Vehicle HVAC Evaporator Temperature Modulation to Cut Reheating
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Solution Overview
Problem
Current vehicle climate control systems consume excessive fuel by operating components beyond necessity, particularly due to cooling air to a minimum temperature and then reheating it, which increases fuel consumption by up to 4 miles per gallon during maximum climate control usage.
Innovation Solution
The system determines a desired temperature and calculates a temperature offset to cool the air to a temperature higher than conventional minimums, optimizing evaporator operation by using a blend door position and evaporator temperature to directly achieve the desired temperature, thereby reducing compressor cycling and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air is cooled to a minimum temperature (e.g., just above freezing) by the evaporator, then all humidity is effectively removed from the air, but the compressor operates more than necessary and fuel consumption increases
Solution Approach 1:
The patent changes the evaporator outlet temperature parameter from a fixed minimum value (just above freezing) to a dynamically adjusted value based on desired temperature. The controller calculates a target evaporator outlet temperature that is higher than the traditional minimum when the desired temperature is above freezing, thereby reducing compressor runtime while maintaining adequate humidity control.
Solution Approach 2:
The system transitions from static evaporator temperature control to dynamic control where the evaporator outlet temperature varies continuously based on the desired temperature setting. The controller continuously adjusts the target evaporator outlet temperature according to the relationship between desired temperature and ambient conditions, optimizing compressor operation in real-time.
2Speed
If the evaporator cools air to a low band temperature regardless of desired temperature, then cooling performance is maximized, but subsequent reheating is required which increases fuel consumption
Solution Approach 1:
The patent applies partial cooling action by adjusting the evaporator outlet temperature to be higher than the traditional minimum when full cooling is not required. Instead of always cooling to the lowest possible temperature and then reheating, the system applies just enough cooling to reach the target temperature, eliminating the excessive cooling and subsequent reheating cycle.
Solution Approach 2:
The controller uses feedback from the desired temperature setting and ambient conditions to continuously adjust the target evaporator outlet temperature. This closed-loop control ensures the evaporator cools air to the appropriate temperature without over-cooling, thereby eliminating the need for reheating and reducing fuel consumption.
3Reliability
If compressor operation is increased to ensure adequate cooling, then cooling reliability is improved, but fuel consumption increases by up to 4 miles per gallon
Solution Approach 1:
The patent changes the compressor operation parameters by adjusting the evaporator outlet temperature setpoint based on desired temperature. This parameter change allows the compressor to operate at reduced capacity when full cooling is not needed, maintaining cooling reliability while significantly reducing fuel consumption associated with excessive compressor runtime.
Solution Approach 2:
The system implements dynamic compressor control where the evaporator outlet temperature and corresponding compressor runtime vary continuously based on desired temperature settings. This dynamic adjustment maintains adequate cooling reliability across different operating conditions while optimizing fuel consumption by matching compressor operation to actual cooling needs.
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 reduces fuel consumption by minimizing unnecessary compressor operation and maintains passenger comfort by accurately matching air temperature to desired settings, while also preventing window fogging and optimizing energy balance.
Implementation Method 1
As the refrigerant liquid inside the evaporator 18 cools the air 24, the liquid absorbs heat from the air 24 and returns to vapor.
Implementation Method 2
the liquid absorbs heat from the air 24 and returns to vapor
Implementation Method 3
the liquid absorbs heat from the air 24
Implementation Method 4
The condenser 14 condenses the refrigerant vapor into a liquid and rejects heat
Implementation Method 5
The heater core 20 heats a portion of the air 24 according to a desired temperature
Data Source
AI summary
A vehicle climate control system operates an evaporator at a minimum temperature adjusted by a temperature offset. The control system determines a desired temperature and a blend potentiometer position that is indicative of the desired temperature. The control system determines a target temperature for the evaporator according to the blend potentiometer position, and calculates the temperature offset according to the target temperature and the blend potentiometer position. A blend door position is controlled according to the blend potentiometer position, the target temperature, the temperature offset, and heater core air temperature in order to optimize the operation of the evaporator.