Perforated Heater Shield for PTAC Whistle Noise Reduction
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Solution Overview
Problem
Packaged Terminal Air Conditioners (PTACs) experience a whistling noise due to the proximity of the electric heater and fan wheel, which is not effectively mitigated by traditional methods of supporting or repositioning components, and the source of the noise is attributed to vortex shedding in the tight space between these elements.
Innovation Solution
The implementation of a noise-abating flow disruptor, such as a perforated plate or wire mesh screen, positioned between the electric heater and the fan wheel to minimize airflow disruption and reduce tonal noise, combined with strategies like selectively energizing heating elements and staggering their placement to reduce noise at specific frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electric heater is positioned close to the fan wheel to minimize space and maximize heating efficiency, then the compactness and heating performance are improved, but a whistling noise is generated due to vortex shedding in the tight space between the heater and fan wheel
Solution Approach 1:
A flow disruptor is introduced as an intermediary component between the electric heater and fan wheel. This flow disruptor modifies the airflow pattern in the narrow space between these components, preventing vortex shedding that causes whistling noise while maintaining the close positioning needed for heating efficiency
Solution Approach 2:
The flow disruptor is strategically positioned only in the specific region where vortex shedding occurs between the heater and fan wheel, rather than obstructing the entire airflow path. This localized intervention maintains heating efficiency while eliminating noise
2Object-affected harmful factors
If a flow disruptor is introduced between the electric heater and fan wheel to reduce noise, then the tonal noise is reduced by at least 5 decibels, but the airflow between the heater and fan wheel is disrupted
Solution Approach 1:
The flow disruptor employs a porous or mesh-like structure that allows airflow to pass through while creating sufficient turbulence to break up vortex shedding. This design reduces noise by at least 5 decibels at peak frequencies between 500 and 1500 Hz while minimizing energy loss from airflow disruption
3Length of moving object
If heating elements are positioned closer to the fan wheel to reduce heater height, then the overall heater height is reduced, but the whistling noise from vortex shedding increases
Solution Approach 1:
The flow disruptor serves as a mediator that enables the heating elements to be positioned close to the fan wheel (reducing heater height) while simultaneously preventing the vortex shedding that would otherwise cause whistling noise in this compact configuration
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
The noise-abating flow disruptor significantly reduces the tonal noise by at least 5 decibels at peak frequencies between 500 and 1500 Hz, making the refrigerant system operate more quietly than without the disruptor, and allows for adjustable heat output by varying the energization of heating elements.
Implementation Method 1
the source of the noise is attributed to vortex shedding in the tight space between these elements
Implementation Method 2
The implementation of a noise-abating flow disruptor, such as a perforated plate or wire mesh screen, positioned between the electric heater and the fan wheel to minimize airflow disruption and reduce tonal noise
Implementation Method 3
an electric heater for selective heating and cooling modes
Data Source
AI summary
A sound-abating flow disruptor quiets a PTAC refrigerant system by disturbing the airflow between an energized electric heater and an adjacent fan wheel. In some embodiments, the flow disruptor is a perforated metal plate that attenuates a whistle, which appears to be caused by vortex shedding in the confined area between the energized heater and the fan. In some cases, the heater comprises selectively energizable heating elements of various wattage. The heating elements closest to the fan wheel are the lower wattage ones to minimize the heat near the fan.