• Journal of Power System Engineering
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• v.17 no.5
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• pp.38-43
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• 2013

In order to design a wave energy generating system, a 6-DOF analysis technique is applied to CFD analysis on of a floating body and the behavior is interpreted according to the nature of the incoming waves. A spring constant is adopted to control the motion of multi floating bodies and to calculate the total average power absorption. Three cases of different wavelengths namely 20D, 30D and 40D have been modeled to analyze the total average power absorption. The average power absorption not only varies with the position of the floating body but also varies with wavelength. From the results obtained, it is concluded that the maximum total average power absorption is 9W approximately in wavelength 30D and the minimum total average power absorption is 4.3W approximately in wavelength 40D.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.7
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• pp.360-365
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• 2017

Recently, development efforts of triple-effect absorption chiller have been increased in order to improve the efficiency of double-effect absorption chiller. However, triple-effect absorption chiller has some disadvantages, including high corrosion characteristic of LiBr solution at high temperature of $200^{\circ}C$. Moreover, it is necessary to develop new components for operation under high pressure of 2 bars even though COP is increased to 1.6 or 1.7. The objective of this study was to introduce a new system by combining double effect absorption chiller with single effect absorption chiller with multi-generators using bypass flow of LiBr dilute solution to $3^{rd}$ generator to overcome the disadvantages of triple-effect chiller and improve energy efficiency. Results indicate that the new absorption cycle had a much higher efficiency than double-effect chiller system, showing significant improvement when bypass solution flow rate of 25% was applied to the $3^{rd}$ generator using the main dilute solution of the absorber. The COP of the new chiller system was found to be 1.438, which was 21.7% higher than that (1.18) of the present double-effect system. The COP was decreased when solution by-pass rate to the $3^{rd}$ generator was increased. In addition, lower cooling water temperature caused higher COP. Therefore, the multi-generator system with by-pass solution might be an excellent chiller alternative to triple-effect absorption chiller with higher efficiency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.270-275
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• 2009

Sound absorption characteristics of membrane system which are used in stadiums and arenas were investigated. Theoretical studies on acoustic properties of single and double leaf permeable membrane conducted. Also, experimental studies on sound absorption characteristics of combined membrane system that is composed of outer and inner membrane material were conducted. In this study, sound absorption characteristics of each membrane were investigated by experiments in reverberation chamber. 4 types of permeable membranes and a non-permeable membrane were used for experiments. Air space behind membrane material and tension on the membrane was varied. Sound absorption performance of permeable membrane materials was confirmed. As increasing air space behind the membrane material, sound absorption coefficient was increased. In a resonance absorption frequency band sound absorption coefficient varied more dramatically. Sound absorption characteristics were flat in mid and high frequency range and sound absorption coefficient was from 0,3 to 0,5. Also sound absorption coefficient was increased by the increment of surface density and air permeability of membrane. However, over the certain value of air permeability, sound absorption coefficient was decreased. These results can be used as design factors and method for the room acoustic design of dome-stadiums and large free-form buildings.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.540-545
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• 2007

The performance of microturbine CHP system equipped with an absorption chiller was analyzed by modelling of a microturbine and an absorption chiller. The microturbine having recuperator was simulated by the Brayton cycle model. The mass flow rate and available heat energy of the exhaust gas from the microtubune were simulated, and this results were utilized as input values for the generator of the absorption chiller. The absorption chiller is a single-effect air cooled type having solution heat exchanger. When heat input to the generator increased, the heat transfer rate and UA of the heat exchangers of the absorption chiller proportionally increased. Besides, the COP of the absorption chiller increased with increase of the heat input to the generator under the sufficient size of the evaporator condition. When the capacity of the CHP system increased from 30 to 60 kW, the mass flow rate of the LiBr for the absorption chiller increased by two times, and UA values for evaporator and condenser were increased by 3.9 and 3.4 times, respectively, under the same COP condition.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.75-83
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• 2003

Diode laser absorption system is advantageous of their non-invasive nature, fast response time, high sensitivity and real-time measurement capability. Furthermore, recent advances in room-temperature, near-IR and visible diode laser sources for telecommunication, optical data storage applications are enabling combustion diagnostics system based on diode laser absorption spectroscopy. So, combined with fiber-optics and high sensitive detection strategies, compact and portable sensor system are now appearing for a variety of applications. The objective of this research is to take advantage of distributed feed-back diode laser and develope new gas sensing system. It experimentally found out that the wavelength, power characteristics as a function of injection current and temperature. In addition to direct absorption and wavelength modulation spectroscopy have been demonstrated in these experiments and have a bright prospect to this diode laser system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.2099-2109
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• 1993

A gas-fired 4RT absorption heat pump was designed as an air-conditioner for domestic use during the summer. The absorption heat pump is air-cooled. double-effect, $LiBr-H_{2}O$ system with parallel flow type. The performance of the absorption heat pump in the cooling mode of operation was investigated through cycle modeling and simulation to obtain the system characteristics with parameter changes. System parameters considered in this analysis were the inlet temperature of cooling air to the absorber, the working solution concentrations, the ratio of the amount of the weak solution from the absorber, and the LTD's of each heat exchange component. The optimum designs and operating conditions were determined based on the operating constraints and the coefficient of performance.

• KIEAE Journal
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• v.1 no.2
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• pp.47-54
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• 2001

Single sound absorbers such as porous materials, panels, and Helmholts resonators have limited performance with some extents of frequency region. For example, porous materials do not attenuate low frequency sounds, while panels do not absorb high frequency sounds. Composite absorption structure with coverings, porous materials, and air gaps are an alternative for wide band sound absorption. Slits, panels, perforated panels are those materials for coverings, glass wool, mineral wool, polyester, and polyurethane are frequently used porous materials. Air gap between the porous material and background surface is one of major factors which governs the absorption characteristics of composite absorption structures, especially in the low frequency area. Calculations and measurements show that the absorption coefficients of composite absorption structure, in mid and low frequency bands, are getting higher with increased air gaps. Perforated panels rather than slits and panels are good coverings with higher number as far as absorption coefficient is concerned. Perforated panels with porous materials and 37 cm of air gaps in background have high absorption coefficients for all frequency bands, above 0.7 to 1.0. All measurements are performed in reverberation chamber, Mokpo National University, according to ISO 354 and ISO 3382.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1428-1436
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• 2000

The absorption of vapor involves simultaneous heat and mass transfer in the vapor/liquid system. In this paper, a numerical study for vapor absorption process into LIBr-H$_2$O solution film flowing over helical absorber has been carried out. Axisymmetric cylindrical coordinate system was adopted to model the helical tube and the transport equations were solved by the finite volume method. The effects of operating conditions, such as the cooling water temperature. the system pressure, the film Reynolds number and the solution inlet concentration have been investigated in view of the absorption mass flux and the total absorption mass flux and the total absorption rate. The results for the temperature and concentration profiles, as well as the local absorption mass flux at the helical absorber are presented. It is shown that solution inlet concentration affected other than operation conditions for a mass flux.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.7
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• pp.486-491
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• 2008

The performance of a microturbine CHP system equipped with an absorption chiller was analyzed by modeling it. The microturbine with recuperator was simulated with the Brayton cycle model. The mass flow rate and available heat energy of the exhaust gas from the microturbine were simulated. These results were utilized as input values for the generator of the absorption chiller. The absorption chiller is a single-effect air cooled type with a solution heat exchanger. The heat input into the generator was proportional to the heat transfer rate and the UA values of the heat exchangers of the absorption chiller. Furthermore, the COP of the absorption chiller increased with respect to an increase of the heat input into the generator, under the sufficient evaporator capacity condition. When the capacity of the CHP system increased from 30 to 60 kW, the mass flow rate of the LiBr for the absorption chiller doubled, and the UA values for evaporator and condenser increased by factors of x3.9 and x3.4, respectively, under the same COP condition.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.653-658
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• 2001

In this study, a new practical method of predicting the sound absorption coefficient for multiple perforated-plate sound absorbing system was developed using transfer matrix method. In order to validate the proposed method, the absorption coefficients calculated by transfer matrix method for single perforated plate were first compared with the absorption coefficients measured by SWR method according to different porosity, hole diameter, and thickness of the perforated plate. Based on the comparison results, transfer matrix method was further applied to double and triple perforated plates to evaluate the absorption coefficients. The experimental results showed that the absorption coefficients from transfer matrix method generally agreed well with the corresponding absorption coefficients from SWR method. However, due to the limitations of the impedance model used in this study, the measured values were differed with the calculated values for small porosity, hole diameter, and thickness in size of the perforated plate indicating the need of impedance model development for multiple perforated-plate sound absorbing system covering wide ranges of porosity, hole diameter, and thickness of the perforated plate.