Systems and methods for reducing frost accumulation on heat pump evaporator coils
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Solution Overview
Problem
Heat pump systems face inefficiencies and energy wastage due to frost accumulation on evaporator coils, which leads to degraded performance and potential component damage, especially in regions with cool but not freezing temperatures, as they require reverse cycle operation and supplemental heating to prevent cooling the building.
Innovation Solution
A system comprising a heat pump assembly with a temperature sensor, fan, and controller that directs warmer ambient air across the evaporator coil after the heat pump has shut down, using a reversing valve to utilize residual refrigerant heat and adjust fan operation based on coil and ambient temperature and humidity levels to prevent frost accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heat pump operates in reverse cycle to melt frost on the evaporator coil, then frost accumulation is reduced, but cool air is injected into the heated building causing unnecessary cooling and energy waste
Solution Approach 1:
The patent extracts the defrosting function from the main heating cycle by operating the fan independently after the heat pump shuts down. The fan continues to blow ambient air across the evaporator coil to melt frost without requiring the heat pump to run in reverse cycle, thereby separating the defrosting operation from the building heating operation and avoiding unnecessary cooling of the building.
Solution Approach 2:
The patent applies preliminary action by shutting down the heat pump before the fan operates for defrosting. This timing arrangement allows the fan to melt accumulated frost using residual heat and ambient air conditions without immediately cooling the building, as the heat pump has already ceased operation and the building has time to maintain its temperature.
2Reliability
If the heat pump operates in reverse cycle to melt frost on the evaporator coil, then frost accumulation is reduced, but supplemental heat is required to warm the cool air injected into the building
Solution Approach 1:
The patent extracts the defrosting function from the main heating cycle by operating the fan independently after the heat pump shuts down. This eliminates the need for supplemental heating systems to warm cool air during defrosting, as the defrosting occurs when the heat pump is not running and no cool air is being injected into the building.
Solution Approach 2:
The system uses itself to defrost by utilizing its own fan and the natural heat transfer from ambient air to the evaporator coil. The fan that operates during normal heating continues to be used for defrosting, and the residual heat in the system and ambient air conditions are sufficient to melt frost without requiring additional supplemental heating equipment or systems.
3Reliability
If the fan operates continuously to prevent frost accumulation, then frost is reduced, but energy consumption increases
Solution Approach 1:
The patent applies periodic action by operating the fan intermittently rather than continuously. The controller monitors conditions such as evaporator coil temperature, ambient temperature, and humidity to determine when frost accumulation is likely and activates the fan only during those periods. After the heat pump shuts down, the fan continues for a predetermined time to complete defrosting, then stops, creating a periodic on-off pattern that reduces energy consumption while maintaining effective frost prevention.
Solution Approach 2:
The system uses feedback from temperature sensors and humidity sensors to control fan operation. The controller receives input from these sensors to determine when the evaporator coil temperature is below threshold and when ambient conditions favor frost formation, activating the fan only when needed. This feedback-based control prevents unnecessary fan operation and reduces energy consumption while effectively preventing frost accumulation.
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 reduces frost accumulation without cooling the building and conserves energy by using ambient air and residual heat to melt frost, thereby maintaining system efficiency and extending component lifespan.
Implementation Method 1
direct air across the evaporator coil... warmer ambient air across the evaporator coil... to melt the accumulated frost
Implementation Method 2
a temperature sensor that can output temperature data indicating a temperature of the evaporator coil
Implementation Method 3
a humidity sensor that can detect a humidity level of ambient air
Implementation Method 4
a reversing valve that can be opened when the controller sends a control signal. When the reversing valve is opened, the residual heat of the refrigerant in the system can provide additional heat to the evaporator coil
Data Source
AI summary
The disclosed technology includes systems and methods of reducing frost accumulation on a heat pump evaporator coil. The disclosed technology can include a heat pump assembly having an evaporator coil, a fan configured to direct air across the evaporator coil, a temperature sensor, and a controller configured to energize the fan to direct air across the evaporator coil when the temperature of the evaporator coil is below a threshold temperature.