• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.17 no.4
• /
• pp.333-340
• /
• 2005

Horizontal air-jet effect has been utilized in some air conditioning systems in order to control the contaminated air indoor. In the present study, the flow and heat transfer of the contaminated air from a range hood system has been investigated with or without horizontal air-jet effect when the hood fan is on or off. For the present numerical experiment, PAT Flow code has been used. From the present numerical simulations, it has been shown that the air jet of a range hood generates coanda effect confining the contaminated air in a certain region. Furthermore, the qualitative relation between the flow rate of the capture air jet and the distribution pattern of the contamination has been discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.5
• /
• pp.291-296
• /
• 2009

Ice accumulating system patterned ice-an-coil is the way of refrigerating regenerative materials on the surface of copper-tube inserted into the inside of ice-storage. The study experimented to understand ice-an-coil type ice making characteristics according to changing shape of ice making tube. The experiment were carried out under various conditions, that used brine temperature($-l0^{\circ}C$, $-6^{\circ}C$) brine flow rate(l.0m/s, 1.8m/s) and inlet water temperature($6^{\circ}C$, $12^{\circ}C$) etc. Mass of ice per making area increased according to the decrease of the brine temperature and inlet water temperature, but that was increased according to the increase of the brine flow rate. And I set up two hypotheses and compared the capacity of ice-making of the two cases; each had the same thermal area and one had an round-shaped copper tube but the other had an oval-shaped copper tube.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.9
• /
• pp.1195-1207
• /
• 1998

Periodic pulsations in the static pressure near turbine surfaces as blade rows move relative to each other is one of the important sources of turbine unsteadiness. The present experiment aims to investigate the effect of the static pressure pulsations on the interaction of film coolant flows from two rows of staggered holes with mainstream and its effect on film cooling heat transfer. Potential flow pulsations are generated by the rotating shutter mechanism installed downstream of the test section, The free-stream Strouhal number based on the boundary layer thickness is in the range of 0.033 - 0.33, and the amplitude of about 10-20%. Measured are time-averaged and phase-averaged velocity variations, pressure variations and temperature distributions of the flow field. Experimental conditions are identified by boundary layer measurements. Injectant behavior is characterized by the measurements of unsteady pressure in the plenum chamber and free-stream static pressure. The film cooling effectiveness is evaluated from the insulated wall temperature measurement. It has been found that bulk flow pulsation provides very large diffusion of the injectants and the effectiveness is significantly reduced by the flow pulsations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.1
• /
• pp.31-37
• /
• 2002

This paper is concerned with the development of a new method for making and separating ice and saving floated ice by installing an evaporation plate at in-water within a storage tank. In a conventional harvest-type ice storage system, a tank saves ice by separating a formed ice from an installed evaporation plate, which is located above an ice storage tank as an ice storage system. A new harvest-type method shows very good heat transfer efficiency than a convectional method. It is because the evaporation panel is directly contacted with water in a storage tank. Also, at a conventional system a circulating pump, a circulating water distributor and a piping are installed, but these components are not necessary in a new method. In this study two kinds of ice storage systems are experimentally investigated to study the thermal characteristics of ice storage tanks. The results showed discharge of cold capacity of new type indicated the high values about 30~40% based on five time of drive, the temperature difference of inlet/outlet occurred the big range about $1.3^{\circ}C$. So, the new type which makes ice in water showed superiorly.

• 유체기계공업학회:학술대회논문집
• /
• 2003.12a
• /
• pp.278-283
• /
• 2003

A generation rate of sludge in Korea had increased dramatically about 200 % for a decade. A requirement for high efficiency dewatering system being possible to produce the low water content cake have suggested due to the appearanceof commercial and social problems about handling of dewatered cake. The conventional dewatering system with mechanical compression device was not suitable to produce the low water content cake and didn'tcope with lots of requirements. Therefore, this paper was to develop the high efficient filter press with the compressive and heating forces through the heating plate to be built between membrane filter plates. It is possible to produce the low water content cake and improve the dewatering rate, so this equipment positively coped with several types of problems related to the sludge dewatering. The plate heated by heat transfer materials such as steam, hot water and thermo-oil made the sludge make the residual moisture within the cake to discharge easilyand to improve the dewatering efficiency of equipment. The pilot scale experiment with 500kg of cake production showed that the dewatering efficiency determined by the final water content and dewatering velocity was improved 30% more than the conventional dewatering equipment.

• Journal of Mechanical Science and Technology
• /
• v.19 no.7
• /
• pp.1449-1459
• /
• 2005

This paper shows the results of local flow speed measurement using tunable AC thermal anemometry, which is suitable for the accurate measurement of wide range flow speed. The measurement accuracy is verified through the comparison between the measurement data and the analytic solution of the sensor temperature oscillation in stationary fluid. The relation between the phase lag and the flow speed is experimentally investigated at various conditions. The measurement sensitivity for low flow speed improves in a low frequency region and that for high flow speed improves in a high frequency region. Also, the sensitivity increases with decreasing thermal conductivity of the surrounding fluid. The local flow speed could be measured as low as 1.5 mm/s and the highest measurement resolution was 0.05 mm/s in the range of 4.5 $\~$5.0 mm/s at 1 Hz in this experiment.

• Journal of ILASS-Korea
• /
• v.26 no.2
• /
• pp.57-66
• /
• 2021

The reactivity controlled compression ignition (RCCI) is the technology that provides two different types of fuel to the combustion chamber with the advantage of significantly reducing particulate matter and nitrogen oxides emissions. However, due to the characteristics of lean combustion, combustion efficiency is worsened. The conventional type of pistons for conventional diesel combustion (CDC) has mostly been used in the researches on RCCI. Because the pistons for CDC are optimized to enhance flow and target spray, the pistons are unsuitable for RCCI. In this study, a piston that is suitable for RCCI is designed to improve combustion efficiency. The new piston was designed by considering the factors such as squish geometry, bowl depth, and surface area. The experiment was carried out by fixing the energy supply to 0.9kJ/cycle and 1.5kJ/cycle respectively. The two pistons were quantitatively compared in terms of thermal efficiency and combustion efficiency.

• Design & Manufacturing
• /
• v.15 no.3
• /
• pp.39-44
• /
• 2021

In molding of continuous fiber-reinforced thermoplastic composites, it is very difficult to impregnate between the reinforcements and the matrix since the matrix has a high melting temperature and high viscosity. Therefore, most of composite molding processes are divided in the manufacturing processes of intermediate materials called prepreg and the forming of products from intermediate materials. The divided process requires additional facilities and thermoforming, and they increase the cycle time and cost of composite products. These problems can be resolved by combining the continuous fiber-reinforced composite molding process with injection molding. However, when a composite material is manufactured by inserting woven fabric into the injection mold, poor impregnation occurs on the surface of the molded product. It affects the properties of the composites. In this paper, through an impregnation experiment using cores with different heat transfer rates and pore densities, the reason for the poor impregnation was confirmed, and molding experiments were conducted to produce composite with improved surface impregnation by inserting the mesh. And also, the surface impregnation and deformation of composites molded using different types of mesh were compared with each other.

• Journal of the Korean Society of Safety
• /
• v.36 no.2
• /
• pp.111-119
• /
• 2021

Multi-dimensional analysis of reactor safety-KINS standard (MARS-KS) is a thermal-hydraulic code to simulate multiple design basis accidents in reactors. The code has been essential to assess nuclear safety, but has mainly focused on light water reactors, which are in the majority in South Korea. Few previous studies considered pressurized heavy water reactor (PHWR) applications. To verify the code applicability for PHWRs, it is necessary to develop MARS-KS input decks under various transient conditions. This study proposes an input model to simulate small-break loss of coolant accidents for PHWRs. The input model includes major equipment and experimental conditions for test B9802. Calculation results for selected variables during steady-state closely follow test data within ±4%. We adopted the Henry-Fauske model to simulate break flow, with coefficients having similar trends to integrated break mass and trip time for the power supply. Transient calculation results for major thermal-hydraulic factors showed good agreement with experimental data, but further study is required to analyze heat transfer and void condensation inside steam generator u-tubes.

• Journal of the Korean Society of Visualization
• /
• v.18 no.3
• /
• pp.61-68
• /
• 2020

Thermographic phosphor (TP) thermometry is a noncontact optical measurement method and has been applied in many fields such as combustion and heat transfer. However, due to the limitation of bonding technology and measurement method, most TP thermometry studies were conducted only on the air environment with water-soluble binders. In this paper, a temperature measurement technology in water using TP is proposed by coatings of manganese activated magnesium fluorogermanate (Mg4FGeO6:Mn4+, MFG) with Polydimethylsiloxane (PDMS). Four MFG-PDMS coatings with different thicknesses were prepared. The lifetime of MFG was not affected by the thickness of the coating as a result of the experiment and analysis of phosphor intensity using a photomultiplier tube. To measure the surface temperature field of an immerged body in water, a cylinder-type cartridge heater was coated with MFG doped PDMS. Transient surface temperature field was successfully measured even the initial temperature is higher than the boiling point of water.