Dual-Loop Vehicle HVAC for Engine-Off Heating and Cooling
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Solution Overview
Problem
Current vehicle HVAC systems require the engine to be running for both heating and cooling, leading to inefficiencies, increased pollution, and potential leaks in high-pressure refrigerant systems, especially in buses that may be stationary for extended periods.
Innovation Solution
A dual-loop HVAC system with a primary high-pressure refrigerant loop and a secondary low-pressure liquid loop, thermally connected via a common heat exchanger, allowing for both heating and cooling without the engine, using electrically driven components and a remote secondary heat source for enhanced efficiency and reduced leak risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the engine is left running to provide heating and cooling, then the passenger compartment can be conditioned, but money is wasted and pollution increases
Solution Approach 1:
The system divides the HVAC functionality into separate electrically-driven components (compressor, condenser fan, evaporator fan, heater) that can operate independently of the engine. This segmentation allows the HVAC system to function during engine-off periods, eliminating the need to run the engine solely for climate control and thus reducing fuel consumption and pollution.
Solution Approach 2:
The patent replaces the traditional engine-belt-driven mechanical compressor with an electrically-driven compressor. This substitution allows the refrigeration cycle to operate using electrical power from the vehicle's electrical system rather than mechanical power from the engine, enabling HVAC operation during engine-off periods and reducing unnecessary fuel consumption.
2Loss of energy
If the engine is turned off to save money and reduce pollution, then fuel consumption decreases, but the cooling system cannot cool the passenger compartment
Solution Approach 1:
The patent replaces the engine-belt-driven mechanical compressor with an electrically-driven compressor that can operate independently of the engine. This substitution enables the refrigeration system to function during engine-off periods using electrical power, thereby maintaining cooling capability while allowing the engine to remain off for fuel savings.
Solution Approach 2:
The electrically-driven HVAC system can service itself during engine-off periods by using the vehicle's electrical system (battery or auxiliary power source) to operate the compressor and other components. This self-service capability ensures continuous climate control functionality without requiring the main engine to be running.
3Productivity
If a high-pressure refrigerant system is used for cooling, then cooling efficiency is improved, but the system becomes prone to leaks
Solution Approach 1:
The patent replaces the traditional engine-belt-driven mechanical compressor with an electrically-driven compressor that operates at lower pressures. This substitution maintains adequate cooling efficiency while reducing the system's reliance on high-pressure refrigerant containment, thereby reducing the risk of leaks and improving overall system reliability.
4Temperature
If a second system is added to provide heating during engine-off condition, then heating capability is improved, but the amount of space required increases
Solution Approach 1:
The electrically-driven compressor and refrigeration system are designed to perform both cooling and heating functions. During cooling mode, the system operates as a conventional refrigeration cycle. During heating mode, the system reverses the refrigerant flow direction using a four-way valve, allowing the evaporator and condenser to swap roles. This multi-functionality eliminates the need for a separate heating system, saving space while providing both heating and cooling capabilities during engine-off periods.
Solution Approach 2:
The patent implements a heat pump system that can reverse the refrigeration cycle to provide heating. By inverting the refrigerant flow direction through a four-way valve, the system transforms the cooling components into heating components, allowing the same equipment to provide both cooling and heating functions without requiring additional space for separate systems.
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
Enables efficient heating and cooling of vehicle compartments without engine operation, reducing energy waste and pollution, while minimizing the likelihood of refrigerant leaks and system complexity.
Implementation Method 1
a primary loop and a secondary loop thermally connected to one another by a common heat exchanger
Data Source
AI summary
An HVAC system for heating and cooling a passenger compartment of a vehicle includes a first heat exchanger that transfers heat between a primary loop and a secondary loop. The primary loop is a reversible loop and uses high pressure refrigerant. A compressor pressurizes the refrigerant. A second heat exchanger selectively transfers heat energy to and from the passenger compartment. The secondary loop is a low pressure liquid coolant loop that passes through the first heat exchanger. A pump moves fluid through the secondary loop. A third heat exchanger transfers heat to and from an external medium from the fluid passing through the secondary loop. A secondary heat source adds heat to the secondary loop during a heating mode. A bypass means selectively bypasses the secondary heat source during a cooling mode.