• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.9
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• pp.979-988
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• 2014

Recently, the interest in the thermal comfort is ever increasing as the time people stay in the automobile is gradually increasing. So far, however, the cooling performance of the HVAC(heating and ventilation air conditioning) system is evaluated by thermal environment criteria such as indoor air velocity and temperature, not by a thermal comfort index. Furthermore, the precise criteria has not been established yet when the thermal comfort for the automobile is evaluated using numerical analysis. In this study, the numerical analysis of automobile indoor thermal comfort according to various parameters such as HVAC operating mode, airflow, passenger boarding conditions is performed during the HVAC system's initial operating time(20 minutes). The solar ray tracing model and S2S radiation model are used and validated to simulate an external heat source. Based on this study, an evaluation model which can predict the thermal comfort index for the combination of the above parameters is presented.

• Advances in environmental research
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• v.4 no.3
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• pp.143-153
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• 2015

The ventilation system is a key device to ensure both healthful indoor air quality (IAQ) and thermal comfort in buildings. The ventilation system should make the IAQ meet the standards such as ASHRAE 62. This study deals with a new approach to modeling the ventilation and IAQ requirement in residential buildings. In that approach, Elite software is used to calculate the air supply volume, and CONTAM model as a multi-zone and contaminant dispersal model is employed to estimate the contaminants' concentrations. Amongst various contaminants existing in the residential buildings, two main contaminates of carbon dioxide ($CO_2$) and carbon monoxide (CO) were considered. CO and $CO_2$ are generated mainly from combustion sources such as gas cooking and heating oven. In addition to the mentioned sources, $CO_2$ is generated from occupants' respirations. To show how that approach works, a sample house with the area of $80m^2$ located in Tehran was considered as an illustrative case study. The results showed that $CO_2$ concentration in the winter was higher than the acceptable level. Therefore, the air change rate (ACH) of 4.2 was required to lower the $CO_2$ concentration below the air quality threshold in the living room, and in the bedrooms, the rate of ventilation volume should be 11.2 ACH.

• Particle and aerosol research
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• v.20 no.2
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• pp.47-56
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• 2024

In this study, an empirical study was conducted to investigate the clean air delivery rate (CADR) and the proper particle cleaned air delivery per hour (PCH) of the air cleaning device installed in passenger car cabin. Changes in internal particle concentration were measured in the cabins of the pick-up type engine-driven car and the electric vehicle depending on cabin air filters, ventilation modes, and blower settings. In the tested cars, PM_2.5 collection efficiency of the HEPA filter was higher than that of the genuine filter. The PM_2.5 collection efficiency of each cabin air filter was measured to be similar regardless of the blower setting of the tested cars. This means that the higher the blower setting, the higher the CADR and the PCH. The infiltration rate varies depending on the air tightness of the car. The cabin was more contaminated with particles under driving. From the CADRs measured inside the passenger car cabin, the recirculation mode of HVAC system is a more effective for managing ultrafine particles than the fresh air mode. From a few assumptions, the proper PCH was derived about 0.8 times/min (48 times/h). From this result and several experiments, the proper operation setting of air cleaning device installed inside cars can be found out to control indoor air quality. Also, an appropriate operation settings of HVAC system can be found with considering cooling and heating conditions for thermal comfort in passenger car cabin.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.454-459
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• 2017

In this study, a thermal system was designed using a 3-way valve and PTC attached to a solar module. This design could help solve the problem of rising fossil fuel costs caused by limited reserves and environmental problems resulting from fossil fuel use. The thermal system is a hot-air and heating control system composed of a temperature sensor part, mode setting part (for hot air and heating modes), supply part, and thermal system control part. The temperature sensor part has piping and an indoor temperature display, and the temperature setting part has multiple monitoring functions. The mode setting part switches between hot air and heating modes and can be used to set the temperature. The thermal system control part performs functions such as PTC control and temperature setting, PTC day and night and time selection, hot air and heating control, and three-way valve selection. The results verify that the system operates with stable response speeds of $680{\mu}s$ in the temperature sensor part, $700{\mu}s$ in the mode setting part, and $610{\mu}s$ in the thermal system control part.

• Journal of the Korean Wood Science and Technology
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• v.43 no.6
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• pp.884-889
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• 2015

Appropriate evaluation of thermal insulation property of structural member and valid control of cooling/heating energy are important for improving building's energy efficiency. The typical heating system of house in Korea is the floor heating one. The radiation heating system is not only appropriate to climate and geographic conditions of Korea, but also advantageous to provide emotional comfort by the warm feeling of floor. Based on living conditions in Korea, scaled models of the wooden house and concrete house were designed. The ceiling was made of styrofoam insulation and the four sided walls and bottom were made of plywood and concrete, respectively. The floor was heated by heating film. Indoor vertical temperature distributions by floor heating system were measured by thermocouple, and surface temperatures on walls were measured by infrared thermography. Also, thermal insulation property of wooden wall was evaluated to build database for improving energy efficiency of wooden building. It is expected that collected data during tests of various types of floor and wall composition could be referenced for evaluating thermal environment of actual conditions of houses.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.10 no.2
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• pp.7-12
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• 2014

Government has recently restricted heating and cooling set temperatures for the commercial and public buildings due to increasing national energy consumption. The goal of this paper is to visualize a future two way indoor set temperature control impact on building energy consumption by using TRNSYS simulation modeling. The building was modelled based on the twin test cell with the same dimension. Air source ground coupled heat pump performance data has been used for modeling by TRNSYS 17. Daejeon weather data has been used from Korea Solar Energy Society. The heating set temperature in the reference room is $24^{\circ}C$ as well as the target room set temperature are $23^{\circ}C$, $22^{\circ}C$, $21^{\circ}C$ and $20^{\circ}C$. The cooling set temperature of the reference room is also $24^{\circ}C$ as well as the target room set temperature of $25^{\circ}C$, $26^{\circ}C$, $27^{\circ}C$ and $28^{\circ}C$. For the air source heat pump system, heating season energy consumption is $35.52kWh/m^2y$ in the reference room. But the heating energy consumption in the target room is reduced to 7.5% whenever the set temperature decreased every $1^{\circ}C$. The cooling energy consumption in the reference room is $4.57kWh/m^2y$. On the other hand, the energy consumption in the target room is reduced to 22% whenever the set temperature increased every $1^{\circ}C$ by two way controller. For the geothermal heat pump system, heating energy consumption in the reference room is reduced to 20.7%. The target room heating energy consumption is reduced to 32.6% when the set temperature is $22^{\circ}C$. The energy consumption in the target room is reduced to 59.5% when the set temperature is $26^{\circ}C$.

• Journal of the Korean housing association
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• v.24 no.6
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• pp.189-197
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• 2013

The purpose of the study was to analyze the improvement elements depended on housing quality measurement tool related to mental health. The data for the analysis was collected through questionnaire survey method from November 1, 2012 to January 17, 2013, and the sample consisted of 720 respondents living in single detached houses, multi-families detached houses, apartments, and town houses in 4 cities, Seoul, Busan, Daejeon, and Kwangju. The data were analyzed using descriptive statistics. The results of improvement elements are as follows: 1) Pedestrian-threaten street from cars in physical safety 2) A secluded or dark spot and fear of walking at night in social security, 3) Indoor noise, outdoor noise, and evidence of abandoned trash heap/bottle in neighborhood in health & sanitation, 4) Illegal parking and heating control system in facility convenience, 5) Extra kitchen, number of bathrooms, and community spaces in space convenience, 6) Openness and spaciousness of indoor room, and satisfaction of house and neighborhood in comfort, 7) Management common/sharing space in maintenance, 8) Energy saving facility and environment friendly materials use in sustainability, 9) Burden on housing cost, asset value on house, and school district in economic value, 10) Reflection of residents style, surrounding building's number of layers, and neighborhood appearance of preference in housing environment image.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.2
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• pp.251-255
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• 2015

Thermal deformation, such as bending and twisting, occurs among the polymer parts of air-conditioner indoor units because of repetitive temperature change during heating operation. In this study, a numerical method employing finite-element analysis to efficiently simulate the thermal deformation of an assembly is proposed. Firstly, the displacement of an actual assembly produced by thermal deformation was measured using a 3D optical measurement system. The measurement results indicated a general downward sag of the assembly, and the maximum displacement value was approximately 1 mm. The temperature distribution was measured using a thermographic camera, and the results were used as initial-temperature boundary conditions to perform temperature-displacement analysis. The simulation results agreed well with the measured data. To reduce the thermal deformation, the stiffness increased 100%. As the results, the maximum displacement decreased by approximately 5.4% and the twisting deformation of the holder improved significantly.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.10
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• pp.678-686
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• 2011

Simulation study on the operating characteristics in the solar hybrid R744 heat pump system for residential applications was carried out with heat pump operating temperature, outdoor temperature and solar radiation. As a result, collector operating time is decreased by 1.5 hours due to the increase of water temperature in the heat storage tank when the heat pump operating temperature rises. Heat pump operating time is reduced by 19.4% owing to the high temperature of a heat storage tank. Besides, indoor heating time is decreased from 10.3 to 5.5 hours as the indoor temperature increases from $3^{\circ}C$ to $11^{\circ}C$. In addition to, when the solar radiation rises from 10 to 20 MJ/$m^2$, the maximum outlet temperature of a solar collector is increased from $65^{\circ}C$ to $71^{\circ}C$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.6
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• pp.521-537
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• 2012

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2011. 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) Research trends of thermal and fluid engineering have been surveyed as groups of fluid machinery and fluid flow, thermodynamic cycle, and new and renewable energy. Various topics were presented in the field of fluid machinery and fluid flow. Research issues mainly focused on the rankine cycle in the field of thermodynamic cycle. In the new and renewable energy area, researches were presented on geothermal energy, fuel cell, biogas, reformer, solar water heating system, and metane hydration. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer, nanofluids and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer above liquid helium surface in a cryostat, methane hydrate formation, heat and mass transfer in a liquid desiccant dehumidifier, thermoelectric air-cooling system, heat transfer in multiple slot impinging jet, and heat transfer enhancement by protrusion-in-dimples. In the area of pool boiling and condensing heat transfer, researches on pool boiling of water in low-fin and turbo-B surfaces, pool boiling of R245a, convective boiling two-phase flow in trapezoidal microchannels, condensing of FC-72 on pin-finned surfaces, and natural circulation vertical evaporator were actively performed. In the area of nanofluids, thermal characteristics of heat pipes using water-based MWCNT nanofluids and the thermal conductivity and viscosity were measured. In the area of industrial heat exchangers, researches on fin-tube heat exchangers for waste gas heat recovery and Chevron type plate heat exchanger were implemented. (3) Refrigeration systems with alternative refrigerants such as $CO_2$, hydrocarbons, and mixed refrigerants were studied. Heating performance improvement of heat pump systems were tried applying supplementary components such as a refrigerant heater or a solar collector. The effects of frost growth were studied on the operation characteristic of refrigeration systems and the energy performance of various defrost methods were evaluated. The current situation of the domestic cold storage facilities was analyzed and the future demand was predicted. (4) In building mechanical system fields, a variety of studies were conducted to achieve effective consumption of heat and maximize efficiency of heat in buildings. Various researches were performed to maximize performance of mechanical devices and optimize the operation of HVAC systems. (5) In the fields of architectural environment and energy, diverse purposes of studies were conducted such as indoor environment, building energy, and renewable energy. In particular, renewable energy and building energy-related researches have mainly been studied as reflecting the global interests. In addition, various researches have been performed for reducing cooling load in a building using spot exhaust air, natural ventilation and energy efficiency systems.