Reciprocating Compressor Economizer Inlet for Lower Compression Work
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Solution Overview
Problem
Refrigeration devices with reciprocating compressors and secondary economizer branches face inefficiencies due to complex synchronization systems and increased compressor complexity, with pressure differences between the secondary economizer branch and conventional suction ducts not optimally enhancing efficiency.
Innovation Solution
A refrigeration device with a reciprocating compressor featuring side inlet ports for coolant flow from a secondary economizer branch, where the inlet pressure is set such that P8−P1≤4 bar, allowing for increased volumetric flow rate and reduced compression work, with inlet ports strategically positioned at the bottom dead centre of the piston to minimize work and loss of piston stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a secondary economizer branch is connected to a reciprocating compressor with a side inlet port, then the refrigeration efficiency can be improved, but the compressor complexity increases due to the need for synchronization mechanisms
Solution Approach 1:
The piston itself serves as the synchronization mechanism by exposing and covering the side inlet port through its reciprocating motion. The piston's position automatically controls the timing of secondary flow injection without requiring external synchronization mechanisms, thereby maintaining refrigeration efficiency while avoiding increased compressor complexity
Solution Approach 2:
The piston performs multiple functions: it compresses the refrigerant, controls the timing of secondary flow injection through its position relative to the side inlet port, and regulates the compression process. This multi-functionality eliminates the need for separate synchronization components
2Ease of operation
If the piston speed is varied to control the side inlet port exposure time, then fine temperature regulation can be achieved, but the compressor complexity and control system complexity increase
Solution Approach 1:
Instead of varying piston speed to control temperature, the invention changes the spatial parameter of the side inlet port position relative to the piston stroke. By adjusting when during the stroke the port is exposed, precise temperature control is achieved without modifying the piston speed or adding complex control systems
Solution Approach 2:
The compression stroke is segmented into distinct phases based on piston position: the side inlet port is exposed during a specific portion of the stroke to allow secondary flow injection, and covered during other portions. This segmentation allows independent control of different compression phases without complex mechanisms
3Loss of energy
If the secondary economizer branch pressure is significantly higher than the suction duct pressure, then the refrigeration efficiency is enhanced, but the pressure difference creates operational challenges in reciprocating compressors
Solution Approach 1:
The system dynamically manages the pressure difference by timing the secondary flow injection to occur when the cylinder pressure is lowest (near bottom dead center). This dynamic timing allows the acceptance of high-pressure secondary flow without creating excessive backpressure, maintaining both efficiency and operational feasibility
Solution Approach 2:
The side inlet port is positioned to expose the secondary flow path before the main compression process significantly increases cylinder pressure. This preliminary action allows the high-pressure secondary flow to enter the cylinder when resistance is minimal, avoiding operational challenges while maintaining the pressure differential benefits
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 significantly increases the efficiency and refrigeration load of the device without adding complexity, achieving a 22.4% higher coefficient of performance (COP) and doubling the refrigeration load compared to conventional systems under similar conditions.
Implementation Method 1
a piston reciprocatingly moving inside the cylinder, between a top dead centre and a bottom dead centre
Implementation Method 2
the inlet pressure of the first fraction of flow rate being such that P8−P1≤4 bar, wherein P1 is a pressure of a flow rate of the coolant entering the cylinder
Data Source
AI summary
A refrigeration device having a closed circuit in which a flow rate of coolant is circulating is provided. The closed circuit has a condenser and a main branch provided with a reciprocating compressor inside which a defined flow rate of the coolant enters, from the main branch, at a defined suction pressure, of an evaporator and a first expansion valve that is arranged between the condenser and the evaporator. The closed circuit further has a first secondary economizer branch for a first fraction of flow rate of the coolant, the first secondary economizer branch fluidically connecting the compressor to a section of the closed circuit between the condenser and the first expansion valve, wherein the compressor has a first side inlet port for the entrance of the first fraction of coolant flow rate.