Multi-Segment Heat Exchanger for Cold Climate Heat Pump Defrost
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Solution Overview
Problem
Cold climate heat pumps experience capacity and efficiency degradation below 17° F, often requiring backup heating and defrost cycles that reduce energy efficiency and necessitate improved systems operable in cold climates.
Innovation Solution
A modular cold climate heat pump system incorporating a heat pump module, thermal energy storage module, and end use modules connected via a heat transfer fluid, utilizing a multi-segmented heat exchanger and phase change materials to enhance energy efficiency and eliminate the need for backup heating during defrost cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional heat pump systems are used in cold climates, then heating capacity is maintained at moderate temperatures, but capacity and efficiency degrade significantly below 17° F requiring backup heating
Solution Approach 1:
The heat exchanger is divided into multiple segments (first, second, and third heat exchangers) that can independently handle different refrigerant states and temperature ranges. This segmentation allows the system to maintain efficient heat transfer across varying outdoor temperatures without requiring backup heating, resolving the contradiction between reliability and energy efficiency.
Solution Approach 2:
The system changes the thermal parameters of the refrigerant through sequential processing in different heat exchanger segments. The refrigerant is de-superheated, condensed, and sub-cooled in separate stages, allowing optimal heat extraction at each temperature level. This parameter transformation enables the heat pump to maintain high efficiency even at low outdoor temperatures below 17° F.
2Reliability
If defrost cycles are implemented to remove frost buildup, then heat exchanger performance is restored, but heat is drawn back out of the building reducing heating capacity and efficiency
Solution Approach 1:
The system converts the harmful effect of frost buildup into a beneficial process by using the sub-cooled refrigerant to provide controlled defrosting. The third heat exchanger delivers sub-cooled refrigerant that can melt frost on the outdoor coil without requiring reverse cycle operation, thereby maintaining heating capacity while restoring heat exchanger performance. This eliminates the need to draw heat back from the building during defrost cycles.
Solution Approach 2:
The sub-cooled refrigerant acts as an intermediary medium that transfers heat to melt frost on the outdoor heat exchanger surface. Instead of using a separate defrost system that would extract heat from the building, the sub-cooled refrigerant serves as the heat transfer medium, allowing defrosting to occur without compromising heating capacity or efficiency.
3Use of energy by moving object
If multiple heat exchangers are used to maximize energy use, then system complexity increases, but energy efficiency and heating capacity are maintained
Solution Approach 1:
The first, second, and third heat exchangers are merged into a single integrated heat pump system with shared refrigerant flow paths and common control mechanisms. This merging allows the system to maximize energy efficiency through sequential heat extraction while avoiding the excessive complexity that would result from completely separate systems. The integrated design enables coordinated operation of all heat exchanger segments.
Solution Approach 2:
The multi-segment heat exchanger system performs multiple functions within a unified structure: de-superheating in the first segment, condensation in the second segment, and sub-cooling in the third segment. This multi-functionality allows the system to maintain high energy efficiency across different operating conditions without requiring separate dedicated systems for each function, thereby balancing energy efficiency with acceptable system 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
The system maximizes energy use, maintains heating capacity, and reduces energy consumption by using superheated refrigerant for multiple end uses, eliminating the need for backup heating during defrost, and providing efficient space heating and water heating while maintaining operation during defrost modes.
Implementation Method 1
the second heat exchanger is configured to condense the refrigerant resulting in a condensed refrigerant
Implementation Method 2
the refrigerant and the heat transfer fluid are in thermal communication in the heat pump module
Implementation Method 3
the TES module includes a phase change material, and the phase change material includes a salt hydrate
Data Source
AI summary
A modular cold climate heat pump system which, in some embodiments includes a multi-segment heat exchanger. The modular cold climate heat pump system includes a heat pump module, a thermal energy storage module, and at least one end use module. Exemplary end uses include heating, ventilation, and air conditioning applications or domestic hot water heating. The thermal energy storage module may enable the heat pump module to continue operating even during temperatures below freezing.