• Journal of Bio-Environment Control
• /
• v.28 no.4
• /
• pp.335-341
• /
• 2019

In order to provide basic data for uniformization of temperature distribution in heating greenhouses, heating experiments were performed in two greenhouses with a hot water heating system. By analyzing heat transfer characteristics and improving pipes layout, measures to reduce the variation of pipe surface temperature and to improve the uniformity were derived. As a result of analyzing the temperature distributions of two different greenhouses and examining the maximum deviation and uniformity, it was found that the temperature deviation of greenhouses with a large amount of hot water flow and a short heating pipe was small and the uniformity was high. And it was confirmed that the temperature deviation was reduced and the uniformity was improved when the circulating fan was operated. The correlation between the surface temperature of the heating pipe and the indoor air temperature was a positive correlation and statistically significant(p<0.01) in both greenhouses. It was confirmed that the indoor temperature distribution in a hot water heating greenhouse was influenced by the surface temperature distribution of heating pipe, and the uniformity of indoor temperature distribution could be improved by arranging the heating pipe to minimize the temperature deviation. Analysis of the heat transfer characteristics of heating pipe showed that the temperature deviation increased as the pipe length became longer and the temperature deviation became smaller as the flow rate in pipe increased. Therefore, it was considered that the temperature distribution and the uniformity of environment in a greenhouse could be improved by arranging the heating pipe to shorten the length and controlling the flow velocity in pipe. In order to control the temperature deviation of one branch pipe within $3^{\circ}C$ in the tube rail type hot water heating system most used in domestic greenhouses, when the flow velocity in the pipe is 0.2, 0.4, 0.6, 0.8, $1.0m{\cdot}s^{-1}$, the length of a heating pipe should be limited to 40, 80, 120, 160, 200m, respectively.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.1262-1266
• /
• 2009

The study aims to analyzed and identify the heat transfer characteristics of heating unit for car using experimental method in order to design DPH. The temperature comparison processes were done with various experimental conditions. In addition, the optimal conditions of DPH design were proposed as field test in real car, hot air flow, transient situation.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.04a
• /
• pp.140-141
• /
• 2022

CFD analysis was performed to analyze the temperature distribution of the inner space of the curing house according to blocking the opening of the gang-form with a tent in case of concrete pouring and heat curing of the apartment house during the winter season. If the gang-form opening is closed with a tent during internal heating using a hot air blower in the winter, the internal temperature rises compared to the non-reserved due to air-tightness of the curing spaces, and uniform temperature distribution can be ensured. In addition, it is possible to increase curing efficiency by reducing the amount of heat supplied and shortening the heating time.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.22 no.12
• /
• pp.821-827
• /
• 2010

Study on the performance characteristics of the solar hybrid system with heat pump operating temperature during winter season has performed by using an experimental test. The system performance and operating characteristics with the heat pump operating temperature, hour and load condition were investigated and analyzed. As a result, the hot water temperature was significantly affected by the heat pump operating temperature at the morning(time 1) and noon(time 2). However, hot water temperature was set by the radiation quality and collecting operation hour at the afternoon(time 3). In addition to the solar fraction was decreased for the high heat pump operating temperature because the heat pump operated with a long operating time and short operating period.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.5
• /
• pp.235-241
• /
• 2002

The process of energy separation in a low pressure vortex tube with air as a working medium is studied In detail. Experimental data of the temperature of the cold and hot air leaving the vortex tube are presented. The variation of the maximum wall temperature along the inner surface of the vortex tube and the temperature distribution in the vortex tube provides useful information about the location of the stagnation point of the flow field at the axis of the vortex tube. In this study Outer tube is used for the application of Diesel engine exhaust. The hot gas flow is fumed 180° and passes the outside of the vortex tube a second time heating it. From this geometric setup of a vortex tube the effects of energy separation and the prediction of the ignition of Diesel Soot is presented by experimental data.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.24 no.1
• /
• pp.117-123
• /
• 2010

Proposed induction-heated system is innovative system which applied special high-frequency power circuit technique for thermal converse technique and IH(Induction-Heating) magnetic induction heating generated from induction-heated metallic package that is for distillation unit. This electromagnetic induction heating technique is used high frequency inverter. By using high frequency inverter high frequency alternative current in the range of [kHz] can be made with conventional alternative current. In this contribution IGBT module is used for high frequency inverter. Resonant high frequency inverter make system of high capacity and high efficiency. This paper describes the temperature control of induction heating system hot air producer using the voltage-fed series resonant high-frequency inverter which can operate in the frequency range from 20 to 44[kHz].

• Proceedings of the SAREK Conference
• /
• 2007.11a
• /
• pp.552-557
• /
• 2007

Due to the recent improvement of living standard of residential buildings, the requirements of the thermal comfort and energy saving in heating system have been raised. The radiant floor heating system has been widely used as a residential heating method, which has been modernized to use hot water running into the tubes embedded in the floor structure. The uniform flow distribution is very important factor for a radiant floor heating system such as a blood vessel system in human body. Therefore, it is necessary to investigate the operating characteristics to develop an optimal radiant floor heating system. In this study, numerical analyses were carried out, using a commercial CFD code, FLUENT, to obtain the velocity distribution under steady, three-dimensional, standard k-$\varepsilon$ model and no-slip condition. Results are graphically depicted with various parameters.

• Journal of the Korean Solar Energy Society
• /
• v.35 no.6
• /
• pp.25-33
• /
• 2015

In this study, heating performance of the air-cooled heat pump with vapor-injection (VI) cycles, re-heater and solar heat storage tank was investigated experimentally. Devices used in the experiment were comprised of a VI compressor, re-heater, economizer, variable evaporator, flat-plate solar collector for hot water, thermal storage tank, etc. As working fluid, refrigerant R410A for heat pump and propylene glycol (PG) for solar collector were used. In this experiment, heating performance was compared by three cycles, A, B and C. In case of Cycle B, heat exchange was conducted between VI suction refrigerant and inlet refrigerant of condenser by re-heater (Re-heater in Fig. 3, No. 3) (Cycle B), and Cycle A was not use re-heater on the same operating conditions. In case of Cycle C, outlet refrigerant from evaporator go to thermal storage tank for getting a thermal energy from solar thermal storage tank while re-heater also used. As a result, Cycle C reached the target temperature of water in a shorter time than Cycle B and Cycle A. In addition, it was founded that, as for the coefficient of heating performance($COP_h$), the performance in Cycle C was improved by 13.6% higher than the performance of Cycle B shown the average $COP_h$ of 3.0 and by 18.9% higher than the performance of Cycle A shown the average $COP_h$ of 2.86. From this results, It was confirmed that the performance of heat pump system with refrigerant re-heater and VI cycle can be improved by applying solar thermal energy as an auxiliary heat source.

• Journal of the Korean Solar Energy Society
• /
• v.31 no.5
• /
• pp.77-84
• /
• 2011

Korea and some other countries located in the northern hemisphere employ the air conditioner for the space cooling in the hot summer season and also some kinds of heaters for the space heating in the cold winter season. Especially in Korea, a great number of air conditioners of about 12,700,000 sets have been used these days. However, they are used for a short operation period of only 58 days a year, which results in the material and economic losses. To solve this problem and employ this system for the emergency shelter, a new conversion unit which could convert the existing air conditioner to a heat pump system for simultaneous heating and cooling was developed in this study, and the thermal performance was tested. The results indicated that the indoor air could be heated from $27^{\circ}C$ to $39^{\circ}C$ by the air conditioner converted to a heat pump system with the ambient temperature variation of $-10^{\circ}C{\sim}10^{\circ}C$, and cooled from $20^{\circ}C$ to $15^{\circ}C$ by the converted system with the ambient temperature variation of $20^{\circ}C{\sim}35^{\circ}C$. And also the heating COP increased from 3.3 to 5.3 in case of the heat exchange of the super cooling(HESC) circuit and from 3.0 to 4.0 in case of the By-pass with the ambient temperature variation of $-10^{\circ}C{\sim}10^{\circ}C$, respectively, whereas the cooling COP decreased from 3.1 to 2.1with the increase of the ambient temperature from $20^{\circ}C$ to $35^{\circ}C$.

• Journal of the Korean Wood Science and Technology
• /
• v.29 no.4
• /
• pp.16-24
• /
• 2001

Conventional hot-air oven-drying method takes at least four hours to determine the moisture content of wood sample and this method is not always acceptable to wood industry. In this study samples of six different specifications from Paulownia coreana, Pinus densiflora and Quercus acutissima were dried in domestic microwave oven to their oven dry weights to investigate the possibility of rapid moisture content determination technique using microwave-oven drying method. Continuous heating time, cooling time and intermittent heating time were determined by each species and sample specifications. Temperatures of surface and center of samples were also measured during drying. Oven-drying times were reduced to 1/7~1/10 of conventional hot-air oven-drying method. Therefore microwave heating and drying techniques appear attractive for wood industry as a rapid moisture content determination method.