Tandem Compressor Suction Balancing for Partial-Load Lubrication

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Solution Overview

Problem

HVAC systems with multiple compressors face disproportionate fluid distribution during partial load conditions, leading to inadequate lubrication and reduced performance and lifespan of compressors due to mechanical devices' wear and maintenance costs.

Innovation Solution

A compressor system with a suction equalization line and obstruction devices in branch suction lines to regulate fluid flow, ensuring prescribed liquid levels in compressors during partial load operations by restricting flow to deactivated compressors and optimizing suction pressure differentials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If mechanical devices such as flow restrictors are used to regulate fluid flow to each compressor, then fluid distribution can be controlled, but the devices are subject to wear and increased maintenance expense

Engineering Contradiction:

Improvefluid flow regulationVSAvoiddevice wear and maintenance

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent removes mechanical flow restrictors from the system entirely and replaces them with a suction equalization line that uses pressure differential and fluid dynamics to automatically balance flow distribution. This extraction of the mechanical component eliminates wear and maintenance issues while preserving flow regulation functionality.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The suction equalization line creates a self-regulating system where the pressure differential between compressors automatically controls fluid distribution without external mechanical devices. The system self-adjusts based on operating conditions, eliminating the need for maintenance-prone mechanical restrictors.

Inventive Principle:

Principle #25Self-service

2Productivity

If multiple compressors operate in parallel to increase capacity, then system capacity is improved, but disproportionate fluid distribution occurs between compressors during partial load conditions

Engineering Contradiction:

Improvesystem capacityVSAvoidfluid distribution balance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The suction equalization line equalizes the suction pressure between parallel compressors by providing a common suction source. This pressure equalization ensures that during partial load conditions, fluid distributes proportionally to each compressor's actual demand, preventing disproportionate flow while maintaining the ability to operate multiple compressors in parallel for increased capacity.

Inventive Principle:

Principle #12Equipotentiality

3Productivity

If fluid flow is not properly balanced between compressors, then performance is maintained, but inadequate lubrication occurs and compressor lifespan is reduced

Engineering Contradiction:

Improvecompressor performanceVSAvoidcompressor lifespan

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The suction equalization line creates a feedback mechanism where the suction pressure from the evaporator serves as a common reference for both compressors. Each compressor draws suction fluid through this equalization line, which automatically adjusts flow distribution based on each compressor's actual operating conditions, ensuring proper lubrication and protecting compressor lifespan while maintaining performance.

Inventive Principle:

Principle #23Feedback

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 maintains balanced fluid flow and prescribed liquid levels in compressors, reducing wear and maintenance costs while enhancing performance and lifespan by preventing fluid imbalance and lubrication issues during partial load conditions.

Implementation Method 1

A suction equalization line is configured such that a suction pressure differential between individual compressors in the multiple compressor system is reduced

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 2

An obstruction device is disposed in at least one of the first branch suction line and the second branch suction line. Responsive to deactivation of at least one of the first compressor and the second compressor, the obstruction device is at least partially closed thereby causing prescribed liquid levels in the first compressor and the second compressor during partial-load operation

Methodology Applied

Scientific EffectFluid flow restriction:

Data Source

PatentUS11415347B2Method and apparatus for balanced fluid distribution in tandem-compressor systems

Publication Date: 2022.08.16 LENNOX IND INC

AI summary

A compressor system includes a first compressor and a second compressor. A suction equalization line fluidly couples the first compressor and the second compressor. A first branch suction line is fluidly coupled to the first compressor and a second branch suction line is fluidly coupled to the second compressor. A main suction line is fluidly coupled to the first branch suction line and the second branch suction line. An obstruction device is disposed in at least one of the first branch suction line and the second branch suction line. Responsive to deactivation of at least one of the first compressor and the second compressor, the obstruction device is at least partially closed thereby causing prescribed liquid levels in the first compressor and the second compressor during partial-load operation.