Compressor Unloading Valve Control for Part-Load Energy Savings
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Solution Overview
Problem
Conventional refrigeration systems waste energy by recirculating compressed refrigerant back to the suction side during unloading, reducing overall system efficiency and increasing operating costs due to the need for frequent maintenance.
Innovation Solution
A variable-capacity compressor system with dedicated valves controlled by an unloading controller, allowing for modulation of refrigerant flow by cycling valves between open and closed states in response to analog control signals, minimizing energy waste and optimizing system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a gas bypass system is used to unload compressors, then compressor capacity can be reduced, but energy is wasted by recirculating compressed refrigerant back to the suction side
Solution Approach 1:
The compressor discharge flow is segmented into multiple paths: a first portion is recirculated back to the suction side through the gas bypass system for unloading, while a second portion is directed to a separate receptacle. This segmentation allows the system to maintain compressor unloading capability while capturing useful refrigerant that would otherwise be wasted, thereby reducing overall energy loss.
2Loss of energy
If compressor capacity is modulated to match reduced load, then energy savings can be achieved, but system complexity increases
Solution Approach 1:
The system merges the functions of compressor unloading and refrigerant management into a single integrated architecture. The gas bypass system is combined with a receptacle and control valve arrangement that handles both the recirculated refrigerant and the diverted portion, allowing capacity modulation while reducing the need for separate complex control systems.
Solution Approach 2:
The receptacle serves multiple functions: it receives the second portion of discharged refrigerant, acts as a storage buffer, and enables flexible routing options. This multi-functional component reduces the need for dedicated separate systems, thereby managing complexity while achieving energy savings through capacity modulation.
3Measurement precision
If dedicated valves are assigned to selected compressing elements, then precise refrigerant flow control is achieved, but device complexity increases
Solution Approach 1:
Instead of providing dedicated valves for all compressing elements, the system applies local quality by assigning dedicated valves only to selected compressing elements. This selective approach allows precise control over specific portions of the refrigerant flow while avoiding the complexity of having dedicated valves for every element, thereby achieving sufficient precision without excessive complexity.
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
The system effectively reduces energy consumption and operating costs by allowing precise control of refrigerant flow, maintaining efficiency and extending the lifespan of components through optimized loading and unloading operations.
Implementation Method 1
The at least one valve comprises a plunger and a solenoid configured to control movement of the plunger
Data Source
AI summary
A variable-capacity compressor that includes a housing having an inlet for receipt of refrigerant and an outlet for return of refrigerant, and a plurality of compressing elements contained in the housing between the inlet and the outlet. The variable capacity compressor includes a valve having an electrical control. The valve is dedicated to fewer than all of the compressing elements. The valve is movable between a first state which communicates refrigerant flow to the compressing elements, and a second state that reduces or stops flow to the compressing elements. In an embodiment of the invention, an unloading controller has an operational modulation mode that includes cycling the valve between on and off states to provide a portion of compressor capacity. The unloading controller is further programmed to provide a minimum delay time between transitions between the first and second states, but no maximum dwell time between transitions.