Refrigeration system and controlling method for starting the refrigeration system
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Solution Overview
Problem
In two-stage compression refrigeration systems, liquid phase refrigerant accumulates in the economizer during shutdown, leading to liquid impact issues when the compressor starts, as pneumatic valves open due to pressure differences, causing the compressor to suck in liquid refrigerant.
Innovation Solution
A refrigeration system design that includes a pneumatic valve with a drive gas phase refrigerant chamber connected to a low-pressure portion of the system, and a first valve controlling the on/off state of the gas phase refrigerant path, which is kept closed until the liquid phase refrigerant in the economizer falls below a threshold, preventing liquid impact during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pneumatic valve is used to replace electromagnetic valve or electric valve, then cost is reduced, but liquid phase refrigerant may enter compressor during startup causing liquid impact
Solution Approach 1:
A first valve is introduced as an intermediary component on the first gas phase refrigerant path to control the supply of drive gas to the pneumatic valve. This first valve acts as a mediator that prevents liquid phase refrigerant from causing liquid impact by controlling when the pneumatic valve opens, while still allowing the use of the lower-cost pneumatic valve instead of expensive electromagnetic or electric valves.
Solution Approach 2:
The system performs preliminary action by closing the first valve before compressor startup to prevent drive gas from reaching the pneumatic valve. This preliminary closure of the first valve ensures that when the compressor starts, the pneumatic valve remains closed even if liquid phase refrigerant is present in the economizer, thereby preventing liquid impact before it can occur.
2Ease of operation
If pneumatic valve opens based on pressure difference between evaporator and economizer, then flow path control is achieved, but compressor may suck in liquid phase refrigerant during startup
Solution Approach 1:
The first valve serves as an intermediary that controls the drive gas supply to the pneumatic valve. By positioning this first valve on the first gas phase refrigerant path, it mediates between the pressure difference control mechanism and the pneumatic valve, preventing liquid phase refrigerant from triggering premature opening that would cause liquid impact.
Solution Approach 2:
The control system monitors the operating state of the refrigeration system and provides feedback to control the first valve. Based on this feedback, the system determines when to open or close the first valve, ensuring that the pneumatic valve only opens when safe conditions are met, thereby preventing liquid impact while maintaining proper flow path control.
3Reliability
If first valve is kept closed during startup, then liquid impact is prevented, but gas phase refrigerant flow to pneumatic valve is blocked
Solution Approach 1:
The first valve transitions from a static closed state during startup to a dynamic open state during normal operation. This dynamic adjustment allows the system to prevent liquid impact during startup by keeping the first valve closed, then restore full gas phase refrigerant flow to the pneumatic valve once the compressor is running safely, thereby resolving the contradiction between reliability and productivity.
Solution Approach 2:
The first valve is closed preliminarily during startup to prevent liquid impact. Once the compressor has started and conditions are safe, the first valve is opened to restore gas phase refrigerant flow to the pneumatic valve, ensuring that productivity is not compromised during normal operation while maintaining reliability during critical startup phases.
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
Prevents liquid phase refrigerant from entering the compressor, ensuring reliable operation by maintaining the pneumatic valve in a closed state until the economizer's liquid content is reduced, thus avoiding liquid impact and enhancing system stability.
Implementation Method 1
the pneumatic valve may work according to a pressure difference between an evaporator and the economizer
Implementation Method 2
the drive gas phase refrigerant chamber being connected to a low pressure portion of the refrigeration system via a first gas phase refrigerant path
Data Source
AI summary
A refrigeration system, including: a compressor, a condenser, an economizer, a throttle valve, and an evaporator which are connected via a pipeline; and a pneumatic valve that includes a valve body and a drive gas phase refrigerant chamber, an gas phase refrigerant outlet of the economizer being connected to an interstage gas phase refrigerant inlet of the compressor via the valve body, and the drive gas phase refrigerant chamber being connected to a low pressure portion of the refrigeration system via a first gas phase refrigerant path, the lower pressure portion having a pressure lower than that in the economizer; wherein a first valve for controlling on/off of the first gas phase refrigerant path is disposed on the first gas phase refrigerant path. The refrigeration system can avoid liquid phase refrigerant accumulated in the economizer from entering the compressor during start to cause a liquid impact problem.