PTAC Unit Makeup Air Duct Design for Code-Compliant Ventilation
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Solution Overview
Problem
Traditional PTAC units have insufficient makeup air ventilation capacity, which fails to meet current codes and regulations due to the influence of outdoor fans and interior room static pressure on the airflow through the bulkhead vent aperture.
Innovation Solution
An air conditioning unit with a separate makeup air duct structure built into the bottom plate, extending from the outdoor to the indoor portion, and a unique indoor heat exchanger design that can switch between a condenser and an evaporator, allowing for independent makeup air flow and improved airflow management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a traditional PTAC unit uses a bulkhead with vent aperture for makeup air flow, then the unit structure is simple and compact, but the makeup air ventilation capacity is insufficient and fails to meet code requirements
Solution Approach 1:
The patent divides the air handling function into separate pathways: a dedicated makeup air duct system and a return air system. The makeup air duct is segmented as a separate component built into the bottom plate, allowing independent airflow management. This segmentation enables the makeup air system to operate independently from the return air system, ensuring sufficient ventilation capacity while maintaining structural organization.
Solution Approach 2:
The patent introduces a vertical dimension by building the makeup air duct into the bottom plate of the unit, extending from the outdoor portion upward through the partition plate to the indoor portion. This three-dimensional integration allows the makeup air pathway to be established without expanding the horizontal footprint, thus increasing ventilation capacity while maintaining compact unit dimensions.
2Reliability
If makeup air flows through the bulkhead vent aperture driven by indoor fan suction, then the unit operation is simple, but the flow rate is substantially influenced by outdoor fan and interior room static pressure
Solution Approach 1:
The patent segments the airflow systems by providing a dedicated makeup air duct that is physically separated from the return air pathways. This separate duct system allows the makeup air flow to be controlled independently from the return air fan operations, eliminating the interference from outdoor fan and room static pressure variations that affect bulkhead vent aperture flow.
Solution Approach 2:
The patent introduces a dedicated makeup air fan as an intermediary device that actively drives makeup air through the dedicated duct system. This intermediary fan provides positive pressure to overcome the influences of outdoor fan suction and room static pressure, ensuring stable and reliable makeup air delivery regardless of the operating conditions of other system components.
3Quantity of substance
If the vent door in the bulkhead is opened to allow makeup air flow, then fresh air can enter the conditioned room, but some fresh air may be drawn by the outdoor fan to flow through the outdoor heat exchanger to the outside
Solution Approach 1:
The patent segments the fresh air pathways into two completely separate systems: a dedicated makeup air duct that delivers fresh air directly to the conditioned room, and an outdoor air intake system for the outdoor heat exchanger. This segmentation ensures that fresh air entering through the makeup air duct cannot be siphoned off by the outdoor fan, as the pathways are physically isolated. The vent door in the bulkhead can remain closed, eliminating the air theft problem while maintaining fresh air delivery.
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
Enhances makeup air ventilation capacity to meet regulatory requirements, ensuring better indoor air quality and occupant health by providing a dedicated pathway for fresh air intake and mixing with room return air effectively.
Implementation Method 1
a makeup air fan located in the makeup air duct... allow makeup air to flow therethrough
Implementation Method 2
makeup air moving by a suction force created by an indoor fan
Implementation Method 3
an outdoor heat exchanger disposed in an outdoor portion, an indoor heat exchanger disposed in an indoor portion
Data Source
AI summary
An air conditioning unit is disclosed. The air conditioning unit may include a makeup air system having a makeup air duct with a first end and a second end. The makeup air duct may be separate structure built in a bottom plate of the air conditioning unit and define an air flow passage in fluid communication between the first end and the second end to allow makeup air to flow therethrough.