Vehicle Air Conditioner Parallel Defrosting Control
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Solution Overview
Problem
Vehicle air conditioners face significant heating performance deterioration due to frost formation on outdoor heat exchangers when absorbing heat from low-temperature outside air, necessitating efficient defrosting methods that also maintain heating operations.
Innovation Solution
A vehicle air conditioner system that performs parallel condensation heat defrosting and heating operations using a refrigeration cycle with a controller managing compressor and expansion valve operations to achieve appropriate refrigerant temperatures and pressures, allowing for efficient defrosting of the outdoor heat exchanger while maintaining heating performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the outdoor heat exchanger absorbs heat from low-temperature outside air to the refrigerant during heating operation, then heating performance is improved, but frost forms on the outdoor heat exchanger deteriorating heat exchange performance
Solution Approach 1:
The refrigeration cycle is divided into two parallel operational paths: one for heating (compressor → heating heat exchanger → expansion valve → outdoor heat exchanger) and one for defrosting (compressor → evaporator → expansion valve → outdoor heat exchanger). This segmentation allows independent control of heating and defrosting functions, enabling the system to switch between modes or operate both simultaneously to prevent frost accumulation while maintaining heating performance.
Solution Approach 2:
The controller dynamically adjusts refrigerant parameters (temperature, pressure, flow rate) by controlling compressor speed and expansion valve opening degrees to achieve different operational states. During defrosting operation, the system changes refrigerant parameters to enable heat absorption in the evaporator for melting frost, while during heating operation, parameters are adjusted for efficient heat exchange in the outdoor heat exchanger.
2Reliability
If a condensation heat defrosting operation is performed to melt frost on the outdoor heat exchanger, then frost is removed, but heating operation must be suspended or performance is reduced
Solution Approach 1:
The patent merges the defrosting function and heating function into a single integrated system that can operate both functions simultaneously. By providing two separate expansion valves and controlling refrigerant flow distribution, the system combines the defrosting path (through the evaporator) and heating path (through the heating heat exchanger) into one refrigeration cycle, allowing both operations to proceed in parallel without mutual interference.
Solution Approach 2:
The outdoor heat exchanger serves multiple functions: it acts as a condenser during cooling operation, an evaporator during defrosting operation, and maintains heat exchange capability during simultaneous heating operation. The heating heat exchanger also serves dual purposes as both a heating component and a condenser. This multi-functionality allows the system to maintain heating performance while performing defrosting operations.
3Power
If the compressor discharge pressure is increased to improve heating performance, then heating efficiency is improved, but the temperature difference between heating heat exchanger and outdoor heat exchanger increases making parallel operation difficult
Solution Approach 1:
The system dynamically adjusts the opening degrees of two expansion valves and compressor speed in real-time based on operational requirements. During parallel heating and defrosting operation, the controller continuously modifies refrigerant flow distribution and pressure parameters to maintain appropriate temperature differences across heat exchangers, enabling flexible adaptation to varying heating loads and outdoor conditions.
Solution Approach 2:
The controller acts as an intermediary that coordinates between the heating path and defrosting path by adjusting expansion valve openings and compressor speed. It mediates the refrigerant flow distribution to balance the temperature and pressure requirements of both the heating heat exchanger and outdoor heat exchanger, enabling stable parallel operation despite the inherent temperature difference caused by high compressor discharge pressure.
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 melts frost on the outdoor heat exchanger using absorbed heat from the evaporator and controls refrigerant temperatures and pressures to maintain both efficient defrosting and heating operations, improving overall air conditioning performance.
Implementation Method 1
the evaporator is configured to cause the refrigerant decompressed by the second expansion valve to absorb heat and evaporate
Implementation Method 2
the heating heat exchanger condenses the refrigerant discharged from the compressor during a heating operation of heating a space to be air conditioned
Implementation Method 3
the outside air heat exchanger in which the refrigerant absorbs heat from outside air during the heating operation
Implementation Method 4
The compressor can be configured to compress and discharge a refrigerant
Data Source
AI summary
In a vehicle air conditioner with a refrigeration cycle, a controller includes a compression control unit and a decompression control unit, which perform control when a condensation heat defrosting operation and a heating operation of the space to be air conditioned are performed in parallel. The compression control unit achieves any one of a temperature or a pressure of a refrigerant required in a heating heat exchanger, or a temperature or a pressure of the refrigerant required in an outside air heat exchanger by operation control of a compressor. The decompression control unit achieves the other one of the temperature or the pressure of the refrigerant required in the heating heat exchanger, or the temperature or the pressure of the refrigerant required in the outside air heat exchanger by operation control of the first expansion valve.