VFD Waste Heat Oil Conditioning for Chiller Compressors

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Solution Overview

Problem

Refrigeration systems with VFD compressors face challenges in achieving optimal oil viscosity without supplemental electric heat or excessive parasitic losses from oil cooling, which affects compressor reliability and efficiency.

Innovation Solution

A refrigeration system that thermally couples an oil conditioning circuit with a VFD to utilize waste heat produced by the VFD for heating the oil, eliminating the need for external cooling methods and electric heaters, thereby achieving the desired oil viscosity and improving compressor reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If supplemental electric heat is used to achieve optimal oil viscosity, then oil viscosity control is improved, but energy consumption and system complexity increase

Engineering Contradiction:

Improvecompressor reliabilityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent converts the waste heat generated by the VFD, which is normally a harmful factor requiring cooling, into a beneficial resource for heating the oil to optimal viscosity temperature. This eliminates the need for supplemental electric heaters and reduces overall energy consumption while maintaining compressor reliability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system uses its own internally generated waste heat from the VFD to service the oil heating requirement, making the system self-sufficient for temperature control without external energy inputs.

Inventive Principle:

Principle #25Self-service

2Reliability

If oil cooling is used to achieve optimal oil viscosity, then oil temperature control is improved, but parasitic losses increase and system efficiency decreases

Engineering Contradiction:

Improvecompressor reliabilityVSAvoidparasitic losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

Instead of using parasitic oil cooling methods that waste energy, the patent utilizes the waste heat from the VFD to heat the oil to the required viscosity temperature, converting a harmful thermal byproduct into a useful resource and eliminating the need for energy-consuming cooling systems.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system changes the thermal parameter approach from active cooling to passive heating using waste heat, fundamentally altering how oil temperature is managed and eliminating parasitic energy losses associated with cooling systems.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If VFD waste heat is used for oil conditioning, then system efficiency is improved, but the VFD operating temperature may increase

Engineering Contradiction:

Improvesystem efficiencyVSAvoidVFD operating temperature

Core Design Contradiction:

Loss of energyVSTemperature

Solution Approach 1:

The patent introduces an intermediary heat exchanger between the VFD and the oil conditioning system. This allows thermal energy transfer from the VFD to the oil without direct thermal coupling, enabling waste heat recovery while maintaining the VFD within its operating temperature limits.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution enhances compressor reliability and system efficiency by utilizing waste heat for oil conditioning, reducing the need for external cooling and electric heaters, leading to more efficient operation and reduced parasitic losses.

Implementation Method 1

the oil conditioning circuit is thermally coupled to the VFD and configured to heat oil from the oil separator with heat produced by the VFD

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentUS10260783B2Chiller compressor oil conditioning

Publication Date: 2019.04.16 CARRIER CORP

AI summary

In one aspect, a refrigeration system is provided. The refrigeration system includes a compressor coupled to a variable frequency drive (VFD), a condenser, an evaporator, an oil separator, and an oil conditioning circuit. The oil conditioning circuit is thermally coupled to the VFD and configured to heat oil from the oil separator with heat produced by the VFD.