Hot Gas Bypass and Desuperheat Lines for Low-Load Compressor Operation

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Solution Overview

Problem

Conventional refrigeration systems experience compressor damage and operational disruptions due to frequent start-and-stop cycles when operating at low load conditions, which disrupts the system oil return and reduces system efficiency.

Innovation Solution

A low load operating system is introduced, featuring a hot gas bypass line from the compressor's discharge side to its suction side, a desuperheat line from upstream of the expansion valve to the suction side, and an oil return line, controlled by a monitoring system to manage compressor operation and maintain optimal pressure and oil circulation during low load conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the compressor rack is unloaded to match low load conditions, then the system adapts to low load operation, but the compressors stop and start frequently causing damage and disrupting oil return

Engineering Contradiction:

Improveload matching capabilityVSAvoidcompressor operation stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent maintains continuous compressor operation during low load conditions by implementing a hot gas bypass system. The bypass line redirects a portion of the compressed hot gas from the discharge side back to the suction side, allowing the compressor to continue running at a reduced effective load while maintaining operational continuity and preventing frequent start-stop cycles that would damage the compressors and disrupt oil return.

Inventive Principle:

Principle #20Continuity of useful action

2Productivity

If the compressor operates at very low load, then the system matches low cooling demand, but oil return is disrupted and compressor damage occurs

Engineering Contradiction:

Improvecooling outputVSAvoidcompressor damage and oil return disruption

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The hot gas bypass line acts as an intermediary mechanism that modifies the operating conditions within the compressor system. By introducing a controlled amount of hot discharge gas back to the suction side, it creates a minimum load condition that prevents oil return disruption and compressor damage while still allowing the system to operate during low cooling demand periods.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If frequent start and stop cycles occur, then the compressor matches varying load conditions, but system efficiency decreases and component wear increases

Engineering Contradiction:

Improveload response capabilityVSAvoidsystem efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The hot gas bypass system enables the compressor to maintain continuous operation during low load conditions by recirculating a portion of the discharge gas back to the suction side. This continuity prevents the energy losses and efficiency reductions associated with frequent start-stop cycles while still allowing the system to adapt to varying load conditions through controlled bypass flow.

Inventive Principle:

Principle #20Continuity of useful 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 prevents frequent compressor starts and stops, ensures continuous oil return, and extends the lifespan of refrigeration system components by maintaining stable operation and reducing wear on compressors during low load conditions.

Implementation Method 1

a hot gas bypass line extending from a discharge side of the compressor to a suction side of the compressor

Methodology Applied

Scientific EffectHot gas bypass:

Implementation Method 2

a desuperheat line extending from upstream of the expansion valve to the suction side of the compressor

Methodology Applied

Scientific EffectDesuperheating:

Implementation Method 3

the liquid refrigerant is passed through an expansion device that reduces both the pressure and the temperature

Methodology Applied

Scientific EffectPressure reduction:

Implementation Method 4

The liquid refrigerant absorbs heat from the surrounding area in an evaporator coil and evaporates to a vapor

Methodology Applied

Scientific EffectHeat absorption:

Implementation Method 5

the compressed vapor is cooled and condensed within a condenser by heat exchange with ambient air drawn or blown against a condenser coil

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Data Source

PatentUS11092370B2Systems and methods for low load compressor operations

Publication Date: 2021.08.17 HEATCRAFT REFRIGERATION WUXI CO LTD

AI summary

The present application provides a low load operating system for a refrigeration system having a compressor, a condenser, an expansion valve, and an evaporator. The low load operating system may include a hot gas bypass line extending from a discharge side of the compressor to a suction side of the compressor and a desuperheat line extending from upstream of the expansion valve to the suction side of the compressor.