Dual-Pass Airflow Coil Layout to Prevent AC Coil Freezing
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Solution Overview
Problem
Conventional air conditioning units are not suitable for conditioning outside air without significant modifications, as they are designed for return air and cannot handle the different properties of outside air, leading to potential freezing of cooling coils due to inadequate heat transfer.
Innovation Solution
A dual pass air conditioning device configuration with a pre-conditioned air passage chamber, a post-conditioned air passage chamber, and a partially-conditioned air passage chamber, where air passes through the cooling coil system twice, allowing the same cooling coil and blower system used in return air conditioning units to condition outside air efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional return air conditioning units are used to condition outside air, then the existing cooling coil and blower system can be utilized, but the cooling coils may freeze due to inadequate heat transfer from the warmer outside air
Solution Approach 1:
The air passage is divided into multiple segments with different flow velocities. The cooling coil is exposed to both high-velocity air (from the return air pathway) and low-velocity air (from the outside air pathway), allowing different portions of the coil to serve different functions without freezing
Solution Approach 2:
The patent combines the return air conditioning pathway with the outside air conditioning pathway into a single dual-pass system. The cooling coil serves both pathways simultaneously, with return air providing high-velocity flow to prevent freezing while outside air provides the cooling load
2Temperature
If the face velocity of outside air through the cooling coil is reduced to achieve desired temperature reduction, then cooling effectiveness improves, but the cooling coils freeze due to insufficient heat transfer
Solution Approach 1:
The air flow is segmented into two passes: one pass for temperature reduction (outside air at lower velocity) and another pass for preventing coil freezing (return air at higher velocity). This allows the system to achieve both cooling effectiveness and freeze prevention simultaneously
Solution Approach 2:
The system changes the velocity parameter of air flow through the cooling coil by introducing a second air stream (return air) with different velocity characteristics. This parameter change allows the coil surface temperature to remain above freezing while still achieving the desired air temperature reduction
3Device complexity
If conventional single pass air flow configuration is used, then the system design is simple, but it cannot adequately handle the different properties of outside air compared to return air
Solution Approach 1:
The cooling coil is designed to perform multiple functions simultaneously: cooling outside air, dehumidifying outside air, and preventing itself from freezing. The dual-pass air flow configuration allows the same coil to handle both return air and outside air with different properties without requiring separate cooling systems
Solution Approach 2:
The air flow path is segmented into distinct passes that can be independently controlled. This segmentation allows the system to optimize each pass for its specific function while using the same physical cooling coil, achieving versatility without proportionally increasing device complexity
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
Enables the use of existing cooling coil and blower systems in outside air conditioning units, preventing coil freezing and ensuring efficient air conditioning without the need for costly replacements, while maintaining performance and energy efficiency.
Implementation Method 1
The return air is conditioned by passing through a cooling coil
Implementation Method 2
An impermeable partition separates the pre-conditioned air passage chamber and the post-conditioned air passage chamber
Data Source
AI summary
Apparatus and methods provide for a dual pass air flow configuration in an air conditioning system to improve efficiency and performance of the air conditioning system. An air conditioning device includes a pre-conditioned air passage chamber separated from a post-conditioned air passage chamber by an impermeable partition. A coil system separates the pre-conditioned air passage chamber and the post-conditioned air passage chamber from a partially-conditioned air passage chamber. The coil system is configured to receive air from the pre-conditioned air passage chamber and to condition the air passing through the coil system into the partially-conditioned air passage chamber. The coil system is also configured to receive the air from the partially-conditioned air and further condition the air as it passes through the coil system into the post-conditioned air passage chamber.