Expansion Valve Control During Refrigeration Defrost Cycles

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Solution Overview

Problem

Refrigeration and air conditioning systems face challenges in efficiently defrosting evaporators without disrupting coolant flow, particularly when solenoid valves for diverting coolant flow are spatially distant from the control device associated with the electronic expansion valve, leading to potential damage and noise pollution during defrosting.

Innovation Solution

A temperature sensor is placed upstream of the expansion valve to detect temperature changes, allowing the control device to recognize the start of defrosting without electrical connections to solenoid valves, enabling the expansion valve to be moved into a static state, thus preventing damage and noise during the defrosting process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If solenoid valves are placed far from the evaporator for centralized control, then ease of operation and system management are improved, but device complexity and difficulty of establishing electrical connections increase

Engineering Contradiction:

Improvecentralized controlVSAvoidelectrical connection complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent introduces a temperature sensor as an intermediary element that detects temperature changes in the coolant circuit and transmits this information to the control device. This mediator enables the control device to recognize defrosting conditions without requiring direct electrical connections to the solenoid valves, thus resolving the contradiction between centralized control and electrical connection complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical/electrical signal transmission system with a temperature-based detection system. Instead of using electrical signals from solenoid valves to indicate defrosting conditions, the system uses temperature sensor readings to detect coolant flow changes, thereby substituting the electrical connection requirement with a thermal field-based detection method

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If the expansion valve continues to operate during defrosting, then control function is maintained, but damage to the expansion valve and noise pollution occur

Engineering Contradiction:

Improvecontrol function continuityVSAvoidexpansion valve damage and noise

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback mechanism where the temperature sensor continuously monitors the coolant temperature and feeds this information back to the control device. Based on this feedback, the control device automatically adjusts the expansion valve operation - closing it during defrosting conditions and reopening it after defrosting completes, thus preventing damage and noise while maintaining control function continuity

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent makes the expansion valve operation dynamic by enabling it to switch between different operational states (open during normal operation, closed during defrosting) based on real-time temperature conditions. This dynamic adjustment allows the system to adapt to changing operational requirements and avoid harmful effects during defrosting cycles

Inventive Principle:

Principle #15Dynamics

3Productivity

If defrosting is performed quickly to minimize food exposure to increased temperatures, then productivity is improved, but the risk of expansion valve damage during the process increases

Engineering Contradiction:

Improvedefrosting speedVSAvoidexpansion valve protection

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent performs preliminary action by detecting the start of defrosting conditions through temperature sensor readings before the actual defrosting process begins. The control device proactively closes the expansion valve in advance, preparing the system for the upcoming defrosting cycle and preventing any potential damage before it can occur

Inventive Principle:

Principle #10Preliminary action

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 solution allows for efficient defrosting without electrical connections between solenoid valves and control devices, ensuring the expansion valve is protected and noise-free, while reducing the effort and complexity of electrical line layout, enabling seamless transition back to normal operation post-defrosting.

Implementation Method 1

A temperature sensor is connected upstream of the expansion valve on its side remote from the evaporator in the coolant circuit, with the control device being designed for the interruption of its control function and for the arresting of the expansion valve in a static state when the temperature sensor delivers a temperature value lying below a predetermined threshold value

Methodology Applied

Scientific EffectTemperature detection:

Data Source

PatentUS7698904B2Control device for refrigeration or air conditioning systems

Publication Date: 2010.04.20 COPELAND EUROPE GMBH

AI summary

The invention relates to a control unit for controlling the expansion valve of a refrigeration or air conditioning system, comprising a temperature sensor that is connected upstream of the expansion valve in the coolant circuit. If the control unit detects a decrease in temperature of the aforementioned temperature sensor, which is generally caused by the start of a defrosting process, it displaces the expansion valve into a static state, to protect said valve during the defrosting process.