• Economic and Environmental Geology
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• v.25 no.3
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• pp.225-232
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• 1992

The hydrothermal alteration is evaluated using multicomponent equilibrium calculations with the program CHILLER for the reactions between hydrothermal water and rhyolite at the temperature of $300^{\circ}C$ and pressure of 500 bars. The chemical-reaction model on the depositional processes of the sericitite confirms that the hydrothermal water-rock interaction(hydrothermal alteration) is the main mechanism of the sericitite formation. The principal change in the aqueous phase during the reaction is the pH increase. Overall trends for the major species are the increase in total molalities of K, Ca, $SiO_2$, Al, Mg, Fe, Na, and sulfide in solid phase with hydrothermal water-rhyolite reaction and the decrease of them in aqeous solution by precipitation of hydrothermal products. Quartz and sericite are the first minerals to form. The sequence of minerals to precipitate following them is chlorite, epidote, pyrite and microcline as water/rock ratio decreases. Although calculated results cannot duplicate the complexities of natural hydrothermal alteration, the calculation provides thermodynamic constraints on the natural process. The calculation results resemble those of experimental studies. Sericitite forms where pH decreases and water/rock ratio increases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.87-96
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• 2008

Flow condensation heat transfer coefficients(HTCs) of R123 and R245fa are measured in a horizontal plain tube. The main test section in the experimental flow loop is made of a plain copper tube of 9.52 mm outside diameter and 530 mm length. The refrigerant is cooled by passing cold water through an annulus surrounding the test section. Tests are performed at a fixed saturation temperature of $50\;{\pm}\;0.2\;^{\circ}C$ with mass fluxes of 50, 100, $150\;kg/m^2s$ and heat flux of $7.3{\sim}7.7\;kW/m^2$. Heat transfer data are obtained in the vapor quality range of $10{\sim}90%$. Test results show that the flow condensation HTCs of R245fa are overall 7.9% higher than those of R123 at all mass fluxes. The pressure drop of R245fa is smaller than that of R123 at the same heat flux. In conclusion, R245fa is a good candidate to replace ozone depleting R123 currently used in chillers from the view point heat transfer and environmental properties.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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• pp.971-976
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• 2006

The objectives of this paper are to study the characteristics of pool boiling heat transfer for enhanced tubes used in the evaporator of turbo chiller and to provide a guideline for optimum design of an evaporator using HFC134a. Three different enhanced tubes are tested at 4 different saturation temperatures. The wall super heated temperature difference ranges from $0.5^{\circ}C\;to\;3.5^{\circ}C$. The refrigerant, HFC134a evaporates on the outside of the tube while the chilled water flows inside the tube. This study provides experimental heat transfer coefficients for evaporation on the enhanced tubes. It is found that the turbo-II tube provides the highest heat transfer coefficient.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.2
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• pp.1-10
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• 2000

This research is concerned with the enhancement of heat transfer by surfactant added to the aqueous solution of LiBr. Different vertical tubes were tested with and without an additive of normal octyl alcohol. The test tubes are a bare tube, a groove tube, a corrugated tube and a spring-inserted tube. The additive concentration is about 0.08 mass%. The heat transfer coefficient is measured as a function of the film Reynolds number in the range of 20~200. Experiments are carried out at higher cooling water temperature of $35^{\circ}C$to simulate an air cooling condition for several kinds of absorber testing tubes. The experimental results with and without surfactant are compared. The enhancement of heat transfer by Marangoni convection effect which is generated by addition of the surfactant is observed in each test tube. Especially, it is clarified that the tube with an spring-inserted has the enhancement effect.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.1
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• pp.65-74
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• 2008

In Korea, air source heat pump system is less efficient than conventional heat source facilities, such as ground source, river water, because the air temperature in winter season is so low that COP of air source heat pump system drops below 3.0. Therefore, the study on the application of heat pump heating and cooling systems is crucial for the efficient popularization of heat pump. In this work, we present the dynamic analysis of energy consumption for the large resident building by heat resistance-capacitance method. The system simulation of water storage air source heat pump is additionally performed by changing of sizes and locations of the hospital building. The computed results show that energy cost of water storage air source heat pump is low, so it is more economical than absorption chiller & heater.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.5
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• pp.357-363
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• 2008

In order to investigate $CO_2$ heat transfer coefficient and pressure drop by PAG oil concentration during $CO_2$ evaporation, the experiment on evaporation heat transfer characteristics in a horizontal micro-fin tube was performed. The experimental apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiment was conducted for various mass fluxes($400{\sim}1200\;kg/m^2s$), heat fluxes($10{\sim}30\;kW/m^2$) and saturation temperatures ($-5{\sim}5^{\circ}C$), and PAG oil concentration($0{\sim}5\;wt%$). The variation of the heat transfer coefficient was different in accordance with the oil concentration. With the increase of the oil concentration, the evaporation heat transfer coefficient decreased and the delay of dryout by oil addition was found. Pressure drop increased with the increase of the oil concentration and heat flux, and the decrease of saturation temperature.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.4
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• pp.17-26
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• 2001

Simulation was conducted using TRNSYS to evaluate the thermal performance of a facility. This facility has a condensing-type heat exchanger which is able to recover the latent energy for the purpose of reducing the heating energy in winter. The boiler and chiller are selected based on the annual peak loads and controlled to maintain the facility at the set temperature of 14~$17^\circ{C}$. Supplied energy by the boiler and recovered energy by the heat exchanger were calculated as a function of number of pass through heat exchanger, kind of fuel and hot water velocity. Simulation results show that about 20% of the total heating load can be recovered by the heat exchanger and the amount of latent heat is increasing with the number of pass. This means that the efficiency of the waste energy recovery system can be increased by using a condensing-type heat exchanger rather than a traditional sensible heat exchanger.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.3
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• pp.267-276
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• 2000

A numerical study has been carried out to find out the optimal design condition of a solar absorption cooling system. The system was composed of solar collectors and an absorption chiller with LiBr/water The System performance with commercial single effect(SE) cycle and a new single effect/double lift(SE/DL) cycle utilizing low temperature hot water was calculated and compared. It was found that the required solar collector area grew exponentially as the overall heat loss coefficient of solar collectors increased. For instance, the required area for cooling capacity of 1 USRT was $17m^2$ if heat loss coefficient was 4 W/$m^2\;cdot\;K$. If heat loss coefficient was doubled($8\;W/m^2\;cdot\;$K), the required collector area was increased by 6 times($100m^2$) .It was also found that the SE-cycle as the heat loss coefficient of solar collectors increased. Generally, a SE/DL-cycle seems to be more advantageous than a SE-cycle if loss coefficient of solar collector is greater than 4 W/$m^2\;cdot\;K$.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.33 no.3
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• pp.50-57
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• 2004

This article reviews absorption cooling R＆D in Europe from the viewpoint of fundamentals, cycle development and applications. The review contains information on R＆D, predominantly of public projects in the field of sorption cooling. We report on research which is performed in Europe with some stress on Germany. There is progress in fundamentals, thermodynamic cycle design, and also applications. In the fundamentals part the discussion about thermodynamics, working pairs, and heat and mass transfer is reflected. Today's discussion on thermodynamic cycles is not very strong. Main focus is on special solid sorption cycles, compression­sorption hybrids, and open cycles, In the applications part the chilling business is the main issue. Some interest is given to the improvement of efficiency on and the adaptation to low temperature waste heat use, but the stress is on the use of solar energy as heat source. The area of heat pumping for heating purposes is less prominent but not at all negligible. Finally, industrial heat pumping involves the reverse cycle (heat transformer, heat pump type Ⅱ) also, but there is no significant activity.

• Korean Journal of Poultry Science
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• v.41 no.3
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• pp.159-164
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• 2014

This study was conducted to investigate whether water chilling had effect on water retention, freshness or internal temperature of chicken carcasses during chilling or storage in two different chicken processing plants (designated as A and B). A total of 240 carcasses from chicken processing plants (n = 120 per chicken processing plant) was randomly sampled and evaluated the effect of water chilling on carcass characteristics (i.e., water retention, water loss or freshness during chilling or storage). Torrymeter value was used as an indicator of freshness in chicken carcasses. Water chilling did not affect carcass water retention between the processing plants. However, chicken carcasses processing in B plant exhibited significantly higher freshness (p<0.05) compared with those in A plant. This difference in freshness was mainly due to the longer transit time through the water chiller in A versus B plants. Water loss of carcasses during storage was not different between plants. It was found that carcass freshness can be affected by water chilling time as manifested in this study. Further study is warranted to see whether freshness or microbiological status of chicken carcasses may be affected depending on the chilling methods, i.e., air or water chilling.