Intermediate Heat Exchanger Isolation for Single-Package HVAC Units
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Solution Overview
Problem
Traditional HVAC systems face challenges in isolating refrigerant from airflow to prevent environmental contamination, as refrigerants used for environmental compliance may not be suitable for mixing with conditioned air, leading to potential refrigerant exposure in temperature-controlled environments.
Innovation Solution
Incorporating an intermediate heat exchanger, such as a brazed plate heat exchanger, that isolates the refrigerant loop from the air handling unit by placing the refrigerant in a heat exchange relationship with an intermediate working fluid like water or CO2, which is then directed to the air handling unit to exchange heat with the airflow, thereby preventing refrigerant mixing with the airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If refrigerant is directly used in the air handling unit heat exchanger, then heat transfer efficiency is improved, but refrigerant may mix with airflow causing environmental contamination
Solution Approach 1:
The patent introduces an intermediate heat exchanger that uses water or other fluids as a mediator between the refrigerant and the airflow. The refrigerant transfers heat to the intermediate fluid, which then transfers heat to the airflow, preventing direct contact between refrigerant and air while maintaining efficient heat transfer.
Solution Approach 2:
The heat transfer process is divided into two separate stages: first, heat exchange between refrigerant and intermediate fluid in the intermediate heat exchanger; second, heat exchange between intermediate fluid and airflow in the air handling unit. This segmentation prevents refrigerant contamination while preserving thermal efficiency.
2Device complexity
If refrigerant loop and air handling unit are integrated in a single package, then device complexity is reduced, but refrigerant exposure risk increases
Solution Approach 1:
The intermediate heat exchanger serves as a physical and functional barrier within the single-packaged unit, using an intermediate fluid to mediate heat transfer between the refrigerant loop and air handling unit. This allows system integration while preventing refrigerant exposure.
Solution Approach 2:
The refrigerant is effectively extracted from the air handling process by isolating it in a separate loop that only interacts with the system through thermal coupling via the intermediate fluid, eliminating the risk of refrigerant mixing with conditioned air.
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 solution effectively isolates refrigerant from the airflow, ensuring that even if refrigerant escapes, it does not mix with the conditioned air, thus maintaining environmental safety and compliance with regulations while providing efficient heat transfer.
Implementation Method 1
the first heat exchanger is configured to place the refrigerant in a first heat exchange relationship with a working fluid
Implementation Method 2
the second heat exchanger is configured to place the working fluid in a second heat exchange relationship with an airflow
Data Source
AI summary
A heating, ventilating, and air conditioning (HVAC) system includes a refrigerant loop having a compressor, where the compressor is configured to circulate a refrigerant through the refrigerant loop, a first heat exchanger disposed along the refrigerant loop, where the first heat exchanger is configured to place the refrigerant in a first heat exchange relationship with a working fluid, and an air handling unit having a second heat exchanger, where the second heat exchanger is configured to place the working fluid in a second heat exchange relationship with an airflow, and where the air handling unit is isolated from the first heat exchanger to reduce or eliminate mixing of refrigerant with the airflow.