• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.7
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• pp.564-571
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• 2001

The present study investigated the effect of key parameters on the performance of a cascade system using R-22 and R-23 refrigerants. Experimental data for the cascade system have been compared with simulation results using thermodynamic analysis. The cascade system tested at the evaporating temperature of $-80^{\circ}C $ and the condensing temperature of$40^{\circ}C $. The key experimental parameters were the evaporating temperature of the HTC(-35, -30, -25, -20, $-15^{\circ}C $) and mass flux of the HTC(200, 250, 300kg/$m^2$s). As the evaporating temperature and the mass flux of the HTC were increased respectively, the COP and the refrigerating efficiency were increased and then decreased while the volume flow rate per unit refrigeration capacity showed the opposite trend. The maximum COP and refrigerating efficiency were obtained at the evaporating temperature of the HTC of $-25^{\circ}C $ and the mass flux of 250 kg/$m^2$s.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.1
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• pp.73-79
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• 2011

In this paper, cycle performance analysis of cascade refrigeration system using alternative FREON refrigerants are presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooled and superheated degree, and evaporating and condensing temperature, temperature difference of cascade heat exchanger in cascade refrigeration system. The COP of cascade refrigeration system increases with the increasing subcooled degree, but there is no significant changes with the increasing superheated degree. The COP of cascade refrigeration system depends on evaporating and condensing temperatures of cascade heat exchanger. Therefore, subcooled degree, evaporating and condensing temperature of cascade heat exchanger using alternative FREON refrigerants have an effect on the COP of this system. In this paper, COP of cascade refrigeration system using R23 for low temperature system and R507A for high temperature system is higher 8 ~ 29 % than using R13 for low temperature system and R22 for high temperature system.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.70-75
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• 2009

In this paper, cycle performance analysis of R744($CO_2$) two-stage compression and one-stage expansion refrigeration system is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include superheating degree, compressor efficiency, gas cooling pressure, mass flowrate ratio, outlet temperature of gas cooler and evaporating temperature in the carbon dioxide two-stage refrigeration cycle. The main results were summarized as follows : The cooling capacity of two-stage compression and one-stage expansion refrigeration system increases with the increasing superheating degree, compressor efficiency and gas cooling pressure, but decreases with the increasing mass flowrate ratio and evaporating temperature. The compression work of two-stage compression and one-stage expansion refrigeration system increases with the increasing superheating degree, outlet temperature of gas cooler, gas cooling pressure and evaporating temperature, but decreases with the increasing compressor efficiency and mass flowrate ratio. The COP of two-stage compression and one-stage expansion refrigeration system increases with the increasing compressor efficiency, but decreases with the increasing superheating degree, gas cooling pressure, mass flowrate ratio and evaporating temperature. Therefore, superheating degree, compressor efficiency, gas cooling pressure, mass flowrate ratio, outlet temperature of gas cooler and evaporating temperature of R744($CO_2$) two-stage compression and one-stage expansion refrigeration system have an effect on the cooling capacity, compressor work and COP of this system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2565-2571
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• 2009

In this paper, cycle performance analysis of cascade refrigeration system using $NH_3-CO_2$(R717-R744) is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree and condensing and evaporating temperature in the ammonia(R717) high temperature cycle and the carbon dioxide low temperature cycle. The COP of cascade refrigeration system increases with the increasing superheating degree, but decreases with the increasing subcooling degree. The COP of cascade refrigeration system increases with the increasing condensing temperature, but decreases with the increasing evaporating temperature. Therefore, superheating and subcoolng degree, evaporating and condensing temperature of cascade refrigeration system using $NH_3-CO_2$ have an effect on the COP of this system. A multilinear regression analysis was employed in terms of subcooling, superheating, evaporating, condensing, and cascade heat exchanger temperature difference in order to develop mathematical expressions for maximum COP and an optimum evaporating temperature.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.3
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• pp.219-230
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• 2004

Most of the low-level liquid radioactive wastes generated from PWR plants are classified into high or low total suspended solid(HTDS or LTDS), and into radiochemical and radioactive laundry waste. Although the evaporation process has a high decontami- nation ability, it has several problems such as corrosion, foam, and congestion. A new liquid waste disposal process using the ion-exchange demineralizer(IED), instead of the current evaporation process, has been introduced into the Yonggwang NPP #5 and 6. These two methods have been compared to understand the differences in this study. Aspects compared here were the released radioactivity amount of the liquid radioactive wastes, the dose of off-site residents, the decontamination factor, and the amount of the solid radioactive wastes. The IED system is designed to discharge higher radioactivity about 20% than the evaporating system, and the actual radioactivity released from the evaporating and IED system were 0.473mCi and 1.098mCi, respectively. The radioactivity released from the IED was 2.32 times higher than that of the evaporating system. The dose of off-site residents was $2.97{\times}10^{-6}$mSv for the evaporating system, and $6.47{\times}10^{-6}$mSv for IED. The decontamination factor(DF) of the evaporator is, in most cases, far lower than the lower limits of detection(LLD) with the Ge-Li detector. Due to the low concentration of the liquid wastes collected from the liquid waste system, the decontamination factor of IED is very low. Since there is not enough data on the amount of solid radioactive wastes generated by the evaporation system, the comparison on these two systems has been conducted on the basis of the design, and the comparison result was that the evaporating system generated more wastes about 40% than IED.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.32-38
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• 2009

In this paper, cycle performance analysis for cooling capacity, compression work and COP of R744($CO_2$) transcritical vapor compression refrigeration system is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include superheating degree, outlet temperature of gas cooler and evaporating temperature in the R744 vapor compression cycle. The main results were summarized as follows : The cooling capacity of R744 increases with superheating degree, but decreases with the increasing evaporating temperature and outlet temperature of gas cooler. The compression work increases with superheating degree and cooling pressure of R744, but decreases with the increasing evaporating temperature. And, The COP increases with outlet temperature and evaporating temperature of R744 gas cooler, but decreases with the increasing superheating degree. Therefore, superheating degree, outlet temperature and evaporating temperature of R744 vapor compression refrigeration system have an effect on the cooling capacity, compression work and COP of this system. With a thorough grasp of these effect, it is necessary to design the compression refrigeration cycle using R744.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.05a
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• pp.156-159
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• 2006

In order to design an evaporation system, geometric simulation of film thickness distribution profile is required. In this paper, a geometric modeling algorithm is introduced for process simulation of the evaporating process. The physical fact of the evaporating process is modeled mathematically. Based on the developed method, the thickness of the thin-film layer can be successfully controlled.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.10
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• pp.828-834
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• 2003

A diffusion absorption refrigerator is a heat-generated refrigeration system. It uses a three-component working fluid consisting of the refrigerant (ammonia), the absorbent (water) and the auxiliary gas (hydrogen or helium). In this study, experimental investigations have been carried out to examine the effects of charging conditions of working fluids on the evaporating temperature for diffusion absorption refrigerator. Experimental parameters considered in the present experiments are charging concentration, solution charge and system pressure determined by auxiliary gas charged. As a result, in the charging condition of 35% of concentration and 20 kg$_{f}$cm$^2$ of system pressure, the system has the lowest evaporating temperature. It was found that there exists a minimum value of solution charge for the operation of diffusion absorption refrigerator.r.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.209-213
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• 2005

The effects of density change of ambient gas on mixture formation process have been investigated in high temperature and pressure field. To analyze the mixture formation process of evaporating diesel spray is important for emissions reduction in actual engines. Ambient gas density was selected as experimental parameter. The ambient gas density was changed from $r_a=5.0kg/m^3\;to\;r_a=12.3kg/m^3$ with a high pressure injection system(ECD-U2). For visualization of the experiment phenomenon, a CVC(Constant Volume Chamber) was used in this study. The ambient temperature and injection pressure are kept as 700K and 72MPa, respectively. The images of liquid and vapor phase in the evaporating free spray were simultaneously taken by exciplex fluorescence method. As experimental results, with increasing ambient gas density, the tip penetration of the evaporating free spray decreases due to the increase in the drag force from ambient gas.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1405-1414
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• 1993

The purification of sewage deriving from agricultural and food industries is today a serious problem mainly in areas characterized by intensive production plants. The solution examined in this work, involves a system of natural evaporation which employs special panels with a large evaporating surface constituted by an internal cellular structure in polyethilene. Using renewable energy they allow to speed up the natural evaporating effect thus eliminating some drawbacks such as swamps and obtaining sewage concentration with relatively low costs. The institute of agricultural engineering has carried out tests on the disposal of sewage deriving from two very important production sectors; pig-breeding and olive oil production . at a were gathered in order to verify the operating capacity of plants and their variables . On the remaining concentrated part tests were also carried out in order to know its chemical and chemical-physical features and to study the possibility for its us .