Vehicular air conditioner
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Solution Overview
Problem
In vehicular air conditioners, the dehumidifying and cooling mode faces challenges at low outdoor temperatures, where increasing compressor speed to enhance radiator heating capability leads to frost formation in the heat absorber, reducing refrigerant flow and compromising radiator pressure, thus hindering heating performance.
Innovation Solution
The system incorporates an injection circuit that returns a portion of the refrigerant from the radiator to the compressor, controlled by a control means to manage radiator capability shortages and low outdoor temperatures, adjusting the injection refrigerant superheat degree to optimize refrigerant flow and prevent frosting, while controlling compressor speed and valve positions to maintain target pressures and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of revolution of the compressor is increased to acquire a flow rate of refrigerant into the radiator, then the heating capability of the radiator is improved, but the temperature of the heat absorber drops and frost is generated in the heat absorber
Solution Approach 1:
The refrigerant flow is segmented into two paths: one path goes through the heat absorber for cooling, and another path is injected directly into the compressor. This segmentation allows independent control of refrigerant flow to the heat absorber and compressor, enabling the compressor speed to be increased for radiator heating capability while preventing excessive refrigerant flow to the heat absorber that would cause frosting.
Solution Approach 2:
The injection circuit serves multiple functions: it returns refrigerant to the compressor to increase compression temperature and discharge pressure (improving radiator heating capability), while simultaneously controlling the refrigerant flow rate to the heat absorber to prevent frosting. This multi-functionality resolves the contradiction between improving heating capability and preventing frost formation.
2Productivity
If the number of revolution of the compressor is increased to increase refrigerant flow rate, then the heating capability improves, but the flow rate of refrigerant into the heat absorber increases causing frost generation
Solution Approach 1:
The refrigerant flow is divided into two separate paths: one path through the heat absorber for cooling, and another path injected into the compressor. This segmentation enables independent control of refrigerant flow rates, allowing the compressor speed to be increased for higher productivity while preventing excessive refrigerant flow to the heat absorber that would cause frosting.
3Stress or pressure
If the valve position of the outdoor expansion valve is decreased to increase refrigerant flow, then the pressure of the radiator increases, but the flow rate of refrigerant into the heat absorber increases causing frost generation
Solution Approach 1:
The refrigerant flow path is segmented into two independent paths: one through the outdoor expansion valve and heat absorber, and another through the injection circuit to the compressor. This segmentation allows the outdoor expansion valve to be adjusted to increase radiator pressure while the injection circuit controls the refrigerant flow rate to the heat absorber, preventing frosting.
Solution Approach 2:
The injection circuit acts as an intermediary mechanism that returns refrigerant to the compressor, increasing compression temperature and discharge pressure. This intermediary action allows the outdoor expansion valve to be adjusted for pressure control without directly increasing refrigerant flow to the heat absorber, thus preventing frost formation while achieving the desired pressure increase.
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
This approach enhances radiator heating capability in dehumidifying and cooling mode by increasing refrigerant flow to the radiator, preventing frost formation in the heat absorber, and maintaining optimal temperatures and pressures, ensuring smooth dehumidifying and cooling operations.
Implementation Method 1
a compressor which compresses a refrigerant
Implementation Method 2
a radiator which lets the refrigerant radiate heat to heat air to be supplied to a vehicle interior
Implementation Method 3
a heat absorber which lets the refrigerant absorb heat to cool the air to be supplied to the vehicle interior
Implementation Method 4
an outdoor heat exchanger disposed outside the vehicle interior to let the refrigerant radiate heat
Data Source
AI summary
A vehicular air conditioner includes a dehumidifying and cooling mode, in which a heating capability of a radiator can be acquired without increasing a flow rate of a refrigerant into a heat absorber. The dehumidifying and cooling mode lets the refrigerant discharged from a compressor (2) radiate heat in a radiator (4) and an outdoor heat exchanger (7), decompress the refrigerant by which heat has been radiated, and then let the refrigerant absorb heat in a heat absorber (9). The vehicular air conditioner includes an injection circuit (40) which distributes a part of the refrigerant flowing out from the radiator (4) to return the part of the refrigerant to the compressor (2). In the dehumidifying and cooling mode, the injection circuit (40) is operated to return the refrigerant to the compressor (2) when there is a predetermined radiator capability shortage condition and/or predetermined low outdoor air temperature startup condition.