Two-Stage Refrigeration Compression Startup for Pressure Inversion Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional two-stage compression refrigeration cycle devices face issues with pressure inversion during startup, leading to wear and reduced durability of compression mechanisms when operating with a pressure difference between the high and low sides, especially when starting both mechanisms simultaneously.
Innovation Solution
The device intermittently controls the low-pressure and high-pressure side compression mechanisms, starting the mechanism with the smaller pressure difference first and adjusting the throttle opening degrees of expansion valves to reduce pressure differences, and optionally uses an oil separator to manage pressure and reduce wear on components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If both compression mechanisms are started simultaneously under pressure equalization, then the system can achieve balanced pressure distribution, but pressure inversion occurs when the low-pressure side has larger discharge capacity
Solution Approach 1:
The control device determines the discharge capacities of both compression mechanisms before startup, and based on this preliminary assessment, establishes the correct startup sequence. The compression mechanism with smaller discharge capacity starts first, creating a foundation for stable pressure distribution before the second mechanism joins, thereby preventing pressure inversion.
Solution Approach 2:
The control device continuously monitors the actual pressure distribution and discharge capacities, using this feedback information to dynamically adjust the startup sequence and operating parameters. This closed-loop control ensures that pressure inversion is prevented while maintaining stable pressure distribution during operation.
2Productivity
If the compression mechanism starts under remaining pressure difference, then the system can operate intermittently to meet temperature targets, but component wear increases due to load on operating components
Solution Approach 1:
Before each startup cycle, the control device assesses the current pressure difference between high and low pressure sides. Based on this preliminary evaluation, it determines the optimal startup sequence that minimizes the load on compression mechanism components, thereby reducing wear even when pressure difference exists during intermittent operation.
Solution Approach 2:
The control device adjusts operating parameters such as startup sequence and throttle opening degrees based on the measured pressure difference. By changing these parameters dynamically, the system enables intermittent operation to meet temperature targets while minimizing component wear through optimized startup conditions.
3Power
If the low-pressure side compression mechanism has larger discharge capacity, then the loads on compression mechanisms are reduced, but pressure inversion occurs during simultaneous startup
Solution Approach 1:
The control device determines the discharge capacities of both compression mechanisms before startup, and based on this preliminary assessment, establishes the correct startup sequence. The compression mechanism with smaller discharge capacity starts first, creating a foundation for stable pressure distribution before the second mechanism joins, thereby preventing pressure inversion.
Solution Approach 2:
Instead of simultaneously starting both compression mechanisms or starting the larger capacity one first, the control device inverts the conventional approach by starting the smaller discharge capacity mechanism first. This reversed sequence prevents pressure inversion while still allowing the larger capacity mechanism to reduce overall compression loads.
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 approach protects both compression mechanisms by minimizing pressure differences during startup and shutdown, reducing wear, and maintaining stable refrigerant evaporation temperatures, thereby extending the lifespan of the components and optimizing energy consumption.
Implementation Method 1
a low-pressure side compression mechanism which compresses a low-pressure refrigerant into an intermediate-pressure refrigerant
Implementation Method 2
a high-pressure side compression mechanism which compresses the intermediate-pressure refrigerant discharged from the low-pressure side compression mechanism into a high-pressure refrigerant
Implementation Method 3
a radiator in which the high-pressure refrigerant discharged from the high-pressure side compression mechanism is heat-exchanged with outside air to radiate heat from the refrigerant
Implementation Method 4
an intermediate-pressure expansion valve which decompresses and expands the high-pressure refrigerant flowing from the radiator into the intermediate-pressure refrigerant
Implementation Method 5
a low-pressure expansion valve which decompresses and expands the high-pressure refrigerant flowing from the radiator into the low-pressure refrigerant
Implementation Method 6
an evaporator in which the low-pressure refrigerant decompressed and expanded by the low-pressure expansion valve is evaporated by exchanging heat with a fluid blown into a cooling space
Data Source
AI summary
In a two-stage compression refrigeration cycle device, a low-pressure side compression mechanism and a high-pressure side compression mechanism are intermittently operated to control such that the temperature of air blown into a freezer approaches a target temperature. Under the control, the high-pressure side compression mechanism is first stopped, and then the low-pressure side compression mechanism is stopped. Further, when a reference time has elapsed after driving the high-pressure side compression mechanism, then the low-pressure side compression mechanism is driven. The refrigeration cycle device can reduce a high-pressure side pressure difference upon driving the high-pressure side compression mechanism, and can also reduce a low-pressure side pressure difference upon driving the low-pressure side compression mechanism.