addition of separate components, as one heat exchanger performs multiple tasks simultaneously.
Solution Approach 2:
The system changes the temperature parameter of the heat medium dynamically by controlling the heat exchange process in the return line heat exchanger. By adjusting the heat exchange efficiency and flow rates, the heat medium temperature is optimized to maintain stable stirling engine operation, improving reliability through parameter optimization rather than structural complexity.
3Duration of action of stationary object
If direct water is supplied directly to the hot water tank without heat exchange, then the response time is fast, but the heat medium temperature remains high causing durability deterioration
Solution Approach 1:
The return line heat exchanger performs preliminary cooling of the heat medium before it returns to the stirling engine. By pre-cooling the heat medium through heat exchange with direct water, the system prevents the heat medium from reaching the stirling engine at excessively high temperatures, thereby protecting the engine's durability while maintaining efficient hot water supply through the direct water line.
Solution Approach 2:
The high temperature of the returning heat medium, which initially appears harmful to the stirling engine's durability, is converted into a beneficial resource by using it to preheat the direct water in the return line heat exchanger. This converts the harmful thermal energy into useful heat for the hot water supply, protecting the engine while maintaining productivity.
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 maintains high electricity production efficiency while preventing durability deterioration by cooling the stirling engine and optimizing its operation based on hot water consumption and natural radiation.
Implementation Method 1
a return line heat exchanger that allows the heat medium to undergo heat exchange with low-temperature direct water introduced through a direct water line before returning to the stirling engine
Implementation Method 2
combined with a circulation pump to adjust the flow rate
Implementation Method 3
a stirling engine is used to convert low- or medium-temperature heat energy into shaft power (high quality energy)
Data Source
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AI summary
The present invention provides a heat medium circulation structure for a micro-combined heat and power (micro-CHP) generator in which a heat medium that primarily looses heat by undergoing heat exchange with water in a hot-water tank and thus has a low temperature further performs heat exchange with low-temperature direct water supplied through a direct water line, thereby further loosing heat, in a return line heat exchanger, and then returns to a stirling engine through a heat medium return line, thereby effectively cooling a low temperature portion of the stirling engine. Thus, the heat medium circulation structure enables high electricity production efficiency. Further provided is a hot water temperature control method for a micro-CHP generator in which the consumption of hot water is detected by a flow sensor. First and second predetermined temperatures are defined to operate a stirling engine in the case of temperature droppings of hot water respectively due to natural radiation and consumption of hot water.