Compressor Unloading Valves via Pulse-Width Modulation
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Solution Overview
Problem
Conventional refrigerant compressors face challenges in achieving accurate temperature control, particularly in the frozen temperature range, due to high pressure ratios resulting from low suction port pressures, which can cause compressor damage and inefficiencies in cooling potential control.
Innovation Solution
The use of unloading valves that actuate between closed and open positions, controlled by a pulse-width-modulated signal, to adjust the compressor capacity and discharge port pressure, allowing for precise temperature control within a temperature-controlled space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If suction pressure throttling is used to control cooling potential, then the cooling capacity is reduced, but the pressure ratio increases causing compressor damage
Solution Approach 1:
The patent introduces a bypass valve as an intermediary component that provides an alternative flow path around the compression chamber. This mediator allows excess refrigerant to bypass the compression process, reducing the pressure ratio across the compressor while maintaining control over the cooling capacity delivered to the system.
Solution Approach 2:
The patent segments the refrigerant flow into two separate paths: one through the compression chamber for cooling and another through the bypass valve for pressure regulation. This segmentation allows independent control of cooling capacity and pressure ratio, resolving the contradiction between reducing cooling capacity and maintaining safe operating pressures.
2Temperature
If suction pressure is reduced to control temperature, then cooling potential decreases, but temperature control accuracy deteriorates
Solution Approach 1:
The patent implements a feedback control system where the bypass valve is modulated based on temperature sensor readings from the controlled space. The controller continuously adjusts the bypass valve position to maintain the desired temperature, providing accurate temperature control while optimizing cooling capacity delivery rather than simply reducing it through suction throttling.
Solution Approach 2:
The patent transitions from static suction pressure throttling to dynamic bypass valve modulation. The bypass valve can continuously adjust its opening degree in response to temperature feedback, enabling precise temperature control while dynamically optimizing the balance between cooling capacity delivery and pressure ratio management.
3Temperature
If compressor capacity is reduced for temperature control, then cooling potential decreases, but system efficiency deteriorates
Solution Approach 1:
The patent maintains continuous useful action by keeping the compressor running at full capacity while using the bypass valve to regulate the amount of compressed refrigerant delivered to the cooling circuit. This approach maintains compressor efficiency and avoids the energy losses associated with cycling the compressor on and off or operating at reduced capacity.
Solution Approach 2:
The bypass valve serves as a mediator that regulates refrigerant flow without requiring the compressor to reduce its operating capacity. By placing the flow control function in the bypass valve rather than in the compressor itself, the system maintains compressor efficiency while achieving the desired temperature control through controlled bypass of excess refrigerant.
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 enables accurate temperature control across a wide range, from frozen to fresh temperatures, while maintaining low pressure ratios, thus avoiding compressor damage and improving cooling efficiency by varying the compressor's capacity and discharge pressure.
Implementation Method 1
pulse-width-modulation can be used to vary the capacity of the refrigerant compressor
Data Source
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AI summary
A refrigerant compressor assembly for a refrigeration circuit controls the temperature within a temperature controlled space. The refrigerant compressor assembly includes a first unloading valve, a first valve actuator, and a first valve control system that adjusts the first valve actuator via a pulse-width-modulated signal, a second unloading valve, a second valve actuator, and a second valve control system that adjusts the second valve actuator via a pulse-width-modulated signal. The refrigerant compressor assembly also includes a third unloading valve. The first valve actuator is coupled to the first and third unloading valves and controlled by the first valve control system. The unloading valves selectively allow or resist fluid flow from higher to lower pressure areas within the refrigerant compressor assembly.