Vehicle Heat Pump Cooling with Refrigerant-Water Temperature Glide
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Air-conditioning systems in vehicles with electromotive or electrochemical drives face inefficiencies due to the lack of exhaust heat for heating, particularly with refrigerants like R744 and R1234yf, where the temperature of the refrigerant before expansion is typically too high, reducing system capacity and efficiency.
Innovation Solution
The method involves maintaining the refrigerant temperature before expansion between -20 to 30°C, achieved by adapting the water circulation's temperature profile to match the refrigerant's, using a fluid/fluid heat exchanger and optimizing the flow rate and temperature difference in the condenser/gas cooler, allowing for efficient cooling of the refrigerant and improved heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the gas cooler/condenser is moved into the second row of the heat exchanger to cool power electronics or charge air, then the cooling of power electronics or charge air is improved, but the cooling of the refrigerant is no longer optimal, reducing system efficiency and performance
Solution Approach 1:
The system dynamically switches between different operating modes: in the first mode, the gas cooler/condenser is positioned in the first row to optimize refrigerant cooling; in the second mode, it moves to the second row to optimize power electronics or charge air cooling. This dynamic repositioning resolves the contradiction by adapting the system configuration to different operational requirements.
Solution Approach 2:
The system employs periodic switching between different cooling priorities, alternating between refrigerant cooling optimization and power electronics/charge air cooling optimization based on operational conditions. This periodic action allows the system to maintain high efficiency across different operating scenarios.
2Temperature
If water circulation flows through the condenser/gas cooler at high volumetric rate of flow and low temperature difference, then heat transfer occurs, but the refrigerant temperature remains too high (50-60°C), reducing heat pump efficiency
Solution Approach 1:
The system changes the operating parameters of water circulation by switching between two modes: in the first mode, high volumetric flow rate with low temperature difference is used for general cooling; in the second mode, low volumetric flow rate with high temperature difference is used specifically for heat pump operation. This parameter change allows the refrigerant temperature to be reduced to the optimal range of -20 to +30°C, significantly improving heat pump efficiency.
3Loss of energy
If the gas cooler/condenser receives the same cooling water as power electronics or charge air in parallel flow, then residual heat is collected and utilized, but the refrigerant cooling is optimized for conventional operation rather than heat pump efficiency
Solution Approach 1:
The system dynamically switches between parallel flow configuration for residual heat collection and optimized refrigerant cooling configuration. During heat pump operation, the system adjusts the flow configuration to prioritize refrigerant cooling efficiency while still utilizing residual heat when appropriate, resolving the contradiction between energy recovery and circulation efficiency.
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 significantly enhances the efficiency of the refrigerant circulation, particularly for R744 and R1234yf, by reducing the volumetric flow rate and increasing the temperature difference in the heating heat exchanger, leading to improved performance and efficiency in heat pump applications.
Implementation Method 1
the water circulation and the refrigerant circulation are thermally coupled across a fluid/fluid heat exchanger, the condenser/gas cooler (5), wherein heat is transferred on the one side to the water, that is from the refrigerant circulation to the water circulation
Implementation Method 2
The refrigerant circulation comprises furthermore the customary components for a vapor compression process, such as the compressor, an expansion element and an evaporator
Implementation Method 3
the refrigerant circulation comprises furthermore the customary components for a vapor compression process, such as the compressor, an expansion element and an evaporator
Data Source
AI summary
A method for operating an air-conditioning system of a motor vehicle, wherein the air-conditioning system comprises a refrigerant circulation and a water circulation which are thermally coupled with one another across a condenser/gas cooler. Water circulation flows through the condenser/gas cooler at a low volumetric rate of flow and a high temperature difference so the water circulation transfers heat in the heating heat exchanger to the air in a similar temperature range. Refrigerant circulation cools from 65° C. to 70° C. to −10° C. to +30° C. and water circulation raises to a temperature of 55° C. to 65° C. and that an adaptation of the temperature profile of the water circulation to the temperature profile of the refrigerant circulation takes place in the condenser/gas cooler utilizing a temperature glide of the refrigerant. The refrigerant is significantly cooled.