• Journal of Korean Association for Spatial Structures
• /
• v.7 no.3 s.25
• /
• pp.67-77
• /
• 2007

The purpose of this study is to provide fundamental heating design data for the large public enclosures as gymnasium. This study executed indoor thermal environment verification of the existing gymnasium by measuring temperature distribution with and without heating the space in winter. Heating loads from human body was not considered. We examined various indoor thermal environment factors of the large enclosed space in this study which include vertical and horizontal temperature distribution, supply and return air flow feature, thermal comfort environment feature, amount of ventilation and etc.

• KIEAE Journal
• /
• v.16 no.6
• /
• pp.13-19
• /
• 2016

Purpose: In this study, we examined outdoor air fraction using historical data of actual Air Handling Unit (AHU) in the existing building during intermediate season and analyzed optimal outdoor air fraction by control types for economizer. Method: Control types for economizer which was used in analysis are No Economizer(NE), Differential Dry-bulb Temperature(DT), Diffrential Enthalpy(DE), Differential Dry-bulb Temperature+Differential Enthalpy(DTDE), and Differential Enthalpy+Differential Dry-bulb Temperature (DEDT). In addition, the system heating and cooling load were analyzed by calculating the outdoor air fraction through existing AHU operating method and control types for economizer. Result: Optimized outdoor air fraction through control types was the lowest in March and distribution over 50% was shown in May. In case of DE control type, outdoor air fraction was the highest of other control types and the value was average 63% in May. System heating load was shown the lowest value in NE, however, system cooling load was shown 1.7 times higher than DT control type and 5 times higher than DE control type. For system heating load, DT and DTDE is similar during intermediate season. However, system cooling load was shown 3 times higher than DE and DEDT. Accordingly, it was found as the method to save cooling energy most efficiently with DE control considering enthalpy of outdoor air and return air in intermediate season.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.17 no.5
• /
• pp.436-443
• /
• 2005

Experimental study was performed to understand the operation of an on-site showcase working in a super discount store. Inlet and outlet temperatures of evaporator, condenser, expansion valve and compressor were measured for both air and refrigerant sides. Electric power consumption of compressors, defrosting heaters, cooling water pumps and etc. were measured. The operating characteristics of the showcase system under various working conditions were analyzed and discussed. During the defrosting process, the air temperature inside the showcase increased to $15^{\circ}C$, which gave harmful effect to the frozen food. The collected data will serve as valuable information for diagnosing and improving the performance of showcases.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2000.11b
• /
• pp.498-505
• /
• 2000

Performance of a hydraulic system is influenced by its working temperature. Therefore, it is very important to make the system perform uniformly in an entire range of the working temperature. In this study a simulation of a hydraulic control system for the powershift transmission of tractors was conducted and the effect of the temperature was investigated in terms of design conditions of the system. Results of the simulation are as follows. The hydraulic control system with a spring accumulator was found to be more convenient to control the shifting time than that with a gas accumulator. By returning the oil from the clutches to the system through a path between the filter and pump, the time delay due to the pressure difference between the low and high temperatures could be reduced. Therefore, it was recommended that the hydraulic control system for the powershift transmission of tractors must be equipped with a spring accumulator and a circuit to return oil from the clutches to the system through a path between the filter and pump.

• Journal of Veterinary Clinics
• /
• v.19 no.2
• /
• pp.139-146
• /
• 2002

The purpose of this study was to construct fundamental information for the usefulness and effects of thermography in Thoroughbred horses. total 10 horses were examined to determine a normal thermal pattern before and after sedation in lower limbs and ophthalmic area, and to investigate the effects of thermography during 42 days after induced wound and arthritis. In normal horses, the range of temperature difference(${\Delta}T$) of symmetry site in lower limbs was 0.20 to $0.68^{\circ}C$ on pre-sedation, which was simillar to that of post sedation, 0.17 to $0.74^{\circ}C$, and eyeball area was 0.34 to $0.68^{\circ}C$. Thermographically, the warmest area in normal limbs were coronary band of frontal view and the region between heel bulbs of back view. And temperature difference(${\Delta}T$) after clipping in left forelimb was increased 1 to $3^{\circ}C$ more than before clipping. However, there was no significant change of the temperature difference and degree of clinical signs by the process of inflammation healing during the experiment period in the all groups. These results suggest that the thermography was especially helpful in following clinical course of a disease because the thermal pattern will return to normal with declining clinical signs and healing of the lesion.

• Journal of Institute of Convergence Technology
• /
• v.7 no.1
• /
• pp.1-6
• /
• 2017

The Heat exchanger for deep geothermal system is very important to enhance the efficiency of the system. The co-axial heat exchanger is used due to the limitation of digging space. The heat transfer on the external surface of outer pipe should be high to receive a large amount of heat from the ground. However, the inner pipe should be insulated to reduce the heat loss and increase the temperature of discharge water. This study made experiment apparatus to describe the co-axial heat exchanger and measure the heat transfer coefficients on the internal and external surface. And the pin-fin was designed and fixed on the internal surface to increase the efficiency of heat exchanger. Finally, we calculated the temperature of discharge water using the heat transfer circuit of co-axial heat exchanger and heat transfer coefficient which from experimental results. The water temperature was reached the ground temperature at -500 m and following the ground temperature. When the water return to the ground surface, the water temperature was decreased due to heat loss. As the pin-fin case, the heat transfer coefficient on the internal surface was decreased by 30% and it mean that the pin-fin help to insulate the inner pipe. However, the discharge water temperature did not change although pin-fin fixed on the inner pipe.

• Journal of the Korean Society of Safety
• /
• v.39 no.3
• /
• pp.7-13
• /
• 2024

This study examines the physical characteristics of self-regulating heating cables caused by increased temperature and fire risk due to local degradation. A thermo hygrostat system, a convection dryer, a digital multimeter (Agilent 34465 A), NI DAQ, and the LabVIEW program were used to assess the physical properties in response to temperature fluctuations. As the temperature increases, the resistance of the self-regulating heating cable increases; however, when the critical point is exceeded, the resistance sharply decreases. A problem arises when the resistance value cannot return to its original state even though the temperature is lowered to the initial state. Moreover, when the ambient temperature rises while power is applied, the resistance value initially increases, and the flowing current decreases, maintaining a constant state. However, when the critical temperature is exceeded, the flowing current increases because of a rapid decrease in the resistance value, progressing to ignition. When the resistance value decreases because of the deterioration of one local area, the total resistance value becomes less than the initial resistance value. Therefore, the flowing current increases and an ignition problem occurs at one location where deterioration occurs. Despite the sustained flames and arcs resulting from the changes in the overall physical properties of the self-regulating heating cable and resistance variations due to local decline, the fire continued as the flowing current was lower than the operating current of the circuit breaker, failing to cut the power. In the case of self-regulating heating cables and heating wires, which are the leading causes of fires in winter, efforts are needed to ensure the need for periodic maintenance and the use of KS-certified products.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.05a
• /
• pp.88-92
• /
• 2003

In this paper, the characteristics of the ZnO films deposited on AI bottom electrode and the temperature effects on the ZnO film growth are presented along with the fabrication and their evaluation of the film bulk acoustic wave resonator (FBAR) devices. All the films used in this work were deposited using a radio-frequency (RF) magnetron sputtering technique. Growth characteristics of the ZnO films are shown to have a strong dependence on the deposition temperatures ranged from room temperature to 35$0^{\circ}C$ regardless of the RF power applied for sputtering the ZnO target. In addition, according to the growth characteristics of the distinguishably different micro-crystal structures and the degree of the c-axis preferred orientation, the deposition temperatures can be divided into 3 temperature regions and 2 critical temperatures in-between. Overall, the ZnO films deposited at/below 20$0^{\circ}C$ are seen to have columnar grains with a highly preferred c-axis orientation where the full width at half maximum (FWHM) of X-ray diffraction rocking curve is 14$^{\circ}$. Based on the experimental findings, several FBAR devices were fabricated and measured. As a result, the FBAR devices show return loss of ~19.5dB at resonant frequency of ~2.05GHz.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.9 s.240
• /
• pp.1235-1242
• /
• 2005

A district heating(DH) system supplies environmentally-friend heat and is appropriate for reduction of energy consumption and/or air pollutions. The DH transmission pipe, composed of supply and return pipes, has been used to transmit the heat and prevent heat loss during transportation. The two types of pipes are operated at a temperature of $75\~115^{\circ}C\;and\;40\~65^{\circ}C$, respectively, with an operating pressure of less than 1.568MPa. The objectives of this paper are to systematize data processing of transition temperature and investigate its effects on fatigue life of DH pipes. For the sake of this, about 5 millions temperature data were measured during one year at ten locations, and then available fatigue lift estimation schemes were examined and applied to quantify the specific thermal fatigue life of each pipe. As a result, a relational database management system as well as reliable fatigue lift evaluation procedures is established for Korean DH pipes. Also, since the prototypal evaluation results satisfied both cycle-based and stress-based fatigue criteria, those can be used as useful information in the future fer optimal design, operation and energy saving via setting of efficient condition and stabilization of water temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.12
• /
• pp.837-842
• /
• 2015

In this study, the characteristics of electrostatic attenuation in plain shape glass filament sample (0.29 mm thickness, cross section of $12.25cm^2$, $16cm^2$, $20.25cm^2$) for insulator has been measured at temperature of $5^{\circ}C{\sim}38^{\circ}C$, humidity of 50%~90%. The results of this study are as follows. In case of samples that the cross section is $12.25cm^2$, $16cm^2$, $20.25cm^2$ at humidity of 50%~90%, it found that the electrification voltage of electrostatic increased with increasing temperature, with a return to decrease at $20^{\circ}C$. In case of samples that the cross section is $12.25cm^2$, $16cm^2$, $20.25cm^2$ at temperature of $5^{\circ}C{\sim}38^{\circ}C$, it found that the electrification voltage of electrostatic decreased with increasing humidity. In case of the sample at temperature of $20^{\circ}C$ and humidity of 65%, 75%, it found that the electrification voltage of electrostatic increased with increasing cross section. In case of the sample at humidity of 65% and cross section of $12.25cm^2$, the time that it takes to reduce electrification voltage of electrostatic in half decreased to 0.912s, 0.736s, 0.673s with increasing temperature to $10^{\circ}C$ $20^{\circ}C$, $30^{\circ}C$.