Thermostatic Mixing Valve Segmented Flow Passages
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Solution Overview
Problem
Large bore thermostatic mixing valves face challenges in achieving sufficient mixing of hot and cold water across a range of flow rates, particularly at low demand, leading to potential false temperature signals due to laminar flow and the need for additional hardware to prevent excess flow from bypassing the sensing chamber.
Innovation Solution
A thermostatic mixing valve design with a housing, seats, and a plunger that includes low-flow and high-flow passageways connecting the mixing and sensing chambers, along with a check valve that ensures excess flow does not bypass the sensing chamber, even at high flow rates, maintaining accurate temperature control and mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large bore TMV is used to accommodate high flow rates, then the valve can pass substantial amounts of mixed water without high pressure drop, but the velocity of hot and cold-water streams drops at low demand and mixing becomes insufficient leading to laminar flow and false temperature signals
Solution Approach 1:
The invention divides the flow path into two separate passages: a first passage that directs flow through the sensing chamber containing the thermal motor, and a second passage that bypasses the sensing chamber. This segmentation allows the valve to handle high flow rates through the bypass while ensuring that a controlled portion of flow always passes through the sensing chamber to maintain accurate temperature sensing and mixing control.
2Reliability
If a small bore TMV is used to ensure sufficient mixing at low flow rates, then the velocity of water streams remains high enough for proper mixing, but the valve cannot pass substantial amounts of water when multiple outlets are used simultaneously
Solution Approach 1:
The invention segments the flow paths to create dedicated mixing and sensing pathways. The first passage ensures that water flows through the sensing chamber for proper mixing and temperature sensing, while the second passage provides additional capacity for high flow demands. This allows the valve to maintain mixing quality at low flows while accommodating high flow rates when needed.
Solution Approach 2:
The valve body is designed with multi-functional passages that serve different purposes under different operating conditions. The first passage handles both low-flow mixing and high-flow sensing, while the second passage provides bypass capability for high-flow conditions. This universal design allows a single valve to replace both small-bore and large-bore TMVs.
3Measurement precision
If a flow-directing element is used to direct flow toward the thermal motor at low flow rates, then accurate temperature control is achieved, but the element must be flexible and expand under pressure which complicates the design
Solution Approach 1:
Instead of using a flexible flow-directing element that expands under pressure to direct flow, the invention inverts the approach by using fixed geometric passages with different flow resistance characteristics. The first passage is designed with dimensions and geometry that naturally direct flow through the sensing chamber at low flow rates, while the second passage provides a bypass route that becomes more favorable at high flow rates. This eliminates the need for flexible materials and expansion mechanisms.
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 solution allows for accurate mixing and temperature regulation across a wide range of flows without excess flow bypassing the sensing chamber, ensuring reliable operation and reduced complexity and cost compared to existing solutions.
Implementation Method 1
The mixed fluids are caused to impinge upon the thermal motor, which in turn expands and contracts and controls the relative proportions of hot and cold fluids passing through the valve
Implementation Method 2
The check valve is adapted to open and allow additional flow from the mixing chamber to the sensing chamber upon fluid flow through the thermostatic mixing valve rising to at least a predetermined high flow rate
Data Source
AI summary
A thermostatic mixing valve (TMV) having a mixing chamber with a plurality of pockets defined therein. The mixing chamber receives cold water flow and hot water flow that has been passed through respective flow inlets and mechanically forced into the pockets defined within the chamber due to axial movement of the plunger. As the hot and cold flow moves into and out of the pockets, the flow streams disperse rather than being maintained in separate flow streams toward the thermostatic element. Because of the increased agitation, the thermostatic element is therefore able to sense a more accurate mixed flow temperature even at low flow rates.