The viscosity of working fluids is an essential thermophysical property to design heat exchanger, efficient processes, equipment, and simulation. Different types of conventional methods are used to measure the viscosity of fluids. The capillary tube method is based on the theoretical principle, and it is a reliable method. Nevertheless, it is tough to measure viscosity precisely because of problems involved in an equipment. In the present study, the tandem capillary tube method is proposed, and reliability of this method is explained. In this method, the pressure changes at the ends of the tube can be canceled, and the viscosity can be easily obtained from the Hagen-Poiseuille equation. A way to eliminate an effect of diameter difference between tubes is also proposed. The reliability and accuracy have been verified by comparing the measured viscosities of R134a to the reference values calculated by REFPROP ver.9.1. Most of the data agreed well within ±1.5 % deviation. These results show the validity of the proposed equation in the present viscosity measurement system. The expanded uncertainty of viscosity measurement was estimated as 2.2 %.

We investigated the blockage condition of erythritol slurry flowing in cooled pipe to avoid the blockage of the pipe. In this work, we focused on the effect of the fixation of the solid on the inner surface of the pipe. The fixation condition was investigated by varying the flow velocity and cooling rate. The PMMA pipe was used to investigate the effect of surface properties of the pipe, and the result was compared with that of previous work in which silicone tube was used. As the results of the experiment, we found 4 flow patterns in the slurry flow depending on flow velocity and solid fraction. When flow velocity is low, erythritol crystals sinks the bottom of the pipe, and fixation causes on the top and bottom surface of the pipe. The sinking crystals cause blockage because of accumulation of the crystals. When flow velocity is larger and it forms heterogeneous flow, erythritol crystals fix on the top of the pipe, while they do not fix on the bottom. Because crystals on the bottom surface are separated by collision of the flowing crystals. When it forms homogeneous flow, the fixation is inhibited, because the separation by the collision occurs in the whole side. Comparing silicone tube, the fixation is facilitated on the surface of PMMA pipe. As a result, it can be said that the blockage condition depends on flow velocity, cooling rate, flow pattern and surface properties of the pipe.

The foaming of lubricating oil in a compressor induces oil to flow out from the compressor when starting. This study investigated the dynamic characteristics of the flowing oil in a horizontal compressor connected with an oil separator or an accumulator when starting, in a refrigerant-oil experiment. We used the oil separation system to measure the dynamic oil flow rate and visualized the liquid level in the horizontal compressor to measure the liquid volume. The experimental results showed that the oil separator reduces the oil circulation rate and the accumulator reduces the amount of oil flowing out of the compressor when starting.

This paper reports the effect of D. C. high electric field application on sterilization of ice. The sample was Escherichia coli (JM103) in 1×10^-3 mol/L or 5×10^-3 mol/L NaCl aqueous solution. The experimental sample placed in a cuvette with parallel electrode plates (the distance between the electrodes was 1 mm), cooled at -20℃ for 20min. After freeging, D.C. voltage 500V were applied to the sample at -20℃. The survival ratio of E. coli in 1×10^-3 mol/L was decreased under freezing injury. The survival ratio of E. coli in 5×10^-3 mol/L was decreased under freezing injury and D.C. voltage application. In 1×10^-3 mol/L or 5×10^-3 mol/L NaCl aqueous solution, we could not be confirmed that effect of application time of D.C voltage on the survival ratio of E. coli.

The safety factor for the refrigerant charge not requiring safety measures is examined. Even if the safety factor is set to 2, for mildly flammable refrigerants with a molecular weight of R 32 or higher, it is found that a flammable space with significant size that could cause an ignition accident was not formed for indoor units not equipped with a compressor and not of a floor mounted type, within the range of influence factors studied in this paper.