• Transactions of the KSME C: Technology and Education
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• v.3 no.1
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• pp.15-21
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• 2015

In this paper a prediction method of GHP performance is proposed for increasing design accuracy. Two compressors with different capacity and 2311cc gas engine are used for prediction and the target capacity of GHP is 25HP. For predicting GHP performance at first the operation points are randomly selected and then as compared with compressor performance date and heat exchanger characteristic, more accurate operating points are decided through recursive calculation. Lastly engine performance date is used for calculating gas consumption volume. Predicting heating mode performance of GHP, evaporator is separated to the two section of absorbing heat in outdoor air and in engine. From the experimental results, it was found that the simulation model is good for the predicting GHP efficiency and the difference of predicted and measured efficiency is less than 5%.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.488-493
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• 2012

In this study, in order to utilize the seawater as a heat source at Gangneung city near the East Sea in Korea, an annual heating performance of a screw heat pump was simulated. For a simulation, the maximum heating capacity of heat pump was assumed at 3.5 MW. An ambient temperature at Gangneung city was calculated from the TMY2 weather data, while the seawater temperature was calculated from the regression equation based on the measurement by the National Fisheries Research and Development Institute of Korea. The heating load was assumed linearly dependent on the ambient temperature, while the maximum heating load was assumed to appear when the ambient temperature is below $-2.4^{\circ}C$, which is the temperature of TAC 2.5% for heating at Gangneung city. A heat pump performance at full-load was calculated from the regression equation, which involves refrigerant's evaporating and condensing temperatures, based on a commercial screw compressor performance map. A heating supply temperature which determines refrigerant's condensing temperature was assumed linearly dependent on the heating load. A performance degradation due to the part-load operation of heat pump was also considered. Simulation results show that an annual heating coefficient of performance ($COP_H$) of a seawater-source screw heat pump is approximately 2.8 and that it is necessary to improve part-load performance to increase an annual performance of the heat pump.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.17 no.2
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• pp.30-41
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• 2021

This paper presents the heating performance analysis results of a heat pump system using a dual heat source. In this paper, a dual heat source refers to the ground-coupled heat exchanger using both a surface water heat exchanger (SWHE) and a vertical ground heat exchanger (VGHE). In order to evaluate the system performance, we installed a monitoring system to measure the temperature and power consumption of a heat pump and then collected operation data with 4 different load burdened ratios of the dual heat source heat exchanger. During the whole measurement period, the average heating capacity of a water-to-water heat pump unit was 37.3 kW. In addition, the compressor of the heat pump consumed 9.4 kW of power, while the circulating pump of the dual heat source heat exchanger used 6.7 kW of power. Therefore the average heating coefficient of performance (COP) for the heat pump unit was 4.0, while the entire system including the circulating pump was 2.7. Finally, the parallel use of SWHE and VGHE was beneficial to the system performance; however, further researches are needed to optimize the design data for various load ratios of the dual heat source heat exchanger.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.30 no.2
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• pp.100-106
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• 2018

Recently, the development of a heat pump technology to recover process waste heat and to generate steam of $120^{\circ}C$ or higher required for industrial processes, has attracted attention. The research of conventional heat pump utilizing the available energy is used primarily for air conditioning, and the production temperature is about $60^{\circ}C$, so it is difficult to utilize it for industrial use. Therefore, in this study, we developed a steam heat pump (SGHP) which recovers the waste heat of process and generates steam at $120^{\circ}C$. The low-pressure refrigerant R245fa, considered to be an eco-friendly refrigerant, has been selected as the refrigerant for SGHP in this study since its Ozone Depletion Potential (ODP) is zero and the Global Warming Potential (GWP) is relatively low. A flash tank functioning as a phase separator was installed in the rear stage of the condenser, and the saturated water of high temperature was decompressed to generate steam. It was started at the initial temperature of $70^{\circ}C$, and it was confirmed that $120^{\circ}C$ steam was produced after the system stabilized. We have conducted experiments by modifying the system, and ultimately achieved a heating capacity of 101.4 kW and a COP of 3.05.

• KIEAE Journal
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• v.16 no.6
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• pp.109-114
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• 2016

Purpose: The underground air is the warm air discharged from the porous volcano bedrock 30-50m underground in Jeju, including excessive humidity. The temperature of the underground air is $15-20^{\circ}C$ throughout the year. In Jeju, the underground air was used for heating greenhouses by supplying into greenhouses directly. This heating method by supplying the underground air into greenhouses directly had several problems. The study was conducted to develop the heat pump system using underground air as heat source for resolving excessive humidity problem of the underground air, adopting the underground air as a farm supporting project by Ministry of Agriculture, Food and Rural Affairs(MAFRA) and saving heating cost for agricultural facilities. Method: 35kW scale(10 RT) heat pump system using underground air installed in a greenhouse of area $330m^2$ in Jeju-Special Self-Governing Province Agricultural Research & Extension Services, Seogwipo-si, Jeju. The inlet and outlet water temperature of the condenser, the evaporator and the thermal storage tank and the underground air temperature and the air temperature in the greenhouse were measured by T type thermocouples. The data were collected and saved in a data logger(MV200, Yokogawa, Japan). Flow rates of water flowing in the condenser, the evaporator and the thermal storage tank were measured by an ultrasonic flow meter(PT868, Panametrics, Norway). The total electric power that consumed by the system was measured by a wattmeter(CW240, Yokogawa, Japan). Heating COP, rejection heat of condenser, extraction heat of evaporator and heating cost were analyzed. Result: The underground air in Jeju was adopted as a farm supporting project by Ministry of Agriculture, Food and Rural Affairs(MAFRA) in 2010. From 2011, the heat pump systems using underground air as a heat source were installed in 12 farms(16.3ha) in Jeju.

• KIEAE Journal
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• v.12 no.3
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• pp.89-94
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• 2012

The international community is paying close attention to the climatic changes caused by the meteorological anomalies. In response to such phenomena, after the adoption of the United Nations Framework Convention on Climate Change in 1992, efforts to actively respond to the meteorological changes are proliferating all over the world; even in the Republic of Korea, the issue to tackle the meteorological changes has emerged as a top-priority national agenda. In the year of 2008, after the declaration of the low-carbon, green-growth paradigm by the government, the UNFCCC COP15 has announced a 30% reduction target of the emission of the greenhouse gases by 2020 as compared to the "Business As Usual, BAU" and has also confirmed, as a commitment plan to achieve reduction in the emission of greenhouse gases, the reduction target of greenhouse gases for all sectors, industries and years. (26.9% for buildings) Since the construction of the new apartment houses in the year of 2001, the "Building Energy Efficiency Rating", has been applied to newly constructed building complexes, built in 2010; the accumulated emission reduction has been evaluated at around 450,000toe and the accumulated carbon dioxide emission reduction is at $826,000tCO_2$ And through the prediction of these values under various scenarios (New construction, new construction / expansion of existing uses, when transferred to 1stgrade), the effects on the degree of reduction of greenhouse gases by the increased certification of the Building Energy Efficiency Rating are an alyzed and it is our aim to express the importance of the certification system capable of carrying out a quantitative evaluation of the building energy in order to establish the strategy to reduce the emission of carbon dioxide.

• Korean Journal of Applied Biomechanics
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• v.32 no.1
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• pp.9-16
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• 2022

Objective: The purpose of this study was to investigate how the chronic ankle instability affects postural control during forward jump landing. Method: 20 women with chronic ankle instability (age: 21.7 ± 1.6 yrs, height: 162.1 ± 3.7 cm, weight: 52.2 ± 5.8 kg) and 20 healthy adult women (age: 21.8 ± 1.6 yrs, height: 161.9 ± 4.4 cm, weight: 52.9 ± 7.2 kg) participated in this study. For the forward jump participants were instructed to stand on two legs at a distance of 40% of their body height from the center of force plate. Participants were jump forward over a 15 cm hurdle to the force plate and land on their non-dominant or affected leg. Kinetic and kinematic data were obtained using 8 motion capture cameras and 1 force plates and joint angle, vertical ground reaction force and center of pressure. All statistical analyses were using SPSS 25.0 program. The differences in variables between the two groups were compared through an independent sample t-test, and the significance level was to p < .05. Results: In the hip and knee joint angle, the CAI group showed a smaller flexion angle than the control group, and the knee joint valgus angle was significantly larger. In the case of ankle joint, the CAI group showed a large inversion angle at all events. In the kinetic variables, the vGRF was significantly greater in the CAI group than control group at IC and mGRF. In COP Y, the CAI group showed a lateral shifted center of pressure. Conclusion: Our results indicated that chronic ankle instability decreases the flexion angle of the hip and knee joint, increases the valgus angle of the knee joint, and increases the inversion angle of the ankle joint during landing. In addition, an increase in the maximum vertical ground reaction force and a lateral shifted center of pressure were observed. This suggests that chronic ankle instability increases the risk of non-contact knee injury as well as the risk of lateral ankle sprain during forward jump landing.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.2
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• pp.207-212
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• 2013

In this study, distributed the ship's Centralized Air Conditioning System the way an individual to replace the air conditioning system by using Air-cooled air conditioner. Research results, Individually separated air conditioning system complement the heat source control and thermal efficiency problems and improves the efficiency of the device was confirmed. In addition, under the same conditions refrigeration capacity and coefficient of performance of the device, an average of about 3 %, 23 ~ 26 %, higher, Chilled Water Plants Compressor power consumption is about 12 % lower. Also while heating under the same conditions, power consumption is about 33.5 % lower. Therefore Individually Separated Air Conditioning System greatly contributed to the improved performance of the device and living spaces for comfortable temperature and humidity control as well as heating source could be obtained.

• Korean Journal of Applied Biomechanics
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• v.26 no.3
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• pp.249-255
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• 2016

Objective: This purpose of this study was to analyze the relationship between dimensionless leg stiffness and kinetic variables during gait performance, and its modulation with body weight. Method: The study sample consisted of 10 young women divided into 2 groups (Control, n=5 and Obese, n=5). Four camcorders (HDR-HC7/HDV 1080i, Sony Corp, Japan) and one force plate (AMTI., USA) were used to analyze the vertical ground reaction force (GRF) variables, center of pressure (COP), low limb joint angle, position of pelvis center and leg lengths during the stance phase of the gait cycle. Results: Our results revealed that the center of mass (COM) displacement velocity along the y-axis was significantly higher in the obese group than that in control subjects. Displacement in the position of the center of the pelvis center (Z-axis) was also significantly higher in the obese group than that in control subjects. In addition, the peak vertical force (PVF) and dimensionless leg stiffness were also significantly higher in the obese group. However, when normalized to the body weight, the PVF did not show a significant between-group difference. When normalized to the leg length, the PVF and stiffness were both lower in the obese group than in control subjects. Conclusion: In the context of performance, we concluded that increased dimensionless leg stiffness during the gait cycle is associated with increased velocity of COM, PVF, and the change in leg lengths (%).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.3
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• pp.250-255
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• 2005

The objective of this paper is to develop a new energy transport system for district cooling application by using type 2 absorption cycle. Cold energy from the LNG storage system is utilized as the cooling source of the condenser and the rectifier. The pressures of the system, UAs of the evaporator and the desorber, and the inlet temperatures of the refrigerant to each component are considered as the key parameters. The results show that UA of the evaporator is more dominant parameter on COP than that of the desorber and the optimum system pressure for the demand side is estimated as 525 kPa. For the present system, it is recommended that the refrigerant inlet temperature of the evaporator be lower than $4.3^{\circ}C$ for long-distance transportation. It is concluded that the cold energy from the LNG storage system can be effectively applied to the long-distance transportation system for district cooling application with the type 2 absorption cycle. The optimum operation conditions are also predicted from the parametric analysis.