Abstract
In this paper, the performance of a compact Three-Fluid Combined Membrane Contactor (3F-CMC) is investigated using Computational Fluid Dynamics (CFD), supported and validated with a good agreement by an experimental campaign made on a fully working prototype. This internally-cooled membrane contactor is the core component of a hybrid air conditioning system for electric vehicles (EVs) developed in a successful H2020 project called XERIC. In the adopted numerical approach, the conjugate heat and mass transfer inside the 3F-CMC is described by non-isothermal incompressible flows and vapor transport through a PTFE hydrophobic membrane. The sensitivity of the 3F-CMC performance to air/desiccant flow rates, temperature, humidity, and desiccant concentration is analyzed numerically through the validated CFD codes. According to this study, the moisture removal increases by the inlet humidity ratio, nearly linearly. Under the considered conditions (where the inlet air temperature is 26.2 °C), when the inlet relative humidity (RH) is 75% the moisture removal is about 450% higher than the case RH = 37%, while the absorption effectiveness declines about 45%. Furthermore, this study shows that the amount of absorbed vapor flux rises by increasing the airflow rate; on the other hand, the higher the airflow rate, the lower is the overall absorption efficiency of the 3F-CMC. This investigation gives important suggestions on how to properly operate a 3F-CMC in order to achieve the requested performance, especially in hot and humid climates.
Highlights
The air-conditioning system (AC) is one of the most energy-demanding auxiliary loads in electric vehicles (EVs) that limits their driving range
In order to reduce the energy consumption, it is important to develop more energy-efficient AC systems, compact enough to be used in EVs
Due to the water vapor absorption and heat transfer between the hot supply air and liquid desiccant, the temperature of liquid desiccant rises reducing the vapor absorption potential along the desiccant path. To deal with this issue, Isetti et al [7] drawn attention to the performance improvement of liquid desiccant cycles (LDCs) by designing and developing the first prototype of a combined membrane contactor, which is internally cooled by a refrigerant flow directly derived by a vapor compression cycle
Summary
The air-conditioning system (AC) is one of the most energy-demanding auxiliary loads in electric vehicles (EVs) that limits their driving range. Due to the water vapor absorption (latent heat release) and heat transfer between the hot supply air and liquid desiccant, the temperature of liquid desiccant rises reducing the vapor absorption potential along the desiccant path To deal with this issue, Isetti et al [7] drawn attention to the performance improvement of LDCs by designing and developing the first prototype of a combined membrane contactor, which is internally cooled by a refrigerant flow directly derived by a vapor compression cycle. As the core component of a LDC to dehumidify the air in an energy-efficient way This cycle is integrated with a traditional vapor compression cycle (VCC) to form a climate-control system for serving in electric vehicles (EVs). Both numerical and experimental results show noteworthy dehumidification performance of the compact 3F-CMC, especially for hot and humid conditions
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