• Economic and Environmental Geology
• /
• v.39 no.4 s.179
• /
• pp.485-494
• /
• 2006

This paper summarizes the history of geothermal research in Korea since 1920s and also describes the present status of research on heat flow, origin of thermal waters and geothermal exploitation and utilization. Geothermal research in Korea has been mainly related with hot spring investigation until 1970s. 1t was not until 1980s before heat flow study became continuous by research institute and academia and first nation-scale geothermal gradient map and heat flow map were published in 1996. Also in 1990s, geochemical isotope analysis of Korean hot spring waters and measurements of heat production rate of some granite bodies were made. Attempts to develop and utilize the deep geothermal water has been tried from early 1990s but field scale exploitations for geothermal water was activated in 2000s. Considering recent increase of demands on both deep and shallow geothermal energy utilization, outlook on future goethermal research and development is encouraging.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.33 no.6
• /
• pp.282-287
• /
• 2023

The effect of stress relief heat treatment temperature and duration time on the microstructure, residual stress and Vickers hardness of additively manufactured Ti-6Al-4V alloy using laser powder bed fusion process was clarified. As a result of stress relief heat treatment for 240 minutes at 823 K and 60 minutes or more at 873 K, residual stress was decreased less than 30 MPa without grain growth and phase transformation which causes dimensional distortion and deterioration of mechanical properties. In addition, hardness was increased with increasing heat treatment temperature and duration time. It was deduced that the refinement of acicular martensitic α' phase due to the increasing duration time of isothermal heat treatment at 773~873 K, which was not detected by XRD and phase map analysis using SEM-EBSD, probably increases the hardness.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.2
• /
• pp.199-206
• /
• 2004

The heat transfer enhancement by pulsating flow in a plate heat exchanger has been experimentally investigated in this study. The effect of the pulsating flow, such as pulsating frequency and flow rate on the heat transfer as well as pressure drop in a plate heat exchanger has been studied in detail. Reynolds number in cold side of a plate heat exchanger is varied 100∼530 while that of hot side is fixed at 620. The pulsating frequency is considered in the range of 5∼30 Hz. The results of the pulsating flow are also compared with those of steady flow. It is found that the average heat transfer rate as well as pressure drop is increased as flow rate is increased for both steady flow and pulsating flow cases. When pulsating flow is applied to the plate heat exchanger, heat transfer could be substantially increased in particular ranges of pulsating frequency or Strouhal number; St=0.36∼0.60 and pressure drop is also increased, compared with those of steady flow. However, in the region of low pulsating frequency or high pulsating frequency, heat transfer enhancement is in meager. Heat transfer enhancement map is suggested based on Strouhal number and Reynolds number of pulsating flow.

• Journal of Energy Engineering
• /
• v.23 no.3
• /
• pp.27-35
• /
• 2014

The existing flow regime map on mixed convection in vertical cylinders was investigated through an analysis of original literatures and its re-formation. The original literatures related to the existing map were reviewed. Using the investigated data and heat transfer correlations, the map was redrawn independently, and compared with the existing map. The redrawn map showed that mixed convection regime was not curved lines but straight lines and the transition regime was unable to be reproduced. Unlike the existing map with a little data, there are lots of data in the redrawn map. The reviews revealed that the existing map used the data selectively among the experimental and theoretical results, and a detailed description for lines forming mixed convection and transition regime was not provided. While considerable studies on mixed convection have been performed since that of Metais and Eckert, the existing map has still been used as the best method to distinguish natural, forced and mixed convection regime.

• Journal of Korean Society for Atmospheric Environment
• /
• v.16 no.4
• /
• pp.363-372
• /
• 2000

In order to overtake a quantitative analysis of effect of anthropogenic heat and different land-use on urban thermal environment numerical simulation of surface energy budget was carried out under typical summer synoptic condition. It is beneficial to understand surface temperature of complex urban surace. The different land-use types are classified of rice field farm fruit garden residential region forest water and swamp by using map scaled 1/25000 of Pusan metropolitan. The model predicts that maximum heat island intensity in the central part of Pusan is 7$^{\circ}C$ at 2000 LST in summertime. The surface temperature is propotional to the density of constructions. The effect of anthropogenic heat generation on surface temperature is the increase of 0.3$^{\circ}C$ at 1400LST in the central part of Pusan during summertime.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.1226-1231
• /
• 2009

This paper presents operating characteristics of internal heat exchanger(IHX) for $CO_2$ geothermal heat pump in the heating mode. Mass flow rate of $CO_2$, inlet temperatures of $CO_2$ at high and low pressure side were selected as main effect factors by using fractional factorial DOE(Design of Experiments). And RSM(Response Surface Method) was used in optimization phase. The results show that heat transfer rate of IHX increases when either inlet temperature of low pressure side decreases or inlet temperature of high pressure side increases. Effectiveness of IHX increases with increasing of inlet temperature of either high pressure side or low pressure side. Finally, performance contour map was provided over the operation ranges of the main design factors.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.11 no.2
• /
• pp.193-204
• /
• 1999

Performance of a variable-speed, roller-type vane compressor was evaluated at low evaporating temperature. First, an experimental investigation was conducted to examine the performance variation as functions of both outdoor temperature and rotating speed. For this purpose, a typical heat pump was implemented as a test apparatus to measure mass flow rate and power input. Secondly, computational investigations corresponding to the heat pump test conditions were performed to predict compressor performance using ORNL Map-Based compressor model. Results obtained from the heat-pump experiments showed that both mass flow rate and power consumption were sensitively dependent on both evaporating temperature and compressor speed as was predicted from the computational results. From the comparisons of both experimental and computational results, it was well recognized that the ORNL model was subjected to larger error in the accuracy of prediction as outdoor temperature decreased. When the outdoor temperature was above $-5^{\cire}C$, errors of predicted values corresponding to both mass flow rate and power consumption were estimated as $\pm$10% and $\pm$ 15%, respectively. Finally, it is suggested that the ORNL model needs to be re-evaluated if compressor map data tested below $-5^{\cire}C$(in evaporating temperature) are available.

• Journal of Convergence for Information Technology
• /
• v.11 no.7
• /
• pp.1-6
• /
• 2021

The purpose of this study is to improve the performance of the artificial neural network system for facial image analysis through the image landmark selection technique. For landmark selection, a CNN-based multi-layer ResNet model for classification of facial image age is required. From the configured ResNet model, a heat map that detects the change of the output node according to the change of the input node is extracted. By combining a plurality of extracted heat maps, facial landmarks related to age classification prediction are created. The importance of each pixel location can be analyzed through facial landmarks. In addition, by removing the pixels with low weights, a significant amount of input data can be reduced.

• Journal of The Korean Society of Emergency Medicine
• /
• v.29 no.5
• /
• pp.500-508
• /
• 2018

Objective: The aim of this study was to evaluate the clinical characteristics of heat stroke in a bath facility and investigate predictive factors of multiple major complications in heat stroke patients. Methods: This was a retrospective study on heat stroke patients who visited an urban emergency center from January 2010 to March 2018. We compared clinical characteristics, complication, and outcomes of heat stroke patients in bath and non-bath facilities. Multivariate logistic regression analysis were performed to identify independent predictors of multiple major complications in heat stroke patients. Results: A total of 67 heat stroke patients with heat stroke were enrolled, of which 42 (62.6%) were in a bath facility and 25 (37.3%) were in a non-bath facility. Patients with heat stroke in the bath facility were characterized by old age, past medical history of hypertension and diabetes mellitus, and high incidence of hypotension compared with those in the non-bath facility but also low incidence of acute renal failure, seizure, and multiple major complications. In the multivariate analysis, predictive factors of multiple major complications in heat stroke patients were non-bath facility (odds ratio [OR], 5.4; 95% confidence interval [CI], 1.2-29.9), Glasgow Coma Scale (GCS)${\leq}8$ (OR, 8.2; 95% CI, 1.3-49.4), and mean arterial pressure (MAP), body temperature above $40.5^{\circ}C$ (OR, 8.1; 95% CI, 1.1-58.8) <60 mmHg (OR, 14.8; 95% CI, 1.8-122.9). Conclusion: Heat stroke in the bath facility resulted in less major complications, and high body temperature, GCS ${\leq}8$, and MAP <60 mmHg were independent predictive factors of multiple major complications in heat stroke patients.

• Journal of Mechanical Science and Technology
• /
• v.15 no.12
• /
• pp.1711-1727
• /
• 2001

Heat transfer coefficient were measured and new correlations were developed for two-phase heat transfer in a horizontal pipe for different patterns. Flow patterns were observed in a transparent circular pipe (2.54 cm I. D. and L/D=96) using an air/water mixture. Visual identification of the flow patterns was supplemented with photographic data and the results were plotted on the flow regime map proposed by Taitel and Dukler and agreed quite well with each other. A two-phase heat transfer experimental setup was built for this study and a total of 150 two-phase heat transfer data with different flow patterns were obtained under a uniform wall heat flux boundary condition. For these data, the superficial Reynolds number ranged from 640 to 35,500 for the liquid and from 540 to 21,200 for the gas. Our previously developed robust two-phase heat transfer correlation for a vertical pipe with modified constants predicted the horizontal pipe air-water heat transfer experimental data with good accuracy. Overall the proposed correlations predicted the data with a mean deviation of 1.0% and an rms deviation of 12%.