Refrigeration System Warm Defrost Using MT Compressor Suction Heat
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Solution Overview
Problem
Existing refrigeration systems face inefficiencies in defrosting processes, particularly those using carbon dioxide (CO2) compression systems, which often require high-pressure differentials and specialized valves, posing safety concerns and increasing operational complexity.
Innovation Solution
A refrigeration system design utilizing a low temperature (LT) compressor, medium temperature (MT) compressor, low and medium temperature evaporators, and a hot gas tank, where warm refrigerant from the MT compressor is used in a reverse direction through the evaporators for defrosting, managed by a control system that includes valves and sensors to regulate pressure and fluid flow, eliminating the need for high-pressure differentials and specialized valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-pressure differentials and specialized valves are used for defrosting in CO2 compression systems, then defrosting efficiency is improved, but safety risks and device complexity increase
Solution Approach 1:
The patent extracts the defrosting function from the main refrigeration cycle by using a separate hot gas tank and dedicated defrosting circuit. The hot gas tank stores warm refrigerant separately, and defrosting is achieved by directing this stored hot gas through the evaporator without requiring high-pressure differentials or specialized valves in the main system.
Solution Approach 2:
The hot gas tank serves as an intermediary device that decouples the defrosting function from the main refrigeration cycle. By storing hot gas in this intermediate reservoir and using it for defrosting, the system avoids the need for complex high-pressure control mechanisms while maintaining effective defrosting capability.
2Productivity
If high-pressure differentials are used for defrosting in CO2 compression systems, then defrosting capability is improved, but safety risks increase
Solution Approach 1:
The patent removes the high-pressure differential requirement from the defrosting process by using a separate hot gas tank system. The defrosting function is achieved through controlled release of stored hot gas at lower pressure differentials, eliminating the safety hazards associated with high-pressure operations during defrosting.
Solution Approach 2:
The system converts the potentially harmful high-pressure refrigerant into a beneficial defrosting agent by storing it in a hot gas tank under controlled conditions. The hot gas is then safely directed through the evaporator for defrosting, transforming a high-risk element into a useful function without requiring dangerous pressure differentials.
3Ease of operation
If specialized valves are used for defrosting operations, then defrosting control is improved, but operational complexity increases
Solution Approach 1:
The patent extracts the specialized valve requirements from the defrosting system by using a hot gas tank with simple inlet and outlet connections. The defrosting control is achieved through basic valve operations on the tank rather than requiring complex specialized valves integrated into the main refrigeration circuit.
Solution Approach 2:
The hot gas tank serves multiple functions: it stores hot gas for defrosting, acts as a pressure equalization chamber, and provides a simple control interface. This multi-functional design eliminates the need for specialized single-purpose valves, reducing overall system complexity while maintaining effective defrosting control.
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 achieves efficient defrosting without high-pressure risks, reduces operational complexity, and lowers electricity consumption by using warm refrigerant from the MT compressor, enhancing safety and efficiency in defrosting operations.
Implementation Method 1
warm refrigerant from a suction side of the MT compressor... directing the warm refrigerant to pass through the medium temperature evaporator in a reverse direction
Implementation Method 2
the warm refrigerant used for the defrost cycle... efficient defrosting without high-pressure risks
Data Source
AI summary
A method for defrosting an evaporator of a refrigeration system includes providing a refrigeration system including a low temperature (LT) compressor, a medium temperature (MT) compressor, a low temperature evaporator, and a medium temperature evaporator. The method includes initiating a defrost cycle for the refrigeration system by closing a return valve to shut off refrigerant return to the LT compressor from an outlet of the low temperature evaporator and opening a defrost supply valve to define a fluid flow path between a suction side of the MT compressor and an outlet of the low temperature evaporator. The method includes operating the LT compressor and the MT compressor such that warm refrigerant from the suction side of the MT compressor is provided through the low temperature evaporator and returned to a suction side of the LT compressor through a hot gas tank.