• 설비공학논문집
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• 제27권6호
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• pp.293-299
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• 2015

In Korea, it is the law that an apartment building which consists of over 100 households must have a ventilation system installed, either natural or mechanical. The heat recovery ventilator (HRV) is great way to reduce energy consumption. In this research we confirmed that based on site's construction plan and existing diffuser form, performed purpose CFD which simulates operation in temperatures below $-5^{\circ}C$ to circumstances of installation of an HRV in an apartment. As a result of this research we found that when the diffuser's aperture area was adjusted, the distribution of air temperature and residence time of air was more equally distributed and air temperature was higher, compared to when the diffuser has an identical aperture area. We also found that we are able to increase even more air temperature and air distribution of air temperature and residence time of air was even more equally distributed when run in parallel with a splitter damper.

• 한국지역사회생활과학회지
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• 제24권4호
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• pp.583-589
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• 2013

This study was to provide the information for optimum utilization of the air-conditioning system in the human health and energy saving perspective. Subjects were 17 male and female college students(7 males and 10 females) with normal weight. They wore a short sleeved shirt, knee length trousers, socks, and underwear(0.4clo). They were asked to choose the preferred temperature from different environmental temperatures($28^{\circ}C$, $25^{\circ}C$). The physiological responses were measured and the subjective sensation was voted during the step changes of environmental temperature, starting at $28^{\circ}C$ to $25^{\circ}C$ with $1^{\circ}C$ decrease every 20 minutes. The preferred temperature was $25.9{\pm}0.4^{\circ}C$ for males and $26.9{\pm}0.2^{\circ}C$ for females at $28^{\circ}C$ and $24.8{\pm}0.6^{\circ}C$ for males and $25.6{\pm}0.1^{\circ}C$ for females at $25^{\circ}C$. The preferred temperature decreased about $1.3^{\circ}C$ while the environmental temperature changed $3^{\circ}C$. During the environmental step changes, mean skin temperature decreased more in females while the oxygen uptake and rectal temperature were kept constant for both males and females. We found the preferred temperature was affected by the exposed temperature and the thermal sensation in the condition. Subjects preferred a lower environmental temperature when they were exposed to a lower temperature with cooler sensation. Therefore, in the perspective of human health and energy saving, it is recommended to start setting the air-conditioning temperature higher than the preferred temperature.

• 한국전기전자재료학회논문지
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• 제24권12호
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• pp.1018-1022
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• 2011

Nowadays, with improvement of economical income and life qualities, life pattern changes have been brought such as increasing of avocational activities. Consequently, following those life trends, utilization of car is getting increased. Thus, the perceptions of car have been changed from the only means of transport in the past to a 2nd residental space. that is why the car's endo environmental factors are getting so important. Air conditioner regulating air ventilization in vehicle's indoor automatically sets the right temperature based on the differences of indoor and outdoor's temperature with development of advanced functions to provide better environmental qualities in vehicle. However, even those advanced techniques for functional development are got so diverse though, the essential technique for preventing the growth of bateria and mold inside of the air conditioner are not even severals. Especially, evaporator one of the vehicle air conditioning equipments generates cooled air by vaporizing refrigerant in liquid state with the water as the adduct for this reactions. It has structural difficulties for water vaporation then cause the growth of germs. That's why this reseach was focused on the way of eliminating germs in the vehicle air conditioner efficiently. Direct air sterilizer by using UVC(Ultraviolet C) is manufactured and that performances are evaluated.

• 설비공학논문집
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• 제12권8호
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• pp.782-790
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• 2000

A numerical study has been conducted to characterize the transient pressure in a building water supply system with an air chamber by utilizing a commercial code that employs the method of characteristics. Some results produced for the purpose of verification in the study agree quite well with the previously reported. Several parameters are then varied. Among them are the valve closure time, the wave speed, the static pressure, the polytropic exponent, the air chamber volume, the inner diameter and the shape of orifice in the air chamber, etc, while the water temperature and velocity are kept constant at $20^P{circ}C $,/TEX> and 0.8 m/s, respectively, Results reported in this parametric study may be useful to understand the unsteady behavior of the system.

• 설비공학논문집
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• 제6권4호
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• pp.380-387
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• 1994

An experimental study was performed to investigate the characteristics of refrigerant flow rate control and superheat in an evaporator with an electronic expansion valve(EEV). The EEV used in this study was devised using a needle valve coupled with a stepping motor controlled by a personal computer. A Pill control equation was used to control the superheat of the evaporator and to set the superheat to $5^{\circ}C$. In order to determine an optimum running condition for the system, Pill parameters were varied for the wide range of values. The running condition of an air conditioning system with a PI control was reasonably stable compared with that of the Pill control. Experimental results for the PI control using parameter values, $K_p=1.5$, $T_i=400(sec)$ and $T_s=6(sec)$ show that the superheat reached its target value. When external disturbances were introduced to the system, the superheat target value was reached within about 3 minutes. When the EEV was applied to the air conditioning system driven by an inverter, room temperature control was excellent.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1180-1185
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• 2006

Modern people spend most of time at indoor space, such as office or classroom. Especially, occupants are exposed to the airtight indoor air quality (IAQ) for a long time, At present, many studies on the air-conditioning systems are more focused on the individual thermal comfort than the thermal efficiency due to increase of the concern of health. There are several factors which are influenced thermal comfort, such as temperature, humidity, convection and air movement, etc. Also, the individual factor, such as age, gender, Physical constitution and habit, should be considered. The 4-way cassette type air conditioner is known to bring out better performance about thermal comfort than the traditional one. This study is performed on the higher ceiling environment than the common buildings or classrooms. Also, this study analyzed on the Indoor thermal comfort by diffusing direction of 4-way cassette air conditioner with various discharge angles, $45^{\circ},\;50^{\circ},\;55^{\circ}$ and $60^{\circ}$. Using a commercial code, FLUENT, three-dimensional transient air thermal flow fields are calculated with appropriate wall boundary conditions and standard $k-{\epsilon}$ turbulence model. Results of velocity and temperature distributions are graphically depicted with various discharge angles.

• International Journal of Air-Conditioning and Refrigeration
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• 제8권1호
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• pp.40-49
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• 2000

The capillary tube performance for R-407C is experimentally investigated. The experimental setup is a real vapor-compression refrigerating system. Mass flow rate is measured for various diameter and length while inlet pressure and degree of subcooling are changed. These data are compared with the results of a numerical model. The mass flow rate of the numerical model is about 14% less than the measured mass flow rate. It is found that mass flow rate and length for R-407C are less than those for R-22 under the same condition. Based on this experimental study and the numerical model, a set of design charts for capillary tube of R-407C is proposed.

• 한국태양에너지학회 논문집
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• 제37권1호
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• pp.47-57
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• 2017

Solar energy is one of the important renewable energy resources. It can be used for air heating, hot water supply, heat source of desiccant cooling system and so on. And many researches for enhancing efficiency have been conducted because of these various uses of solar thermal energy. This study was performed to investigate the air heating performance of hybrid solar air-water heater that can heat air and liquid respectively or simultaneously and finding method for improving thermal performance of this collector. This collector has both liquid pipe and air channel different with the traditional solar water and air heater. Fins were installed in the air channel for enhancing the air heating performance of collector. Also air inlet & outlet temperature, ambient temperature and solar collector's inner part temperature were confirmed with different air velocity on similar solar irradiance. As a result, temperature of heated air was shown about $43^{\circ}C$ to $60^{\circ}C$ on the $30^{\circ}C$ of ambient temperature and thermal efficiency of solar collector was shown 28% to 73% with respect to air velocity. Also, possibility of improvement of thermal performance of this collector could be ascertained from the heat transfer coefficient calculated from this experiment. Thus, it is considered that the research for finding optimal structure of hybrid solar air-water heater for enhancing thermal performance might be needed to conduct as further study based on the method for improving air heating performance confirmed in this study.

• 한국자동차공학회논문집
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• 제22권5호
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• pp.84-90
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• 2014

The aim of this paper is to investigate the application of solar energy in reducing cabin thermal load. When a vehicle is parked under the sun in summer, the interior temperature can reach up to $70^{\circ}C$ depending on the solar intensity. Solar power, one of the green energies, is used in automobile air conditioning systems, in order to operate the blower. The power supply of a blower's voltage has been used in a solar sunroof experiment. At the climate wind tunnel, cabin temperature changes were conducted with various operating modes of an air handling system and the preventilation parking conditions of several vehicles, outdoors, was also examined. The test results of the solar sunroof, 39.3W power and 14.1% efficiency were obtained. The thermal load behavior was analysed with the air handling system operating mode differently according to the cabin temperature. By simply operating the blower, average cabin temperature decreased between $5^{\circ}C{\sim}10^{\circ}C$ in those vehicles parked outdoors in summer. This reveals that cabin thermal comfort can be improved without consuming the vehicle's extra energy, and that the performance of the air-conditioning system is better than those currently found in vehicles. Moreover, fuel economy will be increased as a result of the reduction in the use of the air-conditioning system, and many other human advantages will be gained. Such advantages include minimized VOCs and a healthy cabin environment.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권2호
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• pp.107-118
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• 2005

An experimental investigation was made to study two-phase flow distribution in a T-type distributor of slit fin-and-tube heat exchanger using R-22. Experiments were carried out under the conditions of saturation temperature of $5^{\circ}C$ and mass flow rate varying from 0.6 to 1.2kg/min. The inlet air has dry bulb temperature of $27^{\circ}C$, relative humidity of 50% and air velocity varying from 0.63 to 1.71m/s. A comparison was made between the predictions from the previously proposed tube-by-tube method and the present experimental data for the heat transfer rate of evaporator. Results show that $82.5\%$ increase of air velocity is needed for T-type distributor with four outlet branches than that of two outlet branches under the superheat of $5^{\circ}C$, which resulted in increasing of air-side pressure drop of $130\%$ for the former as compared to the latter.