PWM Unloading Valve Control for Precise Compressor Capacity
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Solution Overview
Problem
Conventional refrigerant compressor systems 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 damage and lack precise control over cooling potential.
Innovation Solution
The implementation of unloading valves that actuate between closed and open positions, controlled by a pulse-width-modulation system, allows for variable compressor capacity adjustment, enabling precise control of the refrigerant compressor's cooling potential and avoiding high pressure ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If suction pressure throttling is used to adjust cooling potential, then the cooling potential of the refrigerant circuit can be controlled, but the pressure ratio increases potentially causing damage to the compressor
Solution Approach 1:
The patent employs a variable capacity compressor with movable pistons that can dynamically adjust their position within the cylinder. This allows the compression chamber volume to be varied continuously, enabling the compressor to adapt its capacity to match the required cooling load without resorting to suction pressure throttling, thereby maintaining safe pressure ratios while controlling cooling potential.
Solution Approach 2:
The invention changes the operational parameters of the compressor by varying the compression chamber volume through piston displacement. Instead of maintaining fixed geometry and controlling cooling through pressure throttling, the system varies the physical dimension (chamber volume) to directly control compression ratio and cooling capacity, avoiding harmful high pressure ratios.
2Temperature
If suction pressure throttling is used to control temperature, then the temperature of the temperature controlled space can be adjusted, but accurate temperature control in the frozen temperature range cannot be achieved
Solution Approach 1:
The variable capacity compressor with adjustable piston positions enables continuous modulation of cooling capacity. This dynamic adjustment capability allows precise control over the refrigeration effect, facilitating accurate temperature maintenance in the frozen temperature range by matching the cooling output exactly to the thermal load requirements.
Solution Approach 2:
The system incorporates temperature sensing and control mechanisms that provide feedback to the variable capacity compressor. Based on the measured temperature in the controlled space, the compressor adjusts its capacity through piston positioning to maintain the desired setpoint temperature, achieving accurate temperature control through closed-loop regulation.
3Productivity
If a larger compressor capacity is used to increase cooling potential, then the cooling potential of the refrigerant circuit increases, but the ability to control temperature precisely decreases
Solution Approach 1:
The variable capacity compressor allows the system to operate with a large maximum cooling potential while enabling continuous reduction of capacity through piston adjustment. This dynamic range adjustment provides both high productivity capability and fine control resolution, allowing the system to deliver large cooling when needed while maintaining precise temperature control at partial loads.
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 provides accurate temperature control within a temperature-controlled space by varying the compressor's capacity, reducing the risk of high pressure ratios and enhancing the system's efficiency and reliability.
Implementation Method 1
pulse-width-modulation can be used to vary the capacity of the refrigerant compressor
Data Source
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.