• Particle and aerosol research
• /
• v.6 no.1
• /
• pp.1-7
• /
• 2010

Generally, large amounts of DOP(Di-Octyl Phthalate) chemicals are used as plasticizers in PVC compound manufacturing processes. However, it is very important to collect DOP species immediately from a workplace in order to protect worker's heath and recover them. To accomplish these objectives, we need to understand the droplet formation and growth mechanisms of DOP species. In this study, two important parameters such as temperature gradient and residence time were considered to clarify these mechanisms. We found that residence time is very critical to determine the droplet size distribution of DOP, whereas temperature gradient in general operating conditions(less than $-6.8^{\circ}C/cm$) is negligible.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.2
• /
• pp.239-248
• /
• 1997

Steady components and unsteady components of second-order velocity and temperature within pulse tube refrigerators were obtained. Second-order solutions were obtained from the first-order solutions of continuity, momentum and energy equations, assuming that the amplitude of the piston motion is small. The axial temperature gradient was considered in the analysis. The flow direction of the streaming was consistent with previous experimental observations. Effects of axial temperature gradient on secondary flow and second-order temperature were shown.

• Journal of computational fluids engineering
• /
• v.21 no.2
• /
• pp.32-39
• /
• 2016

The Gradient Biome is a unique and large greenhouse(length 200 m, width 50 m, height:40 m) in which the elements of the weather, such as temperature and humidity, are controlled and reproduced in such a way as to create a continuous gradient from the tropical to frigid zones along specified longitudinal or transvers lines on the earth. One of the main purposes of the Gradient Biome is to observe the possible responses of the ecosystems (mainly plants), which are to be corresponding to each test climate and be introduced in the Biome, to the expected global warming. As one of the expected responses is the shift of the ecosystem(s) toward the region of suitable environment, there should be no artificial obstacles, which can prevent the shift, inside the facility. However, it is important but not so easy to find the ways of how the temperature and humidity in the Biome could be reproduced since the environmental variables tends to be homogeneous. In this paper, numerical simulations were carried out to find the effective control methods for air temperature and humidity inside the real scale Biome. One of the contributed solvers of OpenFOAM, which is an open source physics simulation code, was modified and used for the simulations.

• Steel and Composite Structures
• /
• v.29 no.1
• /
• pp.53-66
• /
• 2018

A high-order nonlocal strain gradient model is developed for wave propagation analysis of porous FG nanoplates resting on a gradient hybrid foundation in thermal environment, for the first time. Material properties are assumed to be temperature-dependent and graded in the nanoplate thickness direction. To consider the thermal effects, uniform, linear, nonlinear, exponential, and sinusoidal temperature distributions are considered for temperature-dependent FG material properties. On the basis of the refined-higher order shear deformation plate theory (R-HSDT) in conjunction with the bi-Helmholtz nonlocal strain gradient theory (B-H NSGT), Hamilton's principle is used to derive the equations of wave motion. Then the dispersion relation between frequency and wave number is solved analytically. The influences of various parameters (such as temperature rise, volume fraction index, porosity volume fraction, lower and higher order nonlocal parameters, material characteristic parameter, foundations components, and wave number) on the wave propagation behaviors of porous FG nanoplates are investigated in detail.

• International Journal of Concrete Structures and Materials
• /
• v.10 no.1
• /
• pp.39-46
• /
• 2016

In this study, different proportions of glass beads used for road marking were added into the concrete samples to reduce the temperature gradient through the concrete pavement thickness. It is well known that decreasing the temperature gradient reduces the risk of thermal cracking and increases the service life of concrete pavement. The extent of alkali-silica reaction (ASR) produced with partial replacement of fine aggregate by glass bead was investigated and compressive strength of concrete samples with different proportion of glass bead in their mix designs were measured in this study. Ideal results were obtained with less than 0.850 mm diameter size glass beads were used (19 % by total weight of aggregate) for C30/37 class concrete. Top and bottom surface temperatures of two different C30/37 strength class concrete slabs with and without glass beads were measured. It was identified that, using glass bead in concrete mix design, reduces the temperature differences between top and bottom surfaces of concrete pavement. The study presented herein provides important results on the necessity of regulating concrete road mix design specifications according to regions and climates to reduce the temperature gradient values which are very important in concrete road design.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.1E
• /
• pp.3-6
• /
• 2001

Sound pressure level (SPL) measurements were performed on a controlled test track vehicle coast-by runs of a passenger vehicle with six different sets of tires across a range of temperatures. A small but significant reduction of noise level with positive temperature increases was observed for some tires. The temperature gradient of the different tires at 80㎞/h ranged from -0.07 to + 0.01 dB/℃. Frequency analysis of the tire noise identified that noise content in the range of 1,300 to 1,900Hz was particularly sensitive to temperature changes. Differences in SPL due to speed and tire type were much greater than that due to temperature.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.15 no.4
• /
• pp.65-72
• /
• 2011

Numerical simulation has been performed to investigate the bubbly flow in the liquid with vertical temperature gradient. The objective of this study is to establish an accurate numerical prediction program of gas-liquid two-phase flows in a vertical temperature gradient condition, whose mathematical model is formulated by the Eulerian-Lagrangian model. The present numerical results reveal the temperature mixing mechanism and the fluid dynamical characteristics induced by the bubbly flow in the liquid with stratified temperature. The effects of bubble radius, void fraction, and gas flow rate on bubble-driven convective flow are considered, too.

• 한국연소학회:학술대회논문집
• /
• 2004.06a
• /
• pp.7-14
• /
• 2004

The lift-off characteristics of the triple flame have been studied experimentally with various mean velocities and concentration gradients using a multi-slot burner, which can control the concentration gradient and the mean velocity independently, Lift-off height, axial maximum velocity, flame temperature, and some other characteristics were examined for methane and propane flame, It was found that minimum values of the lift-off heights exist at a certain concentration gradient for constant mean velocity, and this result implies that the propagation velocity has a maximum value at this condition, OH radical distribution was measured with LIF method and velocity variation along streamline was measured with PlV system. In addition maximum temperature along streamline was measured with CARS system. The intensity of the diffusion flame affects on the propagation velocity of triple flame in the region of very weak concentration gradient.

• Journal of Acupuncture Research
• /
• v.17 no.1
• /
• pp.89-105
• /
• 2000

In order to obtain the clinical data on the different effects of the three different methods of indirect moxibustion, moxa-combustion time, peak temperature, average temperature, maximum gradient temperature, average gradient temperature, and moxa-combustion calorie rate of the input period in ARIRANG, JANG, PUNG were measured through this experiment. The results of the experiment were as follows : 1. In the combustion time, during the input period ARIRANG had the longest combustion time followed by PUNG, JANG in a descending order but these were not acknowledged to have significant difference each other. 2. In the peak temperature of the input period, PUNG had the highest temperature followed by ARIRANG, JANG in a descending order. ARIRANG and JANG were acknowledged to have significant difference with PUNG. ARIRANG and JANG however were not acknowledged to have difference each other. 3. In the average temperature, during the input period, PUNG had the highest temperature followed by JANG, ARIRANG in a descending order. ARIRANG and JANG were acknowledged to have significant difference with PUNG. ARIRANG and JANG however were not acknowledged to have difference each other. 4. In the maximum gradient temperature, during the input period, PUNG had the highest temperature followed by ARIRANG, JANG in a descending order. ARIRANG and JANG were acknowledged to have significant difference with PUNG. ARIRANG and JANG however were not acknowledged to have difference each other. 5. In the average gradient temperature, during the input period, PUNG had the highest temperature followed by ARIRANG, JANG in a descending order. ARIRANG and JANG were acknowledged to have significant difference with PUNG. ARIRANG and JANG however were not acknowledged to have difference each other. 6. In the moxa-combustion calorie rate, during the input period, JANG had the highest temperature followed by ARIRANG, PUNG in a descending order. ARIRANG and PUNG were acknowledged to have significant difference with JANG. ARIRANG and PUNG however were not acknowledged to have difference each other.

• Journal of Welding and Joining
• /
• v.16 no.2
• /
• pp.111-121
• /
• 1998

It is well recognized that a excessive temperature gradient from the junction of head to skirt in axial direction in a hot pressure vessel can cause unpredicted high thermal stress at the junction and/or in axial direction of a skirt. this thermal stress resulting from axial thermal gradient may be a major cause of unsoundness of structural integrity. In case of cyclic operation of hot pressure vessels, the thermal stress becomes one of the primary design consideration because of the possibility of fracture as a result of cyclic thermal fatigue and progressively incremental plastic deformation. To perform thermal stress analysis of the junction and cylindrical skirt of a vessel, or, at least, to inspect quantitatively the magnitude and effect of thermal stress, the temperature profile of the vessel and skirt must be known. This paper demonstrated the temperature distribution and thermal stress analysis for the junction of skirt to head using F.E. analysis. Effect of air pocket in crotch space was quantitatively investigated to minimize the temperature gradient causing the thermal stress in axial direction. Effect of the skirt height on thermal stresses was also studied. Analysis results were compared with theoretical formulas to verify th applicability to the strength calculation in design field.