• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.2
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• pp.127-133
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• 2002

The objectives of this paper are to develop an advanced GAX cycle named HGAX (Hybrid Generator Absorber heat exchanger) cycle, and to study the effect of key parameters on the cycle performance and the hot-water temperature from the condenser. New types of the HGAX cycle are developed by adding a compressor between the generator and the condenser- Type C (performance improvement and reduction of the generator temperature) and Type D (Hot-water temperature application). The solution temperature in the generator outlet is reduced to 168$^{\circ}C$ with the COP improvement of 19% compared to the standard GAX cycle. The hot-water temperature from the condenser is raised to 106$^{\circ}C$ for panel heating (Ondol heating) application.

• Journal of Power System Engineering
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• v.10 no.2
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• pp.41-46
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• 2006

This study shows a water cooling system by using a steam ejector and jet condenser to drop the temperature of the water by about $5^{\circ}C\;from\;25^{\circ}C$ or higher. In this research, to replace the present water cooling system, we focused on a water cooling system by latent heat of evaporation, thus this system needs a vacuum pressure to evaporate the water in enclosed tank. The water cooling effects are depended on the vacuum pressure in the enclosed tank, and the cooling water is generated by latent head of evaporation. As the experimental results, the absolute vacuum pressure obtained was about $5{\sim}8$ mmHg using a steam driven ejector with jet condenser.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.4
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• pp.408-417
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• 1988

This study optimized the condenser dimension of heat pump system with the heat sources which are solar irradiation and ambient air. At first, the author selected the principal design factors influencing the performance of heat pump system. And the author considered the variation of condenser dimension according to the variation of the selected design factors, that is, ambient air temperature, condenser temperature, degree of superheating, degree of sub-cooling and irradiation. As a result this study, among refrigerants R12, R22 and R500, refrigerant R22 has more heating output than R12 and R500, and the coefficient of performance on this heat pump system is not greatly influenced by the degree of superheating and degree of sub cooling. The ambient air temperature is below $5^{\circ}C$ at balance point and the optimal tube length of condenser dimension is about 3.8 m. Also the author gained the optimal design diagram for the optimization of condenser dimension according to various design factors.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.3
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• pp.193-205
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• 1994

A simulation program of the plate finned-tubes condenser widely used in the air conditioning system was developed. The program took into account the variations of the flow properties and fluid friction factor of refrigerant, and the heat transfer coefficients of refrigerant and air sides. The program was applied to a copper tube condenser which has outside diameter of 10.05mm, inside diameter of 9.35mm, length of 5.20m and three rows arraied staggered. Simulation results were such that refrigerant was super-heated state from the entrance to the 0.14m point, two-phase flow from the 0.14m point to the 4.10m point, sub-cooled state from the 4.10m point to the outlet. The degree of sub-cooled was $6.1^{\circ}C$. The variations of refrigerant quality, temperature, pressure, velocity, specific enthalpy, specific volume and air temperature, tube temperature were showed.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.81-91
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• 2013

A novel design process of a parallel multi-flow type air-cooled condenser of a dual-loop waste heat recovery system with Rankine steam cycles for improving the fuel efficiency of gasoline automobiles has been investigated focusing on reduction of the pressure drop inside the micro-tubes. The low temperature condenser plays a role to dissipate heat from the system by condensing the low temperature loop working fluid sufficiently. However, the refrigerant has low evaporation temperature enough to recover the waste from engine coolant of about $100^{\circ}C$ but has small saturation enthalpy so that excessive mass flow rate of the LT working fluid, e.g., over 150 g/s, causes enormously large pressure drop of the working fluid to maintain the heat dissipation performance of more than 20 kW. This paper has dealt with the scheme to design the low temperature condenser that has reduced pressure drop while ensuring the required thermal performance. The number of pass, the arrangement of the tubes of each pass, and the positions of the inlet and outlet ports on the header are most critical parameters affecting the flow uniformity through all the tubes of the condenser. For the purpose of the performance predictions and the parametric study for the LT condenser, we have developed a 1-dimensional user-friendly performance prediction program that calculates feasibly the phase change of the working fluid in the tubes. An example is presented through the proposed design process and compared with an experiment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.1
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• pp.42-53
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• 2004

An experimental study on the refrigerant-side pressure drop of slit fin-tube heat exchanger has been carried out. A comparison was made between the predictions of previously proposed empirical correlations and experimental data for the pressure drop on design conditions of condenser in micro-fin tube for R22 and its alternatives, R407C (R32/125/134a, 23/25/52 wt.％) and R410A (R32/125, 50/50 wt.％). Experiments were carried out under the conditions of inlet refrigerant temperature of 6$0^{\circ}C$ and mass fluxes varying from 150 to 250 kg/$m^2$s for R22, R407C and R410A. The inlet air conditions are dry bulb temperature of 35$^{\circ}C$, relative humidity of 40% and air velocity varying from 0.68 to 1.43 m/s. Experiments show that pressure drop for R410A and R407C were 17.8∼20.2％ and 5∼6.8％ lower than those of R22 respectively for the degree of subcooling of 5$^{\circ}C$. For the mass fluxes of 200∼250 kg/$m^2$s, the deviation between the experimental and predicted values for the pressure drop was less than $\pm$20％ for R22, R407C and R410A.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.749-754
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• 2006

This study performed of a water cooling system by using a steam ejector and jet condenser to drop the temperature of the water in aquafarm by about $5^{\circ}C$ from $25^{\circ}C$ or higher in this research, to replace the present water cooling system, Ive focused on a water cooling system operated by latent heat of evaporation, thus this system needs a vacuum pressure to evaporate the water in enclosed tank. The water cooling effects are dependent on the vacuum pressure in the enclosed tank, and the cooling water is generated by evaporation. As the experimental results, the absolute vacuum pressure obtained was about $5{\sim}8mmHg$ using a steam driven ejector with jet condenser in experiments. The obtained results are respectively ${\Delta}T=7^{\circ}C$, ${\Delta}T=5^{\circ}C$ and ${\Delta}T=5.5^{\circ}C$ at heat exchanger flow rate 4L/M. The obtained results are respectively ${\Delta}T=5.5^{\circ}C$, ${\Delta}T=5.5^{\circ}C$ and ${\Delta}T=5.5^{\circ}C$ at heat exchanger flow rate 4.5L/M.

• ETRI Journal
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• v.20 no.3
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• pp.284-300
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• 1998

A new thermosyphon cooling module (TSCM) has designed, fabricated and tested to cool the multi-chip module consists of a cold plate and an integrated condenser. With an allowable temperature rise of $56^{\circ}C$ on the surface of the heater, the cooling module TSCM can handle a heat flux of about 2.7 $W/cm^2$ using R11 as working fluid. The transient characteristics of the cooling module have been proved to be excellent: that is, when a heat load is applied inside of the system, steady state can be achieved within 10 to 15 minutes. It has been found that the length of the vapor channel between the cold plate and the condenser in addition to the ambient and the condenser temperatures affect the system performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1630-1637
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• 2002

A slab-wick heat pipe was fabricated and tested for applications where the condenser temperature is in a range of 80 to 12$0^{\circ}C$. The pipe material was 9.53 mm O.D. copper tube and the working fluids were ethanol and water. The total length of the heat pipe was 1.6 m, in which evaporator section was 1.4 m and the condenser was 0.10 m. The slab was a composite wick structure fabricated with STS316 wire screens. Thermal load was varied for a specified fill charge ratio and inclined angle. The optimum fill charge ratio was identified to be 110% based on a theoretical calculation of the pore space in the slab wick of the heat pipe. The maximum thermal load was 120W for ethanol and the same was 200W for water with the condenser temperature of 8$0^{\circ}C$. The thermal performance of the slab wick heat pipe is analysed in terms of temperature characteristics and thermal resistance against thermal load, tilt angle and fill charge ratio.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.10
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• pp.408-413
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• 2016

The objective of this study is to investigate the performance of a heat recovery heat pump dryer using a R245fa refrigerant experimentally. In this study, the main components of the heat pump dryer were an evaporator, a compressor, a condenser, and an expansion valve. As a result, when the amount of refrigerant varied from 15 kg to 16 kg, the hot air outlet temperature in the condenser and the heat transfer rate were almost kept constant. Therefore, the amount of refrigerant at 16 kg was considered to be a suitable amount in the heat pump. As the air inlet velocity varied from 0.5 m/s to 1.5 m/s, the highest temperature in the condenser could be obtained when the air inlet velocity was 0.5 m/s. The heat transfer rate, system (COP), and hot air outlet temperature were 5.6 kW, 3.4, and $102.5^{\circ}C$, respectively, when the bypass ratio and water temperature were 0% and $60^{\circ}C$.