Cooling system and a method for control thereof
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Solution Overview
Problem
Compressor cooling systems in household refrigerators experience efficiency losses due to non-optimal refrigerant flow rates through capillary tubes, which vary with pressure differences between the condenser and evaporator, leading to energy wastage during compressor on and off phases.
Innovation Solution
A valve is strategically controlled to open a short time before the compressor on-phase and close a short time before the compressor off-phase to optimize refrigerant flow, ensuring better alignment with optimal working conditions and reducing energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a capillary tube is used to reduce refrigerant pressure from condenser to evaporator, then pressure reduction is achieved, but the refrigerant mass flow rate becomes non-optimal and varies with pressure differences
Solution Approach 1:
The patent applies a dynamic expansion valve that can adjust its opening degree in real-time to optimize refrigerant mass flow rate. The valve dynamically responds to changing pressure differences between condenser and evaporator, maintaining optimal flow conditions throughout the compressor cycle rather than relying on a fixed capillary tube restriction.
Solution Approach 2:
The patent changes the flow resistance parameter of the expansion device by using an adjustable valve mechanism. The valve opening degree is modified as a control parameter to match the optimal refrigerant mass flow rate with system conditions, particularly during different phases of the compressor cycle.
2Duration of action of moving object
If the compressor runs in cycles with on-phase and off-phase, then system operation is achieved, but energy losses occur during compressor off-phase due to refrigerant vapor migration
Solution Approach 1:
The patent closes the expansion valve before the compressor enters the off-phase to prevent refrigerant vapor migration from condenser to evaporator. This preliminary action stops the harmful flow before it can occur, eliminating the energy loss associated with uncontrolled refrigerant migration during compressor idle periods.
Solution Approach 2:
The patent applies a counter-action by closing the valve to prevent the harmful effect of refrigerant migration. The valve closure creates a barrier that opposes and prevents the natural pressure-driven flow of refrigerant vapor during compressor off-phase, thereby protecting system efficiency.
3Force
If the valve is opened a predetermined period before compressor start to equalize pressure difference, then start torque requirement is reduced, but refrigerant flow timing becomes misaligned with optimal working conditions
Solution Approach 1:
The patent uses dynamic control of the expansion valve timing rather than a fixed predetermined opening schedule. The valve opening timing is adjusted in real-time based on actual system pressure conditions and compressor cycle phase, allowing optimization of both start torque requirements and refrigerant flow alignment with optimal working conditions.
Solution Approach 2:
The patent implements feedback control where the valve operation timing is based on real-time monitoring of pressure differences and system conditions. This feedback mechanism allows the control system to adjust valve timing to simultaneously address start torque requirements and maintain optimal refrigerant flow alignment during compressor operation.
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 results in increased energy savings, particularly in systems with short compressor cycles and large thermal mass evaporators and condensers, by ensuring a more efficient refrigerant flow that matches the system's requirements, thereby enhancing overall system efficiency.
Implementation Method 1
use a capillary tube to reduce the pressure of the refrigerant flowing from condenser to evaporator
Implementation Method 2
use an open/close valve located on the path from the condenser to the evaporator to prevent refrigerant migration from the condenser to the evaporator
Data Source
AI summary
A refrigerator apparatus having a compressor, a condenser, an evaporator, and a valve interconnected in the flow from the condenser to the evaporator. The valve is operatively controlled to a first, open, state and to a second, closed, state by a controller. The controller is configured to the valve to operate in accordance with at least one of: opening the valve a time period of 0-180 seconds before the compressor is switched to an on-phase; and closing the valve before the compressor is switched to an off-phase.