No abstract

No abstract

The flash tank separator is one of the most important components that can be used to improve the performance of a refrigeration cycle by separating the liquid from the gas–liquid two-phase flow and providing the evaporator with only liquid refrigerant. This technique increases the effective area and enhances the heat transfer coefficient in the evaporator. To optimize the size of the vertical flash tank separator for obtaining high separation efficiency, the effect of the size of the vertical flash tank separator needs to be considered. This paper investigates the effect of the size on the liquid separation efficiency of the vertical flash tank separator. This paper also assesses the usefulness of Computational Fluid Dynamic (CFD) in flash tank design, and this is achieved through experiments and simulations on a range of relevant configurations using water as the working fluid. The results revealed that the size has a significant effect on the liquid separation efficiency, as the highest value was achieved by the largest size (VFT-V5). The CFD simulations give a good agreement with the experiments; all the simulations underestimated the liquid separation efficiency by approximately 0.02 over the range of conditions tested.

The vertical gravitational flash tank separator can be used to increase the performance of a refrigeration cycle. Using the vertical gravitational flash tank separator improves the effective area and enhances the heat transfer coefficient inside the evaporator. However, the vertical gravitational flash tank separator still needs further investigation to improve its performance. This paper provides an investigation study to demonstrate the improvement of separation efficiency using an extractor inside the vertical gravitational flash tank separator. Computational Fluid Dynamic (CFD) was used to assess the optimum configuration and dimension of the extractor. A series of experiments were performed to test and confirm the proposed CFD configuration of the extractor design. The results revealed that the extractor had increased the separation efficiency by 2 %.  The CFD simulations gave a good agreement with the experiments; however, all the simulations underestimated the liquid separation efficiency by approximately 0.02 over the range of conditions tested.

To optimize a vertical flash tank separator, the characteristics of the flow entering the separator are required to be known. A flash tank separator improves the performance of a refrigeration cycle by separating the liquid from liquid-gas flow and providing the evaporator with only liquid refrigerant. This technique improves the effective area and enhances the heat transfer coefficient in the evaporator. This paper investigates the influence of the inlet operating conditions to an expansion device, on the adiabatic two-phase flow development in a horizontal pipe downstream from the expansion device. This work also compares three dimensional numerical simulations and experimental observations for the two-phase flow development after the expansion device in the horizontal pipe. A general trend of the two-phase flow after the expansion device was gradually developed and the expansion length was identified at less than 200 mm from the inlet. The two-phase flow behaviour was recorded using a digital camera recording the flow behaviour at the upstream and downstream of the horizontal tube. The results revealed that an increase of the mass flow rate causes an increase in the void fraction and a reduction in the slip ratio in the developed region. The simulations underestimate the expansion length and the mean difference between the experimental data and the numerical results is 8 %.