• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.247-253
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• 2011

An experimental study on performance characteristics of an evaporative heat exchanger based on tests for various operating conditions was presented. The heat exchanger maximizes the heat transfer rate per unit volume by applying mini-channels for both the air and coolant flow paths, and minimizes the amount of the coolant by using its latent heat of evaporation. The heat exchanger was manufactured by etching the flow paths, brazing the heat exchange plates, and welding the in/out ports of the media. The basic performance test has confirmed that the heat exchanger met its design requirements, and the results of the map test were analyzed to produce the performance characteristics quantitatively depending on the air inlet temperature, the air flow rate, and the coolant flow rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1466-1473
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• 2012

Soft icecream is made by scraping an ice formed on the inside of the cylindrical evaporator, where R-404A is evaporating in the annulus. The heat transfer characteristics of the refrigerant evaporation and those during icecream formation were experimentally investigated. Results show that the refrigerant-side heat transfer coefficients are highly dependent on the location in the evaporator due to the complex annulus configuration. The heat transfer coefficient at the inlet is generally lower than those of other locations. The average heat transfer coefficient increases as heat flux increases or saturation temperature decreases. A correlation is developed to predict the refrigerant-side heat transfer coefficient. The icecream-side heat transfer coefficient oscillates continuously due to the periodic removal of ice formed on the surface. The average heat transfer coefficient during icecream formation is approximately 280 W/$m^2K$, and that during single-phase cooling increased from 150 W/$m^2K$ to 250 W/$m^2K$.

• Journal of the Korean Institute of Gas
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• v.5 no.2 s.14
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• pp.22-29
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• 2001

The number of gas containers and the period of exchanging gas containers are vsy important in designing liquefied petroleum gas(LPG) supply system for small capacity domain. And also the evaluation of remaining LPG in containers to be exchanged is very useful information in commerce. However seldon has been studied on calculating method about those with respect to gas consumption pattern. In this study, a simulation method was developed to estimate the evaporation capacity of LPG container, the mass gas flow rate from LPG container, the temperature and vapor pressure of LPG, and the remained LPG at containers to be exchange by using LPG property equations, mass balance equation, and heat balance equation. The simulation results were correlated well with experimental data. The overall heat transfer coefficient from air to LPG is approximately $9{\~}13 kcal/m^2{\cdot}hr{\cdot}^{\circ}C$ and does not strongly affect on the evaporation capacity of LPG container. The mass gas flow rate from LPG container is constant when the vapor pressure of LPG is within pressure regulator's control range. While, out of range, it suddenly reduce to a evaporation rate which is balanced with heat transfer from air. The evaporation capacity of LPG container increased with surrounding temperature and the composition of propane, and decreased drastically with continuous gas consumption. The number of gas containers divided the number of houses using gas supply system was reduced by using automatic gas feeding device.

• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.79-89
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• 2019

The field measurement and laboratory experiment were conducted to investigate the effect of reducing the surface temperature of the functional aspect of the heat island phenomenon of the permeable block which is made the recycled synthetic resin rather than the existing concrete permeable block. Field measurement was taken for 3 days in consideration of dry condition and wet condition and laboratory experiment was divided into dry condition, rainfall simulating condition, and wetting condition. The variations of temperature and the evaporation rate of water moisture content after experiment were confirmed. As a result of field measurement, it is confirmed that the surface temperature decreases due to the difference in albedo of the pore block surface rather than the cooling effect due to the latent heat of vaporization. The evaporation of moisture in a dry state where drought persisted or a certain level of moisture was not maintained in the surface layer. As a result of laboratory experiment, resin permeable block gives higher surface temperature when it is dry condition than concrete permeable block, but the evaporation of water in the pore is kept constant by capillary force in rainfall simulation condition, and higher temperature reduction rate. As a result of measuring the evaporation rate after laboratory experiment, it is confirmed that the effect of reducing temperature is increased as the evaporation rate of water is higher. Based on these results, correlation formula for evaporation rate and temperature reduction rate is derived.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.91-100
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• 2010

To investigate the thermal properties of a water-retentive artificial turf system (W-ATS), we estimated hydrologic parameters including thermal conductivity, heat capacity, and surface albedo for both the W-ATS and natural grass. We used a model experiment to measure surface temperature and evaporation for both the W-ATS and natural grass. We found that the W-ATS had lower thermal conductivity than natural grass did, and it was difficult for the W-ATS to convey radiant heat to the ground. Compared to natural grass, the W-ATS also had lower heat capacity, which contributed to its larger variation in surface temperature: the W-ATS had higher surface temperatures during daytime and lower surface temperatures during nighttime. The albedo of the W-ATS was one-quarter that of natural grass, and reflected shortwave radiation from the W-ATS surface was lower than that from the surface of natural grass. These results indicate that the W-ATS caused the soil temperature to increase. Furthermore, evaporation from the W-ATS was one-quarter the value of evapotranspiration from natural grass.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.4
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• pp.340-348
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• 2004

The air and refrigerant side heat transfer performances are key parameters to improve heat transfer efficiency of the heat exchanger including the fan performance. Design of the fins, treatment of the tube inside, tube diameter and tube array effect heat transfer performance of the heat exchanger. The heat exchanger is used as a condenser at cooling mode and used as an evaporator at heating mode in the heat pump system. The heat pump system uses R410A as the refrigerant. The heat exchangers are consisted with 7 mm diameter tubes with slit-type fins. The study was conducted with variation of arrangement of the refrigerant path and air flow rate and refrigerant pressure drop and heat transfer rate were measured with a code tester. The capacity of the 3 path heat exchanger is more efficient than 2 or 4 path heat exchangers in heating or cooling modes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.11
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• pp.434-443
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• 2016

The evaporation of water from an aqueous solution is widely used in the food, desalination, pulp, and chemical industries. Usually, a large amount of energy is consumed in the evaporation process to boil off water due to atmospheric pressure. As a way of improving the energy efficiency of the evaporation process, the combination of multiple effect evaporation and thermal vapor recompression has been proposed and has become a successful technique. In this study, 4 multiple-effect falling film type evaporators for sugar solution are designed and the energy efficiency of the system is analyzed in response to the selection of the steam ejector position. Energy efficiency is increased and vapor is more compressed in the steam ejector as the Thermal Vapor Recompression (TVR) is arranged in the rear part of the evaporator system. A simplified 0-dimensional evaporator model is developed using non-linear equations derived from mass balances, energy balances, and heat transfer equations. Steam economy is calculated to compare the evaporation performance of the 4 proposed evaporators. The entrainment ratio, compression ratio, and expansion ratio are computed to check the ejector performance.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.46.2-46.2
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• 2013

The neutral component of the interstellar medium (ISM) is segregated into the cold neutral medium (CNM) and warm neutral medium (WNM) as a result of thermal instability. It was found that the CNM--WNM evaporation interface, across which the CNM undergoes thermal expansion, is linearly unstable to corrugational disturbances, in complete analogy with the Darrieus-Landau instability (DLI) in terrestrial flames. To explore dynamical consequences of the DLI in the ISM, we perform a linear stability analysis of the DLI including the effect of thermal conduction as well as nonlinear hydrodynamic simulations. We find that the DLI is suppressed at short length scales via heat transport. The linear growth time of the fastest growing mode is proportional to the square of the evaporation flow speed of the CNM relative to the interface and is typically >10 Myr. In the nonlinear stage, perturbations grow into cusp-like structure protruding toward the WNM, and soon reach a steady state where the evaporation rate is increased by a factor of 2 compared to the initial state. We demonstrate that the amplitude of the interface distortion and enhancement in evaporation rate are determined primarily by the density ratio between the CNM and WNM. Given quite a long growth time and highly subsonic velocities at saturation, the DLI is unlikely to play an important role in the ISM dynamics.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.4
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• pp.418-429
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• 1992

Recently, many researchers make a great effort to develop high efficient marine diesel engines using low grade heavy oil, and also study substitution fuel oil for engines and boilers. In case of Fisheries Vessels, we need to know that fish oil can be substituted for fuel oil. Therefore, it is studied that evaporation, ignition and combustion phenomena of the single droplet of fish oils (i.e., Sardine fish oil, File fish oil and Alaska pollac oil) on heated plane surface to evaluate appropriateness as substitution oil. Methanol and light oil are tested simultaneously to help the evaluation on these Fish oils. The results are summarized as follows: 1. The type of evaporation and combustion is spherical evaporation in case of methanol and light oil. And fish oil blended with light oil was finished after spherical evaporation happen when high temperature. 2. Ignition of Pure fish oil was shorter than that of fish oil blended with light oil. 3. Heat transferred to droplet could make qualitative comparison by contact diameter of droplet with hot surface as time changes. Life time of droplet according to the change of heated surface temperature was greatly influenced by droplet contact condition on the heated surface. 4. As far as combustion phenomena was concerned, apparent diameter of the fish oil droplet increased after ignition and decreased suddenly by internal boiling of droplet. 5. Three fish oils had similar phenomena on the evaporation, ignition and combustion. 6. Evaporation and combustion feature of fish oil could not be shown by coefficient of evaporation velocity of droplet and coefficient of combustion velocity of droplet.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.1
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• pp.59-66
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• 2003

The purpose of this study is to analyze the characteristics (COP) of the heat pump system for various operating conditions with the use of seawater heat source and exhaust energy. To accomplish the goal, first of all, the computer simulation for heat pump system is carried out. The heat pump system model is made of a waste heat recovery system and a vapor compression refrigeration system, and the working fluid is R-22. The model calculated the change of COP with the variation of temperature and flow rate. The COP and the plate heat exchanger (PHE) area of the heat pump system are considered moderately high in the condensation temperature of $25^{\circ}^C$ and the evaporation temperature of $2^{\circ}^C$ in indoor culture system. The simulation results will be used effectively for the design and the performance prediction of heat pump system using unused energy in a land base aquaculture system.