• Food Science and Preservation
• /
• v.11 no.2
• /
• pp.263-268
• /
• 2004

Two field cooling tests were conducted to evaluate the cooling characteristic of paddy with a prototype grain cooler. The first test was carried out during summer season in a steel bin with 180.3ton of paddy at Sunchon. And the second test was carried out during harvesting season in a steel bin with 272.2ton of paddy at Ulsan. At the first test, initial paddy temperature of 23.6$^{\circ}C$ was dropped to 14$^{\circ}C$, and initial moisture content of 19.9% was dropped to 19.3% after 52.5 hours of cooling. At the second test, initial paddy temperature of 16.1$^{\circ}C$ dropped to 5.5$^{\circ}C$ after 78.0 hours of cooling. And, at the first test, the average air flow rates of chilled air leaving the grain cooler and penetrating the grain layer were 77.5 ㎥/min and 42.5 ㎥/min, respectively. To prevent leakage of chilled air from plenum chamber of steel bin, which was about 45% of the average air flow rates of chilled air leaving the grain cooler, a proper method was required. The average total power consumption at the first test during summer was 22.1 ㎾ with control of fan damper. At the second test, it was 17.4 ㎾ due to controlling the capacity of compressor with unloading solenoid valve and changing the flow rates of hot refrigerant gas flowing into evaporator and reheater from compressor, resulting in 27% reduction of energy consumption.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.20 no.6
• /
• pp.653-662
• /
• 2014

In this study, Mokpo national maritime university Training ship Centralizes Air Conditioning System was upgraded by installing onboard an Air-cooled Air conditioner. This resulted in the improvement of the performance and operation. This study compared refrigeration performance to former equipment and improving one. And through the actual measurement study about the cabin thermal environment, it will be used as basic data for marine air conditioning design and plan in the future. At same climate condition, when the Centralized Air Conditioning System and an improved air conditioning system operated, cabin temperature was at $24{\sim}28^{\circ}C$, humidity was 55~75 % as comfortable condition, Generator load measurement showed a saving of 48KW in the average load and 8 % in the full load factor. This also resulted in a saving of daily fuel oil consumption(FOC) at around 222 [${\ell}/day$] average. On the other hand, one cadet cabin(Cadet No.21) indicated a higher temperature due to heat transmission of engine room. It found us not to consider installing additional diffuser to reduce the heat transmission.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.4
• /
• pp.1850-1858
• /
• 2014

The object of this study is to develop an cooling control algorithm for electronics devices of the electric vehicle. In order to estimate the existing cooling control logic of the electronic devices for the small and medium sized electric vehicle, the experiments on the coolant temperature variation of the cooling system were conducted under 4 different seasons conditions. As a result, the existing cooling control logic were overcooled when it was compared with the reference temperature for a required cooling load. In addition, the newly developed optimum cooling control logic for improving the mileages of the tested electric vehicle with consideration of the ambient temperature, vehicle speed, and refrigerant temperature of the air conditioning on/off is necessary.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.6
• /
• pp.762-767
• /
• 2012

This study presents the effect which the condensation water affects on performance characteristics of apparatus when the condensation water injects to the condenser. The experimental results are the following. The inlet outlet refrigerant temperature in condenser and outlet air temperature showed a little lower than that of the existing method. Also, the refrigeration capacity and COP(coefficient of performance) increased about 3%, 13~16% and the compressor work decreased about 27% than that of the conventional method. So, these results contribute not only the performance improvement of apparatus but also the solution of problem according to the discharge of periodic condensation water.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.5
• /
• pp.413-421
• /
• 2014

Desiccant cooling system is an air conditioning system that uses evaporative cooler to cool air and it can perform cooling by using heat energy only without electrically charged cooler. Thus, it can solve many problems of present cooling system including the destruction of ozone layer due to the use of CFC[chloro fluoro carbon] affiliated refrigerants and increase of peak power during summer season. In this study, cooling performance and exergy analysis was conducted in order to increase efficiency of desiccant cooling system. Especially, using exergy analysis based on the second law of thermodynamics can resolve the issue related to system efficiency in a more fundamental way by analyzing the cause of exergy destruction both in whole system and each component. The purpose of this study is to evaluate COP[coefficient of performance], cooling capacity and exergy performance of desiccant cooling system incorporating a regenerative evaporative cooler in various regeneration temperature and outdoor air conditions.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.29 no.1
• /
• pp.27-33
• /
• 2023

An optimized design of the transportation insulated box must be considered to control the thermal damage in order to maintain the fresh condition for temperature-sensitive medicine and frozen food safety. The inside temperature of the insulated box is a natural convection enclosure state, thermal stratification naturally occurs as time passes in case of with outside heat load. The latent heat material (LHM) placement inside the box maintains the target temperature of the product for temperature fluctuations during transport, and LHM application is a common and efficient method. In this work, inside temperature stratification in an insulated box depending on the LHM pack position is numerically simulated and experimented. The insulated box is made up of vacuum insulation panel (VIP), and LHM modules are placed over six faces inside the box, with the same weight. The temperature curves for 72 hrs as experiment results clearly show the temperature stratification in the upper, middle, and lower at the LHM melting time region. However, the temperature stratification state is uniformly changed in accordance with the condition of the upper and lower placement weight of the LHM pack. And also, the temperature uniformity by changed placement weight of LHM has an effect on maintaining time for target air temperature inside the box. These results provide information on the optimized design of the insulated box with LHM.

• Land and Housing Review
• /
• v.12 no.1
• /
• pp.129-137
• /
• 2021

External shading devices are well known solar control devices that can help reduce the cooling load of commercial buildings. For this study, experiments were conducted to examine the feasibility of shading devices in reducing both the cooling and heating loads. The influence of sky radiant cooling during winter was verified for the external shading device, internal roller blind, and window. Results can be summarized as follows. The temperature difference between the inner and outer surfaces of the window with the external shading device was 11.8℃ compared to 14.6℃ for one without the external shading device. This 2.8℃ difference was due to heat exchange by sky radiation when the surface temperature of the shading device was lower than the ambient outdoor air temperature. The roller blind resulted in a lower temperature of 0.8℃ compared to the average temperature of the window's air cavity. This was due to heat exchange by sky radiation of the roller blind surfaces. Without shading devices, the outside surface temperature of the window is about 3℃ higher. The study also found that when external shading devices were installed on both the southwest and southeast sides, the outside surface temperature of the windows were lower on the southwest side than the southeast side.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.2
• /
• pp.85-91
• /
• 2016

The Positive Temperature Coefficient (PTC) is used for cabin air heating of a battery electric vehicle, which is different from conventional vehicles. Since the PTC heater consumes a large quantity of power in a parasitic manner, many valuable studies have been reported in the field of alternative heat pumps. In this study, a model for an R134a heat pump taking into account the thermal environment of the cabin was developed for a MATLAB/SIMULINK(R) platform. Component and cabin models are validated with reference values. Results show that the heat pump is more competitive for parasitic power consumption over all ambient temperature conditions. Additionally, the method of waste heat recovery to overcome disadvantages when temperatures are below zero is applied to efficiently operate the heat pump.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.119-119
• /
• 2010

무한 지속 가능한 지열 에너지를 활용한 공조시스템인 지열원 냉난방 시스템은 기존의 공조 시스템보다 열원이 안정적이기 때문에 높은 효율과 우수한 성능을 가지므로, 기후변화협약 대응의 주요수단으로서 기술개발과 보급이 증대되고 있다. 본 연구에서는 대수층 축열 지열원 열펌프 시스템에 대한 실증 연구를 통하여 대수층 축열 지열원 열펌프 시스템의 하절기 냉방 성능을 분석하였다. 대수층 축열 냉난방 시스템은 주입정과 양수정의 2개의 우물공이 설치되어 있으며, 겨울 난방 운전 중에 한 개의 우물공으로부터 지하수를 열펌프로 유입한 후 낮은 온도의 지하수를 타 우물공에 축열하고, 하절기에 겨울에 저온으로 축열된 우물공으로부터 지하수를 열펌프로 유입하여 온도가 증가된 지하수를 타 우물공에 주입한다. 즉, 계절별로 열펌프에서 생성된 냉수와 온수의 대수층 축열을 위하여 계절별로 주입정과 양수정이 바뀌게 된다. 본 연구의 대수층 축열 지열원 열펌프 시스템의 2009년 8월의 주요일자별 시스템 운전 중의 평균 냉방 열펌프 유닛 COP와 냉방 시스템 COP는 각각 4.7과 3.4이상의 우수한 성능을 나타냈다. 또한, 모든 일자에 대하여 외기온도가 $31.6^{\circ}C$서 $22^{\circ}C$까지 변화가 크게 나타났지만 열펌프 유닛 COP와 시스템 COP의 변화는 미소하였다. 이는 양수정으로부터의 지중 순환수가 운전기간 중에 $17.5^{\circ}C$로 일정하게 유지되었기 때문이다. 양수정과 주입정 사이에 5개의 관측공을 설치하였으며, 양수정 측에 인접한 관측공의 온도는 거의 변화가 없었으며, 단기간이지만 널리 사용되고 있는 수직밀폐형 시스템과 달리 지속적인 냉방운전 중의 양수 온도의 증가는 발생하지 않아 안정적인 성능을 나타냈다. 주입정에 인접한 모니터링 홀의 온도는 심도가 깊은 곳의 온도가 낮은 곳보다 높게 나타났다. 이는 냉방 운전 시 열펌프 유닛의 실외열교환기에서 지중 순환수가 냉매로부터 열을 취득하여 온도가 상승하면서 주입정측에 온열이 축열이 진행되었기 때문으로 분석되며, 하절기의 냉방 운전 시간이 증가할 경우 축열 효과는 더욱 증가할 것으로 예상된다. 양수정과 주입정 중간의 모니터링 홀의 온도는 2009년 8월 가동 중에 온도변화는 없었는데, 이는 양수정과 주입정 사이의 열간섭이 발생하지 않았기 때문으로 분석된다. 일자별로 운전 중의 열펌프 유닛 COP는 차이가 없었지만, 운전 및 정지 시간을 모두 포함한 시스템 소비전력과 냉방용량을 모두 합산하여 산정한 일일 평균 냉방 열펌프 유닛 COP와 냉방 시스템 COP는 일자별로 다소 차이가 발생하였는데, 이는 각 일자별로 열펌프 유닛 가동율의 차이로 인하여 열펌프 유닛 가동 전에 먼저 작동되는 지중순환펌프의 운전 소비전력의 차이와 열펌프의 단속운전 시의 열손실과 추거 소비전력의 차이 때문이다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.3
• /
• pp.493-500
• /
• 2017

Based on the data accumulated through EMU fault management, this paper examines the reliability of old railway car parts and proposes measurements to improve safety. Subway Line 7 of the Seoul Metropolitan Rapid Transit Corporation, auxiliary power unit (Static Inverter) of the EMU second version is a core equipment to supply power to various room-service units in cars and make an effect directly on passenger satisfaction. To analyze the pattern of failure throughout the field data over a long period of time, this analysis of statistics and reliability considers the operating environment and stress factors. This statistical analysis presents the correlation between failure and the temperature stress factors related to frequent failure occurring intensively in summer. In addition, throughout the analysis of the life of the IGBT inverter, the effect of the temperature stress factor was observed before and after the repair. As a result of an analysis of the optimal operating conditions considering two variations of EMU, such as variable load and outside temperature, a difference in the cooling capacity between the optimal operating conditions and frequent failure conditions was observed. Based on this analysis, this paper suggests a way to minimize cooling capacity difference for the optimal operational conditions.