Screw Compressor Slide Valve Economizer Port for Part-Load COP
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Solution Overview
Problem
Existing screw compressors face challenges in achieving a high coefficient of performance over a wide range of operating conditions due to inefficiencies in economizer port design, leading to re-expansion losses and refrigerant leakage, especially during part-load operations where the pressure difference is small.
Innovation Solution
The screw compressor incorporates an economizer port positioned to communicate with the suction-pressure chamber when the slide valve is at the extreme end on the suction side, eliminating re-expansion losses and minimizing refrigerant leakage by optimizing the economizer port's position and diameter relative to the slide valve's movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the economizer port is provided in the casing to allow economizer gas injection, then the coefficient of performance is improved, but re-expansion losses and refrigerant leakage occur especially during part-load operations
Solution Approach 1:
The economizer port is positioned to communicate with the suction-pressure chamber when the slide valve is at the extreme end on the suction side, preparing the system in advance to eliminate re-expansion losses by establishing proper communication paths before part-load operations begin
Solution Approach 2:
The economizer port is strategically positioned at a specific location on the slide valve rather than in the casing, creating localized optimal communication that adapts to different operating conditions and prevents both re-expansion losses and refrigerant leakage
2Productivity
If the economizer port diameter is increased to improve gas flow, then economizer operation effectiveness is enhanced, but refrigerant leakage increases
Solution Approach 1:
The economizer port diameter is optimized to a specific range (0.5mm to 2.0mm) that balances gas flow requirements with leakage prevention, and the port position varies dynamically with slide valve movement to adapt communication characteristics to operating conditions
3Productivity
If the slide valve position is adjusted for capacity control, then part-load operation is achieved, but the pressure difference between intermediate cooling device and compression chamber decreases
Solution Approach 1:
The economizer port positioning communicates with the suction-pressure chamber at the slide valve's extreme suction side position, preparing the system in advance to maintain proper pressure relationships even when slide valve adjustment reduces the pressure difference during part-load operations
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 configuration allows for a high coefficient of performance across various operating conditions by preventing re-expansion losses and refrigerant leakage, enhancing efficiency during both full-load and part-load operations.
Implementation Method 1
a slide valve which adjusts a timing of starting discharge by sliding in a slide groove extending in a direction of a rotating shaft of the screw rotor
Implementation Method 2
an economizer port provided in the slide valve and allowing the economizer passage to communicate with one of the compression chambers in accordance with a position of the slide valve
Implementation Method 3
a screw rotor rotatably housed in the inner cylinder-surface portion of the casing and having a plurality of screw grooves in an outer periphery; a gate rotor having tooth portions that are provided on an outer periphery and come into mesh with the screw grooves, the gate rotor defining compression chambers in combination with the screw grooves and the inner cylinder-surface portion
Data Source
Figure 1~2
Figure 3
Figure 4(a)~5
AI summary
A screw compressor includes an economizer passage (50) provided in a casing (1) and allowing an outside of the casing (1) and a slide groove (14) in which a slide valve (12) is provided to communicate with each other, and an economizer port (12p) provided in the slide valve (12) and allowing the economizer passage (50) to communicate with one of compression chambers (11) in accordance with a position of the slide valve (12). The slide valve (12) gradually advances a timing of starting discharge by moving from a discharge side toward a suction side. The economizer port (12p) is provided at a position where the economizer port (12p) communicates with a suction-pressure chamber (1C) when the slide valve (12) is positioned at an extreme end on the suction side.