Vehicle Cabin Dehumidification Control via Variable Orifice Bypass
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Solution Overview
Problem
Conventional vehicle thermal systems, particularly in heat pump systems, struggle to independently control heating and cooling functions, leading to window fogging issues due to the integrated nature of the A/C compressor, which complicates fog prevention.
Innovation Solution
A thermal system with a high temperature coolant loop and an air conditioning loop, controlled by a processor, regulates refrigerant flow through an evaporator using a variable orifice at the chiller inlet to bypass refrigerant, ensuring the heater core reaches a target temperature while preventing evaporator freezing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the A/C compressor is used to cool air for dehumidification in a heat pump system, then cooling and dehumidification are achieved, but the heater core cannot be independently controlled to reheat air, causing window fogging
Solution Approach 1:
The system dynamically adjusts the opening degree of the expansion valve based on real-time temperature feedback from both the evaporator and heater core. This dynamic control allows the single A/C compressor system to adaptively balance cooling needs with heating needs, preventing window fogging while maintaining dehumidification effectiveness.
Solution Approach 2:
The control unit continuously monitors temperatures at both the evaporator and heater core, using this feedback to adjust the expansion valve opening degree. This closed-loop feedback mechanism enables the system to maintain optimal temperatures for both cooling and heating functions simultaneously, resolving the control contradiction in heat pump systems.
2Reliability
If the A/C compressor runs at high speed to cool air for fog prevention, then dehumidification effectiveness improves, but power consumption increases
Solution Approach 1:
The system dynamically adjusts compressor speed and expansion valve opening based on real-time temperature conditions. Rather than running at constant high speed, the compressor operates at variable speeds optimized for current thermal conditions, maintaining fog prevention effectiveness while reducing unnecessary energy consumption.
Solution Approach 2:
The system changes operating parameters (compressor speed, expansion valve opening degree) based on thermal conditions. By adjusting these parameters dynamically rather than maintaining fixed high values, the system achieves reliable fog prevention with optimized energy consumption.
3Temperature
If refrigerant flow through the evaporator is increased to improve cooling, then cooling capacity increases, but the evaporator temperature drops below freezing causing ice formation
Solution Approach 1:
The control unit monitors evaporator temperature and adjusts the expansion valve opening degree in response. When evaporator temperature approaches freezing, the system reduces refrigerant flow through the evaporator by closing the expansion valve, preventing ice formation while maintaining heater core temperature for fog prevention.
Solution Approach 2:
The system takes preliminary action by monitoring evaporator temperature and adjusting refrigerant flow before freezing occurs. By proactively reducing refrigerant flow when temperature approaches the freezing point, the system prevents ice formation rather than reacting after damage 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
Effectively prevents window fogging by maintaining optimal coolant temperatures without the need for additional hardware, enhancing efficiency and reducing power consumption.
Implementation Method 1
an evaporator, wherein the high temperature coolant loop is thermally coupled to the evaporator
Implementation Method 2
a heater core configured for thermal exchange with an airflow into a cabin of the vehicle
Implementation Method 3
an air conditioning (A/C) loop having a compressor
Data Source
AI summary
A thermal system includes a high temperature coolant loop thermally coupled to a heater core configured for thermal exchange with an airflow into a cabin of the vehicle, and an air conditioning (A/C) loop having a compressor, a condenser, a first expansion device for a heat exchanger, a second expansion device for a chiller, and a third expansion device for an evaporator. The high temperature coolant loop is thermally coupled to the condenser. A controller includes one or more processors and is programmed to perform a window fogging prevention operation by controlling a speed of the compressor such that (i) a coolant temperature at the heater core reaches a first predetermined target temperature, and (ii) a coolant temperature at the evaporator does not fall below a second predetermined target temperature.