• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.25 no.1
• /
• pp.20-27
• /
• 2013

Numerical modeling of $CO_2$ water heater was conducted prior to optimal design of medium and large sized $CO_2$ water heater, and the experimental test with small sized $CO_2$ water heater having heat capacity of 4 kW was completed to verify the present numerical model. The present model estimated the experimental data of COP(coefficient of performance), heating capacity, and the hot water outlet temperature within the range of 3% to 8% of mean deviation. As increase of EEV(electric expansion valve) opening area, decreasing of heating capacity and the hot water outlet temperature, and increasing of COP were found in both experimental and numerical investigation.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.3
• /
• pp.409-424
• /
• 1987

Simulation on the hot water ONDOL heating system was made in order to investigate the variation of room temperature and specific fuel consumption of boiler. Heat balance equation was derived by response factors and solved implicitly. Variation of room temperature and specific fuel consumption of boiler were calculated with respect to the thickness of room floor, the absorptivity of wall for solar radiation, on-off temperature range of boiler and air exchange. The results show that specific fuel consumption of boiler is independent of the thickness of room floor and decreases with increasing the absorptivity of wall and on-off temperature range of boiler. However, it increases with increasing the air exchange. They also show that, when the absorptivity and on-off temperature range of boiler are increased, the amplitudes of room temperature variation increase.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.19 no.7
• /
• pp.74-80
• /
• 2020

The ocher jjimjilbang for a single-person household that will be studied in this study is 2.1 ㎡ in size, and this study was conducted to implement well-being room heating that is beneficial to health by supplying radiant heat provided by hot water during room heating by embedding hot water panels in the walls of the ocher jjimjilbang to configure a hot water circulating system. In addition, the ocher bed and the ocher walls, which have been verified through many study findings and reference materials, were constructed so that the living life with a bed and the ocher jjimjilbang would be implemented simultaneously. As the mass flow rate of the hot water increased, the magnitude of the wall temperature rise thanks to the hot water increased, and as the flow rate of the hot water increased, the transfer rate of the heat transferred from the wall of the ocher jjimjilbang to the air inside the wall of the ocher jjimjilbang increased.

• Proceedings of the Safety Management and Science Conference
• /
• 2010.04a
• /
• pp.81-95
• /
• 2010

Gas turbines generating power operate in high temperature condition and use natural gas as fuel. For that reason, there are many cases where damage is done to the hot gas parts caused by the high temperature and many accidents occur like gas explosions, then various efforts are needed to maintain the hot gas parts and prevent accidents. It is difficult to find the root causes of damage to the hot gas parts from the gas explosion caused by gas leakage through rotor cooling air line from fuel gas heat exchanger during the shut down. To prevent gas turbine from damage, removal of gas leakage inside of gas turbine is required by purging the turbine before firing, improving the fuel gas heating system and installing alarm systems for detecting gas leakage from stop valve to turbine while the gas turbine has shut down.

• Journal of the Korea Safety Management & Science
• /
• v.12 no.2
• /
• pp.75-82
• /
• 2010

Gas turbines for power generating operate in a very high temperature condition and use natural gas for fuel. For this reason, many cases of damage happen at hot gas parts which are severely affected by high temperature gas and many cases of explosion occur by fuel gas. So a lot of efforts should be made to prevent hot gas parts damage and gas explosion accidents. Though there are many damage cases and explosion accidents, it is very difficult to find out the root causes of hot gas parts damage caused by gas explosion due to gas leakage in the heat exchanger for air cooling and gas heating. To prevent gas turbine from damage caused by gas explosion, removal of leakage gas from gas turbine is inevitably required before firing the gas turbine and installing alarm systems is also required for detecting gas leakage at stop valve to turbine while shut down.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.27-32
• /
• 2009

The measuring apparatus such as heat meter is legally obliged to be installed and used for heat rating with heat or flow rate in residential buildings in Korea. There are two kinds of apparatus to measure heat consumed at each households, i.e., heat meter and hot water flowmeter. Contrast to the most of buildings with hot water flowmeter well being used for rating, heat meters have been used only 42.6% in the buildings with central heating system. But there is a critical problem in the course of using hot water flowmeter for heat rating, yielding distorted and unfair result which is different from the real value of heat supplied. Experiments with several parameters were carried out in this study to analyze this phenomenon quantively and alternative methods were proposed for rational heat rating.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2003.05a
• /
• pp.19-22
• /
• 2003

The purpose of this study is to analyze the curing effect of planar surface heater for concreting in cold weather. Some experiments were conducted to evaluate the temperature history of concrete structures cured with heating sheets. Results are as follows ; (1) The temperature of concrete showed continuously rising trend with the heating by planar surface heater under the cold environmental condition of 3~-12$^{\circ}C$. And after about 24 hours the maximum temperature of concrete was reached at 25~3$0^{\circ}C$. (2) The temperature of slab concrete heated by planar surface heater of 130W/$m^2$ was at least $25^{\circ}C$ higher than that of an exterior air, and the curing performance was much more effective than heating by hot wind machine. (3) Through the curing by planar surface heater for 48 hours, the concrete maturity of about 1.5 times to heating by hot wind machine was acquired.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.3 no.3
• /
• pp.185-190
• /
• 1974

Floor panel heating system is popular in Korea as dwelling house heating system. There are two methods for keeping floor surface warm. One method is delivering warm air under the floor such as Roman Hypocaust and Korean traditional Ondol. The other method is imbedding hot water pipes into the concrete floor slab. This paper gives basic equations for steady and transient solutions of heat conduction from hurried pipes. For steady-state solution, fin Efficiency Method and Sink and Source Method were introduced. Sink and Source Method is applied to transient state and basic solution is given in the form of Exponential Integral Function. Numerical solutions can be solved easily by digital computer from these equations.

• Proceedings of the Korean Society for Bio-Environment Control Conference
• /
• 1999.04a
• /
• pp.5-8
• /
• 1999

동일부지내에 설치된 각 단동하우스에 무가온 상태 및 심야전력 전기히터, 온풍난방기를 각각 설치하여, 동절기 시설원예용 하우스의 온열환경, 난방방식별 에너지 소비특성, 난방효율에 대해서 검토하였다. 동절기 하우스의 벽체, 지붕을 통해 유출되는 관류열량을 정량적으로 계산하므로서, 하우스의 단열계획과 효율적 난방방식의 선정 및 난방에너지 절약을 유도할 수 있는 기초데이터를 제시하고자 한다. (중략)

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.3 no.1
• /
• pp.13-16
• /
• 1974

The change in color of vegetables containing chlorophyll on cooking has been of concern to food scientists. This experiment was initiated to determine the effect of different heating methods and time on the chlorophyll of green pepper. Peppers were heated at 100 C for 5, 10, and 15 min by using boiling water, steam and hot air and for 1, 2 and 3 min in microwave oven. The results showed that chlorophyll content decreased with increasing heating time. Among the heat treatments employed steaming gave the greatest effect and boiling water was the next. Hot air and microwave treated samples changed only small amount of chlorophyll. Generally pheophytin formation was increased with decreasing chlorophyll content.