Flash Tank Refrigeration Control for Compressor Suction Cooling

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Solution Overview

Problem

In commercial refrigeration systems, when the low temperature section is used more heavily than the medium temperature section, there is not enough refrigerant from the medium temperature section mixing with the hot refrigerant from the low temperature compressor, leading to a rise in temperature and reduced performance of the medium temperature compressor.

Innovation Solution

An unconventional cooling system that increases the flow of refrigerant to the medium temperature section when the temperature of the mixture at the medium temperature compressor exceeds a threshold, using a flash tank, expansion valve, and compressors to control the refrigerant flow, ensuring adequate cooling and improved compressor performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the low temperature section is used more heavily than the medium temperature section, then the cooling capacity of the low temperature section is improved, but the temperature of the mixture at the medium temperature compressor exceeds the threshold and compressor performance deteriorates

Engineering Contradiction:
Improvecooling capacity of low temperature sectionVSAvoidperformance of medium temperature compressor
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The system uses a temperature sensor to continuously monitor the temperature of the refrigerant mixture at the suction of the medium temperature compressor. When the temperature exceeds a predetermined threshold, the controller automatically adjusts the expansion valve to increase refrigerant flow to the medium temperature section, creating a closed-loop feedback control system that maintains optimal compressor performance under varying load conditions

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts the refrigerant flow distribution between the low temperature and medium temperature sections based on real-time temperature conditions. The expansion valve is controlled to vary the refrigerant flow rate to the medium temperature section, allowing the system to adapt to changing load demands and maintain proper mixture temperature at the compressor suction

Inventive Principle:
Principle #15Dynamics

2Temperature

If the flow of refrigerant to the medium temperature section is increased, then the temperature of the mixture at the medium temperature compressor is reduced, but the refrigerant flow distribution becomes unbalanced

Engineering Contradiction:
Improvetemperature of mixture at medium temperature compressorVSAvoidrefrigerant flow distribution balance
Core Design Contradiction:
TemperatureVSEase of operation

Solution Approach 1:

The controller continuously monitors the mixture temperature at the medium temperature compressor suction and dynamically adjusts the expansion valve position to maintain temperature within the optimal range. This feedback control automatically balances refrigerant flow distribution between sections based on actual operating conditions, preventing both overheating and over-cooling scenarios

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system changes the refrigerant flow parameters (flow rate, distribution ratio) dynamically based on the detected mixture temperature. When temperature exceeds the threshold, the system increases refrigerant flow to the medium temperature section; when temperature is within range, it maintains or reduces flow to preserve balanced operation

Inventive Principle:
Principle #35Parameter changes

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 reduces the temperature of the refrigerant at the suction of the medium temperature compressor, improving its performance by ensuring sufficient refrigerant flow from the medium temperature section, even when it is not being used as heavily as the low temperature section.

Implementation Method 1

The flash tank stores a refrigerant

Methodology Applied
Scientific EffectPhase separation: Density Gradient

Implementation Method 2

The expansion valve controls a flow of the refrigerant from the flash tank

Methodology Applied
Scientific EffectPressure drop and expansion cooling: Joule-Thomson Effect

Implementation Method 3

The first compressor compresses the refrigerant from the second load. The second compressor compresses a mixture of the refrigerant from the first load and the refrigerant from the first compressor

Methodology Applied
Scientific EffectCompression heating: Compression

Implementation Method 4

The first load uses the refrigerant from the flash tank to cool a space proximate the first load. The second load uses the refrigerant from the flash tank to cool a space proximate the second load

Methodology Applied
Scientific EffectHeat absorption and phase change: Heat Exchanger

Data Source

PatentEP3575712B1Cooling system
Publication Date: 2022.09.07 HEATCRAFT REFRIGERATION PRODUCTS LLC
  • EP3575712B1 patent drawingFigure 1
  • EP3575712B1 patent drawingFigure 2
  • EP3575712B1 patent drawingFigure 3

AI summary

An apparatus (200) includes a flash tank (110), a first load (115), a second load (120), a first compressor (125), a second compressor (130), and an expansion valve (205). The flash tank (110) stores a refrigerant. The first load (115) uses the refrigerant from the flash tank (110) to cool a space proximate the first load (115). The second load (120) uses the refrigerant from the flash tank (110) to cool a space proximate the second load (120). The first compressor (125) compresses the refrigerant from the second load (120). The second compressor (130) compresses a mixture of the refrigerant from the first load (115) and the refrigerant from the first compressor (125). The expansion valve (205) controls a flow of the refrigerant from the flash tank (110) to the first load (115) such that the flow of refrigerant to the first load (115) is increased when a temperature of the mixture exceeds a threshold.