• Journal of Biosystems Engineering
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• v.25 no.5
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• pp.385-390
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• 2000

The heat pump is one of heating and cooling systems driven by electricity using natural energy as a heat source. The heat pump system was mainly adopted to a cooling system or a refrigeration system. In regions with a large amount of electricity, it is used as a heating system or a heating and cooling system of houses, buildings and agricultural facilities. During cold weather, air source heat pumps do not work well because of some technical problems, such as frosting on evaporator coil when outside air temperature is below -5$^{\circ}C$. In this research, the heat regenerative technology was employed to eliminate the frosting on evaporator coil and improve the COP of the heat pump system. This fiber belt heat regeneration system(FBHRS) has very simple structure consisting of a geared motor and a porous fiber belt passing through alternatively between cold and warm air duct. The laboratory test showed that the heat pump system with a FBHRS yielded an impressive COP higher than 3.5 at the outside air temperature of -7$^{\circ}C$ in heating mode.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.5
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• pp.610-618
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• 1998

In this study, a tracer gas technique was used to measure ventilation effectiveness in a thermal environmental chamber simulating an under-floor air conditioning system. A tracer gas of $SF_6$ was injected in a supply duct using step-up and step-down methods. Local mean ages and room mean ages were calculated from the measured concentrations under isothermal and cooling conditions with and without diffusers. Ventilation effectiveness is found to be higher in cooling ventilation operations than in isothermal operations. Results also show that ventilation effectiveness is not significantly affected by a diffuser.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.8
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• pp.739-745
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• 2001

The objective of this research is to analyze the ventilation effectiveness in the non-isothermal air supply using mixing and displacement ventilation systems for indoor air quality control and management. In this study, a ventilation effectiveness is evaluated in a simplified model chamber using a tracer gas technique of $CO^2$ gas injected into a supply duct as a function of ventilation rates, supply/extract sites and cooling/heating air supply. The ventilation effectiveness decreased with increasing ventilation rate on the cooling and heating conditions. And the ventilation effectiveness of case 3 (down supply and upper extract) was better thant that of case 1(upper supply and upper extract) and case 2(upper supply and down extract) with the cooling supply conditions. but for the heating supply air conditions, the ventilation effectiveness of case 2 was better than that of case 3 and case 1.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.349-354
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• 2013

This study examined a technique for cooling root zone aimed at lowering substrate temperature for sweet pepper (Capsicum annum L. 'Orange glory') cultivation in coir substrate hydroponics during hot season, from the $16^{th}$ of July to $15^{th}$ of October in 2012. The root zone cooling technique was applied by using an air duct (${\varnothing}12$ cm, hole size 0.1 mm) to blow cool air between two slabs during night (5p.m. to 3a.m.). Between the $23^{rd}$ of July and $31^{st}$ of August (hot temperature period), average daily substrate temperature was $24.7^{\circ}C$ under the root zone cooling, whereas it was $28.2^{\circ}C$ under condition of no cooling (control). In sunny day (600~700 W $m^{-2}{\cdot}s^{-1}$), average substrate temperatures during the day (6a.m. to 8p.m.) and night (8p.m. to 6a.m.) were lower about $1.7^{\circ}C$ and $3.3^{\circ}C$, respectively, under the cooling treatment, compared to that of control. The degree of temperature reduction in the substrate was averagely $0.5^{\circ}C$ per hour under the cooling treatment during 6p.m. to 8p.m.; however, there was no decrease in the temperature under the control. The temperature difference between the cooling and control treatments was $1.3^{\circ}C$ and $0.6^{\circ}C$ in the upper and lower part of the slab, respectively. During the hot temperature period, about 32.5% reduction in the substrate temperature was observed under the cooling treatment, compared to the control. Photosynthesis, transpiration rate, and leaf water potential of plants grown under the cooling treatment were significantly higher than those under the control. The first flowering date in the cooling was faster about 4 days than in the control. Also, the number of fruits was significantly higher than that in the control. No differences in plant height, stem thickness, number of internode, and leaf width were found between the plants grown under the cooling and control, except for the leaf length with a shorter length under the cooling treatment. However, root zone cooling influenced negligibly on eliminating delay in fruiting caused by excessively higher air temperature (> $28^{\circ}C$), although the substrate temperature was reduced by $3^{\circ}C$ to $5.6^{\circ}C$. These results suggest that the technique of lowering substrate temperature by using air-duct blow needs to be incorporated into the lowering growing temperature system for growth and fruit set of health paprika.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.9
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• pp.693-698
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• 2012

In the present work, numerical analyses of broadcasting LED light with ion wind generator have been carried out for enhancement of cooling performance. Ion wind generator is produced and experimented before analysis. With the use of result of experiments, broadcasting LED light model is computed. Ion wind velocity into LED light is varied with 0~3 m/s. Based on the numerical results, the area of duct-type ion wind generator was designed to reduce the volume flow rate of ion wind. The modified inlet geometry shows sufficient cooling capability. And, through modified ion wind generator, the volume flow rate of ion wind has been largely reduced.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.590-595
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• 2009

PMV and ADPI were numerically investigated in a large space of various ceiling height with air-conditioning systems of two type. The numerical results showed that it is small that the growth of cooling load according to ceiling height rise in a large space without windows. In case of system air-conditioner of duct type embedded in the ceiling, the air mixing effect in indoor is superior to a case installed 4way cassette type in it. For controling thermal comfort at indoor, a system air-conditioner of duct type embedded in the ceiling is little influenced according to ceiling height rise in a large space considered.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.243-251
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• 2015

This study aimed to determine the effects of root zone cooling using air duct on air temperature distribution and root zone and leaf temperatures of sweet pepper (Capsicum annum L. 'Veyron') grown on coir substrate hydroponic system in a greenhouse. When the air duct was laid at the passage adjacent the slab, the direction of air blowing was upstream at $45^{\circ}$. The cooling temperature was set at $20^{\circ}C$ for day and $18^{\circ}C$ for night. For cooing timing treatments, the cooling air was applied at all day (All-day), only night time (5 p.m. to 1 a.m.; Night), or no cooling (Control). The air temperature inside the greenhouse at a height of 40 and 80cm above the floor, and substrate and leaf temperatures, fruit characteristics, and fruit ratio were measured. Under the All-day treatment, the air temperature was decreased about $4.4{\sim}5.1^{\circ}C$ at the height of 40cm and $2.1{\sim}3.1^{\circ}C$ at the height of 80cm. Under the Night treatment, the air temperature was decreased about $3.4{\sim}3.8^{\circ}C$ at the height of 40cm and $2.2{\sim}2.7^{\circ}C$ at the height of 80cm. The daily average temperature in the substrate was in the order of the Control ($27.7^{\circ}C$) > Night ($24.1^{\circ}C$) > All-day ($22.8^{\circ}C$) treatment. Cooling the passage with either upstream blowing at $45^{\circ}$ or horizontal blowing at $180^{\circ}$ was effective in lowering the air temperature at a height of 50cm; however, no difference at a height of 100cm. Cooling the passage with perpendicular direction at $90^{\circ}$ was effective in lowering the air temperature at the height between 100 and 200cm above the floor; however, no effect on the temperature at the height of 50cm. A greater decrease in leaf temperature was found at 7 p.m. than that at 9. a.m. under both All-day and Night treatments. Fresh weight partitioning of fruit was in the order of the All-day (48.6%) > Night (45.6%) > Control (24.4%) treatment. A higher fruit production was observed under the All-day treatment, in which the accumulated average temperature was the lowest, and it may have been led to a higher proportion of photosynthate distributed to fruit than other treatments.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.3
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• pp.171-179
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• 2010

Thermal performance of louver fin and plate fin in a thermoelectric cooling system with a duct-flow type fan arrangement is analytically evaluated. The thermoelectric cooling system consists of a thermoelectric module and two heat exchanger fins. The analytic results show that the optimized louver fin has lower thermal resistance than plate fin. The COP and heat absorbed rate of the thermoelectric cooling system with optimized louver fins are 10.3% and 5.8% higher than optimized plate fins, respectively.

• Corrosion Science and Technology
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• v.4 no.4
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• pp.140-146
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• 2005

Fossil fired power plant produces the electric energy by using a thermal energy by the combustion of fossil fuels as like oil, gas and coal. The exhausted flue gas by the combustion of oil etc. contains usually many contaminated species, and especially sulfur-content has been controlled strictly and then FGD (Flue Gas Desulfurization) facility should be installed in every fossil fired power plant. To minimize the content of contaminations in final exhaust gas, high corrosive environment including sulfuric acid (it was formed during the process which $SO_2$ gas combined with $Mg(OH)_2$ solution) can be formed in cooling zone of FGD facility and severe corrosion damage is reported in this zone. These conditions are formed when duct materials are immersed in fluid that flows on the duct floors or when exhausted gas is condensed into thin layered medium and contacts with materials of the duct walls and roofs. These environments make troublesome corrosion and air pollution problems that are occurred from the leakage of those ducts. The frequent shut down and repairing works of the FGD systems also demand costs and low efficiencies of those facilities. In general, high corrosion resistant materials have been used to solve this problem. However, corrosion problems have severely occurred in a cooling zone even though high corrosion resistant materials were used. In this work, a new technology has been proposed to solve the corrosion problem in the cooling zone of FGD facility. This electrochemical protection system contains cathodic protection method and protection by coating film, and remote monitoring-control system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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• pp.274-286
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• 2003

Numerical simulations are performed to investigate the turbulent convective heat transfer of the supercritical carbon dioxide flows in vertical and horizontal square ducts. The gas cooling process at the supercritical state experiences a sudden change in thermodynamic and transport properties. This results in the extraordinary variations of the heat transfer coefficients in the supercritical state, which are much different from those of single or two phase flows. Algebraic second moment closure which can include the effects of large thermophysical property variations of carbon dioxide and of buoyancy is employed to model the Reynolds stresses and turbulent heat fluxes in the governing equations. The previous correlations for the turbulent heat transfer coefficient for the supercritical carbon dioxide flows couldn't reflect the buoyancy effect. The present results are used to establish a new heat transfer coefficient correlation including the effects of large thermophysical property variation and buoyancy on in-duct cooling process of supercritical carbon dioxide.