Development and Validation of a Minichannel Evaporator Model under Dehumidification
[EN] In the first part of the current thesis, two fundamental numerical models (Fin2D-W and Fin1D-MB) for analyzing the air-side performance of minichannel evaporators were developed and verified. The Fin2D-W model applies a comprehensive two-dimensional scheme to discretize the evaporator. On the o...
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| Tipo de recurso: | tesis doctoral |
| Fecha de publicación: | 2016 |
| País: | España |
| Institución: | Universitat Politècnica de València (UPV) |
| Repositorio: | RiuNet. Repositorio Institucional de la Universitat Politécnica de Valéncia |
| Idioma: | inglés |
| OAI Identifier: | oai:riunet.upv.es:10251/71357 |
| Acceso en línea: | https://riunet.upv.es/handle/10251/71357 |
| Access Level: | acceso abierto |
| Palabra clave: | Minichannel Evaporator Cooling and Dehumidification Numerical Modeling Air-side Analysis Refrigerant-side Analysis MAQUINAS Y MOTORES TERMICOS |
| Sumario: | [EN] In the first part of the current thesis, two fundamental numerical models (Fin2D-W and Fin1D-MB) for analyzing the air-side performance of minichannel evaporators were developed and verified. The Fin2D-W model applies a comprehensive two-dimensional scheme to discretize the evaporator. On the other hand, the Fin1D-MB model is based on the one-dimensional fin theory in conjunction with the moving boundaries technique along the fin height. The first objective of the two presented models is to identify and quantify the most influential phenomena encountered in the process of cooling and dehumidification. The second objective is to study the impact of the classical modeling assumptions on the air-side performance of minichannel evaporators. Different comparative studies between the traditional Effectiveness-NTU approach and the proposed numerical models were implemented to achieve the mentioned goals. The results revealed that the modeling assumptions which have the most significant impacts on the heat and mass transfer rates are: the uniform air properties along the fin height, adiabatic-fin-tip at half the height, and negligence of partial dehumidification scenarios. These widely used assumptions resulted in substantial deviations in total heat transfer rate, up to 52%, between the Effectiveness-NTU approach and Fin2D-W model. In the second part of the thesis, the Fin1D-MB model was integrated into the IMST-ART® simulation tool to evaluate the global performance of minichannel evaporators (air- and refrigerant-side). The Fin1D-MB model was selected because of its simplicity, calculation speed, and reasonable solution accuracy relative to the Fin2D-W model. The validation of the complete Fin1D-MB model was conducted against many experimental data and numerical models available in the literature. The validation process was achieved for different heat exchanger geometries, refrigerants, and operating conditions. The results showed that for the R134a minichannel evaporators studied, the Fin1D-MB model successfully predicted the Inlet refrigerant and outlet air temperatures, cooling capacity, and refrigerant-side pressure drop within error bands of ±0.5 ºC, ±5%, and ±20%, respectively. For the CO2 (R744) minichannel evaporator studied, the presented model estimated the cooling capacity and outlet air temperature within error bands of ±10% and ±1.0 ºC, respectively. Regarding the CO2 pressure drop, the Fin1D-MB model generally underpredicted the pressure drop values compared to the experimental data, with a maximum deviation of 11 kPa. |
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