Compressor Oil Heating Control for Low-Standby Refrigeration

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Solution Overview

Problem

Existing refrigeration devices consume excessive standby power due to inefficient heating control, particularly because current methods do not account for the amount of refrigerant dissolved into the lubricating oil, leading to potential refrigerant stagnation and decreased lubricating oil viscosity.

Innovation Solution

A refrigeration device that uses a control device to set an oil temperature target value by adding a predetermined temperature to the saturation temperature of the refrigerant, allowing for simple heater control based on temperature, thereby minimizing refrigerant dissolution and maintaining appropriate oil concentration and viscosity, and reducing standby power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the heater is continuously energized to warm the compressor and prevent refrigerant stagnation, then the lubricating oil temperature is maintained and refrigerant dissolution is prevented, but the standby power consumption increases

Engineering Contradiction:

Improveprevention of refrigerant stagnationVSAvoidstandby power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The control method changes the parameter being monitored from simple temperature to the difference between oil temperature and refrigerant saturation temperature (ΔT). This allows the system to account for refrigerant dissolution effects and make more precise heating decisions, reducing unnecessary heater operation while preventing refrigerant stagnation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system implements feedback control by continuously monitoring both oil temperature and refrigerant saturation temperature, calculating ΔT, and using this information to control heater operation. This feedback mechanism ensures the heater operates only when necessary to prevent refrigerant stagnation, optimizing both reliability and energy consumption.

Inventive Principle:

Principle #23Feedback

2Device complexity

If control is based on simple temperature thresholds, then the control logic is simple and standby power can be reduced, but the control accuracy is insufficient and heating may be inadequate when refrigerant dissolution is significant

Engineering Contradiction:

Improvecontrol logic complexityVSAvoidadequacy of heating control

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The invention introduces a new control parameter ΔT (difference between oil temperature and refrigerant saturation temperature) that captures the physical relationship between temperature and refrigerant dissolution. This single parameter change provides both simplicity and accuracy, avoiding complex control logic while ensuring adequate heating control.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If the heater is controlled based on refrigerant temperature or external air temperature, then some standby power reduction is achieved, but further power reduction is possible and heating adequacy cannot be ensured when refrigerant dissolution is significant

Engineering Contradiction:

Improvestandby power consumptionVSAvoidadequacy of heating control

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The invention transitions from using external parameters (refrigerant temperature or air temperature) to using an internal parameter (ΔT between oil temperature and refrigerant saturation temperature) that directly reflects the conditions for refrigerant dissolution. This enables both further power reduction and ensured heating adequacy.

Inventive Principle:

Principle #35Parameter changes

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 simplifies control, reduces standby power consumption, maintains optimal oil concentration and viscosity, and improves the reliability of the compressor by allowing for appropriate start-up selections and accurate temperature measurements.

Implementation Method 1

a heater for heating lubricating oil in the compressor

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

the proportion of the refrigerant dissolving into the lubricating oil in the crank case increases

Methodology Applied

Scientific EffectDissolution: Solvation

Data Source

PatentUS9939184B2Refrigeration device

Publication Date: 2018.04.10 DAIKIN INDUSTRIES LTD

AI summary

A refrigeration device includes a radiator, an evaporator, a compressor, a heater and a control device. The radiator causes a refrigerant to radiate heat. The evaporator causes the refrigerant to evaporate. The compressor compresses the refrigerant circulating between the radiator and the evaporator. The heater heats lubricating oil in the compressor. The control device controls the heater so that an oil temperature of the lubricating oil in the compressor reaches an oil temperature target value obtained by adding a predetermined temperature to saturation temperature of the refrigerant in the compressor.