Rear Vehicle HVAC Mixing Plenum for Energy Savings
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Solution Overview
Problem
HVAC systems in vehicles face challenges in providing a comfortable thermal environment to rear seat occupants due to the difficulty in packaging long ducts and the resulting high pressure drop, which increases energy consumption, and the added cost and complexity of a dedicated rear HVAC system.
Innovation Solution
A vehicle HVAC system with a heat exchanger in the front portion generating a first airstream, mixed with cabin air in the rear portion to create a second airstream, directed via a nozzle to thermally sensitive areas, using an air moving device and control mechanisms to optimize temperature and flow rate, reducing energy consumption and system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a long duct is used to deliver conditioned air from the front HVAC system to the rear portion of the vehicle cabin, then the thermal environment for rear occupants can be improved, but the packaging difficulty and pressure drop increase significantly
Solution Approach 1:
The invention divides the air delivery system into two separate streams: a first airstream from the front HVAC system and a second airstream from a rear air moving device. These two streams are mixed at the rear to provide conditioned air to rear occupants, eliminating the need for a single long duct spanning the entire vehicle length.
Solution Approach 2:
The invention introduces a mixing plenum as an intermediary component at the rear of the vehicle cabin. This mixing plenum combines the first airstream from the front with the second airstream from the rear air moving device, allowing thermal conditioning without requiring a direct long duct connection.
2Ease of manufacture
If a long duct with multiple turns is used to package the plenum in the vehicle, then the system can be integrated into the vehicle structure, but the pressure drop increases requiring greater power from the air moving device
Solution Approach 1:
The air delivery path is segmented into two separate paths: one from the front HVAC system and another from the rear air moving device. This segmentation allows each path to be optimized independently, with the rear path being short and requiring minimal power.
Solution Approach 2:
The invention uses a mixing ratio where the first airstream from the front HVAC system constitutes only a portion (10-50%) of the total mixed airstream. The remaining majority is provided by the rear air moving device through a short path, reducing the power requirement for the rear device while still achieving thermal comfort.
3Temperature
If a dedicated rear HVAC system with a heat exchanger in the rear portion is implemented, then thermal comfort for rear occupants can be improved, but the cost and system complexity increase
Solution Approach 1:
The front HVAC system's heat exchanger serves a dual function: it conditions air for both front occupants and, through the mixed airstream, for rear occupants. This eliminates the need for a separate dedicated rear heat exchanger while still providing thermal comfort to rear passengers.
Solution Approach 2:
The invention merges the front HVAC system's air conditioning capability with a rear air moving device to create a combined system that serves both front and rear occupants. The mixing plenum combines the conditioned air from the front with air moved by the rear device, creating a unified thermal environment solution.
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 provides energy savings by maintaining a comfortable thermal environment for rear seat occupants with reduced energy requirements, allowing for a smaller plenum and lower power consumption, while simplifying packaging and reducing noise.
Implementation Method 1
a heat exchanger disposed in a front portion of the vehicle. The heat exchanger is configured to provide a first airstream characterized as having a first temperature
Implementation Method 2
an air moving device disposed in the rear portion of the vehicle. The air moving device is configured to generate a pressure difference between a front portion of the vehicle and the rear portion of the vehicle
Implementation Method 3
a nozzle configured to direct the second airstream toward a location in the rear portion of the vehicle cabin. The nozzle may be directed toward the location of a thermally sensitive portion of the occupant
Data Source
AI summary
A heating, ventilation, and air conditioning (HVAC) system is configured for use in a vehicle. A first air moving device blowing air through a heat exchanger provides a first airstream having a first temperature to a second air moving device configured to generate a second airstream having a second temperature that is different from the first temperature. The second airstream is a mixture of the first airstream and cabin air that is drawn from a rear portion of the vehicle cabin. The second air moving device may be disposed in the rear portion of the vehicle. The HVAC system further includes a nozzle that is configured to direct the second airstream toward an occupant in the rear portion of the vehicle cabin to provide spot conditioning.