HVAC Airflow Control Using Vent-Area-Based Blower Calibration
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Solution Overview
Problem
Existing HVAC systems face inaccuracies in airflow control due to the conversion of blower control parameters, which do not account for variations in air intake door positions and front/rear air distribution doors, leading to inconsistent airflow for given climate settings.
Innovation Solution
The system determines desired airflow based on inlet and outlet cross-sectional areas, using lookup tables to calculate blower control parameters, such as PWM fraction, to accurately control airflow through switchable vents in different configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If blower control parameters are converted to airflow using a scaling factor, then airflow can be determined in CMH for downstream heat transfer calculations, but the airflow determination becomes inaccurate for many combinations of air intake door position and front/rear air distribution doors
Solution Approach 1:
The patent changes the control parameters from simple scaling factor conversions to lookup tables that map blower control parameters to airflow values for specific vent configurations. This allows the system to adapt to different combinations of air intake door positions and front/rear air distribution door positions, providing accurate airflow determination for each configuration scenario.
Solution Approach 2:
The patent segments the airflow determination process by creating separate lookup tables for different air intake configurations (fresh air vs. recirculation). Each lookup table contains pre-calculated airflow values corresponding to specific blower control parameters and vent configurations, allowing the system to select the appropriate table based on the current configuration.
2Device complexity
If the system uses fixed scaling factors for airflow conversion, then the control logic remains simple, but the airflow control becomes inconsistent when vent configurations change
Solution Approach 1:
The patent performs preliminary calculations by pre-computing airflow values for all possible combinations of blower control parameters and vent configurations, storing these in lookup tables. This eliminates the need for complex real-time calculations when vent configurations change, maintaining simple control logic while ensuring consistent and reliable airflow control across all configurations.
3Measurement precision
If the system does not account for inlet and outlet cross-sectional areas, then the control system remains simple, but the airflow control accuracy decreases when air intake door or distribution door positions change
Solution Approach 1:
The patent incorporates inlet and outlet cross-sectional areas as additional parameters in the airflow determination process. Lookup tables are created that map blower control parameters to airflow values for specific combinations of inlet area (fresh air vs. recirculation) and outlet area (front/rear distribution door positions). This provides accurate airflow control while maintaining relatively simple system architecture through the use of pre-computed lookup tables.
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 provides more precise airflow control, maintaining consistent airflow levels even with changes in vent configurations, enhancing user comfort and system efficiency.
Implementation Method 1
a blower configured to move air from an inlet to a plurality of outlet vents
Implementation Method 2
The resulting airflow may be used in downstream heat transfer computations for the HVAC system
Data Source
AI summary
Aspects of the subject disclosure relate to airflow control for heating ventilation and air conditioning (HVAC) systems, including HVAC systems for vehicles. The airflow control may include controlling a blower to provide a constant amount of airflow through an open one of multiple outlet vents, before and after a switch, between an open configuration and a closed configuration, of one or more others of the multiple outlet vents. For example, controlling the blower to provide the constant amount of airflow may include controlling the blower based at least in part on a cumulative outlet area of a set of the multiple outlet vents that are in the open configuration.