Multi-Evaporator Trans-Critical Cooling With Lower Throttling Loss

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Solution Overview

Problem

Aircraft cooling systems face inefficiencies due to bulky gas-based systems and significant throttling losses from back pressure regulators, which limit their ability to effectively manage varying ambient conditions and provide multiple evaporator temperatures.

Innovation Solution

A multi-evaporator cooling system with a compressor circuit generating multiple levels of evaporating pressures, using non-isenthalpic expansion and multiple heat exchangers to optimize refrigerant flow and reduce throttling losses, allowing for efficient operation across different heat loads and temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a gas-based cooling system is used to cover the range of ambient conditions, then the system can accommodate wide operating conditions, but the system becomes bulky and low efficiency

Engineering Contradiction:

Improveaccommodation of ambient conditionsVSAvoidsystem efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The system changes the refrigerant operating parameters by using a trans-critical cycle instead of a conventional sub-critical cycle. The refrigerant operates above its critical pressure in the heat exchanger, allowing the system to adapt to wide ambient conditions while maintaining higher efficiency through non-isenthalpic expansion processes that reduce throttling losses

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional isenthalpic expansion device (throttling valve) with a non-isenthalpic expansion mechanism such as an expansion turbine or ejector. This substitution eliminates the throttling losses inherent in isenthalpic expansion, improving system efficiency while maintaining adaptability to varying ambient conditions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Temperature

If back pressure regulators are installed downstream of each evaporator to maintain different evaporating pressures, then multiple evaporator temperatures can be achieved, but significant throttling losses occur resulting in thermodynamic loss

Engineering Contradiction:

Improveevaporator temperaturesVSAvoidthrottling losses

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The patent substitutes the isenthalpic back pressure regulators with non-isenthalpic expansion devices such as expansion turbines or ejectors. These devices recover work during the expansion process or use momentum transfer to reduce pressure, eliminating the throttling losses that occur with conventional regulators while maintaining the ability to provide different evaporator temperatures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary non-isenthalpic expansion device between the high-pressure refrigerant source and the low-pressure evaporators. This intermediary device enables pressure reduction without the harmful throttling effect, allowing multiple evaporators to operate at different temperatures while minimizing energy loss

Inventive Principle:

Principle #24Intermediary (Mediator)

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 system enhances cooling performance by reducing bulk and improving efficiency, enabling tailored temperature control for various aircraft components while minimizing thermodynamic losses.

Implementation Method 1

at least one compressor configured to compress a refrigerant to a first pressure

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 2

a heat exchanger configured to receive the compressed refrigerant from the at least one compressor and cool the compressed refrigerant

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 3

a first evaporator circuit configured to receive the compressed refrigerant from the heat exchanger, expand the compressed refrigerant to a second pressure that is lower than the first pressure

Methodology Applied

Scientific EffectNon-isenthalpic expansion:

Data Source

PatentUS9657969B2Multi-evaporator trans-critical cooling systems

Publication Date: 2017.05.23 ROLLS ROYCE CORP

AI summary

A multi-evaporator cooling system includes a compressor circuit that generates multiple levels of evaporating pressures, the circuit comprising at least one compressor configured to compress a refrigerant to a first pressure, a heat exchanger configured to receive the compressed refrigerant from the at least one compressor and cool the compressed refrigerant, a first evaporator circuit configured to receive the compressed refrigerant from the heat exchanger, expand the compressed refrigerant to a second pressure that is lower than the first pressure, and return the refrigerant to the compressor circuit, and a second evaporator circuit configured to receive the compressed refrigerant from the heat exchanger, expand the compressed refrigerant to a third pressure that is lower than the second pressure, and return the refrigerant to the compressor circuit.