Modulating Bypass Damper Control for Zoned HVAC Airflow and Noise

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Solution Overview

Problem

Conventional HVAC systems face challenges in precisely controlling airflow and pressure balance, leading to noise issues and inefficiencies due to the lack of precise control in bypass dampers, which can result in over-conditioning or under-conditioning of zones and potential damage to temperature control elements.

Innovation Solution

An intelligent HVAC system with a modulating bypass damper treated as a virtual zone, controlled by a system controller that adjusts damper positions to bypass conditioned air precisely, maintaining a set point temperature and closing the bypass when temperatures exceed a threshold, ensuring efficient operation and noise reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional bypass dampers are used to relieve static pressure, then airflow noise is reduced, but the amount of conditioned air returned to the return duct cannot be precisely controlled, causing over-conditioning or under-conditioning of zones and potential damage to temperature control elements

Engineering Contradiction:

Improveairflow noiseVSAvoidcontrol precision of conditioned air amount

Core Design Contradiction:

Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The bypass damper is transformed from a static two-position device to a dynamic modulating damper that can incrementally adjust to multiple positions, enabling continuous control of the amount of conditioned air returned to the return duct. This dynamic adjustment capability allows precise matching of bypass airflow to system requirements.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

A control system with feedback mechanism is implemented to monitor the amount of conditioned air being returned through the bypass damper and adjust the damper position accordingly. The feedback loop ensures that the bypass damper returns only the necessary amount of conditioned air to relieve static pressure without causing over-conditioning or damaging temperature control elements.

Inventive Principle:

Principle #23Feedback

2Ease of operation

If modulating bypass dampers are used to provide incremental control, then the amount of conditioned air returned can be controlled, but the nonlinear behavior of airflow with damper position changes affects the ability to accurately determine airflow at each damper position

Engineering Contradiction:

Improvecontrol capability of conditioned air amountVSAvoidaccuracy of airflow determination

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The control system replaces purely mechanical damper positioning with an intelligent control mechanism that uses algorithms to calculate and compensate for nonlinear airflow characteristics. The control system incorporates airflow-damper position relationships and uses this information to accurately determine the amount of air flowing through the bypass damper at each position.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system changes the parameter representation from direct damper position to calculated airflow amount by incorporating the nonlinear relationship between damper position and airflow into the control algorithm. This parameter transformation allows the control system to accurately determine airflow despite the nonlinear behavior of the modulating damper.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If alternate techniques are used to relieve static pressure without bypass systems, then the HVAC system can avoid using bypass dampers, but the system must shut down when noise reduction attempts are exhausted, leaving zones under-conditioned

Engineering Contradiction:

Improvecontinuous operation capabilityVSAvoidairflow noise

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The bypass damper acts as an intermediary mechanism that provides a dedicated pathway for excess conditioned air to return to the return duct. This intermediary bypass system allows the HVAC system to relieve static pressure and reduce airflow noise in occupied zones without shutting down, maintaining continuous operation and zone conditioning.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10677489B2Intelligent bypass damper operation in an HVAC system with zones

Publication Date: 2020.06.09 RHEEM MFG CO

AI summary

An HVAC system includes at least one zone comprising a zone damper and a bypass comprising a bypass damper associated with a virtual zone. When an airflow of conditioned air to the at least one zone exceeds a maximum airflow value for the at least one zone and/or when other airflow reduction techniques have been exhausted, a system controller of the HVAC system controls the bypass damper to incrementally bypass a portion of conditioned air to the virtual zone. The portion of the conditioned air that is bypassed is a minimum amount of the conditioned air that is needed to reduce the airflow of the conditioned air below the maximum airflow value and keep the HVAC system running. Further, the system controller closes the bypass damper when a temperature of the portion of the conditioned air exceeds a threshold temperature value.