Dual-compressor refrigeration unit
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Solution Overview
Problem
Dual-compressor refrigeration units face inefficiencies in load management, particularly in preventing short cycling and optimizing compressor operation to maintain consistent heat transfer fluid temperatures across varying loads.
Innovation Solution
A method and system where the second compressor is initialized when the first compressor reaches a dynamically controlled crossover frequency, computed based on its capacity and maximum speed, to prevent short cycling and ensure efficient operation, with a controller executing an algorithm to manage compressor speeds and prevent minimum speed operation when both compressors are active.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the second compressor is initialized when the first compressor reaches a fixed frequency threshold, then the control logic is simple, but short cycling occurs and operational efficiency deteriorates
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed frequency threshold to a dynamically computed crossover frequency that adapts to the first compressor's actual capacity and maximum speed characteristics. The crossover frequency is calculated as a function of these parameters, allowing the control system to optimize the second compressor initialization point based on real-time operating conditions, thereby preventing short cycling while maintaining operational reliability.
2Reliability
If the second compressor is initialized early to prevent short cycling, then compressor operation stability improves, but the first compressor may not reach optimal operating speed, reducing overall system efficiency
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the crossover frequency parameter based on the first compressor's capacity and maximum speed. This allows the system to find the optimal initialization point for the second compressor that balances operational stability with maintaining the first compressor's efficient operating range, thereby resolving the trade-off between reliability and productivity.
3Use of energy by moving object
If both compressors run at minimum speeds, then energy consumption is reduced, but the heat transfer fluid temperature consistency deteriorates
Solution Approach 1:
The patent applies feedback by implementing controller logic that monitors system conditions and adjusts compressor speeds dynamically. The controller prevents both compressors from operating at minimum speeds simultaneously, using feedback from system performance to maintain temperature consistency while optimizing energy consumption through intelligent speed management.
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 approach enhances operational efficiency by preventing short cycling and maintaining consistent heat transfer fluid temperatures, ensuring efficient operation across varying loads while being compatible with different compressor sizes and speeds.
Implementation Method 1
a first compressor (24) constructed and arranged to compress a first heat transfer fluid that may be a first refrigerant
Implementation Method 2
a first condenser (28) operatively coupled to the first compressor
Implementation Method 3
an evaporator (44) constructed and arranged to flow the first and second refrigerants received from the respective first and second condensers for chilling a heat transfer fluid
Implementation Method 4
the crossover frequency is dynamically controlled and computed based on a capacity and a maximum speed of the first compressor
Data Source
Figure 1
Figure 2
AI summary
A refrigeration unit may include a first compressor constructed and arranged to compress a first refrigerant, and a second compressor constructed and arranged to compress a second refrigerant. A first condenser of the refrigeration unit is operatively coupled to the first compressor, and a second condenser is operatively coupled to the second compressor. An evaporator of the refrigeration unit is constructed and arranged to flow the first and second refrigerants received from the respective first and second condensers for chilling a heat transfer fluid. A controller of the refrigeration unit includes a computer processor and a storage media for executing a pre-programmed algorithm for initialing the second compressor when a predetermined crossover frequency of the first compressor is reached as a system load increases.