Remote Heat Transfer Circuit for Low-GWP AHU Refrigerant Isolation
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Solution Overview
Problem
Air handling systems using heat pumps with high global warming potential (GWP) refrigerants pose a fire hazard due to the risk of refrigerant leaks, while transitioning to low GWP refrigerants introduces flammability concerns, and existing solutions do not effectively isolate the refrigerant from occupied areas.
Innovation Solution
A heat transfer device with a vapour compression circuit remotely located from the air handling unit, using two independent heat transfer fluid circuits to minimize refrigerant exposure and control heat exchange, employing a refrigerant with a GWP value less than or equal to 650, such as R290, and incorporating pumps to manage heat transfer fluid flow rates for efficient temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a heat pump with refrigerant is integrated into the air handling unit, then heat transfer efficiency is improved, but the risk of refrigerant leakage into occupied areas increases
Solution Approach 1:
The system is divided into two separate units: a remote heat pump unit containing the refrigerant circulation system, and an air handling unit that processes air. The heat pump unit is segmented from the air handling function, allowing efficient heat transfer while preventing refrigerant contact with air streams.
Solution Approach 2:
The vapour compression circuit with refrigerant is extracted from the air handling unit and placed in a separate remote location. This extraction eliminates the direct fluid path between refrigerant and air supply passages while maintaining the heat transfer function through a dedicated heat exchanger.
2Reliability
If flammable low GWP refrigerant is used, then environmental impact is reduced, but fire hazard increases
Solution Approach 1:
The system design incorporates inherent safety features by locating the refrigerant containment system remotely from air supply passages and occupied areas. This spatial separation acts as a cushioning measure that prevents refrigerant vapour from reaching concentrations that could create fire hazards, while still allowing the use of environmentally friendly low GWP refrigerants.
3Object-affected harmful factors
If refrigerant is located remotely from air handling unit, then safety is improved, but system complexity increases
Solution Approach 1:
A dedicated heat transfer fluid circuit acts as an intermediary between the remote refrigerant system and the air handling unit. This intermediary system with pumps and heat exchangers enables safe remote operation while managing the complexity through functional specialization and clear separation of duties between systems.
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
Significantly reduces the risk of refrigerant contamination and fire hazards in occupied areas by isolating the vapour compression circuit, enhances energy efficiency through thermal energy reuse, and maintains safe operation by keeping flammable refrigerant charges below maximum allowable limits.
Implementation Method 1
a first heat exchanger operable to exchange heat between the refrigerant and the first heat transfer fluid
Implementation Method 2
a second heat exchanger operable to exchange heat between the refrigerant and the second heat transfer fluid
Implementation Method 3
a first pump for pumping first heat transfer fluid to the air supply passage
Implementation Method 4
a second pump for pumping second heat transfer fluid to the return-from-area passage
Implementation Method 5
a vapour compression circuit comprising a compressor
Data Source
Figure 1
AI summary
A remote heat transfer device for use with an air handling unit comprises: a vapour- compression circuit, the vapour-compression circuit comprising a first heat exchanger adapted to exchange heat between a refrigerant in the vapour compression circuit and a first heat transfer fluid; and a first outlet arranged to provide the first heat transfer fluid to an air supply passage of the air handling unit, so that the first heat transfer fluid exchanges heat with supply air passing through the air supply passage.