01. Experimental/Computational Fluid Dynamics

Using weather-independent drying machines for agricultural products significantly improves the stability of the food supply and butter national food security. A vapor-compression heat pump dryer (VC-HPD) is proven to use less energy to extract an equal amount of water from moist air. However, utilizing the computational fluid dynamics (CFD) method to optimize the VC-HPD is still rare due to the current optimization’s focus on the thermal aspect. At the same time, the CFD simulation could analyze finer VC-HPD design optimization. However, it is problematic to directly simulate the mass transfer between vapor and water in moist air using CFD numerical simulation during a cooling or heating process because it involves three phases while two interact in mass exchange. Moreover, the calculation process needs to be conducted in a transient model. This study uses CFD simulation to analyze the impact of the evaporator-condenser distance variation on the VC-HPD performance. The humidity-related calculations are carried out indirectly based on the results of temperature, pressure and velocity distribution from CFD simulations using dry air to lighten the calculation load in numerical simulations. The indirect calculation refers to the stated inlet relative humidity (RH) at 55% at 305.15 K. The investigated VC-HPD in this study has a one-meter length with a 0.4*0.4-square maximum cross-section. The CFD simulation found that the 0.3-m-distance VC-HPD has an outlet temperature of 307 K with 35% RH. This case is then considered optimal due to its low RH. This result suits the experiment tests, in which this VC-HPD case dries the rough rice faster than in other cases. In a short evaporator-condenser distance VC-HPD, the airflow is not developed enough inside the central chamber before entering the condenser. In contrast, a far evaporator-condenser VC-HPD opens the chance for airflow recirculation, causing dead zones in some places.

Mr.

Wahyu Hidayat