Heat Pump Evaporator Anti-Icing Control in Vehicle HVAC
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Solution Overview
Problem
Existing heat pump systems in vehicles face inefficiencies and performance losses due to icing issues at ambient air temperatures below 0°C, leading to reduced heating capacity, increased energy consumption for defrosting, and operational disruptions.
Innovation Solution
A device and method for anti-icing control that regulates the refrigerant flow and surface temperature of the heat pump evaporator using a controllable expansion valve, compressor speed, and ambient air flow, ensuring continuous operation and improved efficiency by maintaining a predetermined temperature difference between the refrigerant and ambient air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heat pump operates at refrigerant temperatures at or below 0°C to provide heating, then heating performance is improved, but icing occurs on the evaporator surface reducing system reliability
Solution Approach 1:
The control unit preemptively switches off the compressor before icing can occur on the evaporator surface. By monitoring ambient air temperature and predicting icing conditions, the system performs the protective action in advance, preventing the harmful effect rather than reacting after icing has formed and degraded performance.
Solution Approach 2:
The system uses ambient air temperature sensors and control units to continuously monitor operating conditions and provide feedback to the compressor control. This closed-loop feedback mechanism allows the system to adjust compressor operation in real-time based on temperature conditions, switching off the compressor when temperatures approach the icing threshold to maintain reliable operation.
2Reliability
If the heat pump is switched off to prevent icing, then evaporator icing is avoided, but heating capacity is reduced and energy consumption increases
Solution Approach 1:
Instead of completely switching off the heat pump system, the control unit applies partial action by selectively switching off only the compressor while maintaining other system components in operation. This partial shutdown prevents icing on the evaporator while preserving residual heating capacity through alternative heat sources or reduced-load operation, thereby reducing energy consumption compared to full system shutdown.
Solution Approach 2:
The system changes operational parameters by adjusting compressor operation based on ambient temperature conditions. When temperatures approach the icing threshold, the compressor is switched off or operated at reduced capacity, changing the system's operating state to prevent icing while maintaining acceptable heating performance and energy efficiency.
3Reliability
If the evaporator is defrosted by switching to air conditioning mode, then ice is melted, but heating capacity is further reduced and defrosting energy is consumed
Solution Approach 1:
The control unit applies preliminary anti-action by switching off the compressor before icing can form on the evaporator surface. This preventive measure eliminates the need for subsequent defrosting operations, thereby avoiding the energy losses associated with defrosting cycles and maintaining continuous heating capacity without interruption.
Solution Approach 2:
By preventing icing through proactive compressor shutdown, the system maintains continuous useful heating action without interruption for defrosting cycles. The evaporator remains functional throughout operation, and heating capacity is preserved continuously rather than being periodically interrupted by defrosting sequences, thereby eliminating defrosting energy losses.
4Reliability
If the refrigerant flow is interrupted to defrost the evaporator, then ice is removed, but electrical energy consumption increases and heating function is unavailable
Solution Approach 1:
Instead of using the conventional defrosting approach of reversing refrigerant flow or switching to air conditioning mode, the system applies inversion by switching off the compressor entirely to prevent icing in the first place. This inverted approach eliminates the need for complex defrosting control sequences and refrigerant flow reversal mechanisms, simplifying the control system while maintaining evaporator performance.
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, maintains heat pump performance, reduces energy consumption, and enhances heating system efficiency, even at low ambient temperatures, thereby extending the range of electric vehicles and optimizing fuel consumption.
Implementation Method 1
In the evaporator, the refrigerant liquid absorbs the heat from the ambient air and evaporates
Implementation Method 2
The refrigerant condenses in the condenser and heats the medium of the heating circuit
Implementation Method 3
The compressor uses mechanical energy to compress the refrigerant vapor, thereby increasing the pressure and temperature
Implementation Method 4
In the expansion valve, the pressure and temperature of the refrigerant liquid are reduced by opening the valve
Implementation Method 5
the fan draws ambient air over one side of the evaporator, causing ambient air to flow over the evaporator surface
Data Source
Figure 1
Figure 2
Figure 3a
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 assigned to the heat pump evaporator (3) and which draws ambient air (11) upstream of 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 of 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.