Zero-load output non-stop control method and apparatus, and unit
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Solution Overview
Problem
Conventional fixed-frequency screw units cannot achieve zero-load output without shutting down, limiting their operation to a minimum 25% load.
Innovation Solution
A load control device with a three-way valve, mixing tank, electronic expansion valves, and electromagnetic valve, controlled by a controller, to manage refrigerant flow and maintain operation at zero-load without shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fixed-frequency screw unit operates with slide valve control, then the unit can maintain stable operation, but the minimum load is limited to 25% and zero-load operation is not achievable
Solution Approach 1:
The refrigerant flow path is segmented into multiple channels: a main channel through the condenser and evaporator, and a bypass channel through the mixing tank. The bypass channel is further divided into two sub-channels controlled by different valves. This segmentation allows independent control of refrigerant flow proportions to achieve various load levels including zero-load operation.
Solution Approach 2:
The mixing tank serves as an intermediary component that receives refrigerant from two different sources (compressor discharge and condenser outlet) and mixes them before returning to the compressor suction. This intermediary mixing mechanism enables precise control of the refrigerant cycle and achieves load adjustment down to zero-load while maintaining stable compressor operation.
2Loss of energy
If the unit shuts down at zero-load, then the compressor avoids operating at minimum load, but the startup and shutdown time increases and response speed decreases
Solution Approach 1:
The compressor continues to operate continuously at its optimal fixed frequency without shutdown. The useful action of refrigerant circulation is maintained continuously by adjusting the flow distribution through the mixing tank bypass, allowing the compressor to operate efficiently at zero-unit-load conditions without the energy losses and time penalties of shutdown and restart cycles.
3Reliability
If the compressor operates at minimum 25% load, then the compressor maintains stable operation, but the unit cannot achieve zero-load output without shutdown
Solution Approach 1:
Different parts of the refrigerant flow receive different treatments: most refrigerant flows through the normal condenser-evaporator path, while a controlled portion bypasses through the mixing tank. By locally diverting and mixing refrigerant streams, the system achieves zero-load output capability while the compressor continues to operate stably at its designed minimum load condition.
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
Enables stable and reliable zero-load operation, reducing startup and shutdown times, improving response speed, and extending service life while preventing oil temperature drops.
Implementation Method 1
a mixing tank, provided between a suction inlet of the compressor and a condenser, and configured to mix refrigerant discharged from the compressor with refrigerant throttled through the condenser
Implementation Method 2
a first electronic expansion valve, provided on a first pipeline between the condenser and the mixing tank, and configured to control an amount of the refrigerant throttled by the condenser and entering the mixing tank
Data Source
AI summary
Disclosed in the present invention are a zero-load output non-stop control method and apparatus, and a unit. The apparatus comprises: a three-way valve, provided at an exhaust port of a compressor; a mixing tank, provided between an air suction port of the compressor and a condenser and used for mixing a refrigerant discharged by the compressor with a refrigerant throttled by the condenser; a first electronic expansion valve, provided on a first pipeline from the condenser to the mixing tank and sued for controlling the amount of the refrigerant throttled by the condenser and entering the mixing tank; and an electromagnetic valve, provided on a second pipeline between the three-way valve and the mixing tank and used for controlling the amount of the refrigerant discharged by the compressor and directly entering the mixing tank.