Staged expansion system and method
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Solution Overview
Problem
Refrigeration systems face performance issues due to increased discharge temperatures caused by new refrigerants, especially under high ambient conditions, which require additional cooling for compressors.
Innovation Solution
A refrigeration system design incorporating a first expansion device downstream of the condenser and upstream of a heat exchanger, and a second expansion device downstream of the condenser and upstream of the compressor, to cool the refrigerant and reduce compressor discharge temperature without impacting cooling capacity, using a liquid suction heat exchanger or brazed plate heat exchanger for efficient heat exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If replacement refrigerants are used in the refrigeration system, then refrigerant regulations are met, but compressor discharge temperature increases causing performance issues
Solution Approach 1:
The patent divides the single expansion device into two separate expansion devices positioned at different locations in the refrigerant loop. The first expansion device is positioned downstream of the condenser and upstream of the evaporator, while the second expansion device is positioned downstream of the evaporator and upstream of the compressor. This segmentation allows independent control of refrigerant expansion at different stages, enabling temperature management that reduces compressor discharge temperature while maintaining regulation compliance.
Solution Approach 2:
The patent introduces a heat exchanger as an intermediary component between the two expansion devices. This heat exchanger facilitates heat exchange between the refrigerant from the condenser and the refrigerant from the evaporator, allowing thermal energy transfer that cools the refrigerant before it enters the compressor. This intermediary component enables temperature control without directly modifying the compressor or refrigerant properties.
2Temperature
If additional cooling for the compressor is implemented, then discharge temperature is reduced, but system complexity increases
Solution Approach 1:
The heat exchanger serves multiple functions within the system: it cools the refrigerant before compression, recovers heat from the evaporator outlet refrigerant, and integrates into the existing refrigeration cycle without requiring separate cooling systems. The two expansion devices work together with the heat exchanger to provide both temperature control and refrigerant flow management, reducing the need for additional dedicated cooling components.
Solution Approach 2:
The patent combines the cooling function with the existing heat exchanger that is already part of the refrigeration system, rather than adding a completely separate cooling system. The heat exchanger merges the cooling of compressor inlet refrigerant with the heat recovery from evaporator outlet refrigerant, achieving temperature reduction while utilizing existing system infrastructure.
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
Effectively controls compressor suction/discharge temperature, reducing discharge temperature while maintaining cooling capacity performance, suitable for transportation refrigeration systems handling temperature-sensitive cargo across varying conditions.
Implementation Method 1
A heat exchanger is disposed downstream of the condenser and upstream of the evaporator, and disposed downstream of the evaporator and upstream of the compressor, the heat exchanger configured to facilitate heat exchange between the refrigerant supplied from the condenser and the refrigerant supplied from the evaporator
Implementation Method 2
a second expansion device is disposed downstream of the condenser and upstream of the heat exchanger. The second expansion device is configured to cool the refrigerant passing therethrough
Data Source
AI summary
A refrigeration system includes a compressor configured to compress a refrigerant, a condenser, and an evaporator. A heat exchanger is disposed downstream of the condenser and upstream of the evaporator, and disposed downstream of the evaporator and upstream of the compressor, the heat exchanger configured to facilitate heat exchange between the refrigerant supplied from the condenser and the refrigerant supplied from the evaporator. A first expansion device is disposed downstream of the heat exchanger and upstream of the evaporator, and a second expansion device is disposed downstream of the condenser and upstream of the heat exchanger. The second expansion device is configured to cool the refrigerant passing therethrough to cool the refrigerant in the heat exchanger supplied from the evaporator to the compressor.