Electronic Mixing Valve Control for Stable Hot Water Temperature
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Solution Overview
Problem
Existing hot water heater systems with electronic mixing valves face issues such as oscillatory states, increased wear, and prolonged response times due to inefficient temperature control, which can lead to reduced mixing performance and fault detection challenges.
Innovation Solution
Implementing a method that monitors input temperatures, sets a position limit for the mixing valve between fully closed and fully open positions, and operates the valve within this constrained range to reduce oscillations and improve response time, using a controller that stores extremum temperatures and correlates them with valve positions through a lookup table.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If PID control with temperature tolerances is used to control the mixing valve, then the valve can maintain temperature stability, but the valve enters oscillatory states and increases wear
Solution Approach 1:
The patent changes the control parameters from continuous PID adjustment to discrete position limits stored in a lookup table. The controller selects predetermined position limits based on stored extremum temperatures, transforming the control mechanism from analog to digital/discrete, thereby eliminating oscillatory behavior and reducing valve wear while maintaining temperature stability.
2Adaptability or versatility
If the mixing valve operates with large range of movement to achieve desired temperature, then the valve can respond to temperature changes, but the response time increases and wear increases
Solution Approach 1:
The patent implements preliminary action by storing extremum temperatures and pre-calculating corresponding position limits in a lookup table before operation. When temperature adjustment is needed, the controller quickly retrieves the predetermined position limit based on the stored extremum, eliminating the need for gradual valve adjustment and significantly reducing response time while maintaining full temperature adaptability.
3Productivity
If the valve operates near fully open or fully closed positions, then the mixing range is maximized, but fault detection becomes difficult and wear increases
Solution Approach 1:
The patent applies preliminary anti-action by setting predetermined position limits that prevent the valve from operating near the fully open or fully closed extremes. The lookup table contains position limits that maintain the valve within a safe intermediate range, proactively preventing conditions that would lead to difficult fault detection and excessive wear, while still achieving the required mixing capacity through optimized position selection.
Data Source
AI summary
Hot water heater systems including electronic mixing valves and methods for controlling such valves are provided. An electronic mixing valve provides a flow of water in a mixed output line. A method includes monitoring an input temperature of cold water supplied to the valve, storing a value of the input temperature, and setting a position limit of the valve based on the stored value, wherein the position limit of the valve is greater than a fully closed position of the valve and less than a fully open position of the valve.