• 설비공학논문집
• /
• 제14권6호
• /
• pp.485-492
• /
• 2002

Heat transfer and pressure drop on the air side of a plate-louvered fin heat exchanger with new shape of louver fin have been investigated experimentally. Water is employed inside the flat tube to transfer heat with air for convenience. This problem is of particular interest in the design of a plate-louvered heat exchanger. The effect of air flow rate, water flow rate and water temperature on pressure drop as well as heat transfer in air side are studied in detail. The present results showed a good agreement qualitatively with the previous results in general. Based on the experimental data, f-factor and j -factor correlations of the present louvered-fin are suggested. It is also found that heat transfer could be enhanced with new shape of louver fin, compared with the conventional louvered-fin, while the f-factor remains unchanged.

• 설비공학논문집
• /
• 제3권1호
• /
• pp.34-41
• /
• 1991

The effect of flow conditions on flow measurement is difficult to identify from the inherent characteristics of the flowmeters and flow standard system. A new experimental approach has been attempted to detect the turbine meter error due to inlet flow conditions. In this try not only the design of the turbine meter package but also the data analysis method was altered. It was found that k factor slope of the turbine meter responds to the change of flow conditions in the test line with higher sensitivity than the degree of the data scattering. The flow standard system of $0.1m^3/s$ was chosen for the investigation. The systematic and random error of the system were less than ${\pm}0.08%$ and ${\pm}0.13%$ respectively.

• 설비공학논문집
• /
• 제2권4호
• /
• pp.288-294
• /
• 1990

A study has been conducted experimentally on heat transfer characteristics of louvered fin heat exchangers with various fin spacings in air. The experimental results are as follows; 1. Mean heat transfer coefficient is increased with increasing air velocity and the optimum fin spacing shows at S=5mm. 2. Pressure drop is increased with increasing air velocity and its maximum value shows at S=3.5mm and its minimum value shows at S=6mm. 3. $\bar{h}/{\Delta}P$ is decreased with increasing air velocity and its maximum value shows at S=5mm and its minimum value shows at S=3.5mm.

• 설비공학논문집
• /
• 제3권1호
• /
• pp.78-85
• /
• 1991

An experimental result for heat transfer of pulsating turbulent pipe flow was presented under the condition of fully developed dynamic regime and uniform wall heat flux. Experiments were performed at following conditions ; Inlet time-averaged Reynolds number varied from 5000 to 11000; The peak pressure fluctuation were 1.3, 2.3 and 3.5 percent of the mean pressure; Pulsating frequency ranged from 53 Hz to 320 Hz The measurements showed that the effect of pulsation on local heat transfer is greater at downstream, in which pulsating source exists, than upstream and the heat transfer rate, averaged over the pipe length, was higher or lower than in an equivalent non-pulsating flow according to the pulsating conditions. In addition, the significant change of heat transfer rate was observed in acoustically resonant conditions, when the pulsating frequency of the flow corresponded to the pipe natural frequency.

• 설비공학논문집
• /
• 제2권4호
• /
• pp.257-267
• /
• 1990

A numerical and experimental investigation has been carried out to understand a characteristic of natural convection within a horizontal non-circular annulus. A finite-difference method has been used to solve the governing equations numerically. The effect of Rayleigh number. Prandtl number, aspect ratio and diameter ratio is studied analytically. The ranges of the parameters studied herein are Rayleigh number from $10^3$ to $2{\times}10^4$, Prandtl number from 0.1 to 10, aspect ratio from 0.25 to 1.5 and diameter ratio from 1.5 to 9.0. A Mach-Zehnder interferometer is used to obtain isothermal fringes for a diameter ratio Do/Di=2.6 and aspect ratio H/L=0.75 experimentally. A comparison between the experimental and numerical results under similar conditions shows good agreement.

• 설비공학논문집
• /
• 제3권1호
• /
• pp.61-68
• /
• 1991

The purpose of this study is to investigate the heat transfer characteristics and the flow structure in the case of rectangular air jet impinging vertically on the flat heating surface. The maximum value of Nusselt number at stagnation point is observed at H/B=10. It is found that this trend has been caused by the effect of stretching of large scale vortex in the stagnation region. For potential core region the Nusselt number distribution in the downstream of the stagnation point decreases gradually and begins to increase at about X/B=3. From the flow visualization it could be seen that small eddy produced from the nozzle edge grows in large scale and that large scale eddy disturbed the thermal boundary layer on the heating plate. The local average Nusselt number becomes maximum at X/B=0.5 regardless of H/B variation.

• 설비공학논문집
• /
• 제11권1호
• /
• pp.38-47
• /
• 1999

An improved one-dimensional modeling of snow melting was obtained by considering both the effect of heat capacity and the decreasing influence of porosity. Using the improved model, the effects of initial snow temperature, initial snow density and the heat flux on the snow melting were investigated. It is found that the drainage starting time is delayed and the drainage rate becomes smaller with lower initial snow temperature. ResuIts also show that the drainage starts at the same time when an initial snow density is over a certain value. Melting efficiency increases linearly with an increasing initial snow temperature. With increasing the initial density of the snow and the amount of heat supplied, the melting efficiency increases, then converges to a constant value.

• 설비공학논문집
• /
• 제7권3호
• /
• pp.353-358
• /
• 1995

The emission characteristics of a semi-Bunsen type burner for gas boilers were studied experimentally. The experimental results reveal that nitric oxide emission increases with fuel flow rate. It is linearly proportional to total fue flow rate at a small amount of fuel up to 0.4 liters per minute. It does not change significantly within the range of fuel flow rate from 0.4 to 1.2 liters per minute per nozzle and increases at large fuel flow rate. The carbon monoxide emission reveals to be dependent upon the fuel flow rate per each nozzle and the number of fuel injection nozzles. Diameter of an injection nozzle could have an effect on the emission characteristics of this type of burners. However, there is no marked change in the nitric oxide emission if the total fuel flow rate is same with different nozzle sizes.

• 설비공학논문집
• /
• 제7권3호
• /
• pp.512-520
• /
• 1995

This study investigates the simultanceous heat and mass transfer between a falling desiccant film and air in cross flow at the interface. The application of this work is the optimization of falling film evaporators for use in potential hybrid air conditioning systems. The specific geometry considered is liquid TEG films falling along the vertical cooled surfaces of a channel with air in cross flow. The equations to describe the coupled heat and mass transfer between a falling desiccant film and air in cross flow for a falling film evaporator have been presented and solved numerically. The effects of important design and operating variables on the evaporator performance predicted by the parametric numerical analysis and suggestions for performance improvements of the evaporator are presented.

• 설비공학논문집
• /
• 제7권3호
• /
• pp.521-527
• /
• 1995

The average particle deposition velocity toward a vertical wafer surface in a vertical airflow chamber was measured by a wafer surface scanner(PMS Model SAS-3600). Polystyrene latex(PSL) spheres with diameters between 0.3 and $0.8{\mu}m$ were used. To examine the effect of the airflow velocity on the deposition velocity, experiments were conducted for three vertical airflow velocities ; 20, 30, 50cm/s. Experimental data of particle deposition velocity were compared with those given by prediction model suggested by Liu and Ahn(1987).