Compressor Preheating Control to Prevent Refrigerant Oil Flow-Out
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional refrigeration cycle apparatuses face reliability issues when starting from low ambient temperatures, as high pressure compressors can lead to refrigerant and oil flow-out due to condensation of overheated gas refrigerant, resulting in insufficient lubrication for the compressor's compressing mechanism and bearing.
Innovation Solution
A refrigeration cycle apparatus with a control unit that operates a heating device when the temperature difference between the heat medium and compressor exceeds a predetermined threshold, ensuring the compressor shell temperature reaches saturation temperature, reducing liquid and oil discharge, and incorporating superheat degree detection to manage refrigerant circulation and expansion valve opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the compressor is started from a halting state at low ambient temperature with high heat medium temperature, then the saturation temperature of refrigerant increases due to heating, but the compressor shell temperature rises slowly due to heat capacity causing refrigerant condensation and oil flow-out
Solution Approach 1:
The control unit operates the heating device before starting the compressor when the temperature difference between heat medium and compressor exceeds a predetermined threshold. This preliminary heating action raises the compressor shell temperature to at least the saturation temperature of the refrigerant, preventing refrigerant condensation and oil flow-out during compressor operation, thus ensuring reliable lubrication from the start.
2Stress or pressure
If the compressor shell temperature is low and heat medium temperature is high, then refrigerant is heated and pressure increases, but the compressor shell temperature rises slowly due to heat capacity
Solution Approach 1:
The heating device is activated before compressor startup to preheat the compressor shell, ensuring that the shell temperature reaches at least the saturation temperature of the refrigerant. This preliminary action prevents the temperature lag caused by heat capacity, avoiding refrigerant condensation and oil flow-out while managing refrigerant pressure effectively.
3Loss of time
If the compressor operates without sufficient heating, then the system can start quickly, but liquid refrigerant and refrigeration oil flow out from the discharge pipe causing lubrication failure
Solution Approach 1:
The control unit activates the heating device before starting the compressor when the temperature difference between heat medium and compressor exceeds a predetermined threshold. This preliminary heating ensures the compressor shell temperature reaches at least the saturation temperature of the refrigerant, preventing liquid refrigerant and oil flow-out that would cause lubrication failure, while minimizing startup delay.
4Reliability
If the heating device is operated continuously, then the compressor shell temperature is maintained high, but energy consumption increases
Solution Approach 1:
The heating device is operated only before compressor startup when the temperature difference between heat medium and compressor exceeds a predetermined threshold, and only until the compressor shell temperature reaches at least the saturation temperature of the refrigerant. This targeted preliminary heating maintains reliability while minimizing energy consumption by avoiding continuous operation.
Solution Approach 2:
The control unit monitors the temperature difference between the heat medium and compressor, and the compressor shell temperature, to determine when to activate and deactivate the heating device. This feedback control ensures the heating device operates only when necessary to maintain the compressor shell temperature at or above the saturation temperature of the refrigerant, optimizing energy efficiency.
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 configuration ensures reliable oil supply to the compressor's mechanisms, enhancing its reliability by minimizing liquid and oil flow-out and maintaining superheat, thus preventing premature condensation and ensuring efficient operation.
Implementation Method 1
a heating device which heats the compressor; and a control unit... the control unit operates the heating device when the temperature detected by the second temperature sensor becomes higher than the temperature detected by the first temperature sensor by a predetermined temperature difference or more
Implementation Method 2
a radiator 112 which functions as a condenser and which heats a flowing heat medium
Implementation Method 3
an expansion valve 113... which decompresses the refrigerant
Implementation Method 4
an evaporator 114... which evaporates the refrigerant
Implementation Method 5
a compressor 111... which compresses the refrigerant
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A refrigeration cycle apparatus comprising: a refrigerant circuit which is formed by annularly and sequentially connecting a compressor 21, a radiator 22, expansion means 23 and an evaporator 24 to one another through refrigerant pipes, and through which a refrigerant is circulated; a first temperature sensor 51; a second temperature sensor 52; a heating device 31; and a control unit 4; characterized in that the control unit 4 operates the heating device 31 when the temperature detected by the second temperature sensor 52 becomes higher than the temperature detected by the first temperature sensor 51 by a predetermined temperature difference or more. Refrigeration oil is reliably supply to a compressing mechanism or a bearing, and reliability of the compressor 21 is enhanced.