• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.12
• /
• pp.844-861
• /
• 2008

The papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during the year of 2007 have been reviewed. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environments. The conclusions are as follows. (1) The research trends of fluid engineering have been surveyed as groups of general fluid flow, fluid machinery and piping, etc. New research topics include micro nano fluid, micropump and fuel cell. Traditional CFD was still popular and widely used in research and development. Studies about fans and pumps were performed in the field of fluid machinery. Characteristics of flow and fin shape optimization are studied in the field of piping system. (2) The research works on heat transfer have been reviewed in the field of heat transfer characteristics, heat exchangers, and desiccant cooling systems. The research on heat transfer characteristics includes thermal transport in pulse tubes, high temperature superconductors, ground heat exchangers, fuel cell stacks and ice slurry systems. For the heat 'exchangers, the research on pin-tube heat exchanger, plate heat exchanger, condensers and gas coolers has been cordially implemented. The research works on heat transfer augmenting tubes have been also reported. For the desiccant cooling systems, the studies on the design and operating conditions for desiccant rotors as well as performance index are noticeable. (3) In the field of refrigeration, many papers were presented on the air conditioning system using CO2 as a refrigerant. The issues on the two-stage compression, the oil selection, and the appropriate oil charge were treated. The subjects of alternative refrigerants were also studied steadily. Hydrocarbons, DME and their mixtures were considered and various heat transfer correlations were proposed. (4) Research papers have been reviewed in the field of building facilities by grouping into the researches on heat and cold sources, air conditioning and air cleaning, ventilation and fire research including tunnel ventilation, flow control of piping system, and sound research with drain system. Main focuses have been addressed to the promotion of efficient or effective use of energy, which helps to save energy and results in reduced environmental pollution and operating cost. (5) Studies were mostly focused on analyzing the indoor environment in various spaces like cars, old tombs, machine rooms, and etc. in an architectural environmental field. Moreover, subjects of various fields such as the evaluation of noise, thermal environment, indoor air quality and development of energy analysis program were researched by various methods of survey, simulation, and field experiment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.12
• /
• pp.1234-1268
• /
• 2004

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2002 and 2003 has been carried out. Focus has been put on current status of research in the aspect of heating, cooling, air-conditioning, ventilation, sanitation and building environment/design. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation in diverse facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat transfer, humidity was also interesting to promote comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing research topics. Well developed CFD technologies were widely applied for analysis and design of various facilities and their systems. (2) Heat transfer characteristics of enhanced finned tube heat exchangers and heat sinks were extensively investigated. Experimental studies on the boiling heat transfer, vortex generators, fluidized bed heat exchangers, and frosting and defrosting characteristics were also conducted. In addition, the numerical simulations on various heat exchangers were performed and reported to show heat transfer characteristics and performance of the heat exchanger. (3) A review of the recent studies shows that the performance analysis of heat pump have been made by various simulations and experiments. Progresses have been made specifically on the multi-type heat pump systems and other heat pump systems in which exhaust energy is utilized. The performance characteristics of heat pipe have been studied numerically and experimentally, which proves the validity of the developed simulation programs. The effect of various factors on the heat pipe performance has also been examined. Studies of the ice storage system have been focused on the operational characteristics of the system and on the basics of thermal storage materials. Researches into the phase change have been carried out steadily. Several papers deal with the cycle analysis of a few thermodynamic systems which are very useful in the field of air-conditioning and refrigeration. (4) Recent studies on refrigeration and air-conditioning systems have focused on the system performance and efficiency enhancement when new alternative refrigerants are applied. Heat transfer characteristics during evaporation and condensation are investigated for several tube shapes and new alternative refrigerants including natural refrigerants. Efficiency of various compressors and performance of new expansion devices are also dealt with for better design of refrigeration/air conditioning system. In addition to the studies related with thermophysical properties of refrigerant mixtures, studies on new refrigerants are also carried out. It should be noted that the researches on two-phase flow are constantly carried out. (5) A review of the recent studies on absorption refrigeration system indicates that heat and mass transfer enhancement is the key factor in improving the system performance. Various experiments have been carried out and diverse simulation models have been presented. Study on the small scale absorption refrigeration system draws a new attention. Cooling tower was also the research object in the respect of enhancement its efficiency, and performance analysis and optimization was carried out. (6) Based on a review of recent studies on indoor thermal environment and building service systems, it is noticed that research issues have mainly focused on several innovative systems such as personal environmental modules, air-barrier type perimeterless system with UFAC, radiant floor cooling system, etc. New approaches are highlighted for improving indoor environmental conditions and minimizing energy consumption, various activities of building energy management and cost-benefit analysis for economic evaluation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.28 no.6
• /
• pp.256-268
• /
• 2016

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2015. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering were carried out in the areas of flow, heat and mass transfer, cooling and heating, and air-conditioning, the renewable energy system and the flow inside building rooms. Research issues dealing with air-conditioning machines and fire and exhausting smoke were reduced. CFD seems to be spreading to more research areas. (2) Research works on heat transfer area were carried out in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the economic analysis of GHG emission, micro channel heat exchanger, effect of rib angle on thermal performance, the airside performance of fin-and-tube heat exchangers, theoretical analysis of a rotary heat exchanger, heat exchanger in a cryogenic environment, the performance of a cross-flow-type, indirect evaporative cooler made of paper/plastic film. In the area of pool boiling and condensing, the bubble jet loop heat pipe was studied. In the area of industrial heat exchangers, researches were performed on fin-tube heat exchanger, KSTAR PFC and vacuum vessel at baking phase, the performance of small-sized dehumidification rotor, design of gas-injection port of an asymmetric scroll compressor, effect of slot discharge-angle change on exhaust efficiency of range hood system with air curtain. (3) In the field of refrigeration, various studies were carried in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, a cold-climate heat pump system, $CO_2$ cascade systems, ejector cycles and a PCM-based continuous heating system were investigated. In the alternative refrigeration/energy system category, a polymer adsorption heat pump, an alcohol absorption heat pump and a desiccant-based hybrid refrigeration system were investigated. In the system control category, turbo-refrigerator capacity controls and an absorption chiller fault diagnostics were investigated. (4) In building mechanical system research fields, eighteen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the user and location awareness technology applied dimming lighting control system, the lighting performance evaluation for light-shelves, the improvement evaluation of air quality through analysis of ventilation efficiency and the evaluation of airtightness of sliding and LS window systems. The subjects of building energy were worked on the energy saving estimation of existing buildings, the developing model to predict heating energy usage in domestic city area and the performance evaluation of cooling applied with economizer control. The studies were also performed related to the experimental measurement of weight variation and thermal conductivity in polyurethane foam, the development of flame spread prevention system for sandwich panels, the utilization of heat from waste-incineration facility in large-scale horticultural facilities.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.2 no.3
• /
• pp.99-106
• /
• 1998

The performance of the turbofan engine, a medium scale civil aircraft which has been developing in Rep. of Korea, was analyzed and the control scheme for optimization the performance was studied. The dynamic and real-time linear simulation was performed in the previous study The result was that the fuel scedule of the step increase overshoot the limit temperature(3105 $^{\cire}R$) of the high pressure turbine and got small surge margine of the high pressure compressor. Therefore a control scheme such as the LQR(Linear Quadratic Regulator) was applied to optimizing the performance in this studies. The linear model was expected for designing controller and the real time linear model was developed to be closed to nonlinear simulation results. The system matrices were derived from sampling operating points in the scheduled range and then the least square method was applied to the interpolation between these sampling points, where each element of matrices was a function of the rotor speed. The control variables were the fuel flow and the low pressure compressor bleed air. The controlled linear model eliminated the inlet temperature overshoot of the high pressure turbine and obtained maximum surge margins within 0.55. The SFC was stabilized in the range of 0.355 to 0.43.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.2
• /
• pp.625-631
• /
• 2014

In order to obtain a low evaporation temperature ranging from $-30^{\circ}C{\sim}-50^{\circ}C$, a cascade refrigeration system and two-stage compression one-stage expansion refrigeration system is required. However, the research results of performance comparison of these refrigeration system are very scarce. This paper were compared the performance characteristics of R744-R404A cascade refrigeration system and R404A two-stage compression refrigeration system. The COP of R404A two-stage compression refrigeration system is about 36~57% greater than that of R744-R404A cascade refrigeration system in the range of evaporation temperature of $-30^{\circ}C{\sim}-50^{\circ}C$. But R404A two-stage compression refrigeration system is unstable because COP is significantly changed when evaporating temperature and compressor efficiency decreased. In particular, when compressor efficiency decreased, COP is significantly decreased. In this case, not efficient for long-term use. Whereas R744-R404A cascade refrigeration system using natural refrigerants. Therefore, it is environmentally friendly. And this system is high-efficiency refrigeration system. The reason it can be configured by selecting the suitable refrigerant at high-temperature side and low-temperature side. From the above results, select the appropriate low temperature refrigeration system by considering the environmental and performance aspects.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.12
• /
• pp.1102-1139
• /
• 2002

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2000 and 2001 has been done. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environment. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation of facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat, humidity was also interesting for comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing topics. Well developed CFD technologies were widely applied for developing facilities and their systems. (2) Most of papers related with heat transfer analysis and heat exchanger shows dealt with convection, evaporation, and channel flow for the design application of heat exchanger. The numerical heat transfer simulation studies have been peformed and reported to show heat transfer characteristics. Experimental as well as numerical studies on heat exchanger were reported, while not many papers are available for the system analysis including heat exchanger. (3) A review of the recent studies on heat pump system shows that performance analysis and control of heat pump have been peformed by various simulations and experiments. The research papers on multi-type heat pump system increased significantly. The studies on heat pipe have been examined experimently for change of working characteristics and strut lure. Research on the phase change has been carried out steadily and operation strategies of encapsulated ice storage tank are reported experimentally in several papers. (4) A review of recent studies on refrigeration/air conditioning system have focused on the system performance and efficiency for new alternative refrigerants. Evaporation and condensation heat transfer characteristics are investigated for tube shapes and new alternative refrigerants. Studies on components of refrigeration/air conditioning system are carried to examine efficiency for various compressors and performance of new expansion devices. In addition to thermophysical properties of refrigerant mixtures, studies on new refrigerants are also carried out, however research works on two-phase flow seemed to be insufficient. (5) A review of the recent studies on absorption cooling system indicates that heat and mass transfer phenomena have been investigated to improve absorber performance. Various experimental data have been presented and several simulation models have been proposed. A review of the recent studies on duct and ventilation shows that ventilation indices have been proposed to quantify the ventilation performance in buildings and tunnels. Main efforts have been focused on the applications of ventilation effectiveness in practice, either numerically using computational fluid dynamics or experimentally using tracer gas techniques. (6) Based on a review of recent studies on indoor thermal environment and building service systems, research issues have mainly focused on many innovative ideas such as underfloor air-conditioning system, personal environmental modules, radiant floor cooling and etc. Also, the new approaches for minimizing energy consumption as well as improving indoor environmental conditions through predictive control of HVAC systems, various activities of building energy management and cost-benefit analysis for economic evaluation were highlighted.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.6
• /
• pp.592-598
• /
• 2015

In this study, we experimentally investigate the performance characteristics of a high-performance summer-cooling heat pump for an R410A by applying an air-cooled-type vapor-injection (VI) cycle. The devices used for the experiment consist of a VI compressor, condenser, oil separator, plate-type heat-exchanger, economizer, evaporator, and re-cooler. The experimental conditions employed for the cooling performance were divided into three cycles. First, in Cycle A, we apply a VI cycle and with no heat exchange between the evaporator outlet refrigerant and the VI cycle suction refrigerant in the re-cooler. For Cycle B, there is heat exchange, and for Cycle C, there is neither a VI cycle nor heat exchange between the evaporator outlet refrigerant and the VI cycle suction refrigerant. From the analysis results, we observe that the performance was highest in the VI cycle with heat exchange between the evaporator outlet refrigerant and the VI cycle suction refrigerant (Cycle B), while it was lowest in Cycle C without application of the VI cycle. Moreover, the cooling coefficient of Performance ($COP_C$) averaged 3.5 in Cycle B, which was 8.6% higher than the corresponding value in Cycle A, and 33% higher than that in Cycle C.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.26 no.5
• /
• pp.569-575
• /
• 2020

In this study, a fuel cell system model for ship power was developed and verified by comparing the experimental results obtained by supplying pure oxygen. To verify the proposed model, the fuel cell output characteristics when oxygen was supplied were compared with those when air was supplied using an air compressor. In addition, the effect of the change in the thermal properties of the fuel cell system on the output of the stack was examined. Within the experimental range of this study, when pure oxygen was supplied as the cathode supply gas, the calculated and experimental voltages and outputs obtained through modeling were almost the same over the entire load range. When air was supplied instead of oxygen for the cathode supply at a constant load of 560 A, each stack voltage was approximately 14 V, the stack output was approximately 8 kW, and the stack efficiency was approximately 3 %. It was confirmed that the overall system efficiency was reduced by approximately 8 %. Among the thermal properties examined in this study, the heat transfer coefficient of the coolant to the stack was found to have the greatest effect on the output of the stack.

• Journal of Bio-Environment Control
• /
• v.21 no.3
• /
• pp.163-169
• /
• 2012

We have conducted three experiments to develop a fertilizer-dissolving apparatus used in fertigation or hydroponics cultivation in order to decrease the fertilizer dissolving time and labor input via automation. All of the experiments were conducted twice. In the first experiment, four selected treatments were tested to dissolve fertilizers rapidly. The first treatment was to dissolve fertilizer by spraying water with a submerged water pump, placed in the nutrient solution tank. The water was sprayed onto fertilizer, which is dissolved and filtered through the hemp cloth mounted on the upper part of the nutrient solution tank (Spray). The second treatment was to install a propeller on the bottom of the nutrient solution tank (Propeller). The third treatment was to produce a water stream with a submerged water pump, located at the bottom of the tank (Submerged). Finally, the fourth treatment was to produce an air stream through air pipes with an air compressor located at the bottom of the tank (Airflow). The Spray treatment was found to take the shortest time to dissolve fertilizer, yet it was inconvenient to implement and manage after installation. The Airflow treatment was thought to be the best method in terms of the time to dissolve, labor input, and automation. In the second experiment, Airflow treatment was investigated in more detail. In order to determine the optimal number of air pipe arms and their specification, different versions of 6- and 8-arm air pipe systems were evaluated. The apparatus with 6 arms (Arm-6) that was made of light density polyethylene was determined to be the best system, evaluated on its time to dissolve fertilizer, easiness to use regardless of the lid size of the tank, and easiness to produce and install. In the third experiment, the Submerged and Arm-6 treatments were compared for their dissolving time and economics. Arm-6 treatment decreased the dissolving time by 8 times and proved to be very economic. In addition, dissolving characteristics were investigated for $KNO_3$, $Ca(NO_3)_2{\cdot}4H_2O$, and Fe-EDTA.

• Plant Journal
• /
• v.16 no.1
• /
• pp.28-33
• /
• 2020

This study analyzes the requirements for international standardization by studying the approach to international standardization of equipment and bulk materials in the offshore oil & gas industry, and describes the prioritization of standardized equipment and the result of standardization in the first stage. Currently, international standardization activities can be classified into three activities. First, international standardization activities of bulk materials led by three major domestic shipbuilders, second, JIP33 equipment standardization activities led by IOGP, and finally, And standardization activities of UEJIP equipment centered on classification society. This study classifies various international standards applied in the offshore oil & gas industry, and introduces the activities of standardization activities of class-leading equipment and actual application examples.