Refrigeration Circuit Valve Control to Reduce Charge Migration Losses
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Solution Overview
Problem
Conventional refrigeration systems experience efficiency losses due to refrigerant migration during compressor OFF cycles, leading to suboptimal performance during the initial phase of compressor ON cycles, as the refrigerant is not in an ideal state throughout the circuit, and heat exchanging members can exacerbate this issue by inhibiting mass flow rate upon startup.
Innovation Solution
The system employs a control logic that considers the location and condition of refrigerant in the circuit, allowing for operation at sub-optimal thermodynamic efficiency during the initial compressor ON cycle to rapidly redistribute refrigerant, thereby improving overall system efficiency by bypassing heat exchanging members during this phase and using a valve system with solenoid-driven or stepper-motor driven valves to direct refrigerant flow through pressure reduction devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If heat exchanging members (suction line heat exchangers and intercoolers) are used to improve steady-state efficiency, then system efficiency during steady-state operation is improved, but refrigerant migration during compressor OFF cycles is prolonged and mass flow rate upon startup is inhibited
Solution Approach 1:
The control system performs preliminary detection of refrigerant conditions (temperature, pressure, state) before compressor startup. Based on this detection, the system pre-adjusts the flow path configuration to optimize startup performance, preventing refrigerant migration issues before they occur. This preliminary preparation allows the system to quickly transition to efficient operation without being hindered by heat exchanging members during the critical startup phase.
Solution Approach 2:
The system dynamically switches between different flow path configurations based on operational conditions. During compressor OFF cycles and startup phases, the system configures flow paths to minimize refrigerant migration and maximize mass flow rate. During steady-state operation, heat exchanging members are engaged to optimize efficiency. This dynamic reconfiguration resolves the contradiction by adapting the system structure to different operational requirements.
2Use of energy by moving object
If the compressor is turned OFF during down periods, then energy consumption is reduced, but refrigerant redistributes and pools in the evaporator causing efficiency losses
Solution Approach 1:
The control system continuously monitors refrigerant temperature, pressure, and state in real-time. Based on this feedback, the system determines the optimal moment to restart the compressor and pre-configures the flow path to prevent refrigerant pooling. This feedback mechanism allows the system to respond to actual refrigerant conditions rather than following a fixed cycle, minimizing efficiency losses during startup while maintaining energy savings during down periods.
Solution Approach 2:
Before compressor restart, the system performs preliminary detection of refrigerant conditions and pre-adjusts the flow path configuration to prevent refrigerant migration to the evaporator. This preliminary action ensures that when the compressor starts, refrigerant flows efficiently through the system without pooling, thereby reducing startup efficiency losses while preserving energy savings during off-periods.
3Productivity
If the system operates to rapidly redistribute refrigerant during initial compressor ON cycle, then overall system efficiency is improved, but thermodynamic efficiency during this phase is sub-optimal
Solution Approach 1:
The compression cycle is segmented into distinct phases: an initial redistribution phase and a subsequent steady-state phase. During the initial phase, the system prioritizes rapid refrigerant redistribution through optimized flow paths, accepting sub-optimal thermodynamic efficiency. Once redistribution is complete, the system transitions to the steady-state phase where heat exchanging members are engaged for optimal thermodynamic efficiency. This segmentation allows the system to optimize for different objectives at different times, improving overall productivity.
Solution Approach 2:
The system employs periodic action by alternating between different operational modes: rapid redistribution mode during startup and efficient steady-state mode during normal operation. This periodic switching between modes allows the system to achieve rapid refrigerant redistribution when needed while maintaining high thermodynamic efficiency during extended operation periods, thereby improving overall system productivity without excessive energy loss.
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 enables the system to reach a more efficient, steady-state operational regime quicker, reducing efficiency losses associated with refrigerant migration and heat transfer inefficiencies, resulting in improved overall efficiency and faster cooling performance.
Implementation Method 1
the compressor operates to increase the pressure and temperature of the refrigerant existing in a vapor state
Implementation Method 2
The refrigerant vapor then travels through the condenser, where it is condensed into a liquid state at constant pressure and temperature
Implementation Method 3
The liquid refrigerant then passes through the pressure reduction device, and experiences a significant drop in pressure
Implementation Method 4
the refrigerant is typically fully vaporized by warmer air that is passed over the evaporator from the compartment intended to be cooled
Data Source
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AI summary
A refrigerator appliance including a refrigerant circuit between a condenser, an evaporator, and a compressor that includes two conduits and pressure reducing devices arranged in parallel between the evaporator and the condenser. The appliance also includes a valve system to direct refrigerant through one, both or none of the conduits and pressure reducing devices, and a heat exchanging member in thermal contact with either one pressure reducing device, or one conduit between the pressure reducing device and the valve system.