Device and method for icing prevention regulation for heat pump evaporators
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Solution Overview
Problem
Existing heat pump systems face inefficiencies and increased energy expenditure when operating at ambient air temperatures below 0°C due to icing issues, which disrupt heat transfer and require additional heating for de-icing, leading to reduced heating output and increased complexity in refrigerant circuit designs.
Innovation Solution
A device and method for icing prevention regulation in heat pump evaporators, utilizing a refrigerant circuit with an externally regulatable expansion valve, temperature sensors, and a control unit to adjust the refrigerant flow and compressor speed, ensuring the refrigerant temperature remains slightly below ambient air temperature, thereby preventing icing and maintaining efficient heat pump operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heat pump operates at ambient air temperatures below 0°C, then heating function is provided, but icing occurs on the evaporator reducing heat transfer efficiency
Solution Approach 1:
The control unit preemptively switches the refrigerant circuit to AC mode before the evaporator temperature reaches the icing point (0°C). This preliminary action prevents ice formation by utilizing the hot refrigerant from the condenser to melt any accumulating ice on the evaporator surface, maintaining heat transfer efficiency throughout the heating operation.
Solution Approach 2:
The system dynamically changes the refrigerant circuit configuration parameter by switching between heat pump mode and AC mode. This parameter change allows the same refrigerant circuit to serve dual purposes: providing heating while simultaneously preventing evaporator icing through periodic AC mode operation that directs hot refrigerant through the evaporator.
2Reliability
If active de-icing is performed by switching to AC mode, then ice is melted on the evaporator, but heat pump function becomes unavailable and fuel consumption increases
Solution Approach 1:
The system uses its own hot refrigerant from the condenser to perform the de-icing function. Instead of requiring external energy sources or separate heating elements, the heat pump leverages the thermal energy already present in the refrigerant circuit to melt ice on the evaporator, making the de-icing process energy-efficient and self-sufficient.
Solution Approach 2:
The system recovers thermal energy that would otherwise be wasted during the de-icing process. By routing the hot refrigerant from the condenser through the evaporator in AC mode, the thermal energy is utilized to melt ice rather than being discarded, thereby reducing overall fuel consumption while maintaining the heat pump function.
3Duration of action of moving object
If the evaporator is operated with ice accumulation, then continuous heating is maintained, but heat transfer resistance increases and suction pressure drops
Solution Approach 1:
The control unit continuously monitors the evaporator temperature and uses this feedback to determine when to switch to AC mode for de-icing. This feedback mechanism ensures that the evaporator temperature is maintained below the icing point, preventing ice accumulation that would increase heat transfer resistance and reduce suction pressure, thereby maintaining efficient continuous heating operation.
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 minimizes icing risks, prevents power loss during de-icing, enhances heat pump efficiency, reduces fuel consumption, and increases the range of electric vehicles by maintaining continuous heat pump function with improved efficiency at low ambient temperatures.
Implementation Method 1
The refrigerant liquid in the evaporator absorbs the heat from the ambient air and evaporates
Implementation Method 2
The compressor compresses the refrigerant vapor using mechanical energy and thereby increases the pressure and temperature
Implementation Method 3
The refrigerant condenses in the condenser and heats the medium of the heating circuit
Implementation Method 4
In the expansion valve, the pressure and the temperature of the refrigerant liquid are reduced by opening the valve
Data Source
AI summary
The invention relates to a device and a method for icing prevention regulation for a heat pump evaporator (3) in air conditioning systems of vehicles, composed of a subsection (1) of a refrigerant circuit which can be operated both as a heat pump and also as an air conditioning system. The device comprises the heat pump evaporator (3), an electrical or mechanical refrigerant compressor (4), a cooler fan (9) which is attached to the heat pump evaporator (3) and which draws ambient air (11) upstream from and through the heat pump evaporator (3) at an adjustable flow speed, and which thus permits a permanent flow of ambient air (11) over the heat pump evaporator surface, a first temperature sensor (6) in or on the refrigerant line (5, 5a) upstream from the heat pump evaporator (3) with respect to the heat pump operating direction, and a control and regulating unit (8). The control and regulating unit (8) is connected via signal lines (10, 10a, 10b, 10c, 10e) at least to the first temperature sensor (6), to further sensors, in particular for detecting the ambient air temperature (Tu) and the vehicle speed (VF), to the expansion valve (2), to the cooler fan (9) and to the refrigerant compressor (4) for the direct or indirect regulation of the flow cross section of the expansion valve (2) and the rotational speed of the electric refrigerant compressor (4) or of the regulating valve of the mechanical refrigerant compressor (4) and for the actuation of the cooler fan (9) of the vehicle during heat pump operation.