Commercial air-conditioning systems are widely used for buildings of various sizes. Design and installation of these systems follow a certain guideline developed by the manufacturer. The guideline also includes the adequate amount of refrigerant to be charged into the system. However, the guideline is often insufficient to reflect all the characteristics of installation, which results in too little or too much refrigerant. Inadequate amount of refrigerant usually causes more power consumption and reduced air-conditioning / heating capacity. This paper focuses on identifying the relationship between adequate refrigerant amount and various state variables such as condensation temperature of the air-conditioning system. This is based on regression analysis of data obtained through the experiments under controlled temperature and humidity.

Ball and roller bearings are commonly used machine elements for supporting rotating motion about shafts in simple devices including bicycles, in-line skates, and electric motors, as well as in complex machines. Heat is generated by the friction in the bearings, which causes the temperature inside the bearing to increase. If the heat is not appropriately removed from the bearing, elevated temperatures may give rise to premature failure. It is, therefore, important to be able to calculate the temperature in the bearings due to friction. Here, we describe a method to estimate the frictional torque in bearings using an empirical formula developed using a method based on bearing analysis tool and the measured frictional torque in a spindle system. Thermal analysis of the spindle system including the bearings was achieved using the finite element method (FEM), and the bearing temperature was compared with measured data to verify the empirical formula.

Fast tool servo (FTS) is an enabling technology to fabricate various shapes of functional surface geometries in a precise and controllable manner. FTS can be also employed as a straightforward and efficient surface treatment way of making such products more durable. In this work, process characteristics using high-precision FTS-based surface texturing were qualitatively and quantitatively investigated to provide a class of surface design rule. The morphologies of surfaces processed with different conditions were first examined by observing the resultant 2D/3D surface profiles. In addition, the effects of the surface treatment using FTS on hardness and wear properties were characterized and compared to those without treatment.