The heat transfer characteristics of binary refrigerant mixtures in a plate-fin condenser are experimentally investigated using a vapor compression heat transformer, in which binary refrigerant mixtures of R 134a/ R 123 are used as the working fluid and water is used as both heat sink and source. Pure refrigerants of R 22 and R 134a are also tested as the working fluid. The experimental ranges of heat flux and mass velocity are from 2 to 20 kW/m² and from 50 to 100 kg/m²s, respectively. The heat transfer characteristics of the condensation and vapor single-phase flow of pure and mixed refrigerants are discussed, and empirical correlation equations of the condensate heat transfer and vapor single-phase heat transfer are proposed. The correlation equation of water-side heat transfer is also presented. Combining these correlation equations with a correlation equation of vapor mass transfer based on the Chilton-Colburn analogy, a prediction model for condensation of the binary refrigerant mixtures in a plate-fin heat exchanger is developed based on the assumption that the phase equilibrium is only established at the vapor-liquid interface. The calculation results for the pure and mixed refrigerants agree well with the present experimental data. The mass transfer characteristics are also revealed from the calculation results.

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The composition separation of R407C is used to improve performance of air conditioners and heat pump water heater units. Therefore, it is important to grasp a separation performance of a packed column rectifier and make a useful nondimensional equation of mass transfer coefficients for design of the rectifier. The experiments were carried out to investigate an influence of the vapor velocity on the separation performance, and an overall mass transfer coefficient of gas side was measured. The nondimensional equation for the mass transfer coefficients was made based on the measured data. The influence of the refrigerant charge and the packed height on the separation performance was evaluated with the experiments and calculated results with the equation. The calculated results agreed with the experimental results.

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An experimental study of the frosting phenomena on the surface of heat exchanger was carried out to obtain the detailed data necessary for developing a high efficient heat exchanger under dry and frosting conditions. The frosting experiment using a fin bundle, which consisted of total 40 copper fins, was performed in 6 test conditions considered air humidity, temperature of heat transfer surface and air velocity as main experimental parameters. The overall heat and mass transfer characteristics such as total frost mass, averaged mass flux, pressure drop, sensible heat flux and latent heat flux, and the local heat transfer characteristics of each fin were investigated. It was found that total frost mass increased with time in all test conditions, and averaged frosting rate and averaged mass flux gradually decreased with time after increasing for the early time period of 0-30minutes. Pressure drop between inlet and outlet of test section also increased with operation time due to narrowing of the cross sectional area between fins by frost deposited. The averaged value of sensible heat flux during each test period was nearly kept constant owing to the same airflow rate, but latent heat flux gradually decreased with running time. It was also found that local heat flux was most large at the fin base, and decreased step by step toward the fin tip.

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The effects of three different sugars (sucrose, trehalose, sorbitol, at 5%) were analyzed and compared against a control for frozen surimi (-25 °C) made from dusky spinefoot, lizard fish and horse mackerel, for a total storage period of 180 days. Kamaboko was prepared at defined time intervals, and its jelly strength (J.S.), water holding capacity (W.H.C.), and whiteness, and the total Ca-ATPase activity of surimi were analyzed. Present results showed that all parameters of sugar free control samples decreased faster than those of sugar added samples during frozen storage.Sugar resulted a good additive for long time surimi conservation for all the species analyzed.

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This paper presents a prediction method for evaporating heat transfer coeffcient of refrigerants fowing in a horizontal spirally grooved tube with consideration of flow regimes. The experimental data employed for development of the correlation equation were measured at pressures 0.2-1.1 MPa, mass velocities 100-300kg/(m²s), heat fluxes5-25 kW/m² and vapor qualities 0.1-0.8 with HCFC123 and HCFC22 using a spirally grooved steel tube with 12mm in average inner diameter, 32 in number of groove, 0.4 mm in depth of groove and 15 degree in helix angle. In the previous paper, the authors showed that the flow patterns of evaporating refrigerant inside a horizontal spirally grooved tube could be classified into four types : annular flow, annular flow with liquid meniscus, separated flow with liquid meniscus and separated flow with dry surface, and proposed the correlations for the borders of each flow regime. In the present paper the correlation equations for heat transfer coeffcient were developed for each flow regime. The calculated heat transfer coefficient showed good agreement with the experimental data for all flow regimes. The mean deviation between the calculated and the measured heat transfer coefficient is ±12.6% for the all present experimental data.

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The spread of absorption heat pump is considered an effective strategy to reduce the emission of greenhouse gases andthe heat island impact. However, its large volume and low efficiency as compare to vapor-compression system haverestricted its application area. In order to develop a compact and high-efficiency absorption heat pump, we propose a newtype of system which adopting triple effect cycle at cooling, while double effect at heating. In addition, unused energy,such as sewage water, is used in this system to improve the COP furthermore.
System performances were evaluated by discussing the COP, highest pressure, highest temperature, strongest solutionconcentration, and energy consumption at part-load operation. By using sewage water as heat source, COP increaseswhile the highest pressure, highest temperature and strongest solution concentration decrease. From a standpointofperformance at heating and energy consumption, it is found that the proposed system works well and more effective thanthe existing system.

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In this study, the thermal characteristics of water including an adsorbent were analyzed by a differential scanning calorimeter, DSC, in the temperature range from -20 to 20°C, and the heat generation by adsorbing the water was measured by a calorific meter, in order to examine the effects of the adsorption characteristics of the adsorbent. As a result, it was found that the surface adsorption water in a micro pore of nanometer order did not freeze and the capillary water could freeze. The capillary water showed the lower melting point than the free water. The latent heat of the capillary water decreased with increasing the adsorption heat of adsorbent.

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Present paper deals with the mist formation in the humid air flowing in the cold parallel plate channel simulating the heat exchanger of air conditioner. The mist formation was numerically predicted by solving boundary layer equations with taking into account the supersaturation due to diameter of foreign nuclei. And the effects of air velocity, temperature and relative humidity of inlet air, cold plate temperature and diameter of foreign nuclei on the mist formation rate were clarified. Furthermore, effects of mist formation on the heat and mass transfer were investigated. The experiment was performed for visualizing the distribution of mist particles at the channel exit and a fairly good agreement with numerical prediction was obtained.

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We have proposed new method that re-circulates vapor refrigerant into the evaporator using an ejector to enhance the evaporating heat transfer in the refrigeration cycle. It makes the evaporating heat transfer coefficient higher by increase of the dryness-quality at the inlet of evaporator. We investigated experimentally the coefficient of performance (COP) of the refrigeration cycle and the evaporating heat transfer coefficient with a proposal means, under various evaporating and condensing temperatures and heat loads. As a result, the COP of proposed cycle is 5-13% higher than the conventional cycle with a D.C. inverter compressor by re-circulation of refrigerant. Furthermore, we investigated the dry-out length in the evaporator by authorized empirical equation and evaluated the optimum flow rate of re-circulation.

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Adhesion between ice and a solid surface causes various problems. In phenomena related to the adhesion of ice, it is important to know the ice adhesion mechanism for optimal design, for instance. It is mentioned that mechanical combination ‘anchor effect’ is the one of the most important factors that determines the adhesion force between ice and a solid surface. The anchor effect is affected by surface roughness. In this paper, the effects of arithmetical mean height and arithmetical mean gradient of a solid surface on adhesive shear strength between pure ice and a copper plate are examined. It was found that the average value of adhesive shear strength between pure ice and a copper plate is 185-633 kPa on Ra=0.0055-0.077 μm and RΔa=0.0024-0.085. Furthermore, it was found that the gradient is more important factor than the height on adhesion from a geometrical model. Because the area dilation rate and force component are depend on the gradient. And on adhesion between pure ice and copper surface, the invariable decided by materials and temperature was calculated and the experimental expression that arranged the relation between surface roughness and adhesive shear strength was proposed.

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In the field of refrigeration and air-conditioning, waste heat to energy using the absorption refrigeration cycle has been gradually familiar. Especially, the expectation has increased to the TFE/NMP as a working fluid that is able to be driven below the atmospheric pressure and under zero degrees Celsius as the next generation absorption working fluid. In the previous study, the performance analysis of the absorption refrigeration cycle with TFE/NMP as a working fluid was examined by the cycle simulation. Moreover the concentration and dilution model was constructed to change the solution concentration in the absorption cycle. In this study, in order to predict the generator outlet vapor concentration related to rectifying process which is necessary for the TFE/NMP, the calculation model which considered the heat and mass transfer was constructed and some calculations were made changing the solution flow rate, inlet concentration of solution, the heat transfer coefficient and the mass transfer coefficient in the generator. Results showed that the calculation model was effective to predict the outlet vapor and solution concentrations.

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The paper presents new measurements on the viscosity for the mixtures of R134a and polyolester oil at low oil-concentrations. The measurements were conducted with a newly developed oscillating cup viscometer making use of polarizer at oil-concentrations between 0 and 16 mass% and temperatures from 278.15 K to 288.15 K. The uncertainty in viscosity was estimated to be less than ±4.3%. It was found that even a small amount of the oil into R134a had a significant effect on the viscosity. It increased exponentially with oil-concentration. Mixing the oil into R134a up to an oil-concentration of 16 mass% tripled the viscosity. A correlation equation as a function of temperature and oil mass fraction was formulated to interpolate the experimental viscosity data.

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Size and shape of ice crystals in frozen food materials are very important because they affect not only quality of foods but also the viability of industrial processing such as freeze-drying of concentration. In this study, 30%wt sucrose solution is used as test samples. For examining the effect of stabilizerspectine and xantan gum is added to the sucrose solution. They are frozen on the cold stage of microscope to be observed their growing ice crystals under the circumstance of -10°C. Their size and shape are measured and quantitatively evaluated by applying fractal analysis. lce crystal of complicated shape has large fractal dimension, and vice versa. It successflly categorized the ice crystals into two groups; one is a group of large size and complicated shape, and the other is a group of small size and plain shape. The critical crystal size between the two groups is found to become larger with increasing holding time. It suggests a phenomenological model for metamorphoses process of ice crystals. Further, it is indicated that xantan gum is able to suppress the smoothing of ice crystals.

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Freeze-thawing process gives significant damages for food structure. Several new techniques have been attempted for quantitative evaluation of the damages. In this study, using NMR (nuclear magnetic resonance) with a stimulated echo method, restricted diffusion phenomena of water molecules was measured for damaged food (onion and tuna) tissues that were subjected to the repeat of freeze-thawing, Through experiments, water permeability of tissue membrane was calculated. The water permeability of fresh tissues for onion showed clearly restricted diffusion, but after freeze-thawing, it disappeared. On the other hand, the water permeability of fresh tuna tissue was small significantly, even though it was a little higher after freeze-thawing. After all, the damage level after freeze-thawing showed a significant difference between onion and tuna. These results support the view that plant tissue is very sensitive to freeze-thawing and that the water permeability of plant is much lower than that of animal.

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A novel technique was developed to monitor the change in three-dimensional (3D) distribution of yeast in frozen bread dough samples in accordance with the progress of mixing process. Application of a surface engineering technology allowed the identification of yeast in bread dough by bonding EGFP (Enhanced Green Fluorescent Protein) to the surface of yeast cells. The fluorescent yeast (a biomarker) was recognized as bright spots at the wavelength of 520 nm. A Micro-Slicer Image Processing System (MSIPS) with a fluorescence microscope was utilized to acquire cross-sectional images of frozen dough samples sliced at intervals of 1 μm. A set of successive two-dimensional images was reconstructed to analyze 3D distribution of yeast. Samples were taken from each of four normal mixing stages (i.e., pick up, clean up, development, and final stages) and also from over mixing stage. In the pick up stage yeast distribution was uneven with local areas of dense yeast. As the mixing progressed from clean up to final stages, the yeast became more evenly distributed throughout the dough sample. However, the uniformity in yeast distribution was lost in the over mixing stage possibly due to the breakdown of gluten structure within the dough sample.

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A novel technique to recognize bubbles in bread dough and analyze their size distribution was developed by using a Micro-Slicer Image Processing System (MSIPS). Samples were taken from the final stage of the mixing process of bread dough which generally consists of four distinctive stages. Also, to investigate the effect of freeze preservation on the size distribution of bubbles, comparisons were made between fresh dough and the dough that had been freeze preserved at .30°C for three months. Bubbles in the dough samples were identified in the images of MSIPS as defocusing spots due to the difference in focal distance created by vacant spaces. In case of the fresh dough, a total of 910 bubbles were recognized and their maximum diameter ranged from 0.4 to 70.5μm with an average of 11.1μm. On the other hand, a total of 1,195 bubbles were recognized from the freeze-preserved sample, and the maximum diameter ranged from 0.9 to 32.7μm with an average of 6.7μm. Small bubbles with maximum diameters less than 10μm comprised approximately 59% and 78% of total bubbles for fresh and freeze-preserved dough samples, respectively. The results indicated that the bubble size of frozen dough is smaller than that of unfrozen one. The proposed method can provide a novel tool to investigate the effects of mixing and preservation treatments on the size, morphology and distribution of bubbles in bread dough.

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To elucidate the effect of freezing rate on the denaturation of myofibrillar protein, we employed a temperature programmable freezer to control the freezing rate. Freezing rates were set from 0.01 to 1 °C/min. Denaturation of myofibrillar protein was assessed by measuring Ca-, Mg-, EDTA(K)- ATPase activities and salt solubility. Freezing at all rates slightly reduced the Ca-ATPase activity, but the difference in the inactivation caused by quick (1°C/min) and slow (0.01°C/min) freezing was less than 12 %. Freezing enhanced the Mg-ATPase, and reduced the EDTA(K)-ATPase activities. The changes were a little greater for the samples frozen slowly indicating that change in the interaction between myosin and actin was modified when frozen slowly. No decrease in the salt solubility was detected for the samples at any freezing rates. The samples were subsequently frozen stored at various temperatures. Myosin denaturation progressed slowly during the storage, and the rate was strongly dependent on the storage temperature. Therefore, it was concluded that freezing rate slightly affected the denaturation of myofibrillar proteins, and storage temperature more severely affected the denaturation.

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The fluctuation in frozen storage temperature was set up by moving the minced meat from chub mackerel reversibly from the room of lower temperature to that of higher temperature for 7 hours every day during 180 days. The freeze denaturation of myofibrillar protein was studied in term the first-order rate (KD) of inactivation of myofibrillar Ca-ATPase. The freeze denaturation rate constant of the myofibrillar protein fluctuated between two different temperatures was same as or higher than the KD in case of constant temperature in higher temperature side.

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