Indirect Reversible Air-Conditioning Circuit Defrost Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Reversible air conditioning circuits in motor vehicles face performance reduction due to frost formation at the evaporator, which is inadequately addressed by switching to air conditioning mode, leading to discomfort for occupants.
Innovation Solution
An indirect reversible air conditioning circuit with a central control unit, pressure sensors, and a front face fan that operates in defrost mode by shutting down internal and external air flows, compressing the refrigerant fluid, and restarting the heat transfer fluid loop when the refrigerant is in a two-phase state with a saturation temperature greater than 0°C, generating an outside air flow to defrost the evaporator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reversible air conditioning system switches to cooling mode to remove frost from the evaporator, then the frost is removed, but cold air is blown into the passenger compartment reducing occupant comfort
Solution Approach 1:
The patent segments the air conditioning system into two independent loops: a refrigerant loop and a heat transfer fluid loop. This allows the evaporator (in the refrigerant loop) to be defrosted by switching refrigerant flow while the heater (in the heat transfer fluid loop) continues operating independently, maintaining passenger comfort without being disrupted by the defrosting operation.
Solution Approach 2:
The patent introduces a heat transfer fluid (glycol-water mixture) as an intermediary between the refrigerant and the passenger compartment air. The heat transfer fluid absorbs heat from the refrigerant in the two-fluid heat exchanger and transfers it to the air in the heater, allowing the evaporator to be defrosted while maintaining heating function through this intermediary medium.
2Productivity
If the system uses an indirect air conditioning circuit with two-fluid heat exchanger, then heat exchange efficiency is improved, but system complexity increases
Solution Approach 1:
The two-fluid heat exchanger serves multiple functions: it enables heat transfer between the refrigerant loop and heat transfer fluid loop for heating operation, and also allows the evaporator to be defrosted during heat pump mode by permitting refrigerant flow while blocking heat transfer fluid flow. This multi-functionality justifies the added complexity by eliminating the need for separate components.
3Reliability
If frost forms on the evaporator during heat pump mode, then heat exchange between outside airflow and refrigerant is reduced, but switching to cooling mode compromises passenger comfort
Solution Approach 1:
The system implements periodic defrosting cycles during heat pump operation. When frost is detected on the evaporator, the system temporarily switches refrigerant flow to bypass the evaporator or reverses flow direction for a short period to remove frost, then returns to normal heating operation. This periodic intervention maintains long-term heat pump performance without permanently disrupting passenger comfort.
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 removes frost from the evaporator without compromising passenger compartment comfort by maintaining heating mode operation, ensuring efficient heat exchange and performance restoration.
Implementation Method 1
the refrigerant from the first refrigerant loop passes successively through the compressor where said refrigerant is compressed
Implementation Method 2
a two-fluid heat exchanger arranged jointly on the first refrigerant loop and on the second heat transfer fluid loop, so as to allow heat exchange between said loops
Implementation Method 3
a first expansion device, a first heat exchanger intended to be traversed by an airflow from inside the motor vehicle, a second expansion device
Implementation Method 4
a first heat exchanger intended to be traversed by an airflow from inside the motor vehicle
Implementation Method 5
a second heat exchanger intended to be traversed by an airflow from outside the motor vehicle
Implementation Method 6
a fourth heat exchanger intended to be traversed by the outside airflow
Implementation Method 7
a low-pressure refrigerant pressure sensor, said pressure sensor being disposed downstream of the bypass line, between said bypass line and the compressor
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention relates to an indirect reversible air-conditioning circuit (1) comprising: – a first, refrigerant fluid loop (A) comprising: – a compressor (3), – a two-fluid heat exchanger (5), – a first expansion device (7), – a first heat exchanger (9), – a second expansion device (11), – a second heat exchanger (13), and – a duct (30) for bypassing the second heat exchanger (13), • a second, heat transfer fluid loop (B) comprising a fourth heat exchanger (64), and • the two-fluid heat exchanger (5) being arranged simultaneously on the first, refrigerant fluid loop (A) and on the second, heat transfer fluid loop (B), • a low-pressure refrigerant fluid pressure sensor (44) arranged downstream of the bypass duct (30), • a central control unit (40) connected to said pressure sensor (44), to the compressor (3) and to the first (7) and second (11) expansion devices such that they can be flowed through with no loss of pressure, or bypassed.