Compressor Oil Sump Heating for Low-Standby Refrigeration
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Solution Overview
Problem
Conventional refrigeration apparatuses face issues with standby power consumption and compressor reliability due to refrigerant stagnation and in-dome condensation, which lead to decreased refrigerator oil viscosity, causing inadequate lubrication during startup.
Innovation Solution
A refrigeration apparatus with a controller that heats the refrigerator oil in the oil sump to a specific target temperature while stopped, minimizing heating and maintaining viscosity for adequate lubrication, and adjusts this temperature based on the amount of oil and expected condensation to balance power consumption and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heater is constantly operated to heat the refrigerator oil inside the compressor while the refrigeration apparatus is stopped, then the refrigerant stagnation is prevented and the oil viscosity is maintained, but the standby power consumption is increased
Solution Approach 1:
The controller performs preliminary heating of the refrigerator oil before the refrigeration apparatus is stopped, raising the oil temperature in advance. This preliminary action ensures that when the apparatus stops, the oil temperature remains sufficiently high to prevent refrigerant stagnation without requiring continuous heater operation, thus reducing standby power consumption while maintaining compressor reliability
Solution Approach 2:
Instead of continuous operation, the heater is operated periodically based on detected oil temperature and stopping time. The controller activates the heater only when necessary to maintain oil temperature above the refrigerant stagnation prevention threshold, creating a periodic heating pattern that reduces overall power consumption while ensuring reliability when needed
2Use of energy by stationary object
If the heater is not operated to reduce standby power consumption, then the power cost is reduced, but the refrigerant stagnation occurs and the oil viscosity decreases causing inadequate lubrication
Solution Approach 1:
The controller detects when the refrigeration apparatus is about to stop and performs preliminary heating of the refrigerator oil in advance. This ensures that when the apparatus stops and power consumption needs to be reduced, the oil temperature is already sufficiently high to prevent refrigerant stagnation, eliminating the need for continuous heating while maintaining lubrication reliability
Solution Approach 2:
The controller continuously detects the refrigerator oil temperature and adjusts heater operation based on this feedback. When the oil temperature approaches the threshold for refrigerant stagnation prevention, the controller activates the heater; when the temperature is sufficiently high, the heater is deactivated. This feedback-based control optimizes the balance between power consumption and compressor reliability
3Use of energy by stationary object
If the refrigerator oil temperature is lowered to reduce standby power, then the power consumption is reduced, but the in-dome condensation occurs and refrigerant condenses on the oil surface causing viscosity decrease
Solution Approach 1:
The controller performs preliminary heating of the refrigerator oil before the refrigeration apparatus stops, ensuring the oil temperature remains above the dew point temperature that would cause in-dome condensation. This preliminary action prevents condensation during the stopping period without requiring continuous heating, thus reducing power consumption while preventing the harmful condensation effect
Solution Approach 2:
The controller substitutes continuous mechanical heating with a control strategy that uses temperature detection and timing information to determine when heating is necessary. By replacing the continuous mechanical heating system with an intelligent control approach, the system reduces power consumption while still preventing in-dome condensation through targeted heating actions
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 reduces standby power consumption and enhances compressor reliability by maintaining optimal oil viscosity during startup, even under low outdoor temperatures, by controlling the heating of the refrigerator oil in the compressor's oil sump.
Implementation Method 1
a heater for heating the refrigerator oil collected in the oil sump
Implementation Method 2
the occurrence of in-dome condensation is prominent, in which refrigerant that has been discharged into the internal space of the casing from a compression element for compressing refrigerant is condensed in the internal space before being sent out of the casing
Implementation Method 3
the amount of refrigerant dissolved in the refrigerator oil in the compressor increases
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A refrigeration apparatus (1) comprises a compressor (21) having a structure in which refrigerant compressed by a compression element (21b) is sent out of a casing (21 a) after being discharged into an internal space (36a) of the casing (21a) in which an oil sump (36c) for collecting refrigerator oil is formed, a heater (28), and a controller (9). While the refrigeration apparatus (1) is stopped, the controller (9) controls the heater (28) so that the temperature of the refrigerator oil collected in the oil sump (36c) reaches a first oil temperature target value for keeping a condensation amount of the refrigerant equal to or less than an allowable condensation amount at which the concentration or viscosity of the refrigerator oil needed to lubricate the compressor (21) can be maintained, the refrigerant condensation amount being caused by in-dome condensation at the start of operation of the refrigeration apparatus (1).