Shell-and-Tube Steam Heating With Blended Outlet Temperature Control
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Solution Overview
Problem
Conventional steam-fired water heaters suffer from thermal lag and inefficiency due to reactive control systems, which lead to varying outlet water temperatures and energy wastage, and lack redundancy and safety features.
Innovation Solution
A closely coupled shell-and-tube heat exchange system with redundant heat exchangers and temperature control valves that blend hot and cold water to maintain precise temperature, using steam traps for continuous heat supply and incorporating safety features to prevent scalding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback-type control system is used to regulate outlet water temperature, then temperature control is achieved, but thermal lag occurs and response time is slow
Solution Approach 1:
The system performs preliminary heating by continuously heating water to a temperature higher than the desired outlet temperature. This pre-heated water is then blended with cold water to achieve the exact desired temperature, eliminating the need for slow reactive control and thermal lag.
Solution Approach 2:
Cold water acts as an intermediary substance to blend with the pre-heated water. This blending mechanism allows precise temperature control by adjusting the ratio of hot and cold water mixing, providing rapid response without thermal lag.
2Quantity of substance
If a bulky storage tank system is used to supply hot water, then large volume of water can be supplied, but floor space is consumed and the system is slow to react
Solution Approach 1:
The invention extracts and eliminates the bulky storage tank from the system by implementing an instantaneous heating approach. Water is heated on-demand as it flows through the heat exchanger, removing the need for large storage spaces while maintaining continuous hot water supply capability.
Solution Approach 2:
The system maintains continuous heating action through the heat exchanger as water flows through it. This continuous process replaces the batch storage approach, providing unlimited hot water supply without requiring physical storage space.
3Loss of energy
If steam flow is controlled to regulate outlet water temperature, then energy efficiency is improved, but thermal lag occurs when flow changes quickly
Solution Approach 1:
The system continuously pre-heats water to a temperature above the desired outlet temperature, eliminating the need for reactive steam flow control. This preliminary heating action ensures immediate response to flow changes without thermal lag while maintaining energy efficiency through the blending mechanism.
Solution Approach 2:
Cold water serves as an intermediary to adjust the final outlet temperature by blending with pre-heated water. This approach replaces steam flow control as the primary temperature regulation mechanism, providing faster response time while maintaining energy efficiency.
4Device complexity
If a single heat exchanger is used, then device complexity is reduced, but reliability decreases due to lack of redundancy
Solution Approach 1:
The heat exchanger system is segmented into multiple independent units (first heat exchanger and second heat exchanger) that can operate independently. This segmentation provides redundancy so that if one unit fails, the other can continue to supply hot water, improving reliability without significantly increasing overall system complexity.
Solution Approach 2:
Each heat exchanger unit is designed with specific local functions and can be independently controlled. The first and second heat exchangers can operate with different steam flows and temperature settings, allowing flexible operation and maintenance while providing redundancy for improved reliability.
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 provides near-instantaneous temperature control with minimal thermal lag, reduces energy wastage, and ensures safety by blending hot and cold water to maintain consistent temperatures and redundancy in case of component failure.
Implementation Method 1
steam traps for continuous heat supply
Implementation Method 2
heat exchange system
Implementation Method 3
temperature control valves that blend hot and cold water
Data Source
AI summary
An improved shell-and-tube steam instantaneous heat exchange system of a closely coupled feedback design which overheats water in the heat exchanger portion of the system and then blends the water, as needed, with proportional amounts of cold water to achieve the correct outlet temperature for a wide range of flow rates. The system uses at least two primary heat exchangers to provide redundancy in the case of failure of a major component of the system. Steam flow through the heat exchangers is controlled by the use of steam traps, rather than using a thermostatically controlled valve to vary the supply of steam. To obtain precise temperature control during varying water volume use, water is directed from the blended outlet of a first water tempering valve into the hot inlet port of a second water tempering valve. The first valve is designed to blend cold and hot water to a predetermined temperature which is higher than the second water tempering valve, so as to bias the second tempering valve, thereby minimizing thermal hunting and providing tighter temperature control from the second tempering valve.