Heat Pump Warm Defrosting to Reduce Heating Mode Interruption
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Solution Overview
Problem
Heat pumps experience reduced efficiency due to icing of the evaporator at low outside temperatures, which requires interrupting the heating mode for de-icing, either by reversing the refrigerant circuit flow or operating in cooling mode, leading to discomfort and inefficiency.
Innovation Solution
A method that maintains the refrigerant circuit in the normal direction during heating mode, reducing compressor output and increasing fan output for warm defrosting, allowing de-icing without reversing flow, and using cold defrosting mode at colder temperatures, ensuring reliable de-icing without completely interrupting heating mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refrigerant circuit is operated in cooling mode or cold de-icing mode to de-ice the evaporator, then the evaporator is reliably de-iced, but the heating mode is completely interrupted causing loss of comfort and increased energy requirements
Solution Approach 1:
The patent applies dynamics by making the refrigerant flow direction changeable through a four-way valve, allowing the system to switch between heating mode, cooling mode, and de-icing mode. This dynamic adjustment enables the refrigerant to flow in different directions (normal and reverse) depending on operational requirements, resolving the contradiction between maintaining heating comfort and achieving reliable de-icing.
Solution Approach 2:
The patent changes the operational parameters of the heat pump system by adjusting the refrigerant flow direction and operating mode based on detected icing conditions. When icing is detected, the system transitions from heating mode to de-icing mode (either warm or cold), changing parameters such as refrigerant flow direction, compressor operation, and fan speed to achieve de-icing while minimizing disruption to heating comfort.
2Reliability
If the refrigerant circuit is operated in reverse normal direction to de-ice the evaporator, then the evaporator is heated from inside for reliable de-icing, but the heating mode must be completely interrupted
Solution Approach 1:
The patent implements periodic action by alternating between heating mode and de-icing mode based on detected icing conditions. The system operates in heating mode normally, and when icing is detected, it periodically switches to de-icing mode (warm or cold) for a limited duration, then returns to heating mode. This periodic switching resolves the contradiction by limiting the time loss while ensuring effective de-icing when necessary.
Solution Approach 2:
The patent changes operational parameters dynamically based on icing detection. When icing is detected, the system changes parameters including refrigerant flow direction (via four-way valve), compressor operation, and fan speed to enter de-icing mode. After de-icing is complete, parameters are changed back to resume heating mode, thus minimizing heating interruption time while achieving reliable de-icing.
3Productivity
If the evaporator surface temperature is reduced to absorb heat from outside air, then heat transfer efficiency is improved, but moisture condensation and icing occur on the evaporator surface
Solution Approach 1:
The patent applies feedback by using sensors to detect icing conditions on the evaporator surface (such as temperature, humidity, or pressure changes). When icing is detected, the system receives feedback and automatically switches from heating mode to de-icing mode (warm or cold) to remove the ice. This feedback mechanism resolves the contradiction by maintaining efficient heat transfer during normal operation while automatically preventing and removing icing when it occurs.
Solution Approach 2:
The patent implements preliminary anti-action by proactively detecting icing conditions and switching to de-icing mode before the ice significantly impacts heat transfer efficiency. The system monitors evaporator surface conditions and takes preventive action (switching to warm or cold de-icing mode) when icing is detected, thus counteracting the harmful effect before it severely degrades productivity.
4Power
If the fan speed is increased to improve air flow and heat transfer, then active power is improved, but the evaporator surface temperature decreases leading to increased icing tendency
Solution Approach 1:
The patent uses feedback by monitoring evaporator surface temperature and air flow conditions to detect when high fan speed is causing excessive cooling that leads to icing. When icing conditions are detected, the system receives feedback and switches to de-icing mode, adjusting fan speed and refrigerant flow to remove ice. This feedback loop resolves the contradiction by allowing high fan speeds for improved power output while automatically preventing icing when it occurs.
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 operational reliability and heating comfort by allowing de-icing without reversing the refrigerant circuit flow, maintaining heating mode operation, and reducing noise pollution through adjustable defrosting modes based on temperature and time conditions.
Implementation Method 1
the evaporator has ambient air, ie outside air, flowing through it. This is cooled down and the corresponding heat is transferred to the refrigerant
Implementation Method 2
the low surface temperature of the evaporator can lead to condensation of the moisture contained in the outside air on the evaporator surface, with the condensed liquid then being able to freeze
Implementation Method 3
the condensed liquid then being able to freeze. Icing of the evaporator occurs
Implementation Method 4
Fluids are used as refrigerants, which evaporate at low pressure and low refrigerant temperature with the supply of heat
Implementation Method 5
With the help of the compressor, the refrigerant is brought to the correspondingly higher pressure, with the refrigerant being in gaseous form
Implementation Method 6
In the condenser that follows in the refrigerant circuit, the refrigerant liquefies and releases heat
Implementation Method 7
The refrigerant is then expanded, for example via expansion valves, a throttle or the like and supplied to the evaporator at low pressure and at a relatively low temperature
Data Source
Figure 1~2
AI summary
The invention relates to a method for defrosting a heat pump comprising a refrigerant circuit (1) with a compressor (2), a condenser (3), and an evaporator (5), wherein the evaporator (5) is associated with a controllable, variable-speed fan (6), and the refrigerant circuit (1) can be operated in heating mode and in a cooling mode with reversed flow direction. To avoid completely interrupting the heating mode for defrosting, the heat pump is operated in a warm defrosting mode for defrosting the evaporator (5), in which the refrigerant circuit continues to operate in the normal direction, while compressor power is reduced and fan power is increased.