Dual-Condenser Refrigerant Flow Control for Vehicle HVAC Heating
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Solution Overview
Problem
Vehicle thermal management systems face challenges in efficiently managing heat transfer in refrigerant loops, particularly in hybrid or electric vehicles where waste heat is less readily available, and in maintaining optimal passenger cabin temperature and humidity levels.
Innovation Solution
A thermal management system that includes a compressor, HVAC system with evaporator and condenser, and an exterior condenser, controlled by variable refrigerant flow valves and a controller to regulate refrigerant flow and fan speed based on target temperatures and occupant inputs, ensuring subcooling and efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single condenser is used in the refrigerant loop, then the system structure is simple, but the thermal management efficiency decreases in hybrid or electric vehicles where waste heat is less readily available
Solution Approach 1:
The single condenser is segmented into two separate condensers: an HVAC condenser for passenger cabin temperature control and an exterior condenser for waste heat rejection. This segmentation allows independent optimization of each condenser's function, improving overall thermal management efficiency in hybrid and electric vehicles where waste heat is less available.
2Productivity
If refrigerant flow to the exterior condenser is increased to vent more heat, then heat transfer efficiency improves, but the HVAC condenser output temperature decreases below the target temperature
Solution Approach 1:
The system employs dynamic control of refrigerant flow distribution between the HVAC condenser and exterior condenser using variable refrigerant flow valves. The controller continuously adjusts the flow split based on real-time conditions (ambient temperature, vehicle speed, thermal demands) to maintain HVAC condenser output temperature at the target level while optimizing heat transfer efficiency.
Solution Approach 2:
The system changes the refrigerant flow rate parameters dynamically by adjusting valve positions and compressor operation. By modifying these parameters based on ambient conditions and thermal demands, the system maintains optimal temperature at the HVAC condenser output while maximizing heat rejection at the exterior condenser.
3Measurement precision
If refrigerant flow rate is dynamically adjusted between HVAC and exterior condensers, then thermal management precision improves, but system complexity increases
Solution Approach 1:
The controller serves multiple functions: it manages refrigerant flow distribution between condensers, monitors temperatures and pressures, adjusts valve positions, and coordinates with the compressor and fan systems. This multi-functionality consolidates control complexity into a single centralized unit, improving thermal management precision without proportionally increasing overall system complexity.
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
The system effectively manages refrigerant flow and heat transfer to maintain optimal passenger cabin temperatures and humidity, improving thermal efficiency and comfort in vehicles by dynamically adjusting refrigerant flow and fan speed according to ambient and vehicle conditions.
Implementation Method 1
a compressor to output a refrigerant in vapor form for circulation in a refrigerant loop
Implementation Method 2
an HVAC condenser, and an exterior condenser in the refrigerant loop configured to vent heat to an exterior of the vehicle
Implementation Method 3
an HVAC system in the refrigerant loop including an evaporator and an HVAC condenser
Implementation Method 4
a fan to increase heat transfer from the exterior condenser to outside the vehicle
Data Source
AI summary
Thermal management in a vehicle involves a compressor to output a refrigerant in vapor form for circulation in a refrigerant loop. A thermal management system includes a heating, ventilation, and air conditioning system in the refrigerant loop including an evaporator and an HVAC condenser, and an exterior condenser in the refrigerant loop configured to vent heat to an exterior of the vehicle. A first variable refrigerant flow valve controls a flow rate of the refrigerant output by the compressor into the HVAC condenser, and a second refrigerant flow valve controls a flow rate of the refrigerant output by the compressor into the exterior condenser. A controller controls the first refrigerant flow valve and the second refrigerant flow valve based on a target output temperature for the HVAC condenser.