Refrigeration apparatus
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Solution Overview
Problem
Refrigeration apparatuses face challenges in maintaining adequate lubrication during low load operations, as refrigerant in a gaseous state is insufficient for lubrication, potentially damaging the compressor, and excessive liquid refrigerant can flood the rotor cavity, causing damage.
Innovation Solution
A refrigeration apparatus with a lubrication refrigerant line connected between the condenser and expansion valve, equipped with a throttle valve, downstream pressure and temperature detectors, and a control unit to monitor and control the refrigerant flow, ensuring it remains in a liquid state and at sufficient flow for any load condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refrigerant flow is increased to ensure sufficient lubrication during low load operation, then lubrication reliability is improved, but the risk of rotor cavity flooding increases
Solution Approach 1:
The patent implements a feedback control system using a pressure detector to monitor the pressure of refrigerant in the lubrication line upstream of the compressor. The control unit receives this pressure signal and adjusts the throttle valve opening accordingly. When pressure indicates insufficient lubrication flow (low load condition), the control unit increases the throttle valve opening to increase flow. When pressure indicates excessive flow risk, the control unit reduces opening to prevent flooding. This closed-loop feedback mechanism dynamically balances lubrication needs against flooding risk.
Solution Approach 2:
The patent employs dynamic adjustment of the throttle valve opening based on real-time pressure conditions rather than fixed positioning. The control unit continuously monitors pressure signals and modifies the throttle valve opening degree adaptively to match varying operational conditions. This dynamic control allows the system to optimize lubrication flow for each operating point, preventing both insufficient lubrication and excessive flooding while accommodating load variations.
2Object-affected harmful factors
If refrigerant flow is reduced during high load operation to prevent excessive lubrication, then flooding risk is reduced, but lubrication sufficiency may be compromised
Solution Approach 1:
The feedback control system continuously monitors pressure in the lubrication line and adjusts throttle valve opening accordingly. During high load operation, the pressure signal reflects sufficient natural flow, so the control unit maintains or reduces throttle opening to prevent excessive lubrication. The feedback mechanism ensures lubrication remains sufficient while avoiding flooding by responding to real-time pressure conditions that indicate flow adequacy.
Solution Approach 2:
The system utilizes the natural pressure conditions in the refrigeration cycle to self-regulate lubrication flow. During high load operation, the high refrigerant flow naturally provides sufficient lubrication pressure and flow to the compressor without requiring active throttle opening. The control system allows the system to self-service by leveraging operational conditions, reducing the need for active intervention while maintaining adequate lubrication.
3Device complexity
If a fixed throttle valve opening is used, then device complexity is reduced, but the ability to adapt to varying load conditions deteriorates
Solution Approach 1:
The patent introduces a feedback control loop with a pressure detector monitoring lubrication line pressure and a control unit that adjusts the throttle valve opening based on this pressure signal. This feedback mechanism enables the system to automatically adapt to varying load conditions without requiring complex manual intervention or multiple fixed throttle settings. The feedback system provides adaptive capability through continuous monitoring and automatic adjustment, balancing complexity with versatility.
Solution Approach 2:
The control unit and pressure detector serve multiple functions: they monitor pressure for both lubrication sufficiency and flooding prevention, adapt to various load conditions, and control the throttle valve across the entire operating range. This multi-functional approach allows a single control system to handle diverse operational requirements, from low load lubrication needs to high load flooding prevention, enhancing adaptability without proportionally increasing complexity.
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
Ensures proper lubrication of the compressor by controlling the refrigerant flow and state, preventing damage from inadequate lubrication during low load operations and flooding from excessive liquid refrigerant.
Implementation Method 1
a throttle valve adapted to vary the lubrication refrigerant flow entering the compressor
Implementation Method 2
a downstream pressure detector configured to measure refrigerant pressure downstream the throttle valve
Implementation Method 3
a downstream temperature detector configured to measure refrigerant temperature downstream the throttle valve
Implementation Method 4
a control unit adapted to determine the state of the refrigerant in the lubrication refrigerant line using the measurements of the downstream pressure detector and the downstream temperature detector
Data Source
Figure 1
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Figure 3
AI summary
This refrigeration apparatus (1) comprises a main refrigerant circuit (2) including a positive displacement compressor (4), a condenser (6), an expansion valve (8), and an evaporator (10), through which a refrigerant circulates successively in a closed loop circulation, a lubrication refrigerant line (18) connected to the main refrigerant circuit (2) between the condenser (6) and the expansion valve (8) or to the condenser (6), in which circulates a portion of the refrigerant of the main refrigerant circuit (2) and connected to the compressor (4) for lubrication of said compressor (4) with the refrigerant. The lubrication refrigerant line (18) comprises, upstream from the compressor (4): a throttle valve (20) adapted to vary the lubrication refrigerant flow entering the compressor (4), a downstream pressure detector (30) configured to measure refrigerant pressure (P3) downstream the throttle valve (20) and upstream the compressor (4), a downstream temperature detector (32) configured to measure refrigerant temperature (T3) downstream the throttle valve (20) and upstream the compressor (4). The refrigeration unit comprises a control unit (UC) adapted to determine the state of the refrigerant in the lubrication refrigerant line (18) using the measurements of the downstream pressure detector (30) and the downstream temperature detector (32), and configured for controlling the throttle valve (20) on the basis of at least the pressure (P3) downstream the throttle valve (20) and the state of the refrigerant in the lubrication refrigerant line (18).