Vehicle HVAC Heat Exchanger Layout for Low-Temperature Heating
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Solution Overview
Problem
The HVAC system in electric and hybrid vehicles faces inefficiencies in low ambient temperatures, leading to reduced refrigerant evaporation, compressor performance degradation, and increased electric heater usage, resulting in reduced electric efficiency and higher manufacturing costs due to dehumidification-side expansion valves.
Innovation Solution
The system incorporates a refrigerant heat exchanger and control valves to manage refrigerant flow and temperature, ensuring sufficient heat absorption and evaporation, even at low ambient temperatures, by using a water-cooled heat exchanger and an exterior heat exchanger in conjunction with control valves to stabilize refrigerant evaporation and condensation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the HVAC system uses a refrigerant to heat the passenger compartment, then heating efficiency is improved, but in low ambient temperatures the refrigerant fails to sufficiently absorb heat from the powertrain-side coolant, causing compressor suction pressure to drop below threshold and compressor efficiency to degrade
Solution Approach 1:
The patent introduces a first heat exchanger as an intermediary component between the powertrain-side coolant and the refrigerant. This heat exchanger pre-heats the refrigerant using waste heat from the powertrain coolant before the refrigerant enters the evaporator, ensuring sufficient refrigerant evaporation even in low ambient temperatures and preventing compressor suction pressure from dropping below threshold.
Solution Approach 2:
The system dynamically adjusts the flow rate of powertrain-side coolant passing through the first heat exchanger based on ambient temperature conditions. When ambient temperature is low, the control unit increases the coolant flow rate through the first heat exchanger to maximize heat transfer to the refrigerant, thereby maintaining refrigerant evaporation efficiency and compressor operation stability.
2Temperature
If the HVAC system uses an electric heater to heat the passenger compartment, then heating is achieved, but electric efficiency of the electric vehicle is reduced
Solution Approach 1:
The patent converts the waste heat from the powertrain coolant, which would otherwise be discarded, into a useful heating source for the refrigerant. By using the first heat exchanger to transfer waste heat to the refrigerant, the system enables efficient refrigerant evaporation and refrigerant-based heating, thereby avoiding the need for energy-intensive electric heaters and improving overall electric efficiency.
3Ease of operation
If the HVAC system operates in heating and dehumidifying mode, then both heating and dehumidification are performed, but when the blower RPM is reduced, the interior condenser fails to sufficiently release heat, reducing refrigerant condensation and increasing compressor discharge pressure
Solution Approach 1:
The patent introduces a second heat exchanger as an intermediary to facilitate additional heat release from the refrigerant. After the refrigerant passes through the interior condenser, the second heat exchanger provides an additional heat dissipation path, enabling sufficient refrigerant condensation even when blower RPM is reduced, thereby preventing excessive compressor discharge pressure.
Solution Approach 2:
The system adds another heat release dimension by introducing the second heat exchanger in parallel or series with the interior condenser. This additional heat exchange pathway provides redundancy and ensures adequate refrigerant condensation under varying blower operating conditions, maintaining system stability without excessive pressure buildup.
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 enhances the coefficient of performance (COP) of the HVAC system, reduces the need for electric heaters, and improves the electric efficiency of vehicles by maintaining compressor efficiency and stable temperature control in heating and dehumidifying modes.
Implementation Method 1
A refrigerant circulating in the HVAC system of the electric vehicle may absorb heat from a powertrain-side coolant circulating in the powertrain cooling system through a water-cooled heat exchanger and be evaporated
Implementation Method 2
the refrigerant may absorb heat from a powertrain-side coolant circulating in the powertrain cooling system through a water-cooled heat exchanger and be evaporated
Implementation Method 3
the interior condenser of the HVAC system may fail to sufficiently release heat to the air, and accordingly condensation of the refrigerant may be relatively reduced
Data Source
AI summary
An embodiment heating, ventilation, and air conditioning (HVAC) system for a vehicle includes a compressor, an interior condenser disposed on a downstream side of the compressor, a water-cooled heat exchanger disposed on a downstream side of the interior condenser and configured to transfer heat between a refrigerant and a coolant circulating in a coolant system, a refrigerant heat exchanger disposed on an upstream side of the compressor and configured to transfer heat between the refrigerant discharged from the water-cooled heat exchanger and the refrigerant discharged from the interior condenser, and a first control valve disposed between the water-cooled heat exchanger and the interior condenser and configured to control a flow of the refrigerant between the interior condenser, the water-cooled heat exchanger, and the refrigerant heat exchanger.