Heat Pump Compressor Speed Control Using Pressure Ratio Feedback
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Solution Overview
Problem
Operating a heat pump in multiple modes can lead to reduced compressor lubrication, increasing the risk of degradation due to high pressure ratios across the compressor, particularly in heating and dehumidification modes.
Innovation Solution
A vehicle system with a refrigerant loop, a compressor, and a controller that adjusts the compressor speed based on the pressure ratio between the compressor inlet and outlet, using a pressure sensor to ensure adequate refrigerant and lubricant flow, thereby reducing the risk of compressor degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heat pump operates in heating or dehumidification mode with high pressure ratios across the compressor, then the heating or dehumidification performance is improved, but the compressor lubrication is reduced leading to increased risk of compressor degradation
Solution Approach 1:
The controller continuously monitors the pressure ratio across the compressor and uses this feedback to dynamically adjust compressor speed. When the pressure ratio exceeds a threshold, the controller reduces compressor speed to maintain adequate lubrication flow, thereby preventing compressor degradation while allowing optimal performance when conditions permit
Solution Approach 2:
The compressor speed is made dynamic rather than fixed, allowing it to vary based on real-time operating conditions. The system transitions between different speed states depending on the pressure ratio, enabling the compressor to operate efficiently under varying thermal loads while maintaining protective measures when high pressure ratios occur
2Adaptability or versatility
If the heat pump operates in multiple modes (heating, cooling, dehumidification), then the versatility and utility of the heat pump is improved, but the control complexity increases making it challenging to ensure adequate compressor lubrication
Solution Approach 1:
A single pressure ratio-based control strategy is applied universally across all heat pump operating modes (heating, cooling, dehumidification). The same controller logic and protection thresholds are used regardless of mode, simplifying the control architecture while maintaining adequate compressor lubrication across diverse operating conditions
Solution Approach 2:
The control system monitors and responds to changes in the pressure ratio parameter, using this single critical parameter to govern compressor speed adjustments across all operating modes. This parameter-based approach unifies the control strategy and reduces complexity compared to mode-specific control algorithms
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 effectively reduces the possibility of heat pump compressor degradation without significant increases in system cost and can be applied to various system configurations.
Implementation Method 1
a refrigerant loop including a compressor
Implementation Method 2
a first pressure sensor; and a controller including executable instructions stored in non-transitory memory to adjust a speed of the compressor in response to a pressure ratio across an outlet of the compressor and an inlet of the compressor, the pressure ratio based at least in part on output of the first pressure sensor
Data Source
AI summary
Methods and systems for providing control of a heat pump of a motor vehicle are presented. In one operating mode, speed of a heat pump compressor is controlled responsive to an outlet pressure of the heat pump compressor. In a second operating mode, speed of the heat pump compressor is controlled responsive to a pressure ratio between an inlet and an outlet of the heat pump compressor.