• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.4
• /
• pp.342-348
• /
• 2017

In this paper, film cooling characteristics at supersonic free stream conditions were examined experimentally by applying an IR-thermography. Film cooling experiments were carried out in a free-jet facility at Mach number of 3.0 and with unit Reynolds number of $42.53{\times}10^6$ and $69.35{\times}10^6$ using wedge shaped film cooling model which has a converging film cooling nozzle. Film cooling efficiency was calculated by measuring the surface temperature of PEEK(Polyether Ether Ketone) and the effects of angle of attack and blowing ratios on the film cooling efficiency were examined. The measured wall temperature was significantly reduced by the film cooling flow compared with the results without the film cooling flow. The usefulness of film cooling was also confirmed by the surface heat flux calculated using the surface temperature history of PEEK. As the blowing ratio increases the protected area of PEEK was also expanded along the direction of free stream and film cooling flow.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.359-366
• /
• 2000

A numerical study has been performed for the 2-dimensional film cooling employed in the cooling of hot components such as gas turbines. The flow and heat transfer characteristics are numerically simulated using FLUENT software. Blowing ratios vary from 0.25 to 5.0 and coolant injection angles vary from $15^{\circ}\;to\;60^{\circ}\;in\;15^{\circ}$ increment. The result shows that, for all cases, there exists a blowing ratio which maximizes film cooling effect (measured by the distance from the slot exit to the downstream wall location at which temperature increases to 900 K) for a given injection angle. It is also observed that the film cooling effectiveness decreases when downstream wall is sunk or lifted. The simulation has been performed using both constant properties and temperature dependent variable properties. It is found that the cases with constant properties overestimate the film cooling effect considerably.

• Proceedings of the KIEE Conference
• /
• 2001.11c
• /
• pp.61-64
• /
• 2001

The electric power load during the peak time in summer is strongly affected by cooling load. which decreases the preparation ratio of electricity and brings about the failure in the supply of electricity in the electric power system. The ice-storage system and heat pump system etc are used to settle this problem. In this study, the method of estimating temperature and humidity to forecast the cooling load of ice-storage system is suggested. And also the method of forecasting the cooling load using neural network is suggested. For the simulation, the cooling load is calculated using actual temperature and humidity. The forecast of the temperature, humidity and cooling load are simulated. As a result of the simulation, the forecasted data approached to the actual data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.8
• /
• pp.626-633
• /
• 2002

The electric power load during the peak time in summer is strongly affected by cooling load, which decreases the preparation ratio of electricity and brings about the failure in the supply of electricity in the electric power system. The ice-storage system and heat pump system etc. are used to settle this problem. In this study, the method of estimating temperature and humidity to forecast the cooling load of ice storage system is suggested. And also the method of forecasting the cooling load using neural network is suggested. For the simulation, the cooling load is calculated using actual temperature and humidity, The forecast of the temperature, humidity and cooling load are simulated. As a result of the simulation, the forecasted data is approached to the actual data.

• 유체기계공업학회:학술대회논문집
• /
• 2001.11a
• /
• pp.334-338
• /
• 2001

In order to investigate the effects of various injection hole shapes on the film cooling of turbine blade, three test models having cylindrical and shaped holes were used. A three-dimensional Navier-Stokes code with standard k-$\epsilon$ model was used to compute the film cooling coefficient on the film cooled turbine blade. Over 330,000 grids were used to compute the flow over the blade. Mainstream Reynolds number based on the cylinder diameter was $7.1{\times}10^4$. The turbulence intensity kept at $5.0\%$ for all inlets. The effect of coolant blowing ratio was studied for various blowing ratios. For each blowing ratios, wall temperatures around the surface of test model were calculated. Temperature was visualized using cartesian cut-cell method to obtain traces of the injected secondary air on the test surface, so we could interpret the film effectiveness as temperature distributions.

• Journal of Mechanical Science and Technology
• /
• v.18 no.6
• /
• pp.1002-1009
• /
• 2004

Direct contact air conditioning systems, in which heat and mass are transferred directly between air and water droplets, have many advantages over conventional indirect contact systems. The purpose of this research is to investigate the cooling and heating performances of direct contact air conditioning system for various inlet parameters such as air velocity, air temperature, water flow rate and water temperature. The experimental apparatus comprises a wind tunnel, water spray system, scrubber, demister, heater, refrigerator, flow and temperature controller, and data acquisition system. The inlet and outlet conditions of air and water are measured when the air contacts directly with water droplets as a counter flow in the spray section of the wind tunnel, and the heat and mass transfer rates between air and water are calculated. The droplet size of the water sprays is also measured using a Malvern Particle Analyzer. In the cooling conditions, the outlet air temperature and humidity ratio decrease as the water flow rate increases and as the water temperature, air velocity and temperature decrease. On the contrary, the outlet air temperature and humidity ratio increase in the heating conditions as the water flow rate and temperature increase and as the air velocity decreases.

• Journal of Biosystems Engineering
• /
• v.32 no.1 s.120
• /
• pp.13-19
• /
• 2007

Storage rough rice in low temperature using the winter cold air avoids rough rice temperature increase which happens from early May, and this is possible by installing a cooling system in the top of a bin, the room between top rice level and bin ceiling. The research objective is to establish low temperature rough rice storage technique, furnishing winter cold air to rough rice, by investigating the cooling system potential of maintaining low rough rice temperature and by analyzing rough rice storage characteristics over a storage period. The rough rice storage characteristics were evaluated from January to August 2003, using a storage and dry bin of 400-ton capacity. Results of this research are as follows: Cooling bin using the cooling system in the top of the bin maintained the rice temperature less than 15$^{\circ}C$ in entire portions in August. Moisture contents and germination rates of rough rice were decreased over the storage period, on the other hand, the rough rice stored in the ambient temperature bin had relatively lower moisture contents and germination rates to compare with the bin using winter cold air. Crack ratio and acid value of brown rice in the ambient temperature bin storage had increased more than the cooling bin storage. The result indicates that the storage bin using winter cold air and the cooling system maintains moisture content and germination of rice, minimizes cracked kernel and acid value, and preserves rice quality as well.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.4
• /
• pp.230-237
• /
• 2008

The objective of this paper is to investigate the performance characteristics of a $CO_2$ cooling and water heating system using a twin-rotary compressor with the compression volume ratio of 0.6. The cooling performances of the $CO_2$ heat pump were measured and analyzed with the variations of charge amount, EEV opening, and compressor frequency. In addition, the performance of the combined system including cooling and water heating was also measured and analyzed by varying inlet temperature of the EEV. As a result, the optimal normalized charge and cooling COP in the cooling mode were 0.307 and 2.06, respectively. The application of the water heating into the $CO_2$ heat pump improved the cooling performance over 78% and decreased the EEV inlet temperature by $8^{\circ}C$, which can increase system reliability.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.2
• /
• pp.177-187
• /
• 2000

Measurements of temperature fields and film-cooling effectiveness have been conducted for a shower-head film cooling on the leading edge of a blunt body, which simulates a first-stage turbine stator. In this study, three injection cases are employed for an average blowing ratio based on freestream velocity, M, of 0.5, 1.0 and 1.5. Two (Case 1), four (Case 2) and six (Case 3) rows of normal holes are symmetrically drilled on the three tested circular-cylinder leading edges. The measurements show that regardless of M, the film-cooling effectiveness increases as the injection row is situated at farther downstream location. In Case 1, the film-cooling effectiveness is highest for M = 0.5 and lowest for M = 1.5. On the contrary, in Case 3, the film-cooling effectiveness is highest for M = 1.0 and lowest for M = 0.5. When M = 0.5, the film coverage by the first row of the injection holes deteriorates as the number of the injection row increases. In particular, the film-cooling effectiveness due to the injection through the first row of the holes in Case 3, has a nearly zero value.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.377-381
• /
• 2001

Film cooling characteristics has been investigated numerically with the aid of FLUENT software for the sunk or the lifted upstream wall from the slot injection exit. In this study, with the fixed blowing ratio of 1 and the fixed coolant injection angle of $30^{\circ}$, the downstream flow field and the downstream temperature field were examined in terms of velocity vector, turbulent kinetic energy, temperature contours, and downstream wall temperature. Upstream wall was sunk or lifted from 1d to 5d(d=slot width). The result shows that the up-Id upstream wall has the best film cooling performance. This is due to the fact that the up-1d upstream wall configuration reduces velocity gradient just enough to minimize the turbulent mixing between the mainstream and the coolant just off the slot exit.