This paper aims to investigate the effect of a twisted-tape insert on heat transfer enhancement in the evaporator of air conditioner. A mixed refrigerant R410A was used in this experiment. Two types of evaporation tubes with different inner diameters, 17.05 mm and 7.93 mm, were prepared at the test section. Experiments were conducted over a wide range of mass velocities from 77 to 613 kg/m²s. In addition, several types of twisted tapes with different twist pitches were made for each tube. The pressure drop and heat transfer coefficient of the test section were measured by changing the refrigerant quality for the smooth tube and the tape-inserted tube. Furthermore, the refrigerant flow patterns were visualized upstream and downstream of the test section. It was found that the increase in pressure drop due to the twisted-tape insert was more pronounced when the flow pattern was a stratified-wavy. While the heat transfer coefficient of the tape-inserted tube was almost the same as that of the smooth tube when the flow pattern was annular, the increase in the heat transfer coefficient due to the tape insertion was clearly observed as the pattern shifted to a mist flow.

A corrugated fin heat exchanger using flat extruded tubes is compact and has high performance, however, when used as an evaporator, it has drainage problems. In this study, we studied the evaporator using flat extruded tubes without corrugated fin and has plates at the sides to improve the drainage. Four types of flat extruded tubes with different channel sizes and plats were prototyped, and single-pass heat exchangers were manufactured. These heat exchangers were installed in a wind tunnel where the air temperature, humidity, and velocity could be controlled, and the heat exchange rate and air-side pressure drop were measured under the two conditions: dry surface, wet surface conditions. The newly developed heat exchangers have the feature that the condensed water flows down without stagnation, and the heat transfer coefficient can be increased compared to the conventional heat exchangers while suppressing the increase in pressure drop.

In this study, we aimed to investigate the effect of blanching treatment on the aroma of frozen green soybeans (edamame). Frozen samples were vacuum-packed and blanched under conditions that yielded the same texture, and sensory evaluation and aroma analysis were conducted by gas chromatography-mass spectrometry-olfactometry (GC-MS/O). The results of sensory evaluation revealed no significant difference in the retronasal aroma while eating; however, the aroma of the frozen-thawed pods with unblanching immediately before eating was significantly better. Furthermore, GC-MS/O analysis detected a more green-like aroma in unblanched edamame, substantiating that blanching treatment undesirably affects the aroma of frozen edamame.

The system for evaluating constitutional risk of heat shock when bathing was constructed and evaluated the performances. This system consists of the thermal stimulation device and the vascular transmissive imaging device. The thermal stimulation device was fabricated utilizing Peltier device and power supply with temperature controller. The vascular transmissive imaging device was made using near infrared LED and a night vision camera. As the results of the performance evaluation, the cooling down to 10°C and the heating up to 40°C of the hand could be performed by the thermal stimulation device. Peripheral blood vessel of a finger could be transmissively shot by the imaging system. After the performance evaluation, both devices were fixed to hand and a finger. Then, peripheral blood vessel was shot during thermal stimulation to the hand and the image was recorded to PC. Blood vessel diameter on the recorded image was measured macroscopically using a graphic software. In the result of diameter measurements, the diameter changed by thermal stimulation. Additionally, the transition of the diameter change varied by time of day. These results suggest that the fabricated system would be useful for evaluating the constitutional risk of heat shock when bathing.

We propose erythritol slurry as a heat transfer medium for unused energy utilization. In this study, heat transfer characteristics of erythritol slurry, with considering solidification and fixation of the solid on the cooling surface, must be understood to prevent any fatal trouble in the practical use. In the experiment, by using double tube heat exchanger, in which slurry flows in the inner tube and cooling water flows in the outer tube, heat transfer coefficient is measured under the condition the solidification is possible to be occur. It was found that the heat transfer coefficient of the erythritol slurry is smaller than the erythritol solution under the turbulent flow condition because of the fixation of the solid. Although enhancement of heat transfer coefficient with the turbulent transition was observed for solid fraction of 5 mass %, it was not observed for 10 and 15 mass %. The heat transfer coefficient increases with flow rate in the same trend with turbulent flow for 10 and 15 mass % even when Reynolds number is low. It was also found that both the heat transfer enhancement by the effect of phase change and the heat transfer suppression by the effect of fixation of the solid are more significant under cooling condition than under heating condition. The heat transfer enhancement by the effect of the phase change increases with the solid fraction until the solid fraction reaches about 10 mass%. It was also found that the heat transfer enhancement is larger than the increase in pressure drop by the effect of the solid particles. From the results, we proposed the model of flow and heat transfer of erythritol slurry in cooling pipe, and supposed supercooling affects the heat transfer characteristics.