Hot gas defrost using medium temperature compressor discharge
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Solution Overview
Problem
Existing refrigeration systems face inefficiencies in evaporator defrosting, requiring long times and high energy consumption, especially when defrosting multiple evaporators, and may not provide adequate defrosting in certain scenarios.
Innovation Solution
A refrigeration system utilizing a medium temperature discharge gas with a defrost-mode expansion valve to depressurize high-pressure, high-temperature refrigerant for efficient defrosting, achieving higher refrigerant flow rates and temperatures to rapidly and efficiently defrost multiple evaporators, even in the absence of low-temperature compressors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If previous defrost processes are used, then evaporators can be defrosted, but the process takes a relatively long time and consumes a relatively large amount of energy
Solution Approach 1:
The patent changes the temperature parameter of the defrosting medium by using medium-temperature compressor discharge gas (e.g., 110°C) instead of conventional defrosting methods. This parameter change enables rapid defrosting of multiple evaporators simultaneously, reducing defrost time while improving productivity
Solution Approach 2:
The patent makes the medium-temperature compressor discharge serve multiple functions: it provides refrigeration cooling during normal operation and serves as a high-temperature defrosting medium when needed. This multi-functionality allows the same system component to address both cooling and defrosting requirements, reducing the need for separate defrosting equipment
2Productivity
If previous defrost processes are used, then evaporators can be defrosted, but a relatively large amount of energy is consumed
Solution Approach 1:
The patent converts the high-temperature discharge gas from the medium-temperature compressor, which would otherwise be wasted heat, into a useful defrosting medium. By utilizing this high-temperature gas to defrost evaporators, the system recovers waste thermal energy and applies it to a useful function, reducing overall energy consumption while improving defrosting efficiency
Solution Approach 2:
The system uses its own medium-temperature compressor discharge to perform defrosting operations, eliminating the need for separate defrosting equipment or external energy sources. The refrigeration system serves itself by utilizing its operational byproducts (high-temperature discharge gas) to maintain its own components
3Productivity
If previous defrost processes are used, then some evaporators can be defrosted, but adequate defrosting cannot be provided when a relatively large number of evaporators need to be defrosted
Solution Approach 1:
The medium-temperature compressor discharge can be distributed to multiple evaporators simultaneously for defrosting, making the defrosting system universal and scalable. This approach maintains reliability across systems with varying numbers of evaporators, as the high-temperature gas can be allocated to any number of evaporators that require defrosting
4Productivity
If high pressure, high temperature discharge gas is used for defrosting, then defrost performance is improved, but the system requires evaporators configured to support operation at increased pressures
Solution Approach 1:
The patent changes the pressure parameter of the refrigerant system by operating evaporators at increased pressures (e.g., 45 bar or 60 bar) to enable the use of high-temperature discharge gas for defrosting. This parameter change allows the system to achieve superior defrost performance while maintaining a relatively simple configuration by integrating pressure-resistant evaporators into the existing system architecture
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 enables rapid and efficient defrosting of multiple evaporators with improved pressure differentials and higher refrigerant flow rates, maintaining efficient refrigeration processes and ensuring effective defrosting across various operational conditions.
Implementation Method 1
The refrigeration system facilitates the development of an increased pressure differential to drive the flow of refrigerant during defrost processes
Implementation Method 2
The gas cooler is configured to receive at least a portion (e.g., up to all when all evaporator units in refrigeration mode) of the compressed refrigerant and facilitate heat transfer from the received refrigerant to the ambient air, thereby cooling the refrigerant
Implementation Method 3
The expanded refrigerant is provided to defrost one or more evaporators of the refrigeration system
Data Source
AI summary
A refrigeration system includes an expansion valve downstream of one or more medium temperature compressors. The expansion valve is configured to decrease pressure of a portion of refrigerant output by the one or more medium temperature compressors. When defrost operation of an evaporator is indicated, the refrigerant with decreased pressure from the expansion valve is provided to the evaporator for at least a period of time sufficient to defrost the evaporator.