• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.7
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• pp.529-536
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• 2007

The perforated type element for a heat recovery ventilation system has been studied to improve the performance. Four holes of diameter of 6mm are punched out for each flow channel to break the boundary layer development and increase the turbulence. KS cooling and heating conditions and test procedures are applied for study. The efficiencies are compared to those of the typical element with smooth surface. For cooling operations, the temperature, latent and enthalpy efficiencies increase 2.5%, 18% and 8%, respectively. For heating operations, the temperature, latent and enthalpy efficiencies increase 3%, 5% and 3.2%, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.455-461
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• 2001

Domestic ice making companies make effort to obtain products and neglect to introduce low cost product improvements with energy savings. The work presented here is an implementation of ice making method to improve both energy efficiency and productivity. In this present investigation, several ice making cycles are proposed for higher efficiency in the system. COP(Coefficient of Performance), ice making time and electric energy consumption are evaluated and compared with the conventional system. Results shows that COP is improved with more efficient use of time for ice making and electric consumption. Therefore, this can offer an opportunity for more efficient use of energy and higher productivity in ice making.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.3
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• pp.414-421
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• 1999

Falling film rectification involves simultaneous heat and mass transfer between vapor and liquid interface. In the present work, the adiabatic rectification process of ammonia-water vapor on the vertical plate was investigated. The continuity, momentum, energy and diffusion equations for the solution film and vapor mixture were formulated in integral forms and solved numerically. The model could predict the film thickness, the pressure gradient, and the mass transfer rate. The effects of Reynolds number and ammonia concentration of solution and vapor mixture, rectifier length, and the enhancement of mass transfer in each phases were investigated. The stripping of water in vapor mixture occurred new the entrance of ammonia solution, which imposed the proper size of an adiabatic rectifier. Rectifier efficiency increased as film Reynolds number increased and as vapor mixture Reynolds number decreased. The improvement of rectifier efficiency was significant with the enhancement of mass transfer in falling film.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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• pp.999-1006
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• 2006

A study of temperature profiles in mixing zone of AHU (air handling unit) can contribute greatly to enhance performance of AHU system, so the study on the temperature distribution between RA (return air) and OA (outdoor air) is important to analyze the mixing characteristics in a mixing zone of AHU. Accordingly, the temperature profiles during RA (return air) and OA (outdoor air) supply process into mixing zone of AHU with an air mixer are studied experimentally. The effect of air mixer, OA temperature and RA/OA flow rate are studied in detail. In this study, the results show that the mixing efficiency is all high for installed the air mixer. The more OA temperature increase and OA flow rate decrease, the more mixing efficiency is high.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.2
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• pp.69-79
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• 2000

Falling film rectification involves simultaneous heat and mass transfer between vapor and solution film. In the present work, the adiabatic rectification process of ammonia-water vapor by the falling solution film on the vertical plate was investigated. The continuity momentum, energy and diffusion equations for the solution film and the vapor mixture were formulated in integral forms and solved numerically, The model could predict the film thickness, the pressure gradient, and the mass transfer rate. The effects of Reynolds number and ammonia concentration of solution and vapor mixture, rectifier length, and the enhancement of mass transfer coefficient in each phases were investigated. The stripping of water in vapor mixture occurred near the entrance of ammonia solution, which imposed the proper size of an adiabatic rectifier. Rectifier efficiency increased as film Reynolds number increased and as vapor mixture Reynolds number decreased. The improvement of rectifier efficiency was significant with the enhancement of mass transfer coefficient in falling film.

• International Journal of Air-Conditioning and Refrigeration
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• v.13 no.1
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• pp.11-21
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• 2005

The present paper investigates the heat transfer characteristics in a cylinder packed with porous medium of solid spheres for various parameters such as mass flow rate, sphere diameter, length of the porous medium, and gas temperatures. Pressures and temperatures at the inlet and outlet regions were measured by using static pressure gages and R-type thermocouples. The modified relationship based on the Ergun equation is suggested for the estimation of pressure drops. In addition, the useful empirical correlation for thermal efficiency is obtained in the current study. Thermal efficiency is expressed in terms of non-dimensional time, sphere diameter, porosity, and pressure drops. It is also found that the pressure drop through the cylinder becomes larger as the gas temperature does higher at the inlet region, whereas it substantially decreases when the inlet flow rate decreases.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.534-539
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• 2007

The objectives of the present work is to investigate the influence of the solution cooled absorber(SCA), refrigerant drain heat exchanger(RSX), exhaust gas/solution heat exchanger(ESX) and high efficiency solution heat exchanger on COP for a double-effect series-flow absorption chiller. A simulation program has been prepared for the cycle analysis of absorption chillers. As a result, Solution heat exchangers(LSX, HSX) are a most effective element for the COP than the others. In spite of the poor contribution to COP, SCA make a rule to reduce the crystallization phenomena of LiBr solution at solution heat exchanger. And the optimum solution split ratio are varied with the relative size of RSX and LSX.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.2
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• pp.189-199
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• 2000

This paper investigates the thermodynamic performance of latent heat thermal energy storage system using two phase change materials(2-PCM system). The thermodynamic merit of using 2-PCM is clear in terms of exergetic efficiency, which is substantially higher than that of 1-PCM system. Optimum phase change temperature to maximize the exergetic efficiency exists for each case. The heat transfer area ratio of high temperature storage unit, X, becomes another important parameter for 2-PCM system if the phase change temperatures of given materials are different from those of optimum conditions. It is a good approximation for X$_{opt}$ to be 0.5 when optimum phase change temperatures are used. Otherwise X$_{opt}$ is determined differently as a function of given phase change temperatures.res.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.7
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• pp.543-551
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• 2002

Gravity ventilators allow the escape of the warm air and air contaminants due to both (either) buoyancy and (or) convection. As a natural ventilation strategy, various gravity ventilators can be installed on the roof. Ventilation efficiency could be affected by various parameters, such as, area of openings, wind velocity and incidence angle, temperature difference between inside and outside, and shape of ventilator. Especially, the shape of roof gravity ventilator might be one of influencing factors for the effective ventilation. The window type gravity ventilators are frequently installed instead of general (standard) gravity ventilator. However, the ventilation efficiencies of them were not proved yet. To compare the ventilation efficiency, general type ventilator and two window type ventilators were numerically tested. Mean age of air, temperature and CO concentration were predicted by using commercial CFD code, AIRPAK (Ver. 2.0) with various conditions. The predicted result showed that general type ventilator is more effective for natural ventilation than window type ventilators.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.8
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• pp.402-408
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• 2015

A series of numerical simulations have been carried out to study the performances of cyclone-type oil separators, which are designed for refrigeration-system compressors. The corresponding working fluid is R22, which is a typical refrigerant, whereby a mineral-oil droplet is supplied (Ed-highlight-My interpretation). The outlet-tube length in relation to the total chamber volume is considered a design parameter. Depending on the tube length, the separation efficiency varies from 98.7% to 99.3%, while the predicted pressure drop is between 5.1 kPa and 6.4 kPa. Considering both the pressure drop and separation efficiency, the length of the outlet-port tube of the separator is 152 mm.