• Proceedings of the SAREK Conference
• /
• 2006.06a
• /
• pp.46-51
• /
• 2006

In order to utilize the refrigerants condensation heat of condenser on the absorption chiller system, the solution cooling condenser(SCC) were proposed, which weak solution of absorber outlet use as a cooling water. As the UA of the solution cooling condenser increased, increasement of COP is about maximum 0.09 in occasion of single effect and is about maximum 0.08 in occasion of double effect series flow. In the case of heat exchanger efficiency is about 0.85, it's increments are 0.08 and 0.072, each. And solution cooling condenser is a more effective device in the single effect absorption system more than double effect system for the principle of operation. In order to increases the heat of solution cooling condenser, if reduce the flow rate of cooling water or the value of UA, it makes COP increase a little, but it brought COP decrease because of increasing the pressure of system.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.17 no.5
• /
• pp.583-589
• /
• 1988

Condensation of water vapor into an absorbent liquid of LiBr-water solution falling over a bank of water cooled horizontal tubes was investigated theoretically. The governing conservation equation for a re-defined physical transport phenomena were solved numerically using a finite difference method. Raw parameters were used in this study, since reliable experimental data is required prior to a dimensionless parametric study. The average values of wall heat transfer coefficient and interfacial absorption rate were defined to see the system performance. Other parameters include tube diameter, streamwise coordinate (and number of tubes in row), mass flow rate, and the wall temperature. The effects of these quantities on the absorption processes and suggestions for a rational system design have been presented.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.4
• /
• pp.499-509
• /
• 1998

In the absorption process of water vapor in a liquid film, the composition of the gas phase, in which a non-absorbable gas is combined with the absorbate influences the transport characteristics remarkably. In the present study, the absorption processes of water vapor into aqueous solution of lithium bromide in the presence of non-absorbable gases were investigated analytically. The continuity, momentum, energy and diffusion equations for the solution film and gas phase were formulated in integral forms and solved numerically. It was found that the mass transfer resistance in gas phase increased with the concentration of non-absorbable gas. However the primary resistance to mass transfer was in the liquid phase. As the concentration of non-absorbable gas in the absorbate increased, the liquid-vapor interfacial temperature and concentration of absorbate in solution decreased, which resulted in the reduction of absorption rate. The reduction of mass transfer rate was found to be significant for the addition of a small amount of non-absorbable gas to the pure vapor, especially at the outlet of an absorber where non-absorbable gases accumulated. At higher non-absorbable gas concentration, the decrease of absorption flux was almost linear to the volumetric concentration of non-absorbable gas.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2006.06a
• /
• pp.261-262
• /
• 2006

The effect of tube diameter on heat transfer characteristics of absorber in absorption chiller/heater using LiBr solution as a working fluid has been investigated by experimental study to develop a high performance and compact absorber. A system Includes a tube absorber, a generator, solution distribution system and cooling water system was set up. The diameter of the heat exchanger tube inside absorber was changed from 15.88mm to 12.7mm and 9.52mm. The experimental results show that the heat transfer coefficient, Nusselt number and heat flux increase as solution flow rate and cooling water flow rate increase. The heat transfer performance increases as tube diameter decreases. Among three different tube diameters, the smallest tube diameter 9.52mm has highest heat transfer performance. A comparison of the heat transfer coefficient obtained by the present study with those of previous experimental results showed good overall agreement.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.4 no.4
• /
• pp.332-341
• /
• 1992

An absorption heat pump cycle has been modeled and simulated to analyze the system performance of water-cooled, series-flow, double-effect absorption heat pump, which can be applied to a direct gas fired cooling system with the medium range of cooling capacity (15RT level). Effect of absorption cooling system parameters, such as concentration difference, inlet temperature of cooling water, 1st generator temperature, leaving temperature differences of condenser and evaporator and efficiency of solution heat exchanger, has been investigated in the view of system cooling performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.9
• /
• pp.738-744
• /
• 2006

In order to utilize the condensation heat of refrigerants in condenser on the absorption chiller system, the solution cooled condenser (SCC) was proposed using the weak solution of absorber as a cooling medium. The increase of COP with the increase of UA of the solution cooled condenser was approximately 0.009 in maximum with single effect one, and is about maximum 0.008 in occasion of double effect one with series flow compared to that without. In the case of heat exchanger, effectiveness is about 0.85, it's increments are 0.008 and 0.0072, respectively. And solution cooled condenser is more effective device in the single effect absorption system than double effect system for the principle of operation. On the other hand, as the solution split ratio increases when the value of UA is fixed, COP is increased and as the solution split ratio increases when the value of UA is fixed, COP is increased. If the flow rate of cooling water or the value of UA is reduced in order to increases the heat recovery of solution cooled condenser, heat recovery of solution cooled condenser is increased a little but COP is decreased as the system pressure is increased.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.3
• /
• pp.865-870
• /
• 2014

Gold nanoparticles (AuNPs) were synthesized by laser (Nd:YAG, ${\lambda}$ = 1064 nm) ablation of a gold target immersed in various aqueous electrolyte solutions (7 mM of LiCl, NaCl, KCl, NaBr, and NaI) as well as in deionized water. The surface plasmon absorption and EDX of AuNPs so produced as well as their TEM images were analyzed to investigate the effects of ambient ions on the growth and aggregation of NPs. The size of AuNPs was reduced by laser ablation in the presence of chloride and bromide ions while it increased drastically when AuNPs were formed in iodide solution. Interestingly, triangular nanoplates were synthesized only in iodide solution. Surface chemistry on AuNPs in various electrolyte solutions was explored to elucidate the role of ions on the size and stability of AuNPs.

• Journal of Advanced Marine Engineering and Technology
• /
• v.30 no.4
• /
• pp.483-493
• /
• 2006

A model for a pressure drop of water vapor flow across tube banks in a horizontal tube absorber of an absorption chiller/heater using LiBr solution as a working fluid has been developed based on a commercial 20RT(70kW) absorption chiller/heater. The numerical results show that the characteristic of the pressure drop in the shell side of the horizontal tube absorber is completely different from that in a conventional shell and tube heat exchanger. Especially, solution film thickness has significant influence on the vapor pressure drop in the horizontal tube absorber. In addition, the effects by the tube diameters, the longitudinal pitch to diameter ratio, and Reynolds number of the vapor flow, on the vapor pressure drop have been studied to evaluate the compactness of tube absorber. It was found that the vapor pressure drop decreases as tube diameter increases, the longitudinal pitch to diameter ratio increases, and Reynolds number of the vapor flow decreases. A comparison of the present study results with well-established experimental and numerical results showed a good overall agreement.

• Journal of Advanced Marine Engineering and Technology
• /
• v.22 no.3
• /
• pp.362-370
• /
• 1998

Absorption systems require a heat source for working but they have a great merit in that relatively low-temperature and low-quality types of thermal energy such as solar heat and exhaust heat can be effectively utilized as heat source. However details research related to absorbers which have a great effect on performances has been rarely done and thus there has been a strong hope for positive developments to improve their efficiencies. This paper describes absorption experiments made with different inside tube diameters and shapes. The purpose of this study is to acquire basic knowledge about heat and mass transfer in a falling film type absorber with vertical inner tubes. Heat and mass transfer were measured for water vapor absorption into a water/LiBr solution flowing down an absorber of vertical inner tubes. As a result absorption acceleration tube compares bare tube and heat transfer improved by order of insert spring tube corrugated tube grooved tube. And the acceleration that is good provided in inserting spring tube for both sides of heat and mass transfer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.8 no.2
• /
• pp.288-298
• /
• 1996

The gas-fired absorption refrigeration system to utilize treated sewage is available for environmental protection and energy conservation. Simulation analysis on the double-effect absorption refrigeration cycles with parallel or series flow type has been performed. The working fluid is Lithium Bromide and water solution. The main purpose of this study is evaluating the possibilities of effective utilization of treated sewage as a cooling water for the absorber and condenser. The efficiency of a couple of cycles has been studied and simulation results show that higher coefficient of performance could be obtained for parallel flow type. The other purpose of the present study is to determine the optimum designs and operating conditions based on the operating constraints and the coefficent of performance in the paralledl flow type.