• Journal of Industrial Technology
• /
• v.26 no.B
• /
• pp.157-162
• /
• 2006

Recently, the humidity adjustment of indoor air is of great importance in air conditioning system as a applied, in buildings, vehicles, and containers for storage and transport of perishable products. Membrane dehumidification or air is potentially attractive because it offers low capital and operating costs, along with low energy consumption. And membrane dehumidification process attracted the attention of the public instead of the other dehumidification processes, such as adsorption, absorption, and refrigeration cycles and so on. In this study, the prepared hydrophilic inorganic membrane-based dehumidifiers(membrane air dehumidification) examined the performance of dehumidification. The surface-modified inorganic membrane prepared in this study showed high dehumidification efficiency(over 80%). The membrane might be very useful for dehumidification industries.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.9
• /
• pp.768-778
• /
• 2003

Numerical analysis has been carried out to investigate laminar convective heat transfer in a tube for supercritical water near the thermodynamic critical point. Fluid flow and heat transfer are strongly coupled due to large variations of thermodynamic and transport properties such as density, specific heat, viscosity, and thermal conductivity near the critical point. Heat transfer characteristics in the developing region of the tube show transition behavior between liquid-like and gas-like phases with a peak in heat transfer coefficient distribution near the pseudocritical point. The peak of the heat transfer coefficient depends on pressure and wall heat flux rather than inlet temperature and Reynolds number, Results of the modeling provide convective heat transfer characteristics including velocity vectors, temperature, and the properties as well as the heat transfer coefficient. The effect of proximity to the critical point is considered and a heat transfer correlation is suggested for the peak of Nusselt number in the tube.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.5
• /
• pp.422-430
• /
• 2001

In the present study, an evaporative generation process of ammonia-water solution film on the vertical plate was analysed. For the utilization of waste heat, hot water of low temperature was used as the heat source. The continuity, momentum, energy and diffusion equations for the solution film and vapor mixture were formulated in integral forms and solved numerically. Counter-current solution-vapor flow resulted in the refrigerant vapor of the higher ammonia concentration than that of co-current flow. Eve the rectification of refrigerant vapor was observed near the inlet of solution film in counter-current flow. For the optimum operation of generator using hot water, numerical experiments, based on the heat exchange and generation efficiencies. revealed the inter-relationships among the Reynolds number of the solution film and hot water, and the length of generator. Enhancement of heat and mass transport in the solution film was found to be very effective for the improvement of generation performance, especially at high solution flow rate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.2
• /
• pp.175-183
• /
• 2004

Performance of the water/air direct contact air conditioning system, in which heat and mass are directly transferred between air and water droplet, is simulated using semi-empirical method. Direct contact system improves transport efficiency compared to conventional indirect contact system. In this study, correlations for h$_{c}$A / c$_{pm}$ which represent the capacity of direct contact system are derived as a function of air and water flowrate from the experimental data. Cooling and heating performance of the water/air direct contact air conditioning system are evaluated using these correlations.ons.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.6
• /
• pp.45-55
• /
• 1998

A theoretical and experimental study is performed to investigate the characteristics of ice slurry product. By diffusion-controlled evaporation model the possibility of ice slurry is theoretically anticipated. The water vapor evaporated from the surface of droplets is extracted continuously from the chamber by a vacuum pump. The droplet diameter is measured by silicon immersion method. The ice slurry is obtained by spraying droplets of ethylene glycol aqueous solution in the chamber where pressure is maintained under the triple point of water. The droplet with the diameter of 300 $\mu\textrm{m}$and the initial temperature of 2$0^{\circ}C$ was changed into ice particle within the chamber of 1.33m in height.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.4
• /
• pp.252-259
• /
• 2008

The purpose of this study is to estimate the movement of microbial contaminant caused by bio-attack using bio-agent such as bacillus anthracis for preventing contaminant diffusion. multizone simulation was carried out in the case of three types of bio-attack scenario in the government building. Simulation results show that severe contaminant diffusion is brought about in all cases of bio-attack scenario in one hour, though pollution boundaries have different mode according to bio-attack scenarios. Simulation results also show that immune building technology such as filter and UVGI technology gives us powerful alternatives to meet the emergent situation caused by unexpected bio-attack.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.6
• /
• pp.462-473
• /
• 2001

Due to the coupling between momentum and energy transport theoretical analysis of the loop performance is very complicate, therefore it is necessary that these problems be solved by experimental investigation before applying th loop thermosyphon to heat exchanger design. The evaporator and condenser of the loop thermosyphon were made of carbon-steel, and distilled water was used as working fluid in the experiments. From the experimental data correlations of heat transfer coefficient for evaporator and condenser sections were obtained. For heat fluxes in th range of 13~78kW/$m^2$, the correlation equations of heat transfer coefficients in evaporator and condenser predict the experimental behavior to within $\p$\pm$5% and\;\pm20$% respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.12
• /
• pp.695-702
• /
• 2009

Dynamic behavior of Libr-water absorption system using low-temperature hot water was investigated numerically. Thermal-hydraulic model of single-effect/double-lift 100 RT chiller was developed by applying transient conservation equations of total mass, Libr mass, energy and momentum to each component. Transient variations of system properties and transport variables were analysed during start-up operation. Numerical analysis were performed to quantify the effects of bulk concentration and part-load operation on the system performance in terms of cooling capacity, coefficient of performance, and time constant of system. For an absorption chiller considered in the present study, optimum bulk concentration was found to exist, which resulted in the minimum time constant with stable cooling capacity. COP and time constant increased as the load decreased down to 40%, below which the time constant increased abruptly and COP decreased as the load decreased further.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.11
• /
• pp.1065-1071
• /
• 2001

To investigate hydraulic and thermal characteristics of ice slurries in a circular tube, ice slurries were tested in a flow loop with a constant heat flux test section, for ranges of flow velocity, ice fraction and heat flux. Heat transfer coefficients and friction factors of ice slurries were calculated by measuring the outer wall temperatures of the test section and the pressure drops over the test section. Heat transfer coefficients of ice slurries were 9% higher than the heat transfer coefficients expected by Petukhov. Friction factors were about 4% lower than the friction factors expected by Petukhov. The effective thermal capacity of ice slurry with 12.8% ice fraction, was found to be about 3 times higher than the thermal capacity of water.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.11 no.2
• /
• pp.176-184
• /
• 1999

Numerical and experimental studies were performed to examine the characteristics of heat and mass transfer processes for a Micro Heat Pipe(MHP) with a triangular cross-section. Solutions on mass flow rate, pressure variation, and radius of meniscus were obtained using the mathematical model developed by Faghri and Khrustalev. To obtain an increase in capillary limitation, a triangular tube with curved walls was designed and fabricated. The measurement by microscope showed that the radius at corners of the tube was ranging between 0.03-0.05mm. Performance test for MHPs using the triangular tube with curved walls proved a substantial increasement in heat transport limitation, with 4.5W and 2.0W in case of using water and ethanol as a working fluid, respectively. In the previous study by Faghri a limitation of 0.5W was reported for a water MHP with a regular triangular tube.