Zone Damper Linearization for Precise HVAC Airflow Control

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Solution Overview

Problem

Conventional HVAC systems assume a linear relationship between damper positions and airflow, leading to nonlinear behavior, causing uneven temperature control, excess airflow noise, and performance issues due to inaccuracies in airflow delivery.

Innovation Solution

A control system that includes a system controller to record static pressures at various damper positions and apply corrections using a mathematical model to determine corrected intermediate positions, ensuring linear airflow behavior through zone dampers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional HVAC systems assume a linear relationship between damper positions and airflow, then the system operation is simplified, but the airflow control accuracy deteriorates due to nonlinear damper behavior

Engineering Contradiction:

Improvesystem operation simplicityVSAvoidairflow control accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent transforms the nonlinear damper position to airflow relationship into a linear relationship by applying a mathematical correction model. The system controller calculates corrected damper positions that compensate for nonlinearities, converting the inaccurate nonlinear parameter relationship into an accurate linear one for precise airflow control.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the direct mechanical assumption of linearity between damper position and airflow with a computational correction system. Instead of relying on the physical mechanical relationship to be linear, the system uses mathematical models and calculations to achieve linearized airflow control through corrected position commands.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Temperature

If zone dampers are adjusted to control airflow to multiple zones, then temperature control in zones is improved, but airflow noise increases due to nonlinear damper behavior

Engineering Contradiction:

Improvezone temperature controlVSAvoidairflow noise

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The patent modifies the damper position parameter through mathematical correction to achieve linear airflow changes. This linearization ensures smooth, gradual airflow adjustments that prevent sudden air movement and associated noise, while maintaining effective temperature control in zones.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If intermediate damper positions are used for incremental airflow control, then zone temperature precision is improved, but system stability deteriorates due to nonlinear airflow behavior

Engineering Contradiction:

Improvezone temperature precisionVSAvoidsystem stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent implements a feedback mechanism where the system controller continuously monitors actual airflow and damper positions, compares them with desired values, and applies corrections based on the nonlinear correction model. This closed-loop feedback ensures stable system operation by compensating for nonlinearities that would otherwise cause instability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies dynamic parameter transformation by calculating corrected damper positions that account for nonlinear behavior. This parameter correction ensures that incremental position changes produce predictable, linear airflow changes, maintaining system stability while achieving precise temperature control.

Inventive Principle:

Principle #35Parameter changes

4Measurement precision

If a mathematical correction model is applied to linearize airflow, then airflow control accuracy is improved, but device complexity increases

Engineering Contradiction:

Improveairflow control accuracyVSAvoidcontrol system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical linearization mechanisms with a computational approach. Instead of using complex mechanical linkages or actuators to achieve linear airflow, the system uses software-based mathematical correction in the system controller, reducing mechanical complexity while improving control accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a mathematical correction model as an intermediary between the damper position command and the actual airflow. This computational intermediary processes the position signal, applies nonlinear compensation, and generates corrected commands, achieving accurate linearized control without adding complex physical components.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10641515B2Linearization of airflow through zone dampers of an HVAC system

Publication Date: 2020.05.05 RHEEM MFG CO

AI summary

A control system can provide a linear behavior of airflow as a function of damper position of each zone damper in an HVAC system. The control system incrementally closes each zone damper from a fully open position to a fully closed position, and records static pressure measurements with each change in damper position. Then, using a mathematical model that is derived from the second fan law, a correction is calculated for each damper position of each zone damper based on the recorded static pressure measurements to provide corrected damper positions at which the airflow through the zone damper exhibits a linear behavior. The corrected damper positions are stored and used during an operational cycle of the HVAC system to obtain a precise airflow through the zone dampers.