Expansion valve with a variable orifice area

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Solution Overview

Problem

Existing expansion valves in vapor compression systems, such as refrigeration and air conditioning systems, face challenges in efficiently managing differential pressure transients and refrigerant supply, leading to energy inefficiencies and potential system instability, especially when transitioning between compressor on and off cycles.

Innovation Solution

The expansion valve design features a piston that moves within an outlet orifice, adjusting the cross-sectional flow area in response to differential pressure changes, allowing for precise control of fluid flow and preventing transient effects by increasing the flow area when pressure increases, thus ensuring adequate refrigerant supply to micro channel evaporators.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the cross-sectional flow area of the orifice decreases as differential pressure increases (conventional design), then the valve provides stable flow control under varying pressure, but it causes pressure transients and instability when the compressor is switched on

Engineering Contradiction:

Improvesystem stabilityVSAvoidrefrigerant supply rate

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent inverts the conventional relationship between differential pressure and flow area. Instead of the flow area decreasing as pressure increases, the piston is designed so that the flow area increases as differential pressure increases. This is achieved by the piston geometry where the outlet end has a larger cross-sectional area than the inlet end, causing the annular flow area between the piston and orifice wall to expand with pressure differential. This inversion eliminates pressure transients and ensures adequate refrigerant supply during compressor start-up.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If a seal is provided between the movable piston and the inner wall of the housing (conventional design), then the valve provides tight closure, but it creates friction that prevents precise movement and flow adjustment

Engineering Contradiction:

Improvevalve tightnessVSAvoidpiston movement precision

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent extracts the sealing function from the interface between the piston and the housing wall. Instead of sealing against the housing wall, the piston seals against the outlet orifice at the outlet end. This is achieved by positioning the outlet end of the piston to abut against the outlet orifice, creating a seal at the closure position. This extraction eliminates the friction between the piston and housing wall, allowing precise piston movement while maintaining valve tightness through the outlet orifice seal.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If the piston cross-sectional area is uniform along its length, then the manufacturing is simpler, but it cannot provide the required variable flow area response to pressure changes

Engineering Contradiction:

Improvepiston manufacturingVSAvoidflow area variability

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by varying the cross-sectional area of the piston along its length. Specifically, the outlet end of the piston has a larger cross-sectional area than the inlet end. This non-uniform geometry is localized to the outlet end region, while the inlet end maintains a simpler form. This local variation in cross-sectional area enables the annular flow area between the piston and orifice wall to vary with piston position and pressure differential, providing the required adaptability while keeping manufacturing complexity manageable.

Inventive Principle:

Principle #3Local quality

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 design enhances energy efficiency by minimizing transient effects and maintaining optimal refrigerant flow, reducing energy consumption and ensuring system stability during varying operational conditions.

Implementation Method 1

The piston (8) is movable inside the outlet orifice (7) in response to a differential pressure across the expansion valve (1)

Methodology Applied

Scientific EffectDifferential pressure: Pressure Gradient

Implementation Method 2

a cross-sectional flow area of the outlet orifice (7) between a circumference at an inner surface of the outlet orifice (7) and a circumference at an outer surface of the piston (8) varies as a function of the position of the piston (8) relative to the outlet orifice (7)

Methodology Applied

Scientific EffectFlow area variation:

Data Source

PatentUS10281181B2Expansion valve with a variable orifice area

Publication Date: 2019.05.07 DANFOSS AS

AI summary

An expansion valve (1) for a vapour compression system, the valve (1) comprising a first valve part (5) having an outlet orifice (7) and a piston (8) movable inside the outlet orifice (7) in response to a differential pressure across the expansion valve (1), controlling a fluid flow through the first valve part (5). A cross-sectional flow area of the outlet orifice (7) between a circumference at an inner surface of the outlet orifice (7) and a circumference at an outer surface of the piston (8) varies as a function of the position of the piston (8) relative to the outlet orifice (7). A first cross-sectional flow area is defined at a first differential pressure, and a second cross-sectional flow area is defined at a second differential pressure, where the first cross-sectional flow area is smaller than the second cross-sectional flow area, and the first differential pressure is lower than the second differential pressure.