Heat Pump Sequential Defrost for Continuous Winter Heating
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Solution Overview
Problem
Conventional air source heat pump systems face inefficiencies due to frost formation on regeneration air heat exchangers at low temperatures, leading to reduced system performance and increased energy consumption, as existing defrosting methods disrupt heating cycles and require additional energy sources.
Innovation Solution
A heat pump system with a regeneration air heat exchanger that includes a damper system allowing independent control of air flow and a refrigeration circuit for sequential defrosting using hot refrigerant, along with an angled design to facilitate water shedding, enabling continuous operation and reduced frost accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heat pump system operates in winter mode with outside temperature below 33-35°F, then heating function is provided, but frost forms on the regeneration air heat exchanger coils requiring system shutdown for defrosting
Solution Approach 1:
The regeneration air heat exchanger is divided into multiple independently controllable zones with separate dampers. This allows one zone to be defrosted while other zones continue to provide heating function, eliminating the need for complete system shutdown and enabling continuous operation.
Solution Approach 2:
The system implements periodic defrost cycles where hot refrigerant is sequentially directed to different zones of the heat exchanger. This periodic action allows frost to be removed in stages while maintaining overall system operation between cycles.
2Reliability
If the heat pump system is shut down for defrosting, then frost is removed from the heat exchanger, but the building loses its heat source or requires auxiliary heating
Solution Approach 1:
By segmenting the heat exchanger into multiple zones with independent defrost control, the system can defrost only the affected zones while other zones continue providing heating. This eliminates complete system shutdown and prevents heating interruption to the building.
Solution Approach 2:
The system merges the defrost operation with continuous heating operation by allowing defrosting in one zone while heating continues in other zones. This combination eliminates the need to choose between defrosting and heating, as both can occur simultaneously in different parts of the system.
3Reliability
If a pre-conditioning coil is used to prevent frost formation, then frost accumulation is reduced, but energy is diverted from the supply air heat exchanger reducing overall system efficiency
Solution Approach 1:
The system uses hot refrigerant from the refrigeration cycle itself to defrost the heat exchanger, rather than requiring separate energy input through a pre-conditioning coil. This self-service approach uses waste heat from the system to maintain its own operation, avoiding additional energy loss.
Solution Approach 2:
The system recovers waste heat from the refrigeration cycle and uses it for defrosting the heat exchanger. Instead of discarding this thermal energy, it is utilized to remove frost, thereby preventing energy loss and maintaining system efficiency.
4Power
If the regeneration air heat exchanger supplies large amounts of heat to regeneration air during summer mode, then cooling capacity is increased, but the efficiency of the heat exchanger substantially decreases
Solution Approach 1:
The system dynamically adjusts the operation of different heat exchanger zones based on seasonal requirements. During summer mode, the regeneration air heat exchanger can operate at high capacity while the supply air heat exchanger maintains efficiency, with the system adapting its configuration to optimize performance for current conditions.
Solution Approach 2:
Different zones of the heat exchanger system are optimized for different functions - the regeneration air heat exchanger is designed to provide high cooling capacity during summer, while the supply air heat exchanger maintains high efficiency for heating operations. Each zone has tailored characteristics suited to its specific role.
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 maintains system efficiency by allowing simultaneous heating and defrosting, reducing energy consumption, and extending the time between defrost cycles, while ensuring effective frost prevention and water management.
Implementation Method 1
A refrigeration circuit is operatively connected to the regeneration air heat exchanger to allow hot refrigerant to sequentially defrost portions of the regeneration air heat exchanger
Implementation Method 2
The regeneration air heat exchanger may be angled within the regeneration air channel. The angle of the regeneration air channel is configured to allow water to shed to an upstream side of the heat exchanger during the defrost mode
Data Source
AI summary
A heat pump system for conditioning regeneration air from a space is provided. The heat pump system is operable in a winter mode and/or a summer mode, and may be selectively operated in a defrost mode or cycle. During a defrost mode, hot refrigerant may be used to directly and sequentially defrost the regeneration air heat exchanger. A compressor may be configured to be overdriven during a defrost cycle.