Movable Economizer Port in Screw Compressors for Partial-Load Efficiency
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Solution Overview
Problem
Traditional refrigeration cycle apparatuses with screw compressors face inefficiencies in partial load modes, where economizing operations are less effective, leading to increased electric power consumption and decreased coefficient of performance, due to the fixed position of economizer ports causing re-expansion losses.
Innovation Solution
The refrigeration cycle apparatus includes a screw compressor with an economizer port positioned to optimize communication with the compression chamber based on pressure differences, allowing for adaptive control of economizer gas injection, either enabling or disabling the economizing operation depending on load conditions to prevent dead volume and re-expansion losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the economizer port is always communicated with the compression chamber, then the economizing operation can be performed, but re-expansion loss occurs that impairs the refrigeration capacity
Solution Approach 1:
The economizer port is made movable relative to the compression chamber, allowing it to dynamically adjust its position between communicating with the compression chamber and being separated from it. This dynamic configuration enables the system to perform economizing operation when needed while avoiding re-expansion loss when not needed, thereby resolving the contradiction between energy loss and refrigeration capacity.
Solution Approach 2:
The economizer port is positioned and configured in advance to communicate with the compression chamber only when the compression chamber is completely closed. This preliminary positioning ensures that economizer gas is injected at the optimal moment, preventing re-expansion loss while maintaining refrigeration capacity.
2Loss of energy
If the economizer port is positioned to communicate with the compression chamber, then economizing operation is effective in full load mode, but it causes re-expansion loss in partial load mode
Solution Approach 1:
The economizer port's position is made dynamic rather than fixed, allowing it to adjust its communication status with the compression chamber based on operating conditions. This enables the system to adapt between full load mode (where economizing is effective) and partial load mode (where it would cause re-expansion loss), resolving the contradiction between economizing effectiveness and adaptability to load conditions.
Solution Approach 2:
The system changes the operational parameter of the economizer port (its communication status with the compression chamber) based on the load condition. By monitoring and responding to changes in operating conditions, the system optimizes performance across different load modes, resolving the contradiction between economizing effectiveness and adaptability.
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 enhances the coefficient of performance and refrigeration capacity across a wide range of operations by optimizing economizer port positioning and controlling the economizing operation based on pressure differences, reducing energy consumption and maintaining efficiency in both full and partial load modes.
Implementation Method 1
The full load mode has a large pressure difference in the refrigeration cycle, which indicates high capacity operation, whereas the partial load mode has a small pressure difference in the refrigeration cycle
Data Source
Figure 1~2
Figure 3(a)~4
Figure 5~6
AI summary
A screw compressor includes a casing (1), a screw rotor (3) rotatable in the casing (1), a compression chamber (5) defined between the casing (1) and the screw rotor (3) to compress refrigerant gas, a slide groove (1a) disposed on the inner peripheral surface of the casing (1) and extending along the direction of the rotational axis of the screw rotor (3), an economizer gas passage (1b) extending through the casing (1) to communicate the outside of the casing (1) with the slide groove (1a), a slidable valve (8) disposed in the slide groove (1a) so as to be slidable along the direction of the rotational axis of the screw rotor (3), and an economizer port (8a) penetrating through the slidable valve (8) to communicate the economizer gas passage (1b) with the compression chamber (5) depending on the position of the slidable valve (8), wherein the slidable valve (8) moves between a first position, which allows the economizer gas passage (1b) to communicate with the compression chamber (5), and a second position, which prevents the economizer port (8a) from communicating with the compression chamber (5).