Dynamic Evaporator Setpoint Control for HVAC Icing Prevention

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Solution Overview

Problem

HVAC systems compromise air conditioning performance by maintaining higher compressor setpoints to prevent evaporator core icing, leading to warmer discharge temperatures and reduced cooling efficiency in cooler conditions.

Innovation Solution

An automatic climate controller identifies operating zones based on evaporator temperature and cabin relative humidity, adjusting compressor cycling and airflow to reduce the risk of icing, allowing for lower evaporator setpoints and improved cooling performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a higher evaporator setpoint is used to prevent icing, then evaporator core freezing is prevented, but A/C performance and cooling efficiency deteriorate

Engineering Contradiction:

Improveevaporator core freezing preventionVSAvoidA/C performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The evaporator setpoint is made dynamic rather than fixed. The climate control module adjusts the setpoint based on real-time operating conditions including ambient temperature, humidity, and compressor runtime. This allows the system to use lower setpoints when icing risk is low and higher setpoints when icing risk is high, resolving the contradiction between preventing freezing and maintaining cooling performance

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the evaporator temperature parameter based on operating conditions. By monitoring ambient temperature and humidity levels, the system adjusts the evaporator setpoint temperature dynamically, allowing optimal cooling performance when conditions permit and preventing icing when conditions require higher temperatures

Inventive Principle:

Principle #35Parameter changes

2Reliability

If compressor cycling is increased to prevent evaporator icing, then evaporator core freezing is prevented, but discharge temperature increases and cooling efficiency decreases

Engineering Contradiction:

Improveevaporator core freezing preventionVSAvoiddischarge temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The system uses feedback from temperature and humidity sensors to control compressor cycling. By continuously monitoring evaporator temperature and ambient conditions, the system determines the optimal compressor runtime to prevent icing while minimizing unnecessary cycling. This feedback mechanism allows the compressor to run longer at lower setpoints rather than cycling frequently at higher setpoints, maintaining lower discharge temperatures

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The compressor control strategy is made dynamic based on real-time conditions. Instead of using fixed cycling patterns, the system adjusts compressor runtime and setpoint dynamically, allowing extended operation at optimal setpoints when conditions permit, thereby reducing discharge temperature while still preventing icing when necessary

Inventive Principle:

Principle #15Dynamics

3Reliability

If a single set of compressor setpoints is used for all conditions, then evaporator core freezing is prevented, but cooling performance is compromised in cooler conditions

Engineering Contradiction:

Improveevaporator core freezing preventionVSAvoidperformance across different conditions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system transitions from static setpoints to dynamic setpoints that adapt to different operating conditions. By monitoring ambient temperature, humidity, and other parameters, the system adjusts the evaporator setpoint in real-time, providing optimal performance for each specific condition while maintaining protection against freezing

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The evaporator setpoint parameter is changed based on operating conditions. The system uses multiple setpoints or continuously adjusts the setpoint value according to ambient temperature and humidity levels, allowing the system to adapt its behavior to different environmental conditions rather than using a single fixed setpoint

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9796243B2Coolest A/C discharge temperature for all operating conditions

Publication Date: 2017.10.24 FORD GLOBAL TECH LLC

AI summary

An automatic climate controller device identifies an operating zone of the climate control system according to at least two input factors, and identifies a discharge temperature of the climate control system. Based on the operating zone and the discharge temperature, the automatic climate controller device determines whether to perform at least one override action to override a climate control system setting to reduce the possibility of evaporator core icing. The automatic climate controller device also adjusts an evaporator set point according to the at least one override action to reduce the discharge temperature. The input factors may include evaporator temperature and cabin relative humidity. The actions may include one or more of increasing blower speed or increasing use of recirculated air.