Heat Pump Defrost Control Using Dew Point and Frost-Collection Rate
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Solution Overview
Problem
Existing heat pump systems inefficiently initiate defrost cycles due to reliance on temperature and time-based algorithms, which fail to consider environmental humidity and temperature conditions, leading to unnecessary energy waste and impaired heating performance.
Innovation Solution
A controller that measures evaporator coil temperature and dew point temperature, calculates frost-collection rate using environmental humidity and temperature data, and initiates a defrost cycle only when the frost-collection rate exceeds a threshold, ensuring accurate determination of frost formation and reducing unnecessary defrost cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If temperature and time-based algorithms are used to initiate defrost cycles, then the control method is simple, but unnecessary defrost cycles occur leading to energy waste and impaired heating performance
Solution Approach 1:
The patent changes the control parameters from simple temperature and time-based algorithms to a multi-parameter system that includes dew point temperature, evaporator coil temperature, and calculated frost collection rate. This allows the system to accurately determine when frost formation is actually occurring, preventing unnecessary defrost cycles and the associated energy waste while maintaining heating performance.
2Reliability
If defrost cycles are initiated frequently to ensure frost removal, then heating performance is maintained, but energy consumption increases
Solution Approach 1:
The system implements feedback control by continuously monitoring evaporator coil temperature and dew point temperature, calculating the frost collection rate, and comparing it against a threshold. This feedback mechanism ensures defrost cycles are initiated only when actually needed (when frost collection rate exceeds threshold), maintaining heating reliability while minimizing energy consumption by avoiding unnecessary defrost operations.
3Ease of operation
If traditional defrost control methods are used, then the system operation is simple, but frost formation is not accurately determined leading to improper defrost timing
Solution Approach 1:
The patent introduces dew point temperature as an intermediary parameter that mediates between ambient conditions and actual frost formation on the evaporator coil. By calculating the frost collection rate based on the relationship between dew point temperature and evaporator coil temperature, the system achieves accurate frost formation detection while maintaining relatively simple operation through automated calculations.
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 approach enhances the efficiency of heat pump systems by minimizing unnecessary defrost cycles, conserving energy, and maintaining effective heating performance by accurately determining when frost formation requires defrosting.
Implementation Method 1
A controller for initiating a defrost cycle of a heat pump system is configured to measure a temperature of an evaporator coil
Implementation Method 2
the controller is configured to determine if a current dew point temperature of air is greater than the temperature of the evaporator coil
Implementation Method 3
the controller is configured to calculate a frost-collection rate
Implementation Method 4
the heat pump system operates as an air conditioner to transfer heat from the interior of an enclosed space, such as, for example, a house, to the exterior coil to melt any frost that has formed thereon
Implementation Method 5
the refrigerant in the exterior coil becomes warmer such that frost that has formed on the exterior coil melts
Implementation Method 6
an exterior fan is typically used to draw exterior ambient air across the exterior coil
Implementation Method 7
a reversing valve shifts from the heating mode to the defrost mode
Implementation Method 8
The auxiliary heating elements are activated to heat the interior air that is blown over the cool interior coil and into the interior of the building
Data Source
AI summary
A method of initiating a defrost cycle using a controller of a heat pump system includes measuring a temperature of an evaporator coil and determining whether the temperature of the evaporator coil is less than a freezing temperature. Responsive to a determination that the temperature of the evaporator coil is less than the freezing temperature, determining whether a current dew point temperature of air is greater than the temperature of the evaporator coil. Responsive to a determination that the current dew point temperature of air is greater than the temperature of the evaporator coil, calculating a frost-collection rate. Determining whether the frost-collection rate is greater than a frost-collection-rate threshold, and, responsive to a determination that the frost-collection rate is greater than the frost-collection-rate threshold, initiating a defrost cycle.