Flash Tank Defrost Cooling Layout for Low-Load Refrigeration
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Solution Overview
Problem
Existing cooling systems face challenges in maintaining sufficient refrigerant flow for hot gas defrost cycles, especially when the system is not operating at full capacity or when space constraints limit the number of loads, leading to insufficient refrigerant availability for defrosting.
Innovation Solution
The cooling system directs flash gas from a flash tank and/or refrigerant from a medium temperature load to a low temperature compressor, allowing for sufficient refrigerant to be redirected to a load for defrosting, even when there are not three times as many operating loads as there are defrosting loads, by using valves to manage the flow during different operational modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the system maintains a 3:1 ratio of loads in refrigeration cycle to loads in defrost cycle, then sufficient refrigerant is available for defrosting, but the system requires more loads and occupies more space
Solution Approach 1:
The patent extracts the refrigerant supply source from the traditional model (relying solely on refrigerant from operating loads) and introduces an alternative source (flash gas from the flash tank). This allows the system to obtain sufficient refrigerant for defrosting without requiring multiple operating loads, thereby reducing the number of loads needed and the overall system footprint.
Solution Approach 2:
The flash tank serves multiple functions: it acts as a refrigerant storage device, a flash gas generation source for defrosting, and a pressure regulation component. By making the flash tank a multi-functional component, the system can perform defrosting operations using flash gas rather than requiring dedicated defrost loads, thus reducing the total number of loads required.
2Area of stationary object
If the system operates with fewer loads due to space constraints, then the system footprint is reduced, but refrigerant availability for defrosting becomes insufficient
Solution Approach 1:
The flash gas acts as an intermediary substance that bridges the gap between the refrigerant circulation system and the defrosting requirement. By introducing flash gas from the flash tank as an intermediate refrigerant source, the system can perform defrosting operations even when the number of operating loads is reduced, thus maintaining defrosting capability while reducing system footprint.
Solution Approach 2:
The patent changes the parameter of refrigerant source from exclusively using refrigerant returned from operating loads to using flash gas from the flash tank. This parameter change allows the system to maintain sufficient refrigerant availability for defrosting while operating with fewer loads, thereby reducing the system footprint.
3Use of energy by moving object
If the system runs less frequently or less strenuously, then energy consumption is reduced, but refrigerant availability for defrosting decreases
Solution Approach 1:
The flash tank generates flash gas from the refrigerant circulation process itself, making the system self-sufficient for defrosting requirements. The flash gas is produced as a byproduct of the refrigerant expanding through the expansion device, and this self-generated flash gas can be used for defrosting without requiring additional operating loads, allowing the system to run less strenuously while maintaining defrosting capability.
Solution Approach 2:
Flash gas serves as an intermediary that decouples the relationship between operating load quantity and defrosting refrigerant availability. By using flash gas from the flash tank as the defrosting refrigerant source, the system can maintain adequate refrigerant availability for defrosting even when operating less frequently or less strenuously, thus reducing energy consumption.
4Quantity of substance
If the system uses flash gas from the flash tank for defrosting, then refrigerant availability for defrosting is sufficient, but additional valve control mechanisms are required
Solution Approach 1:
The first valve serves multiple functions: it controls refrigerant flow to operating loads during normal operation, directs flash gas to the compressor during defrosting, and manages the transition between different operational modes. By making the valve multi-functional, the system achieves sufficient refrigerant availability for defrosting while using a single valve component rather than requiring separate dedicated valves for each function.
Solution Approach 2:
The valve dynamically changes its function based on operational mode. During normal cooling operation, the valve directs refrigerant to loads; during defrosting, it redirects flash gas to the compressor. This dynamic adaptability allows a single valve to handle multiple functions, reducing the need for additional valve control mechanisms while ensuring sufficient refrigerant availability for defrosting.
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 ensures that there is sufficient refrigerant available for defrosting loads, reduces the size and footprint of the cooling system, and allows for more flexible load management by eliminating the need for a 3:1 load to defrost ratio, enabling effective defrosting even in resource-constrained situations.
Implementation Method 1
The first compressor compresses the flash gas from the flash tank during a second mode of operation
Implementation Method 2
directs the compressed flash gas from the first compressor to the first load during the second mode of operation to defrost the first load
Data Source
AI summary
A system includes a flash tank, a first load, a second load, a first compressor, a second compressor, a first valve, and a second valve. The flash tank stores a refrigerant. The first and second loads use the refrigerant to cool first and second spaces. The first compressor compresses the refrigerant from the first load during a first mode of operation and a flash gas from the flash tank during a second mode of operation. The second compressor compresses a mixture of the refrigerant from the first and second loads during the first mode of operation. The first valve directs the flash gas from the flash tank to the first compressor during the second mode of operation. The second valve directs the compressed flash gas from the first compressor to the first load during the second mode of operation to defrost the first load.