## Abstract

Due to its size, the cooling of a vehicle battery by means of a refrigeration system has to be implemented e.g. via parallel evaporator tubes. After the throttle, the two-phase refrigerant flow must be uniformly distributed into several cooling channels so that uniform cooling can be achieved throughout the entire volume. The simulation of the three-dimensional effects in the distributor and also in the collector of an evaporator with several parallel evaporator tubes can only be done by computational fluid dynamics (3D CFD). However, the 3D CFD simulation of the evaporator is time consuming and can be replaced by a 1D calculation applying simple correlations for pressure losses and heat transfer coefficients (HTCs). The 1D model approach is implemented by a script that runs within the commercial software of the industrial partner for a parallel tube evaporator geometry.

The CFD simulation is based on a Eulerian multiphase approach where both phases are modelled as continuous fluids and all conservation equations are solved for each of these phases. The evaporator tubes are discretised in the direction of the tube in order to get the distribution of the variables in longitudinal direction. The used refrigerant is R134a.

In this work, an evaporator consisting of a distributor, a collector and four parallel evaporator tubes that were led at right angles to them was investigated. All these components are located in a plane. This geometry has been chosen in accordance with tests carried out.

The focus of this paper is the coupling method, the simplification that has been made and the efficiency of the simulation. A comparison between simulation and test bench measurements shows deviations in the total mass flow distribution in the order of less than 10%. Liquid and vapor mass distribution show larger deviations in the order of 20-50% in different operating conditions. Possible improvements can be achieved by varying influencing factors in the CFD-simulation, e.g. the droplet diameter. Finally, the results are analysed for the variation of two parameters. The method is also applicable to geometric variations of heat exchangers.

The CFD simulation is based on a Eulerian multiphase approach where both phases are modelled as continuous fluids and all conservation equations are solved for each of these phases. The evaporator tubes are discretised in the direction of the tube in order to get the distribution of the variables in longitudinal direction. The used refrigerant is R134a.

In this work, an evaporator consisting of a distributor, a collector and four parallel evaporator tubes that were led at right angles to them was investigated. All these components are located in a plane. This geometry has been chosen in accordance with tests carried out.

The focus of this paper is the coupling method, the simplification that has been made and the efficiency of the simulation. A comparison between simulation and test bench measurements shows deviations in the total mass flow distribution in the order of less than 10%. Liquid and vapor mass distribution show larger deviations in the order of 20-50% in different operating conditions. Possible improvements can be achieved by varying influencing factors in the CFD-simulation, e.g. the droplet diameter. Finally, the results are analysed for the variation of two parameters. The method is also applicable to geometric variations of heat exchangers.

Original language | English |
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Publication status | Published - 2021 |

Event | 18th International Refrigeration and Air Conditioning Conference at Purdue - Duration: 23 May 2021 → 27 May 2021 |

### Conference

Conference | 18th International Refrigeration and Air Conditioning Conference at Purdue |
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Period | 23/05/21 → 27/05/21 |

## Keywords

- parallel tube evaporator
- battery cooling
- 1D-3D coupling