• Journal of Advanced Marine Engineering and Technology
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• v.24 no.2
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• pp.24-30
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• 2000

The high-pressure natural refrigerant $CO_2$ is now being evaluated for use in the motor vehicle air-conditioning systems and for several types of unitary equipment. In this study thermodynamic properties of $CO_2$ is compared to those of R-22 and R-134a and the performance characteristics of $CO_2$ refrigeration cycle is analyzed. The results show that the optimum discharge pressure for the cycle performance exists. New design concept for the $CO_2$ refrigeration system should be developed due to the high-operating pressure of itself.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.2
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• pp.147-154
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• 2012

Recently, many researchers have studied the performance of the transcritical $CO_2$ refrigeration cycle in order to improve the system efficiency. In this study, the length of IHX in the $CO_2$ ejector cycle was varied so as to evaluate the performance improvement. As a result, compressor work and cooling capacity was increased by 3% and 5% as the length of internal heat exchanger was changed from 3 m to 15 m. The best COP was appeared at internal heat exchanger length of 12 m, and it was 3.01. Besides, the length of internal heat exchanger has a big effect to pressure lift ratio and entrainment ratio in the ejector $CO_2$ cycle and it may be changed with operating conditions and system specifications.

• Journal of the Korea Society of Computer and Information
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• v.24 no.12
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• pp.135-141
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• 2019

In this study, the "Insect Smart Farm Air Conditioning System" is designed and proposed for the control of breeding environment of Protaetia brevitarsis seulensis larvae. The proposed "Insect Smart Farm Air Conditioning System" separates the breeding room from the air conditioning room. It is a system that creates an environment optimized for breeding and distributes it into a breeding room. When controlling the environment through air-conditioning and humidifiers in insect farms, temperature and humidity vary from part of the breeding room to part. The solution to the problem can be suggested as a solution to the difficulty of producing white-spotted flower mounds of uniform size and weight when selling edible insects. By using the "Insect Smart Farm Air Conditioning System," the temperature difference can be reduced by 6℃ and the humidity difference by 24.7% compared to the environmental control of existing insect farms. The temperature and humidity of different parts of the breeding room were improved. Provide the optimal environment of Protaetia brevitarsis seulensis larvae at all times and ensure uniform CO₂ concentration. It can be expected to increase output through annual production and increase income for insect farmers. The proposed "Insecting Smart Farm Air Conditioning System" also controls the set temperature, humidity and CO₂. Environmental control of the breeding of other edible insects and the reproduction of mushrooms that require environmental control in breeding or breeding will also be possible.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.18-24
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• 2015

In this study, a $CO_2$ air-conditioning system was investigated with different types of electrically driven compressors, parallel flow type gas cooler, four-pass type evaporator, internal heat exchanger integrated with accumulator, and electric expansion valve. The experimental study was conducted under various operating conditions (ie., different rotational compressor speeds, air inlet temperatures and air velocity coming into heat exchangers). The experimental results showed the cooling capacity was 3.5kW at $35^{\circ}C$ ambient temperature when the vehicle was idle (ie., the worst condition for cooling off the gas cooler). In terms of performance effect of the compressor, the e-RP model had a slightly better cooling capacity and coefficient of performance than the e-GR model under the same test conditions. An experimental equation for optimum cooling-performance control was also suggested based on the results. A high-pressure control algorithm for the super critical cycle was determined to achieve both maximum cooling performance and efficient energy consumption. The results from the experimental equation coincided with those of previous experimental studies.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.41-48
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• 2000

The characteristics of a combined cycle for the production of fresh water and air-conditioning was analyzed. The combined cycle consisted of an open water cycle and a $CO_2$ refrigeration cycle interlinked in the pre-heater of the water cycle, which is the condenser of the refrigeration cycle. The oprating conditions and criteria for the fresh water production and air-conditioning was described and their effects on the total system were evaluated. The results indicated an increase of desalinated water with the increase of hot water temperature, which resulted in the decrease of cooling capacity of the refrigeration system in this study. However, the energy saving correspond to the pre-heating of the water cycle by the condensing of the refrigeration system shows the avilable advantage of the proposed cycle as compared to other single purpose plants for desalination.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.32 no.6
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• pp.49-56
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• 2003

CO2환기제어는 신축건물에서 흔히 사용되고 있지만, 기존의 건물에서는 그 적용 예가 흔하지는 않다. 아마도 개보수라는 것이 가능하다고 여겨지는 자원절감이나 이익에 대한 방대한 기록이 요구되기 때문이며 게다가 제어에 관한 개보수는 복잡하다는 인식에 기인한다. 공교롭게도, 에너지 사용 패턴에 대하 명확한 기록이 있는 기존의 건물에 가장 에너지절약적인 기회가 많다는 사실이다. 이 기고문에서는 기존 건물의 CO2개보수에 관하여 그 성능 평가에 대한 방법론을 제시하고 있으며, 현장 평가와 이 방법론을 적용한 A-등급 사무소 건물에서의 개보수를 통한 성능개선에 관하여 분석하고 있다. 대상은 첨단 DDC시스템이 있는 미국 환경청의 에너지스타 등급을 획득한 건물이다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.2
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• pp.49-54
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• 2016

The purpose of this study is to analyze the indoor temperature distribution of a room controlled by a personal and portable cooler. As an energy saving strategy, the personal air-conditioning or task conditioning system was developed and installed in office buildings in the 90 s. Many research results regarding the personal air-conditioning (PAC) system were focused on thermal comfort, localized ventilation efficiency and energy savings. However, the conventional PACs were only developed for application in office buildings. In this study, as a type of PAC, a portable cooler was analyzed in terms of indoor temperature distribution changes with the passage of time. The measurement was performed in a bedroom in an apartment house. The results showed that indoor temperature was controlled at about $24^{\circ}C$ around the human body. However, the ambient zone up to 1.5 m away from the the human body stayed at about $27.5^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.2
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• pp.198-207
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• 1996

It is well known that drag reduction in single phase liquid flow is affected by polymer material, molecular weight, polymer concentration, pipe diameter, and flow velocity. Drag reduction in two phase flow can be applied to the transport of crude oil, phase change system such as chemical reactor, pool and boiling flow, and to present cavitation which occurs in pump impellers. But the research of drag reduction in two phase flow is not sufficient. The purpose of the present work is to evaluate the drag reduction by measuring pressure drop, void fraction, mean liquid velocity, and turbulent intensity whether polymer is added in the horizontal two phase system or not. Experiment has been conducted in a test section with the inner diameter of 24mm and the length of 1,500mm. The polymer materials used are two kinds of polyacrylamide[PAAM] and co-polymer[A611P]. The polymer concentration was varied with 50, 100 and 200 ppm under the same experimental conditions. Experimental results showed that the drag reduction of co-polymer is higher than that of polyacrylamide. Mean liquid velocities increased as polymer was added, and turbulent intensity decreased inversely near the pipe wall.

• Korean Journal of Environmental Agriculture
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• v.37 no.4
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• pp.268-276
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• 2018

BACKGROUND: In the month of January 2018, fine dust alerts and warnings were issued 36 times for $PM_{10}$ and 81 times for PM2.5. Air quality is becoming a serious issue nation-wide. Although interest in air-purifying plants is growing due to the controversy over the risk of chemical substances of regular air-purifying solutions, industrial spread of the plants has been limited due to their efficiency in air-conditioning perspective. METHODS AND RESULTS: This study aims to propose a vegetation-based bio-filter system that can assure total indoor air volume for the efficient application of air-purifying plants. In order to evaluate the quantitative performance of the system, time-series analysis was conducted on air-conditioning performance, indoor air quality, and comfort index improvement effects in a lecture room-style laboratory with 16 persons present in the room. The system provided 4.24 ACH ventilation rate and reduced indoor temperature by $1.6^{\circ}C$ and black bulb temperature by $1.0^{\circ}C$. Relative humidity increased by 24.4% and deteriorated comfort index. However, this seemed to be offset by turbulent flow created from the operation of air blowers. While $PM_{10}$ was reduced by 39.5% to $22.11{\mu}g/m^3$, $CO_2$ increased up to 1,329ppm. It is interpreted that released $CO_2$ could not be processed because light compensation point was not reached. As for the indoor comfort index, PMV was reduced by 83.6 % and PPD was reduced by 47.0% on average, indicating that indoor space in a comfort range could be created by operating vegetation-based bio-filters. CONCLUSION: The study confirmed that the vegetation-based bio-filter system is effective in lowering indoor temperature and $PM_{10}$ and has positive effects on creating comfortable indoor space in terms of PMV and PPD.