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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Korean Journal of Air-Conditioning and Refrigeration Engineering
Journal Basic Information
Journal DOI :
The Society of Air-Conditioning and Refrigerating Engineers of Korea
Editor in Chief :
Volume & Issues
Volume 10, Issue 6 - Nov 1998
Volume 10, Issue 5 - Sep 1998
Volume 10, Issue 4 - Jul 1998
Volume 10, Issue 3 - May 1998
Volume 10, Issue 2 - Mar 1998
Volume 10, Issue 1 - Jan 1998
Selecting the target year
Experimental study on flow distribution in manifolds by a tapered header
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 1~10
A header is the device that makes uniform flow distribution in all branches from header of heat exchangers, pipe burner or chemical equipments. In this study, experimental tests have been performed in order to investigate the flow distribution characteristics in a straight header and tapered header which have 6 and 11 glass pipe branches. The experimental equipment consists of a water circulation system where the fluid velocity in each glass pipe is measured by Ar-ion LDV system. From the experiments and the theoretical equation, it could be recommended that tapered header should be determined so that its internal velocities inside the header become uniform according to taper of the header and number of attached branches for uniform flow distribution in energy systems.
Ice-formation phenomena for laminar water flow in a stenotic tube
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 11~21
A numerical study is made on the ice-formation for water flow inside a stenotic tube. The study takes into account the interaction existing between the laminar flow and the stenotic port in the circular tube. In the solution strategy, the present study is substantially distinguished from the existing works In that the complete set of governing equations in both the solid and liquid regions are resolved. In a channel flow between parallel plates, the agreement of predictions and available experimental data is very good. Numerical results are mainly obtained by varying the height and length of a stenotic shape and additionally for several temperatures of the wall and inlet of tube. The results show that the shape of stenotic port has the great effect on the thickness of the solidification layer in the tube. As the height of a stenosis grows and the length of a stenosis decreases, the ice layer thickness near the stenotic port is thinner due to backward flow caused by the sudden expansion of water tunnel. It is also found that the ice layer becomes more fat In accordance with Reynolds number and the temperature of the wall and inlet of tube decreased.
Experimental study on the heat transfer characteristics of separate type thermosyphon
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 22~32
Separate type thermosyphon has larger critical heat flux than non-loop type thermosyphon, because the flooding phenomenon of vapor and liquid occurring in non-loop one does not occur. The experimental study has been carried out separate type thermosyphon with single tube. An investigation of heat transfer characteristics in separate type thermosyphon is performed experimentally. Heat transfer coefficients in an evaporator and condenser were measured experimentally. The effects of liquid filling ratio, height difference, cooling temperature and heat flux on the heat transfer coefficients were examined. As a result, the reasonable range of the liquid filling ratio and the dependence of heat transfer on vapor temperature and heat flux are obtained.
Dynamic behavior of a scroll compressor with radial compliance device
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 33~43
Dynamic behavior of a scroll compressor has been investigated analytically. The equations of motion of moving elements of the scroll compressor such as the orbiting scroll, anti-rotation device, slider bush, and the crank shaft with eccentric crank pin have been set up. As the solutions of these equations, reaction forces between the moving elements, and also between the moving elements and the compressor frame have been calculated. The reaction forces from the moving elements to the frame are the unbalanced forces, which produce accelerations of the compressor body. These accelerations can be used as a measure of the compressor vibration. The major contributions to the unbalanced forces come from the orbiting movement of the orbiting scroll.
Performance evaluation of brazed aluminum heat exchangers for a condenser in residential air-conditioning applications
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 44~55
The evaluation of aluminum flat tube and louver fin heat exchangers for a condenser in residential air-conditioning applications has been conducted. A series of tests for two-different brazed aluminum heat exchangers was performed and the results were compared with conventional fin and tube heat exchangers for residential air-conditioning system. Refrigerant charge amount for a window-system air-conditioner with the brazed aluminum condenser is decreased by 35% and the volume and material of heat exchanger can be reduced by 50% compared to the conventional fin and tube heat exchangers.
Investigation on the selection of capillary tube for the alternative refrigerant R-407C
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 56~65
In this paper, experimental investigation of capillary tube performance for R-407C is performed. The experimental setup is made of real vapor-compression refrigerating system. In this study, mass flow rate is measured for capillary tubes of various diameter and length as inlet pressure and degree of subcooling are changed. These data are compared with the results of a numerical model. The mass flow rates of the numerical model are less than by 14% compared with the measured mass flow rates. It is found that mass flow rate and length for R-407c are less than those of R-22 under the same condition. Also based on this experimental study and the numerical model, a set of capillary tube selection charts for R-407C is constructed.
Balancing air flow at terminal in CAV duct system with DPM method
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 66~78
Adequate ventilation with the proper amount of air to the right place is important factor to achieve a good Indoor air climate. Thus it is of prime importance that the ventilation system is working properly. This requires reliable pressure loss calculation to balance the air flow through duct systems. So a computer program for balancing CAV duct system is developed In this study. The results of CAV duct system is compared with the "Balans" code developed by Larsen from Norway. To obtain the pressure drop characteristics of damper at duct terminal, some experiments are performed using DPM(Dual Pressure Measurement) system. To adjust the resistance of damper, present study suggests that some special diffusers should be designed and damper producers should give the data of air flow vs. pressure drop to the customs when they manufacture the damper. One of the results concludes that the working time can be reduced from several minutes to several seconds per damper in the present experimental site, if the DPM system and the air volume adjusting process are used.
Cycle simulation of a triple effect LiBr/water absorption chiller
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 79~87
Basic design of a 50USRT(175㎾) triple effect absorption chiller driven by hot gas has been carried out for both parallel and series flow cycles. Parallel flow cycle showed higher COP, however, the temperature in the generator was also higher than that in series flow cycle. Dynamic operation behavior of a parallel flow system at off-design conditions, such as the change in heat transfer medium temperature or the construction change of the system components, has been investigated in detail. It was found that the cooling capacity was seriously decreased by reducing hot gas flow rate and UA-value in the high temperature generator. However, the system COP was improved, because thermal load in the system components was reduced. The COP and the cooling capacity was found to be improved as cooling water temperature decreased or chilled water temperature increased. The optimum ratio of solution distribution could be suggested by considering the COP, the cooling capacity and the highest temperature in the system, which is critical for corrosion.
Experimental study on the thermal performance of a cooling tower
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 88~94
The thermal performance of cooling towers is affected mainly by the velocity, temperature and humidity of the entering air, In this paper, the effects of these variables are experimentally investigated for both counter-flow and cross-flow cooling towers. The cooling performance is reduced by up to 50% as the relative humidity of the entering air is increased from 40% to 80%. The higher air velocity and lower coolant flow show better cooling performance. The coolant loss rates in the present experimental conditions are in the range of 0.4 to 1.7%
Analysis of natural convection-radiation heat transfer using the finite volume method in enclosure
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 95~107
Natural convection and radiation heat transfer in a square enclosure containing absorbing, emitting, and isotopically scattering(participating) media is studied numerically using the finite volume method. Various numerical methods are employed to analyze the radiative heat transfer. However, it is very difficult to choose the proper method. In present study, a finite volume method(FVM) and a discrete ordinates method(DOM) are compared in rectangular enclosure. The SIMPLER algorithm is used to solve the momentum and energy equations. Thermal and flow characteristics are investigated according to the variation of radiation parameters such as optical thickness and scattering albedo. The result shows that the accuracy and the computing time of FVM are better than those of DOM in regular geometry.
Study on fluid flow characteristics of aquarium for optimum environment
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 108~117
This study was performed to analyze the fluid flow characteristics and the temperature distribution of the aquarium for fish breeding. In this study, the finite volume method and turbulence k-
model with the SIMPLE computational algorithm are used to study the water flow in the aquarium. The calculation parameters are the circulating flow rate and the basin depth, and the experiments were carried out for the water flow visualization This numerical analysis gives reasonable velocity distributions in good agreement with the experimental data. As the results of the three dimmentional simulations, the sectional mean velocity increased as the sectional mean temperature increases for constant basin depth, and the mean velocity increased more rapidly for small basin depth than that of large basin depth, The mean velocity and temperature can be expressed as the function of the circulating flow rates and the basin depth.
Comparison of refrigerant flow through capillary with short tube orifice
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 118~128
Capillary and short tube orifice have been widely used as an expansion device in refrigeration and air-conditioning system. To improve the system performance, expansion devices need to be optimized with the components of a refrigeration system. In the present study, a numerical model for a capillary, which can predict properties along a tube and flow rate through a tube, was developed by assuming homogeneous two-phase flow, A semi-empirical flow model that can be used to evaluate the flow rate through a short tube orifice was also developed by summarizing the experimental data. Finally, the results of the numerical model for capillaries were compared with those of the semi-empirical model for short tube orifices to verify dominant flow factors for the expansion devices.
Analysis of laminar forced convection for optimal design of parallel plates with protrusions
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 10, issue 1, 1998, Pages 129~136
Pressure drop and heat transfer characteristics of a periodically fully developed flow in the flat channel with protrusions are investigated. The effects of shape and location of protrusion on the pressure drop and heat transfer are numerically analyzed in the present study. Taguchi method is used to optimize these parameters. It is found that the ratio of the height of protrusion to channel height shows larger influence on the pressure drop and heat transfer than the ratio of the length of protrusion to module length. As the height of protrusion increases, pressure drop and heat transfer increase, but if the height of protrusion exceeds 2/3 of the channel height, there is a substantial pressure drop. The results also show that the optimal length and height of protrusion are half of the module length and half of the channel height, respectively.