Workshops with a large area and a high ceiling height without compartments, such as large-scale assembly factories, have an uneven thermal comfort during heating, making it difficult to establish an effective heating strategy. In this study, we evaluate the heating performance of a large-scale factory based on thermal comfort and energy flow and discuss effective heating methods. In addition, an analysis of the heating performance of a large-scale factory is attempted for the first time. To analyze the heating performance, computational fluid dynamics (CFD) and building energy simulation (BES) were used to confirm thermal comfort distribution and energy flow in a large-scale factory. Temperature distribution and thermal comfort were evaluated through CFD, and the temperature of a large-scale assembly factory was compared with experimental data. Based on the CFD results, the current heating level of large factories was predicted to be 15.4 °C, and the ADPIrev was 70%. Moreover, the BES results show that the energy losses due to forced ventilation and the inflow of outside air contributed 35.5% and 27.8%, respectively. The heating strategy proposed in this study could improve thermal comfort by 79% compared to the same energy consumption. Therefore, to improve the heating performance compared to the heating energy consumption of large-scale factory, the imbalance in thermal comfort caused by the inflow of outside air must be resolved.

Abstract:In order to design a swash plate type pump for electro-hydrostatic actuators the performance of the hydrostatic piston shoe bearings in the low speed range needs to be examined, since the pump operates frequently at low speeds, compensating for position control errors as a control element. As a common practice, piston shoes are equipped with inner rings as an auxiliary element to enhance their tribological performance. In this paper, the effects of the inner rings of the piston shoes on the frictional loss and leakage flow rate were investigated, where three piston shoe models, with different inner ring shapes and different inlet orifice sizes, were integrated. The test results showed that a large inner ring and small inlet orifice were advantageous for reducing both the frictional loss and leakage flow rate; this could also be confirmed by computational analyses.

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Abstract:The pumps of electro-hydrostatic actuators operate most frequently in boundary lubrication speed range, as they compensate for the position control errors as a control element. When conventional swash plate type piston pumps are applied to electro-hydrostatic actuators, the frictional power losses as well as the wear rate of sliding components, such as piston shoes can increase drastically under the boundary friction condition. In this paper, the power losses of the piston shoes were investigated which were engendered by a frictional solid-to-solid contact and leakage flow rate of their hydrostatic bearing. In order to reduce them, DLC-coating was applied to the swash plate and the ball joint of pistons along with its effects were demonstrated. In addition, it was also shown that the wear rate of the piston shoes could be markedly reduced using the DLC-coated swash plate.

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