• 설비공학논문집
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• 제16권7호
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• pp.630-638
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• 2004

Liquid desiccant dehumidification systems have the ability to provide efficient humidity and temperature control while saving the electrical energy requirement for air conditioning as compared to a conventional system. The dehumidifier and the regenerator form the heart of this system. The latent part of the cooling load is overcome using liquid desiccant. The model regenerator has been designed to study the absorption characteristic of the aqueous triethylene glycol (TEG) solution which is in the flow range from 20 to 50 LPM. Also, this system designed that was able to change the height of the regenerator and dehumidifier. Because the effect of performance have different result according the height. The effect of performance factors of the regenerator with inlet solution flow rate, air flow rate, solution concentration, solution temperature, brine temperature, air temperature and inlet air relative humidity have been analyzed. Data obtained are useful for design guidance and performance analysis of the hybrid air conditioning system.

• 설비공학논문집
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• 제18권11호
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• pp.888-895
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• 2006

The present study has been conducted to investigate the effects of Reynolds number on heat/mass transfer and pressure drop characteristics in a rotating smooth two-pass duct. For stationary cases, the heat/mass transfer and pressure drop Is decreased on turning region of both leading and trailing surfaces as Reynolds number increases. For rotating cases, increment of Reynolds number affects differently the heat/mass transfer and pressure drop on the leading and trailing surfaces. In the first pass, for example, the heat/mass transfer on the leading surface is greatly increased, though the heat/mass transfer on the trailing surface is almost the same. The reason is that effect of the main flow is more dominant than effect of secondary flow. In particular, it gave decrement of the heat/mass transfer and the pressure drop at turning region and upstream region of second pass for both non-rotating and rotating cases.

• 설비공학논문집
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• 제16권12호
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• pp.1134-1139
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• 2004

The evaporative heat transfer coefficient of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and evaporator (test section). The test section consists of a smooth, horizontal stainless steel tube of inner diameter of 7.75 mm. The experiments were conducted at mass flux of 200 to 500 kg/m$^2$s, saturation temperature of -5 to 5$^{\circ}C$, and heat flux of 10 to 40kW/m$^2$. The test results showed the heat transfer of $CO_2$ has a greater effect on nucleate boiling more than convective boiling. Mass flux of $CO_2$ does not affect nucleate boiling too much, and the effect of mass flux on evaporative heat transfer of $CO_2$ is much smaller than that of refrigerant R-22 and R-134a. In comparison with test results and existing correlations, correlations failed to predict the evaporative heat transfer coefficient of $CO_2$, therefore, it is necessary to develope reliable and accurate predictions determining the evaporative heat transfer coefficient of $CO_2$ in a horizontal tube.

• 설비공학논문집
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• 제16권12호
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• pp.1218-1226
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• 2004

This paper presents thermal behaviors and performances of a fresh air load reduction system by using earth tube system combined with air-heated solar collector. The earth tube system reduces a fresh air load by heat exchange with soil throughout the year. In the previous experimental research, it was clarified that the earth tube system was very useful as a fresh air load reduction system. However, since outlet temperature of the fresh air which was heated by earth tube system was below 15$^{\circ}C$ in winter, it is not suitable to introduce the fresh air into the place of residence directly. Therefore, a simulation model using the simple heat diffusion equation was used to examine a rising effect of outlet air temperature in winter by combining with air-heated solar collector. An improvement of annual performance by control of operation is also quantitatively examined. In conclusion, it is confirmed that its performance is improved by control of operation throughout the year and outlet air temperature rose by combining with air-heated solar collector.

• 식품보건융합연구
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• 제8권3호
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• pp.11-23
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• 2022

Processed meat products are prone to oxidation and spoilage due to prolonged storage. By using natural spices that are harmless to the human body and have antioxidant and antibacterial effects to replace synthetic preservatives in consideration of consumers' qualitative consumption patterns that pursue nutrition and safety, and stimulate appetite with taste, aroma, and color of food. The purpose of this study was to study the effect on the quality characteristics of processed meat products. The spice group had a low crude fat for both the loin and sirloin cuts. Brightness, redness, and yellowness in the chromaticity of beef jerky and PYUNYUK added with spices were different from those of the control group and increased. In terms of texture, all the beef jerky groups increased firmness and friability, and there was a difference between refrigeration and room temperature storage. The elasticity and stickiness decreased with the lapse of storage period. In the PYUNYUK, the flavor of the spice group was low and the meat quality was soft. It was found that the addition of natural spices to replace synthetic preservatives had different effects on processed meat products and had a positive effect on general ingredients, mechanical properties, physicochemical properties, and sensory quality properties.

• 한국축산식품학회지
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• 제23권1호
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• pp.50-55
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• 2003

신선 돈육을 준비하여 두 가지의 conveyer 이동 속도(10과 20 Hz)로 전자선을 조사(3.0 과 5.0 kGy)한 후 저장 중 돈육의 지방 산화와 일반 세균 그리고 중온균의 증식 억제를 비교하여 측정하였다. 본 실험 결과를 종합하여 볼 때 전자선의 처리는 확실하고 뚜렷한 살균 효과가 있는 것으로 밝혀졌으며 대체적으로 3.0 보다는 5.0 kGy 처리육의 살균 효과가 훨씬 우수하였다. 지방의 산화는 전자선 조사에 의해서 촉진되는 것으로 확인되었기 때문에 전자선을 돈육에 활용하려면 전자선 처리에 의한 지방의 산화를 억제해야 하는 필요성이 절실하게 대두되고 있다. 전자선의 conveyer이동 속도를 10에서 20 Hz로 증가시켰을 때 살균 효과가 감소한다는 사실은 의외의 결과이나 전자선의 조사가 대조구에 비해 일반세균과 중온균의 증식은 억제하였다. 한편 conveyer 이동 속도를 10에서 20 Hz로 증가시킨 경우 돈육의 산화가 억제된다는 사실은 매우 고무적이며 전자선 처리에 의한 살균 효과를 식육에서 극대화하기 위하여는 본 실험에서 확인된 전자선 주사 속도의 증가에 의한 항산화 작용 이외에 더 추가적으로 탈기 변형 포장 방법 등을 도입하여 산화를 더욱 억제하여야 할 것으로 생각된다.

• 설비공학논문집
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• 제16권4호
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• pp.355-367
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• 2004

The heat transfer and friction characteristics of the heat exchangers having sinusoidal wave fins were experimentally investigated. Twenty-nine samples having different waffle heights (1.5 mm and 2.0 m), fin pitches (1.3mm to 1.7mm) and tube rows (one to three) were tested. Focus was given to the effect of the waffle configuration (herringbone or sinusoidal) on the heat transfer and friction characteristics. Results show that the sinusoidal wave geometry provides higher heat transfer coefficients and friction factors than the herringbone wave geometry, and the difference increases as the number of row increases. The i/f ratios of the herringbone wave geometry, however, are larger than those of the sinusoidal wave geometry. Compared to the herringbone wave geometry, the sinusoidal wave geometry yielded a weak row effect, which suggests a superior heat transfer performance at the fully developed flow region. Possible explanation is provided considering the flow characteristics in wavy channels. Within the present geometric range, the effect of the waffle height on the heat transfer coefficient was not prominent. The effect of the fin pitch was also negligible. Existing correlations highly overpredicted both the heat transfer coefficients and friction factors. A new correlation was developed using the present data.

• 설비공학논문집
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• 제17권10호
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• pp.914-921
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• 2005

In this study, the 1/20 reduced-scale experiment using Froude scaling were conducted to investigate the effect of longitudinal ventilation velocity on the burning rate in tunnel fires. The methanol pool fires with heat release rate ranging from 2.02 kW to 6.15 kW and the n-heptane pool fires with heat release rate ranging from 2.23 kW to 15.6 kW were used. The burning rate of fuel was obtained by measuring the fuel mass at the load cell. The temperature distributions were observed by K-type thermocouples in order to investigate smoke movement. The ventilation velocity in the tested tunnel was controlled by inverter of the wind tunnel. In methanol pool fire, the increase in ventilation velocity reduces the burning rate. On the contrary in n-heptane pool fire, the increase in ventilation velocity induces large burning rate. The reason for above conflicting phenomena lies on the difference of burning rate. In methanol pool fire, the cooling effect outweighs the supply effect of oxygen to fire plume, and in n-heptane pool vice versa.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.68-73
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• 2006

The present paper deals with an experimental study of boiling heat transfer characteristics of R-290, and is focused on pressure gradient and heat transfer coefficient of the refrigerant flow inside horizontal smooth minichannel with inner diameter of 3.0 mm and length of 2000 mm. The direct heating method applied for supplying heat to the refrigerant where the test tube was uniformly heated by electric current which was applied to the tube wall. The experiments were conducted with R-290 with purity of 99.99% at saturation temperature of 0 to $10^{\circ}C$. The range of mass flux is $50{\sim}250kg/m^2s$ and heat flux is $5{\sim}20kW/m^2$. The heat transfer coefficients of R-290 increases with increasing mass flux and saturation temperature, wherein the effect of mass flux is higher than that of the saturation temperature, whereas the heat flux has a low effect on increasing heat transfer coefficient. The significant effect of mass flux on heat transfer coefficient is shown at high quality, the effect of heat flux on heat transfer coefficient at low quality shows a domination of nucleate boiling contribution. The heat transfer coefficient of the experimental result was compared with six existing heat transfer coefficient correlation. Zang et al.'s correlation(2004) gave the best prediction of heat transfer coefficient.

• 설비공학논문집
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• 제15권8호
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• pp.630-640
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• 2003

As tunnel ventilation has recently been playing a major role in the tunnel construction and maintenance, longitudinal ventilation systems with jet fans have been utilized a great deal because they are economical and effective. However, due to the length of tunnels and heavy traffic, it is hard to take the field measurements. In this study, therefore, the computer simulation and the model experiment of producing a wind tunnel were carried out simultaneously and the results were compared. The ultimate objective of this research was to interpret the air flow pattern inside the tunnel with a jet-fan was set up, and to offer the useful data for jet-fan installation and operation. The experiment was carried out with varying the jet-fan diameters, location of installation, the discharge velocity. Result showed that as the initial static pressure came up with the negative pressure, the tunnel air flowed into the inside of tunnel from outside due to the entrainment-effect and the backflow-phenomenon by separation-effect was observed in the lower half part of the tunnel. As the jet-fan was getting closer to the tunnel wall, the entrainment-effect caused by the interaction with the wall was increased; however, the mixing distance and irregular flow section became longer, and also the air pressure loss generated by wall friction was large.