Heat pump defrosting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Air source heat pumps face inefficiencies in defrosting processes, particularly due to energy consumption and vaporization of melt water, which reduces their overall efficiency and increases energy costs.
Innovation Solution
The heat pump employs alternating run and defrost phases with a controlled evaporator temperature below 4 °C during defrosting, utilizing both passive and active methods, including ambient air defrosting and supplementary heat input, to minimize energy usage and prevent water vaporization, with a focus on maintaining low evaporator temperatures to optimize energy savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reverse-cycle defrosting is used to melt ice on the evaporator, then defrosting effectiveness is improved, but energy consumption increases due to running the compressor at maximum power
Solution Approach 1:
The patent implements periodic defrost cycles where the heat pump alternates between heating operation and defrosting operation. During defrosting, the cycle is reversed to melt ice on the evaporator, then returns to normal heating mode. This periodic approach allows the system to accumulate enough thermal energy in the water circulation system to support defrosting without requiring continuous high-power compressor operation, thereby reducing overall energy consumption while maintaining effective defrosting.
Solution Approach 2:
The patent uses the thermal energy already stored in the water circulation system from previous heating operations to perform defrosting. The hot water that was heated during normal operation circulates through the evaporator during defrosting to melt the ice, allowing the system to defrost itself using its own stored thermal energy rather than requiring external energy input at maximum power.
2Productivity
If higher temperature is used during defrosting to melt ice faster, then defrosting speed is improved, but energy waste increases due to vaporization of melt water
Solution Approach 1:
The patent carefully controls the temperature parameter during defrosting to remain below the vaporization threshold of water. By maintaining the evaporator temperature in a range that melts ice but does not cause water vaporization, the system achieves effective defrosting while avoiding the energy waste associated with phase change from liquid to vapor. This temperature parameter control is critical to balancing defrosting speed with energy efficiency.
3Loss of energy
If the evaporator temperature is kept low to prevent water vaporization, then energy efficiency is improved, but defrosting time increases
Solution Approach 1:
The patent accumulates thermal energy in the water circulation system during normal heating operations before defrosting is needed. This preliminary energy storage ensures that when defrosting begins, there is sufficient thermal energy available to melt the ice efficiently at controlled temperatures without requiring extended time or higher energy input.
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 reduces energy consumption and extends defrost periods, minimizing energy waste by maintaining low evaporator temperatures during defrosting, thereby enhancing the efficiency and reducing operational costs of air source heat pumps.
Implementation Method 1
Heat from the air is transferred via a refrigerant to a water circulation system which distributes the heat within the building
Implementation Method 2
The temperature difference between the evaporator and the ambient air is kept below 10 °C so that the evaporator runs at a higher temperature, which increases efficiency and reduces the need for defrosting
Implementation Method 3
a vapor compression circuit which includes a condenser, a compressor and an evaporator
Implementation Method 4
Heat from the air is transferred via a refrigerant to a water circulation system which distributes the heat within the building
Implementation Method 5
throughout the defrost phases, the temperature of the evaporator is maintained at a low enough level to avoid vaporisation of the melt water
Implementation Method 6
the lower the temperature the lower the amount of water evaporation and the greater the potential energy saving
Data Source
Figure 1
Figure 2~3
AI summary
In an air source heat pump having a vapor compression circuit including a condenser 3, a compressor 2 and an evaporator 5, the vapor compression circuit operates with alternating run phases in which heat is extracted and defrost phases in which a buildup of ice on the evaporator melts. The heat pump is configured such that, throughout the defrost phases, the temperature of the evaporator is maintained at a low enough level (preferably below circa 4 °C) to avoid vaporisation of the melt water. The heat pump includes: - A passive defrost phase in which the compressor 2 of the vapor compression circuit is turned off but the air induction fan 6 remains on. - An active defrost phase in which supplementary heat input is used to defrost the evaporator. The supplementary heat input may be obtained by reversing the cycle of the vapor compression circuit at reduced power or by using an auxiliary heater 15.