Battery Cooler Two-Stage Throttle Design for Uniform Cell Temperature
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Solution Overview
Problem
Existing battery cooler systems for electric and hybrid vehicles face challenges in maintaining homogeneous cooling performance across varying ambient temperatures, leading to uneven temperature distribution among battery cells due to the small pressure drop over branchers, which complicates the distribution of refrigerating medium in a fluid-gaseous admixture.
Innovation Solution
A battery cooler system with a refrigerating medium circuit featuring a compressor, gas cooler, and a pressure reduction device with at least a first and second throttle stage, where the refrigerating medium is distributed in a single phase downstream of the first throttle stage, ensuring uniform distribution across cooling branches, and the second throttle stage is located in the outlet lines to achieve uniform temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a small pressure drop over the brancher is used, then the thermostatic expansion valve can supply sufficient refrigerating medium flow at minimum operating temperature, but the distribution of refrigerating medium in fluid-gaseous admixture becomes non-uniform across cooling branches
Solution Approach 1:
The pressure reduction device is divided into multiple independent throttle stages (first throttle stage, second throttle stage) with a branching location in between. This segmentation allows the refrigerating medium to be distributed to multiple cooling branches at the branching location while maintaining proper phase composition through sequential pressure reduction, resolving the contradiction between sufficient flow supply and uniform distribution.
Solution Approach 2:
The first throttle stage performs preliminary pressure reduction upstream of the branching location, ensuring that the refrigerating medium is in the appropriate phase (fluid or overcritical) before distribution. This preliminary action prevents phase separation issues that would occur with a single-stage throttle, enabling uniform distribution across all branches while maintaining adequate flow quantity.
2Device complexity
If a single throttle stage is used in the pressure reduction device, then the device complexity is reduced, but the ability to maintain single-phase refrigerating medium distribution across varying ambient temperatures is compromised
Solution Approach 1:
The multi-stage throttle configuration with a branching location allows the system to dynamically adapt to varying ambient temperatures. The first throttle stage handles high-temperature conditions by reducing pressure to maintain overcritical or fluid state, while the second throttle stage handles low-temperature conditions. This dynamic adaptation across temperature ranges resolves the contradiction between device simplicity and operational versatility.
Solution Approach 2:
The system changes the pressure parameter in stages rather than in a single step. The first throttle stage reduces pressure to an intermediate level, and the second throttle stage reduces it further. This staged parameter change allows the refrigerating medium to remain in the appropriate phase across a wide range of ambient temperatures, resolving the contradiction between simple device structure and broad operational adaptability.
3Temperature
If the refrigerating medium is present in fluid-gaseous admixture upstream of the brancher, then cooling can occur, but homogeneous distribution over cooling branches becomes difficult to achieve
Solution Approach 1:
The first throttle stage acts as an intermediary between the high-pressure source and the branching location. It transforms the refrigerating medium into a single-phase state (fluid or overcritical) before distribution, preventing the phase separation problems that would occur with direct two-phase distribution. This intermediary transformation ensures both cooling effect and homogeneous distribution across all branches.
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 allows for uniform cooling of all battery cells by maintaining a consistent proportion of fluid refrigerating medium across branches, ensuring a small temperature difference of no more than 5K between cells, even at low ambient temperatures, thus extending the service life of battery cells.
Implementation Method 1
The two throttle stages of the pressure reduction device are adjusted in such a manner that the refrigerating medium is present substantially in a single phase downstream of the first throttle stage
Implementation Method 2
the second throttle stage is located in the outlet lines to achieve uniform temperature distribution
Implementation Method 3
During the cooling of battery modules, it is further the case that a cooling unit also has to operate at low ambient temperatures
Data Source
Figure 1~2
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Figure 5~6
AI summary
A battery cooler system has a refrigerating medium circuit (10) having a compressor (12), a gas cooler (14), a pressure reduction device (40) and a battery cooler circuit (30) which has a plurality of cooling branches (34, 36), the pressure reduction device (40) having a brancher (44) and at least a first and a second throttle stage. There is provided between the first and the second throttle stage a branching location (56) with which the refrigerating medium flow is distributed over the cooling branches (34, 36) of the battery cooler circuit (30). The two throttle stages of the pressure reduction device (40) are adjusted in such a manner that the refrigerating medium is present substantially in a single phase downstream of the first throttle stage.