It can be said that refrigeration and air-conditioning technology in Korea dates back to the ancient dynasty, all the way up to the Sokkuram(700s) and Seokbinggo(1700s), But modern refrigeration and air-conditioning technology was first developed in and introduced to Korea in the1960swith the modernization of Korea, Today it is at a level which meets that of advanced countries in both the industrial and domestic fields. As of 2003, there were about 700 companies that owned cold storage/freezing/refrigeration facilities, with cold storage capacity of about 2,000, 000tons and capacity per company of about 3,000 tons. These facilities most are continuously expanding and automating their facilities. 62 million units of refrigeration and air-conditioning machinery and equipment were produced in 2003, worth a total of 7.7 trillion won(about 7.7 thousand million US$). On the academic side there are 9 universities and 12 junior colleges with courses in either refrigeration and air-conditioning or architectural equipment. Academic societies such as the Society of Air-conditioning and Refrigerating Engineers of Korea(SAREK), and industrial societies like the Korean Association of Refrigeration(KAR) are active members of the refrigeration and air-conditioning industry. The1eare also national/government-established research institutions such as the Korea Institute of Science and Technology(KIST), the Korea Institute of Machinery and Materials (KIMM), the Korea Institute of Energy Research(KIER), and the Korea Institute of Industrial Technology (KITECH).

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Experiments on the natural convective heat transfer of the carbon dioxide to a vertical cooling cylinder were carried out both in the sub-and super-critical pressure regions near the critical point and the fluid flow around the cylindrical heat transfer surface were observed. In the subcritical region, experiments on the condensation were conducted for both saturated and superheated vapors, and in the supercritical pressure region, experiments on the heat transfer from fluid being in the pseudocritical temperature and beyond the pseudocritical temperature have been done. In the supercritical region, the "liquid-like" fluid layer was observed and also heat transfer coefficient showed a very similar tendency to the condensation heat transfer. Thus, similarities of the fluid flow and the heat transfer between the sub- and super-critical pressure regions was found.

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In this study, latent heat of fusion of ice in aqueous solutions was measured to understand latent heat of fusion of ice slurries. Propylene glycol, ethylene glycol, ethanol, NaCl and NaNO₃ solutions were examined as the aqueous solutions. In the measurement, pure ice was put into the solution, and the temperature variation of the solution due to the melting of the ice was measured. Then, the effective latent heat of fusion was calculated from energy balance equation. When ice melts in solution, the concentration of the solution varies due to the melting of the ice, and dilution heat must be considered. Therefore, the latent heat of fusion of ice in aqueous solutions was predicted by considering the effects of dilution and freezing-point depression. The latent heat of fusion was also measured by differential scanning calorimetry(DSC) to compare the results obtained from the experiments with that obtained by DSC. As the result, it was found that the effective latent heat of fusion of ice decreased with the increase of the concentration of solution, and the effective latent heat of fusion was calculated from latent heat of fusion of pure ice and the effects of freezing-point depression and the dilution heat.

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For ice storage, one of authors has studied new ice slurry formed by cooling water-oil mixture with stirring. When the mixture is stirred in a vessel, the oil is charged by static electricity due to friction. If the vessel can attract charged oil, prevention of ice adhesion to cooling wall may be realized. There for, in this paper, in order to observe behavior of charged oil-water droplet or mixture in a electric field by a high speed camera or video camera, two types of experiments were carried out. One was that oil-water droplet charged by static electricity was made to fall plumb down between two electrodes with electric field or without electric field, varying the water content of droplet. The other was that a constant voltage was applied on the vessel filled with oil-water mixture with stirring. From the observations, it was confirmed that attracting force between the charged wall(electrode) and charged oil acted.

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The absorption of vapor by LiBr aqueous solution falling on a vertical wall was analyzed numerically with an assumption of a laminar liquid film with a smooth surface. Giving the wall temperature obtained by the experiment for in-tube absorption, the change in the absorption process along the wall was discussed with looking particularly at the effect of solution subcooling at the inlet. Then the experiment was compared with the theoretical analysis with respect to the wall heat flux, the absorption rate and the heat and mass transfer coefficients to elucidate the effect of wavy, non-uniform liquid film flow on the absorption process.

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This study is focused on an emulsion as a new thermal storage material for ice storage. Two types of emulsions are made of oil-water mixture with a little additive. Oils used are silicone, light and lump oils. Water contents of emulsions are 70,80 and 90 %. The additive is amino group modified silicone oil, and there is no depression of freezing point for the emulsions because of its hydrophobic property. In order to know structures of emulsions, those electric resistances were measured. And components of liquids separating from emulsions were investigated. From above results, it was found that one was W/O type and the other was O/W type. And then, adaptability of two emulsions to the ice storage was discussed, and then, it was found that a high performance ice slurry could be formed by the W/O type emulsion.

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In order to measure cooling capacity of unit coolers, a few methods have been practically used. But all of them have serious defects that worsen measuring accuracy. Authors propose a novel method for measuring cooling capacity, which has distinct superiorities in high accuracy and brief measuring time. The method employs a short duct on which test cooler and electric heater are installed. The duct is thermally insulated and it has a fan to make air flow inside of the duct. The cooling capacity can be measured by reading electric power meter applied to the heater, under the condition that the temperature at the inlet and the outlet of the duct are equal. A test apparatus that realizes the proposed method is developed to make experiments for validating its feasibility. Preliminary tests disclose that there is fatal temperature deviation in a cross section at the outlet of the duct caused by configuration of heater unit, which spoils the measuring accuracy. Then, a specially designed air mixer is applied to the duct, which successfully suppresses the temperature deviation. Through the tests under various conditions, averaged measuring accuracy is obtained as about 2%, which proves the proposed method can be successfully applied.

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A system analysis has been performed for the multi-effect absorption chiller (MEAC) applied as a bottoming system of 30kW class hybrid system including micro gas turbine (MGT) and solid oxide fuel cell (SOFC) hybrid system. In this paper, an intermediate wasted heat utilization (IWHU) system is suggested for lifting up the energy efficiency of the whole system and coefficient of performance (COP) of MEAC. From the results, the suggested IWHU system was found to show the very high energy efficiency compared with a terminal wasted heat utilization (TWHU) system that uses only the heat exhausted from the terminal of MGT/SOFC system. When TWHU system is applied for MEAC, the utilized heat from the MGT/SOFC system is found to remain low because the temperature difference between the high temperature generator and the wasted heat becomes small. Then, the energy efficiency does not become high in spite of high COP of MEAC. On the other hand, the IWHU system could increase the utilized heat for MEAC as performs effectively. The exergy efficiency of IWHU system is also revealed to be higher than that of a direct gas burning system of MEAC, because the wasted heat is effectively utilized in the IWHU system.

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A field-test of solar assisted desiccant evaporative cooling process has been carried out, which is a quite attractive cooling / dehumidification process considering various environmental problems caused by conventional electricity driven air conditioners. The process performance has been examined by means of temperature drop between outside air and supply air and COPs (COP value based on solar irradiation). This cooling performance was strongly influenced by solar irradiation and ambient air condition. Stable irradiation produced a higher regeneration temperature resulting higher dehumidifying performance. At one day with as table solar irradiation, the cooling process could produce cool supply air of 18.7°C against the ambient air of 30.1°C and averaged COP, was 0.41. On the other hand, unstable irradiation due to some clouds made the dehumidifying performance lower. However, decrease in the cooling performance was small compared to that obtained at the stable irradiation condition. This is due to buffering by thermal storage of the water circulating in solar collectors. Influence of ambient humidity on the cooling performance was rather serious. At higher humidity condition, the amount of dehumidified water became larger due to increase of effective adsorption capacity of the desiccant rotor. However, the temperature drop was decreased to 6.9°C. This behavior was mainly due to simultaneous increase of humidity and temperature in the dehumidified air. In this situation, an effective evaporation in the following water spray evaporative cooler did not occur.

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Performance analysis was made for the absorption refrigeration cycle using TFE/NMP as a working fluid. In the calculation the steady states model, and the separation and mixture of refrigerant model were constructed. The experimental equipment of the absorption refrigeration cycle was also manufactured. The calculation model and the experimental equipment consisted of the generator, the condenser, the evaporator, the absorber, the partial condenser, the rectifier, the reservoir, the heat recovery heat exchanger, the solution pump and the expansion valve. The reservoir was used to store the liquid refrigerant for changing the solution concentration in the cycle. The calculation and experimental results showed the agreement at the lower generation temperature, but presented the opposite trend because of the influence of the heat release in the partial condenser. The calculation and experimental results showed the good agreement for the separation and mixture of refrigerant process. In results, it was found that this absorption refrigeration cycle using TFE/NMP as a working fluid had possibility to utilize recovering the wide range waste heat to energy.

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In a factory with a clean room facility in cold regions, dew-condensation on walls of the facility is one of the most serious problems in winter. In this study, a new dehumidification system in which a steam permeability film is located between humid air in a clean room and dry air from outside to exchange steam is proposed. This system can treat a lot of humid air with small energy only for driving fans to flow air. Some films are examined in two kinds of steam exchangers; double tube type and flat p1ate type. Steam permeability resistance and therma1 resistance of each film are first obtained in a double tube type exchanger. An analytica1 model for a flat plate type exchanger is then proposed, which shows good agreement with experimental data. Steam and heat transfer characteristics of a flat plate type exchanger are also evaluated experimentally. One film on a flat plate type exchanger shows dehumidification capacity of 0.033g/s(=120g/h )with its area of 2.232m².

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A functional fluid was made by adding a small amount of additive to a water-silicon oil mixture with 90 vol% water content, and the functional fluid could be transformed into an ice slurry by cooling with stirring. The ice slurry had many excellent characteristics compared with the former ones. By a new ice formation system which authors proposed for ice storage based on previous results of authors' studies, the ice slurry could be formed continuously for 5-10 hours. In this paper, experiments were carried out, varying operating condition, and then, optimal operating conditions were discussed to improve performance of present system still more. From experimental results, the conditions that amount of recovery ice increased were clarified. Moreover, time-dependencies of shape and size for formed ice particles were also shown. Moreover, it was clarified the reason why the freezing point of functional fluid was risen by repeated ice formation, its measure was discussed, and then, it was found that it was possible to form and recover more amount of ice than that before rise of the freezing point.

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A secondary refrigerant can be produced by using a multi-component material-such as a solution of some material in water, where there exists a liquid-solid co-existent region. Using this solid-liquid co-existent region, if we can form a two-phase solid-liquid flow, a high performance secondary refrigerant can be obtained. In addition, if the components of the multi-components material are existent in the nature, the secondary refrigerant can be used as a natural secondary refrigerant. In the present study, possibility of forming a new secondary refrigerant was investigated using a urea-water mixture. We made visual observations on crystal growth in a urea-water mixture, and using this information, we developed a new fluid latent heat storage material. And the differential scanning calorimeter (DSC) was used to investigate the phase diagram and the latent heat of a urea-water mixture. In addition, based on this phase diagram, the experiments were conducted under stirred conditions and fluid latent hest storage materials were investigated for various concentrations of urea-water mixtures.

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This paper described the technique of predicting the performance of a cyclone oil separator. The oil droplet diameters in refrigerant(R407C)-refrigerating oil were predicted from the experiment by nitrogen-oil. Furthermore, at heoretical analysis model in consideration of both the centrifugal separation and the gravity separation was developed, and the oil separation efficiency was predicted by the Monte Carlo method. The numerical result agreed with the experimental result within an error of 3% in the range of the refrigerant f10w rate 100-600kg/h when the inlet velocity of the oil droplets were about 0.5 times of the refrigerant velocity. In addition, the numerical result showed the separation ratio of the gravity separation and the centrifugal separation to the refrigerant flow rate.

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The experiments and calculations were carried out to evaluate the transient operation characteristics of a cooling system with natural circulation loop using CO₂. The characteristics of the reverse circulation observed under the supercritical state were analyzed from a point of the air intake temperature profile in the inlet of the heat exchangers. As a result, the air intake temperature profile causes the driving head difference for the reverse circulation. In addition, the driving head difference for the reverse circulation depends on the density change to temperature under the supercritical state. Also, a new fan control method has been developed to convert the reverse circulation into the normal circulation. The effect of the developed fan control method was confirmed from the experimental results.

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In order to find the optimum operation condition of a distributed power supply system of 30kW class micro gas turbine (MGT) and solid oxide fuel cell (SOFC) hybrid system with the combination of line electric power and supplied gas, a system analysis has been performed. In this study, an absorption chiller and a boiler were mounted to utilize the exhausted heat from the MGT/SOFC system. The time variation of energy consumption in 24 hours for house and market models was taken into consideration for the calculation of the energy saving ratio of the present system. The operation ratio defined with the ratio of power supply of MGT/SOFC system to the power required at the peak load was changed as a parameter. From the comparison with the system using line power and gas, it is found that the present system shows high energy saving ratio around 0.4 of the operation ratio, but the energy saving ratio severely decreases in the range of high operation ratio. In this study, it is revealed that the thermal storage system effectively improves the energy saving ratio especially for the house model in winter season.

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In this paper, the economical and energy saving advantages of the distributed energy system, which consists of a micro gas turbine-solid oxide fuel cell hybrid power generation system, waste heat recovery devices and air-conditioning equipments, are investigated. Firstly, the thermodynamical performance evaluation of the hybrid system with the heat recovery devices is discussed to estimate the energy conversion efficiency of the whole system. Secondly, by using 1inear programming technique, the optimum operation planning of the cogeneration plant based on the hybrid system is discussed to predict the reduction of the primary fuel consumption and utility cost. Throughout detailed investigation, it is found that the energy conversion efficiency, which includes the waste heat utilization, reaches over 80% (LHV). In addition, the optimum operation of the hybrid system, of which power generation capacity is appropriate for the energy demand, achieve the highly effective energy saving against the traditional energy supply scheme, that is, the fuel reduction reaches around 40% to the conventional value.

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For the development of a simple and compact power generator driven by waste heat, working fluids and an expander were studied, then a practical electric power unit was put to test. Many working fluids were calculated with the low temperature power cycle (evaporated at 77°C, condensed at 42°C),and TFE,R123,R245fa were selected to be suitable for the cycle. TFE(Trifluoroethanol CF₃CH₂OH) was adopted to the actual power generator which was tested. A radial turbine was adopted as an expander, and was newly designed and manufactured for working fluid TFE. The equipment was driven by hot water as heat source and cooling water as cooling source, and generated power was connected with electric utility. Characteristics of the power generating cycle and characteristics of the turbine were obtained experimentally.

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