In recent years, studies on frosting and defrosting are actively conducted all over the world. In this study, the papers published on major international journals in 2010-2015 were analyzed and reviewed. Chinese researcher are most active in this field. As the topics of the researches, papers studying on prediction of frost layer growth and defrosting are major. Also, studies on microchannel heat exchangers and wettability of the cooling surfaces are increasing. Some novel attempts for restraining frost growth using ultrasound, or for improving the performance of water discharge in defrosting process using microgrooves on the surfaces were presented in these paper.

In order to improve a heating Coefficient Of Performance (COP) of an air-conditioner it is necessary to understand frost formation on the fin surface of an outdoor heat exchanger on fields. However, the previous a lot of studies of frost formation were conducted in a laboratory. Therefore, in the present study, Frost formation on outdoor heat exchanger in air conditioner on field (Koriyama-city, Fukushima, Japan). The frost formation on fin surface of outdoor heat exchanger was investigated by a digital micro scope. Temperature and pressure of the refrigerant at the suction part of the compressor, the discharge part of the compressor and before the expansion valve were measured by thermocouples and pressure gauges. Furthermore, at the same time, Temperature and Relative humidity near the outdoor unit measured by thermocouple and humidity sensor. The growth time of the frost depends on outdoor humidity and temperature of the refrigerant at discharge part of the compressor, and increases with an increasing temperature of the refrigerant at suction part of the compressor.

Frost formation on the air side heat transfer surface of a heat exchanger for an outdoor unit of air-conditioner under heating condition increases thermal resistance and pressure drop. This results in low heat transfer performance of the heat exchanger. Heat transfer and pressure drop performance were measured to evaluate the effectiveness of the finless flat tube heat exchanger under a continuous frosting condition such as the outdoor unit of air-conditioner. The effect of tube arrangement and inlet air velocity were investigated. The results show that the frost layer thickness of the front part of the first row tube is larger compared with that of the side part of first row tube at the beginning of frost growth. It is suggested that this phenomenon affects the decrease of heat transfer rate. On the other hand, frost growth enhances heat transfer performance due to the increase of the flow velocity by the reduction of flow path. Moreover, heat transfer performance of the staggered tube arrangement case is almost same compared with that of the inline case.

A heat transfer performance as the fin with case of extended surface was estimated with non-frost and frost. The cycle process of frost and defrost was estimated in consideration of the heat loss by defrosting, based on the heat transfer characteristic obtained with frost experimentation. The difference between the best fin specification with the frost and the non-frost was compared. As a result, the following was obtained. Heat transfer performance dropped rapidly in early stages of frost, and the performance decreased showly, finally rapid performance decrement is shown in the state of the blockade between fins. The blockade between fins is early generated, so that fin intermission area is simply small. The rapid drop of the flow velocity between fins is generated in the fixed distance between frost layers. It has a length of 3mm (in this research). Using the evaluated performance by cycle process of frost and defrost, it was shown that the best fin specification from which an effective heating value becomes the maximum differs from non-frost and frost.

Presently, reliable experimental results on the heat transfer in the frost formation phenomenon under natural convection are rare, and to obtain such results, there is a need for improving the measurement methods of heat flux on the cooled surface. In this work, an experimental apparatus is proposed and built to measure the heat flux accompanying frost formation under the condition that the cooling surface temperature changes with time. Using the apparatus, effects of the factors that affect the heat transfer are investigated. The factors considered are: the distance from the leading edge of the cooling surface; wettability of the cooling surface; and the micro-machined pattern on the cooling surface. Experimental results were obtained and compared with calculated results, and the comparisons were found to be reasonably good.

Ice slurry is mixture of ice particles and aqueous solution, and has the many advantages as thermal energy storage medium, since the latent heat of fusion of the ice particles can be used and the heat exchange area is very wide. In this study, the flow characteristics of ice slurry with heterogeneous flow were investigated, experimentally. The ice slurry was produced from 5wt. % ethanol solution. IPF, Reynolds number and flow direction were varied as experimental parameters and the pressure drop were measured. Moreover, flow behavior of the ice slurry was observed and the flow characteristics were classified based on the observations. As the result, the flow behavior of the ice slurry can be classified three flow patterns, homogeneous flow, heterogeneous flow and intermittent flow. The homogeneous flow of the ice slurry was observed in the case of high IPF and high Reynolds number, and the heterogeneous flow and the intermittent flow were observed in the case of low IPF and low Reynolds number due to the buoyancy force. However, it was found that the pressure drop of the ice slurry increases with the Reynolds number and IPF smoothly, despite of the different flow behavior.

Ice slurry is mixture of ice particles and aqueous solution, and has the many advantages as thermal energy storage medium, since the latent heat of fusion of the ice particles can be used and the heat exchange area is very wide. Flow and heat transfer characteristics of ice slurry have been researched by many researchers. In this study, the flow characteristics of ice slurry, in particular, the distribution of IPF (Ice Packing Factor) and energy losses at a T-junction, were investigated experimentally. The ice slurry was produced from 5wt. % ethanol solution. Inlet IPF, Reynolds number in the inlet flow and flow rate ratio were varied as experimental parameters and the pressure drop and IPF of ice slurry before and after T-junction were measured. As the result, it was found that the distribution of IPF is affected by inlet IPF, and the pressure drop before and after T-junction increases with the inlet IPF and Reynolds number. Moreover, the branch loss coefficient of both the branch and main tubes was derived in order to evaluate the energy loss of the branch.

Vapor pressure and saturated liquid density for 1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-pentanone were measured in the temperature range from 300 K to 400 K at intervals of 10 K by the extraction method. The author obtained 11 data points of vapor pressure in the range of 42 kPa to 825 kPa and saturated liquid density in the range of 1210 kg‧m^-3 to 1598 kg‧m^-3. On the basis of the present data, correlations were formulated. The maximum deviations from correlations were 0.8 kPa for vapor pressure and 0.4 kg‧m^-3 for saturated liquid density. The normal boiling point and acentric factor were determined to be 321.95 K and 0.465, respectively. In addition, the saturated vapor pressure and vaporization of heat were also calculated.