Refrigeration system and the control method thereof
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Solution Overview
Problem
Refrigeration systems with Enhanced Vapor Injection (EVI) compressors face efficiency reduction at extremely low ambient temperatures or significant temperature differences between ambient and target temperatures, struggling to maintain performance below -25°C.
Innovation Solution
A refrigeration system incorporating a compressor, condenser, throttling devices, and an ejector loop with a controller that adjusts the opening of the throttling devices based on pressure and dryness differences to optimize the production of gas-liquid two-phase refrigerant, ensuring efficient operation across a broader temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an EVI compressor is used to improve heating capacity at low temperatures, then heating capacity increases by 20%-50% at -15°C, but system efficiency significantly reduces when ambient temperature is below -25°C or temperature difference exceeds 40°C
Solution Approach 1:
The patent implements dynamic control of the first throttling device opening based on real-time pressure difference detection between ejector outlet and suction inlet. The controller continuously adjusts the throttling degree to maintain optimal two-phase refrigerant dryness (0.05-0.5) across varying ambient temperatures, enabling the system to adapt dynamically to extreme temperature conditions while preserving both heating capacity and efficiency
Solution Approach 2:
The patent changes the physical state parameters of the refrigerant by precisely controlling the two-phase refrigerant dryness through adjustable throttling. By maintaining dryness within the optimal range of 0.05-0.5, the system transforms the refrigerant properties to match extreme temperature requirements, resolving the contradiction between power output and energy efficiency at temperatures below -25°C
2Temperature
If the evaporating temperature is lowered below -30°C to extend operating range, then the system can operate at lower temperatures, but the heat exchange capacity of the outdoor unit decreases and compressor power reduces
Solution Approach 1:
The patent implements a feedback control mechanism where pressure sensors detect the pressure difference between ejector outlet and suction inlet, and the controller uses this feedback to continuously adjust the first throttling device opening. This closed-loop control ensures the two-phase refrigerant dryness remains optimal (0.05-0.5) even at evaporating temperatures below -30°C, maintaining heat exchange capacity while extending the operating temperature range
Solution Approach 2:
The patent introduces the first throttling device as an intermediary component between the high-pressure liquid refrigerant and the ejector. This intermediary device precisely controls the throttling process to produce two-phase refrigerant with optimal dryness, acting as a mediator that enables the system to operate at extended low temperatures without sacrificing heat exchange capacity
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
The system enhances efficiency by 5% to 10% and extends the operating temperature range by 5°C to 10°C, allowing effective operation from -25°C to -30°C or lower, improving heating capacity and system performance.
Implementation Method 1
a controller configured to control the opening of the first throttling device based on the pressure difference between the fluid outlet and the suction fluid inlet of the ejector
Implementation Method 2
a first throttling device for throttling liquid refrigerant from the condenser to produce gas-liquid two-phase refrigerant
Implementation Method 3
the fluid outlet of the ejector is connected to a flash tank, the gas-phase outlet of the flash tank is connected to the compressor inlet, the liquid-phase outlet of the flash tank is connected to an evaporator
Data Source
Figure 1
Figure 2
AI summary
The present application provides a refrigeration system and a control method thereof. The refrigeration system comprises a compressor (1) and a condenser (2), and further comprises a first throttling device (51) for receiving liquid refrigerant from the condenser; an ejector (6) having a high-pressure fluid inlet (61), a fluid suction inlet (62) and a fluid outlet (63), wherein the high-pressure fluid inlet of the ejector is connected to the first throttling device, the fluid outlet of the ejector is connected to a flash tank (7), a gas-phase outlet (73) of the flash tank is connected to a compressor inlet, a liquid-phase outlet (72) of the flash tank is connected to an evaporator (8) via a second throttling device (52), and the evaporator is connected to the fluid suction inlet of the ejector; and a controller configured to control an opening of the first throttling device based on a pressure difference between the fluid outlet and the fluid suction inlet of the ejector. The refrigeration system and method can operate efficiently at extremely low ambient temperatures or in a case where there is a considerable indoor-outdoor temperature difference.