For the purpose of determining the optimum operation condition of liquid-ice thermal storage system, the performance analysis has been carried out. The target system was consisted of refrigerator, its auxiliary devices, liquid-ice production device, piping system, and thermal load section. The system performances were widely investigated analytically for the variety of operation conditions including the cycle performance of a refrigerator. The optimum operation condition of the liquid-ice thermal storage system from the viewpoint of coefficient of performance and the performance of heat release were discussed. (C) 2002 Elsevier Science Ltd and IIR. All rights reserved.

Ice slurry has recently been utilized for a variety of engineering fields such as thermal energy storage and high-density energy transportation. In this paper, as a production method of ice slurry, the oscillatory rotating cooled tube method was proposed. A vertical cooled tube was installed in a test vessel that was filled with ethylene glycol solution being forced to move within an aqueous binary solution to produce the ice slurry. Production performance of ice slurry by the present method was determined under a variety of conditions, such as initial concentration of solution, angular acceleration and rotation angle for the oscillation motion of the cooled tube. The production performance was evaluated analytically by constructing a numerical model. The analysis was made to determine the separation condition of ice layer from the cooled tube surface at first, then the production rate of ice slurry was assessed. It was found from the present study that the ice slurry was produced continuously under the appropriate operating conditions in which the separation of ice layer was caused by oscillating motion of the cooled tube.

An experimental study was carried out on the critical heat flux of ice accretion along a horizontal wire immersed in a cold air stream with water spray. The critical heat flux was defined as the minimum heat flux, which could maintain de-icing along a wire. The air stream velocity and temperature range were from about 3 to 8 ms−1 and from −5 to −15 deg. C, respectively, and the average droplet diameter of the water-spray range was from 140 to 640 µm. In order to determine the effect of the wire diameter on the critical heat flux, three diameters, namely, 0.5, 0.8 and 1.0 mm were selected. The critical heat flux was determined from the profile of the variation of the wire temperature with the loading electric power on the wire. It was found for the conditions of the present experiments that the critical heat flux showed a linear increase with an increase in the air stream temperature and velocity. Moreover, the effects of the profile of droplet and wire diameter on the critical heat flux were examined.

Melting phenomena are related to a wide variety of engineering fields: purification of metals, welding, electroslag melting, thawing of moist soil, and latent heat-of-fusion thermal-energy storage are a few of important applications which have motivated research in this area.Melting is a phase transformation process that is accompanied by absorption of thermal energy. The essential feature of the systems that exhibit melting phenomena is the existence of a liquid–solid interface that separates the two phases containing different thermophysical properties and the absorption of thermal energy at the interface. The major problem in melting is thus to determine transport phenomena of the latent and sensible heat of the system. There is quite a large body of literature concerning a variety of such problems in engineering as well as in the applied sciences. Recent reviews summarize prior work in this area 1, 2, 3, 4, 5, 6, 7, 8.In previous studies pertaining to melting of a solid contained in a confined vessel, consideration has been given to either to a melting solid which is constrained to prevent its possible movement owing to gravity or to a solid which is free to fall under gravity [8]. In the first case, the melting solid is maintained at a fixed position inside the vessel throughout the melting process, then is completely surrounded by the liquid melt, and the energy needed for the melting is transported from the heating wall to the solid–liquid interface by free convection within the liquid melt. In the second case, the solid is free to respond to the net force acting on it. If the solid phase has higher density than the liquid phase the solid sinks to the bottom of the vessel. On the contrary, if the solid phase is lighter than the liquid phase the unmelted solid is drawn by buoyancy to the top of the vessel. In either case, a region of close-contact melting arises between the solid and the heating wall.Utilization of thermal-energy storage system for air conditioning has recently evoked energy saving and normalizing the requirement level of the electric power supply 9, 10. For conventional ice-storage systems using a pure ice system as a phase change material (PCM) it has been pointed out 11, 12, 13, 14that the melting heat transfer performance may be reduced with time because the melting ice surface is separated more far from the heat transfer wall.Marked attention has recently been given to a slush ice 15, 16, which is essentially a mixture of fine ice particles and aqueous binary solution, as a new PCM in place of common ice owing to demand of both high efficient ice producing and regulate handling of melting heat transfer performance as well as transportability. With respect to the melting heat transfer performance in releasing the cold thermal energy from the slush ice, the melting characteristics of a quiescent slush ice around a horizontal heated tube [17]and in a rectangular capsule with a vertical heated wall [18]as well as with a top heated wall [18]were determined experimentally.In addition, a solid–gas–liquid three-phase fluidized bed heat exchange system [19]and a direct contact heat-exchange system, in which the slush ice is operated as the fluidized bed, was proposed for releasing the cold thermal energy. Detailed basic data on the melting characteristics of the slush ice are highly required for developing high efficient heat exchanger using the slush ice. However, there seems to be a variety of unknown characteristics on the melting mechanism as well as the melting behavior for releasing both efficiently and regulatively the cold thermal energy from the slush ice.This paper reports a study on the melting characteristics of slush ice in a horizontal cylindrical capsule. In order to inspect the local heat transfer coefficient distribution in circumference direction in detail, the capsule wall was electrically heated to be a constant heat flux condition. Experimental runs were carried out to investigate the effects of heat flux and initial concentration of aqueous binary solution on both the melting behavior and the heat transfer characteristics of the slush ice. Photographs of flow patterns are presented, and dependence of the double-diffusion on the flow structure is discussed. The results obtained form present study have great importance and usefulness not only for design of the high efficient heat exchanger using the slush ice, but also for operations of the thermal energy storage system.

The recent literature dealing with melting heat transfer inside ducts and over external bodies is reviewed mainly in the context of its application to the latent heat-of-fusion thermal energy storage. The emphasis in the paper is on the fundamental, physical transport phenomena observed during melting of phase change material as well as snow layer and porous media. The important role played by buoyancy-driven fluid flow is in particular discussed and some promising areas for further research are also identified.

An experimental study was conducted to investigate the melting heat-transfer characteristics of an inclined ice plate within a hydrophobic liquid. Recently, both melting of an ice layer and freezing of water within a hydrophobic liquid received increasing attention because of their close relation and their use in Science and Engineering. For example, the freezing of an aqueous solution within a hydrophobic liquid gives a basic model for the freezing of biomaterials. Furthermore, the melting of an ice layer has close relations to cold thermal storage using ice. In the present study, both perfluolocarbon (PFC) and silicon oil were adopted as the testing liquids. The ambient liquid temperatures ranged from 5 to 40 degrees C. The inclination angle of the ice plate was varied from 0 to 180 degrees at 30 degrees steps. The experimental results revealed that the inclination angle of the ice layer has a vital effect on the melting heat-transfer characteristics of the ice.

Freezing of turbulent water flow between two horizontal cooled parallel plates with the separated region has been investigated experimentally. The flow separation was induced by vertical plates (two-dimensional orifice) situated at the inlet of the parallel plates. The degree of flow separation was varied by employing vertical thin plates of various heights. Three kinds of the vertical plates with 8.0, 9.8, and 12.5 mm in height were utilized. The Reynolds number and the cooling temperature ratio, respectively, ranged from 3.45 x 10(3) to 1.73 x 10(4) and from 7.0 to 20.0. The measurements show that the flow separation exerts a marked influence on the local ice formation characteristics. The location of the first ice layer step and the average heat transfer at the ice surface were found to be correlated as a function of the Reynolds number, the cooling temperature ratio, and the orifice height ratio.

Measurements of the surface tension, viscosity, and thermal conductivity of LiBr and LiSCN aqueous binary solutions have been performed to determine the thermophysical properties near the equilibrium freezing temperature. A differential capillary-rise method for surface tension and the transient hot-wire method for thermal conductivity were employed. Furthermore, a rotational viscometer was utilized for the measurement of viscosity. Correlation equations for the data of the aqueous binary test solutions as a function of temperature and concentration are presented.

An experimental study has been performed to investigate the melting heat transfer characteristics of a forced-convection slush ice flow in a horizontal rectangular duct. Slush ice, which is a mixture of fine ice particles and ethylene-glycol aqueous solution, was adopted as a testing material and was heated by the top or the bottom wall of the rectangular duct. The heat transfer characteristics at both of the bottom and the top walls were extensively determined under a variety of conditions of heat flux, velocity of slush ice flow, and flow channel height of test section. The results revealed that the forced-convection heat transfer characteristics of slush ice is markedly effected by the I.P.F. (Ice Packing Factor) distribution near the heated walls owing to the change of parameters.

The paper is concerned with measurements of the surface tension of aqueous binary solutions at low temperatures. The effects of both temperature and concentration on the surface tension of CaCl2, NaClO3, and propylene glycol have been investigated. A differential capillary-rise method was employed for the measurements. The results showed that the surface tension of CaCl2 and NaClO3 increases monotonically as the concentration of the solution increases, while for the propylene glycol solution the surface tension decreases with increasing concentration. The surface tension of the testing liquids was found to be an almost-linear function of temperature from 20°C to just above the freezing temperature. Equations for the surface tension of the three aqueous binary solutions as a function of temperature and concentration are presented.

Experiments were performed to determine the effect of salinity level on the melting heat transfer characteristics of a horizontal ice cylinder immersed in quiescent saline water. Emphasis was placed on interpreting the heat transfer mechanism which dominates the solid-liquid interface situation. Measurements were carried out for saline water of 0.5–3.5 wt% in salinity, while the ambient temperature ranged from 1.8 to 24.0°C. Flow visualization was employed to investigate the transient flow patterns and corresponding solid-liquid interface locations. It was found that the flow patterns around the ice cylinder were a strong function of the saline water concentration, which then considerably affected the local heat transfer coefficient along the melting ice cylinder.

Measurements of surface tension have been performed to determine the effects of both temperature and concentration on the surface tension of aqueous solutions of D-Sorbitol, potassium chloride, and ammonium chloride. A differential capillary-rise method was employed for the measurements. The results showed that the surface tension of test solutions increased as the temperature decreased and that the surface tension of chloride solutions increased with an increase in its concentration, while for D-Sorbitol solution the surface tension decreased with increasing concentration. Correlation equations for the surface tension of three aqueous binary solutions as a function of temperature and concentration were determined.

Experiments on the melting of a vertical ice layer immersed in immiscible liquid yielded quantitative results both for the timewise evolution of the melting front and the heat transfer. Vegetable oil, which was contained in a rectangular vessel, was adopted as a testing liquid. A bubble-free ice block stuck on a cooled wall was installed vertically in the vessel. The experiments were carried out for the immiscible liquid temperatures from 7.6 to 30.0 °C, while for the cooled wall temperatures from 0 to −11.5 °C. The flow structure of the liquid and the melting front were extensively observed and recorded photographically. It was found that the heat transfer and the rate of melting are significantly affected by a couple of fluid motions of both the water melt induced by melting of ice and the immiscible liquid based on free convection.

Melting of a vertical ice layer immersed in immiscible liquid has been investigated experimentally to determine the interaction of melt flow based on ice melting and free convection induced by buoyancy in the liquid. Oil, which was contained in a rectangular vessel, was utilized as a testing liquid. During the melting process the solid-liquid interface behavior as well as the ambient liquid flow patterns were extensively observed. Three distinct flow regimes were identified for the ambient liquid temperatures of 7.6 to 30.0°C covered. Photographs of flow regimes are presented, and dependence of the flow structure on the melting morphology is discussed. The local/average heat transfer coefficient at the melting interface and the melt fraction were determined as a function of the ambient liquid temperature as well as melting time.

An experimental study has been performed to determine the melting heat transfer characteristics of a horizontal ice cylinder immersed in an immiscible liquid. Vegetable oil, which was contained within a horizontal heated copper tube, was adopted as a testing liquid. A bubble-free ice cylinder was situated at the center of the tube. The experiments were carried out for the heated tube temperatures ranging from 8.0 to 30.0 °C, while for the cooled tube temperatures from −5.0 to −13.0 °C. The flow pattern of the liquid and the ice-liquid interface shape of the ice cylinder being formed through melting were extensively observed and recorded photographically. The local/average heat transfer coefficient along the ice cylinder at steady state was determined as a function of the heated tube temperature as well as the cooled tube temperature. The measurements show that the ice layer profiles at steady state are quite similar irrespective of the thermal conditions.

Experiments were performed to investigate the melting of liquid ice along a bundle of horizontal heated cylinders. A mixture of fine ice particles and ethylene glycol aqueous solution was adopted as the liquid ice for the test. In one set of experiments, the liquid ice was a quiescent layer, whereas in a second set of experiments the liquid ice was a fluidized bed layer. Measurements were carried out for a range of parameters such as initial concentration of aqueous binary solution, heat flux, and airflow rate for fluidization. The heat transfer coefficient for the fluidized liquid ice bed was found to be more than 25 times as large as that for the quiescent liquid ice bed.

Measurements of the surface tension have been carried out to determine the effects of both temperature and concentration on the surface tension of aqueous solutions of sodium chloride, propylene glycol, and ethylene glycol. A differential capillary-rise method was employed for the measurements. The results show that the surface tension of the ethylene glycol solution and the propylene glycol solution increases as the concentration of the solution decreases, while for the sodium chloride solution the surface tension increases monotonically as the concentration increases. The surface tension of the liquids was found to be an almost-linear function of temperature from 20°C to just above the freezing temperature. Equations for the surface tension of the three binary aqueous solutions as a function of temperature and concentration are presented.

An experimental study of the transient solidification of an aqueous binary solution from a vertical cooled plate is reported in this paper. A copper plate of the flow duct, which has 50 mm×70 mm in cross-sectional dimension and 500 mm in length, was cooled uniformly. Ethylene-glycol solution was adopted as a testing liquid. The dependence of the plate wall temperature, the flow rate, the entry-liquid concentration, and the entry-liquid temperature on the solidification characteristics were extensively determined. The data reveal that the characteristics of the frozen layer at both the onset and the steady state could be favorably classified as a function of Reynolds number and the cooling temperature ratio. The correlation of the averaged frozen-layer thickness at the steady state was determined.