• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.399-404
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• 2008

Condensing gas boiler units may make a big role for the reduction of energy consumption in heating industries. In order to decrease the energy consumption of a condensing gas boiler unit, the effective control of the system is necessary. In this study, control algorithms of a condensing gas boiler were developed. Control algorithms are composed of the setpoint algorithm and the control algorithm. The setpoint algorithm consists of the supply water temperature setpoint algorithm and the pump setpoint algorithm. The control algorithm consists of the gas valve control algorithm and the blower control algorithm. In order to analyse the performance of control algorithms, dynamic models of a condensing gas boiler system were used. Simulation results showed that control algorithms developed for this study may be practically applied to the condensing gas boiler.

• 대한수학회지
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• 제43권1호
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• pp.1-9
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• 2006

Based on the Schauder fixed point theorem, we give a Leray-Schauder type fixed point theorem for countably condensing mappings in a more general setting and apply it to obtain eigenvalue results on condensing mappings in a simple proof. Moreover, we present a generalization of Sadovskii's fixed point theorem for count ably condensing self-mappings due to S. J. Daher.

• 대한수학회보
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• 제40권3호
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• pp.465-473
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• 2003

Introducing the concept of a sequentially condensing operator in a more general framework, we give a new fixed point theorem for sequentially condensing operators in Banach spaces, with the aid of attractors.

• 대한수학회보
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• 제47권1호
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• pp.121-129
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• 2010

Using a degree theory for countably condensing multivalued maps, we show that under certain conditions an invariance of domain theorem holds for countably condensing or countably k-contractive multivalued vector fields.

• 한국대기환경학회지
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• 제29권5호
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• pp.634-641
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• 2013

Condensing species behaviour downstream of a combustor was discussed with particle size distribution in this study. The effects of operating conditions in a biomass combustion facility, i.e. concentration of condensing species, temperature gradient, residence time and injection of adsorbents, on particle size distribution were investigated. Pyroligneous liquid which was completely vaporized at the temperature higher than $350^{\circ}C$ was used as a representative of condensing gaseous species. We found that particle size downstream of a combustor increased with increasing heating temperature (i.e. concentration of condensing species) and residence time. However, temperature gradient was not an important factor to control the particle size. The addition of $SiO_2$ precursor as an adsorbent could effectively prevent the particle formation by adsorbing condensing gaseous species on $SiO_2$ particles, and increased the particle size up to 300 nm, resulting in increasing particle removal efficiency in a conventional air pollution control device.

• 동력기계공학회지
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• 제12권3호
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• pp.19-25
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• 2008

This paper deals with the heat transfer and pressure drop characteristics of R-290 (Propane), R-600a (Iso-butane) and R-1270 (Propylene) as an environment friendly refrigerant and R-22 as a HCFC's refrigerant for condensing. The test section is a horizontal double pipe heat exchanger. Condensing heat transfer and pressure drop measurements were Peformed for 12.70 mm micro-fin tube and compared with the results in smooth tube. The local condensing heat transfer coefficients of hydrocarbon refrigerants were superior to those of R-22 and the maximum increasing rate of heat transfer coefficient was found in R-600a. The average condensing heat transfer coefficients in hydrocarbon refrigerants showed 20 to 28% higher values than those of R-22. Hydrocarbon refrigerants have a higher pressure drop than that of R-22 with respect to refrigerant qualify and mass flux. Also, the condensing heat transfer coefficient and pressure drop of working fluids in smooth and micro-fin tube were compared. The heat transfer enhancement factor (EF) between smooth and micro-fin tube varied from 2.2 to 2.6 in all experimental conditions.

• 대한수학회지
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• 제46권2호
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• pp.271-279
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• 2009

Using an index theory for countably condensing maps, we show the existence of eigenvalues for countably k-set contractive maps and countably condensing maps in an infinite dimensional Banach space X, under certain condition that depends on the quantitative haracteristic, that is, the infimum of all $k\;{\geq}\;1$ for which there is a countably k-set-contractive retraction of the closed unit ball of X onto its boundary.

• Nonlinear Functional Analysis and Applications
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• 제26권1호
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• pp.93-104
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• 2021

In this paper, we present a fixed point theorem for a family of generalized condensing multimaps which have ranges of the Zima-Hadžić type in Hausdorff KKM uniform spaces. It extends Himmelberg et al. type fixed point theorem. As applications, we obtain some new collective fixed point theorems for various type generalized condensing multimaps in abstract convex uniform spaces.

• 대한수학회지
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• 제42권6호
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• pp.1205-1213
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• 2005

Applying a fixed point theorem for compact admissible maps due to Gorniewicz, we prove that under certain conditions each count ably condensing admissible maps in Frechet spaces has a positive eigenvalue. This result has many consequences, including the well-known theorem of Krasnoselskii.

• 대한수학회보
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• 제36권3호
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• pp.565-578
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• 1999

In this paper some common fixed point theorems for pairs of condensing mappings in a Banach space are proved and applications are given to a pair of nonlinear first order ordinary differential equations in Banach spaces for proving the existence of common solution under suitable conditions.