Refrigerant Flow Sequencer for Reheat Coil Flooding Prevention

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Solution Overview

Problem

Vapor-compression air conditioning systems face issues with unwanted refrigerant flow during heat exchanger control valve transitions and compressor flooding due to pressure and temperature fluctuations, leading to system undercharging during heating mode.

Innovation Solution

A refrigerant flow sequencer is introduced between the system reversing valve and the reheat heat exchanger, which includes a flow restrictor and O-ring mechanism to manage pressure differences and prevent undesirable refrigerant flow, acting as a check valve and flow limiting device during valve transitions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a refrigerant bypass is added to return refrigerant from inactive components to the active flow path, then refrigerant recovery is improved, but compressor flooding occurs due to slow transition time of control valve actuator

Engineering Contradiction:

Improverefrigerant recoveryVSAvoidcompressor flooding

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The flow sequencer is pre-configured with check valves and flow restrictors that automatically activate before the control valve completes its transition. This preliminary action prevents refrigerant from entering inactive components during the transition period, avoiding compressor flooding while ensuring complete refrigerant recovery.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The flow sequencer acts as an intermediary device between the refrigerant bypass and the control valve. It mediates the refrigerant flow by using check valves and flow restrictors to control the timing and rate of refrigerant return, preventing harmful compressor flooding while maintaining effective refrigerant recovery.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If pressure and temperature conditions are established during heating mode, then refrigerant can migrate to charge reservoir and reheat coil, but system behaves as though undercharged

Engineering Contradiction:

Improveheating mode operationVSAvoidsystem charge stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The flow sequencer extracts and isolates the charge reservoir and reheat coil from the main refrigerant circulation path during heating mode transitions. By using check valves to block refrigerant migration to these components, the system maintains proper charge distribution and prevents undercharging behavior while preserving heating mode functionality.

Inventive Principle:

Principle #2Taking out (Extraction)

3Stability of the object's composition

If heat exchanger control valve transitions slowly, then refrigerant flow control is stable, but transition time increases causing compressor flooding

Engineering Contradiction:

Improverefrigerant flow control stabilityVSAvoidvalve transition time

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The flow sequencer with check valves performs preliminary action by pre-establishing proper refrigerant flow paths before the control valve completes its slow transition. This prevents refrigerant from entering inactive components during the extended transition period, eliminating compressor flooding while maintaining the stability benefits of slow valve transitions.

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

The refrigerant flow sequencer effectively prevents compressor flooding and ensures stable refrigerant flow, maintaining system charge during heating mode operations by managing pressure differences and sealing off flow when necessary.

Implementation Method 1

manage pressure differences and prevent undesirable refrigerant flow

Methodology Applied

Scientific EffectPressure difference: Pressure Gradient

Implementation Method 2

O-ring mechanism to manage pressure differences and prevent undesirable refrigerant flow

Methodology Applied

Scientific EffectSealing:

Implementation Method 3

acting as a check valve and flow limiting device during valve transitions

Methodology Applied

Scientific EffectCheck valve mechanism: Valve

Data Source

PatentUS7823404B2Air conditioning system with variable condenser reheat and refrigerant flow sequencer

Publication Date: 2010.11.02 LENNOX MANUFACTURING INC

AI summary

A vapor-compression air conditioning system comprising a blower positioned in a return air flow path from a conditioned space, a reheat heat exchanger positioned in the return air flow path and downstream from the blower, a system reversing valve fluidly coupled to the reheat heat exchanger, and a refrigerant flow sequencer interposed the system reversing valve and the reheat heat exchanger. A method of manufacturing an air conditioning system is also provided.