Vehicular air-conditioning unit
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Solution Overview
Problem
Vehicular air-conditioning units in electric vehicles face challenges in heating the vehicle interior at low outside air temperatures due to frost formation on external heat exchangers, leading to decreased performance and increased battery power consumption, which shortens the cruising range.
Innovation Solution
A vehicular air-conditioning unit with a refrigerant circuit including a compressor, radiator, external heat exchanger, internal heat exchanger, and ventilation heat exchanger, where the refrigerant decompressed after heat release in the radiator evaporates in either the external or ventilation heat exchanger for heating, and during cooling, it evaporates in the internal heat exchanger, with a hot gas cycle circuit to enhance heating capacity and efficiency, and an evaporation pressure regulation valve to prevent frost formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the refrigerant evaporation temperature in the external heat exchanger drops to 0°C or below at low outside air temperatures, then heat pump operation can continue, but frost grows on the external heat exchanger causing clogging and deteriorating heat exchange performance
Solution Approach 1:
The patent introduces a ventilation heat exchanger as an intermediary component that recovers heat from exhaust air to preheat the refrigerant before it enters the external heat exchanger. This mediator prevents the refrigerant temperature from dropping too low, thereby preventing frost formation on the external heat exchanger while maintaining heat pump operation continuity.
Solution Approach 2:
The patent changes the temperature parameter of the refrigerant by using heat recovery from exhaust air. The ventilation heat exchanger raises the refrigerant temperature before it reaches the external heat exchanger, ensuring the evaporation temperature stays above freezing point and preventing frost accumulation.
2Reliability
If a defrosting heater is energized to defrost the external heat exchanger, then frost is removed, but battery power is consumed and cruising range is shortened
Solution Approach 1:
The patent enables the ventilation heat exchanger to serve dual functions: normally it recovers heat from exhaust air to improve heating efficiency, and during defrosting it directs warm exhaust air to melt frost on the external heat exchanger. This self-service approach eliminates the need for separate defrosting heaters and their associated power consumption.
Solution Approach 2:
The ventilation heat exchanger is designed to perform multiple functions: heat recovery during normal operation and defrosting during frost conditions. By making this component multi-functional, the system eliminates the need for dedicated defrosting equipment and reduces overall power consumption.
3Power
If the compression ratio of the compressor is increased to maintain heating capacity at low outside air temperatures, then heating performance is maintained, but the temperature difference in pumping becomes significant and efficiency decreases
Solution Approach 1:
The patent applies preliminary heating to the refrigerant using the ventilation heat exchanger before it enters the external heat exchanger. This preliminary action reduces the temperature difference that the compressor must handle, allowing it to operate at lower compression ratios and maintain efficiency while still achieving the required heating capacity.
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 configuration effectively heats the vehicle interior at low outside air temperatures, prevents frost on the ventilation heat exchanger, and reduces battery power consumption, maintaining a comfortable interior environment without significant decreases in cruising range.
Implementation Method 1
an external heat exchanger, an internal heat exchanger
Implementation Method 2
the refrigerant decompressed after the heat release in the radiator evaporates in at least one of the external heat exchanger and the ventilation heat exchanger
Implementation Method 3
a ventilation heat exchanger for recovering heat from the air discharged from the vehicle interior for ventilation
Implementation Method 4
a hot gas cycle circuit for decompressing a part of the refrigerant discharged from the compressor, and causing the decompressed part of the refrigerant to flow through the internal heat exchanger to release heat into the vehicle interior
Data Source
AI summary
The heating capacity particularly at low outside air temperatures in a vehicular air-conditioning unit that heats the vehicle interior by heat pump operation of a refrigerant circuit using a compressor is improved. During heating, a refrigerant discharged from a compressor 2 releases heat in a radiator 4 into the vehicle interior, and the refrigerant decompressed after the heat release in the radiator evaporates in at least one of an external heat exchanger 7 and a ventilation heat exchanger 24. During cooling, the refrigerant discharged from the compressor releases heat in the external heat exchanger, and the refrigerant decompressed after the heat release in the external heat exchanger evaporates in an internal heat exchanger 9 to absorb heat from the vehicle interior. The vehicular air-conditioning unit includes a hot gas cycle circuit 31 for decompressing a part of the refrigerant discharged from the compressor, and causing the decompressed part of the refrigerant to flow through the internal heat exchanger to release heat into the vehicle interior.