Vehicle Heat Exchanger Defrost Control for Stable Cabin Heating
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Solution Overview
Problem
Existing vehicle air conditioning systems face challenges in maintaining heating capacity during defrosting operations due to frost formation on vehicle-exterior heat exchangers, particularly when insufficient heat sources are available, such as in electric vehicles.
Innovation Solution
A vehicle air conditioning system with a refrigerant circuit and a heat medium circuit incorporating multiple vehicle-exterior heat exchangers, a detection unit for frost formation, and a control device to selectively switch the flow of a high-temperature or low-temperature medium based on frost detection, prioritizing defrosting of the upwind heat exchanger to maintain heating capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple vehicle-exterior heat exchangers are used to enhance heating capacity, then heating capacity is improved, but frost formation on heat exchangers occurs more frequently
Solution Approach 1:
The vehicle-exterior heat exchanger is divided into multiple independent heat exchangers (first and second heat exchangers) that can be operated separately. This segmentation allows selective defrosting of individual heat exchangers based on their frost formation status, enabling continued operation of non-frosted heat exchangers to maintain heating capacity while addressing frost issues locally.
Solution Approach 2:
The system changes the operational parameters by switching between different heat exchangers based on detected frost conditions. When frost is detected on one heat exchanger, the system switches to use the other heat exchanger for heat exchange, thereby maintaining heating capacity while avoiding the frosted heat exchanger.
2Object-affected harmful factors
If defrosting operation is performed on frosted heat exchangers, then frost is removed, but heating capacity is reduced during defrosting
Solution Approach 1:
The system merges the functions of multiple heat exchangers and the defrosting heater into a unified heat management system. During defrosting operation, the heater provides heat to the frosted heat exchanger while the other heat exchanger continues to provide heating capacity to the vehicle interior, combining these functions to maintain overall heating performance.
Solution Approach 2:
The system performs preliminary switching to an alternative heat exchanger before initiating defrosting operation on the frosted heat exchanger. This preliminary action ensures that heating capacity is already maintained by the non-frosted heat exchanger before defrosting begins, minimizing the impact on overall heating performance.
3Productivity
If selective defrosting control is implemented based on frost detection, then defrosting efficiency is improved, but system complexity increases
Solution Approach 1:
The system implements feedback control by using frost detection means to monitor the frost formation status of each heat exchanger and automatically switching between heat exchangers and controlling defrosting operations based on this feedback. This automated feedback mechanism improves defrosting efficiency while minimizing the need for complex manual control systems.
Solution Approach 2:
The system enables self-service defrosting control where the frost detection means and switching control automatically manage the defrosting process without requiring complex external control systems. The system monitors its own state and autonomously switches between heat exchangers and initiates defrosting when needed.
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 maintains heating capacity by prioritizing defrosting of the upwind heat exchanger, ensuring efficient heat exchange and early completion of defrosting, allowing the system to resume heating mode quickly.
Implementation Method 1
a heat medium circuit including a high-temperature medium circuit in which a heat medium absorbing heat from the refrigerant in the refrigerant circuit circulates
Implementation Method 2
a low-temperature medium circuit in which a heat medium dissipating heat to the refrigerant in the refrigerant circuit circulates
Implementation Method 3
a vehicle-exterior heat exchanger configured to exchange heat between the heat medium and air
Implementation Method 4
a detection unit configured to detect a degree of frost formation on each of the first heat exchanger and the second heat exchanger
Data Source
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AI summary
Improved are a vehicle air conditioning system including a refrigerant circuit and a heat medium circuit and including a plurality of vehicle-exterior heat exchangers that exchange heat between outside air and a heat medium and a vehicle air conditioning method. The vehicle air conditioning system includes a refrigerant circuit, a heat medium circuit, a vehicle-interior heat exchanger, a vehicle-exterior heat exchanger including a first heat exchanger and a second heat exchanger disposed in series with respect to a flow of air generated by an air blower, a switching unit, a detection unit configured to detect a degree of frost formation, and a control device. The operation mode includes a defrosting mode in which the heat medium in the high-temperature medium circuit is supplied to a defrosting target to be selected as either the first heat exchanger or the second heat exchanger connected in parallel in the heat medium circuit by the operation of the switching unit. The control device selects, as the defrosting target, the first heat exchanger located on an upwind side in preference to the second heat exchanger located on a downwind side when it is determined that both the first heat exchanger and the second heat exchanger need to be defrosted.