• Journal of the Chungcheong Mathematical Society
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• v.35 no.4
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• pp.297-305
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• 2022

First, we generalize homotopy results of O'Regan [6] for Mönch type multimaps to Chandrabhan type multimaps. Second, we show that the better admissible Chandrabhan type multimaps have fixed point properties whenever their ranges are Klee approximable. Finally, we give examples of essential maps for various class of multimaps including 𝚽-condensing multimaps.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4052-4056
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• 2014

These days, household condensing gas boilers are an obligatory trend. The use of environmentally-friendly boilers that emit less pollutant, such as CO and NOx, are strongly recommended. In this paper, heat flow analysis of the additional inner groove in the tube of the secondary latent heat exchanger was studied to increase the efficiency. A 20% difference in the heat transfer area was obtained with the addition of an inner grove, which showed an increase in the amount of heat transferred. This was confirmed using three-dimensional numerical analysis. With the addition of an inner groove, the exit temperature increased by $1^{\circ}C$. This increase in exit temperature was considered to be a substantial increase in the efficiency of the condensing gas boiler.

• International Journal of Air-Conditioning and Refrigeration
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• v.14 no.1
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• pp.7-13
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• 2006

Because the usage of CFC and HCFC based refrigerants are restricted due to the depletion of ozone layer, the $NH_3$ gas, in the experiment is evaluated to the performance characteristics for the superheat control to improve the energy efficiency. The experiment is carried out about the condensing pressure of refrigeration system from 1,500 kPa to 1,600 kPa through the degree of superheat from 0 to $10^{\circ}C$ at each condensing pressure. As a result, in the case of shell and tube type of heat exchanger, the COP is more efficient than other cases at the degree of superheat $1^{\circ}C$ at each condensing pressure. In the case of shell and disk type of heat exchanger, the COP is the most efficient at the degree of superheat 0.

• Archives of design research
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• v.20
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• pp.185-196
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• 1997

There were several methods of conception in seeking a visul idea of the advertising design. However, such conventional methods had a tendency that the degrees of utilization and satisfation are lacking. Also, in a thumbnail sketch phase, there was a great tendency to seek an idea based on pictorial elements only and thus depended chiefly on the existing references. Accordingly, originality was not high. Further, under the background which any common methods of a designer and a copywriter, if they have effective. I would like to propose a visul idea conception method, a condensing & amplification method for maintaining a logical system of advertising intelligence and for facilitating creative visualization through a language-oriented approach. The condensing & amplification method is the method of conception, in which after an appeal point as per advertising intelligence is passed through sentence and phrase and then condensed with word, various variation for the word develop, and by selecting the most creative word of the results, the thumbnail sketch commences based on the results amplified with the phrases and sentences.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2565-2571
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• 2009

In this paper, cycle performance analysis of cascade refrigeration system using $NH_3-CO_2$(R717-R744) is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree and condensing and evaporating temperature in the ammonia(R717) high temperature cycle and the carbon dioxide low temperature cycle. The COP of cascade refrigeration system increases with the increasing superheating degree, but decreases with the increasing subcooling degree. The COP of cascade refrigeration system increases with the increasing condensing temperature, but decreases with the increasing evaporating temperature. Therefore, superheating and subcoolng degree, evaporating and condensing temperature of cascade refrigeration system using $NH_3-CO_2$ have an effect on the COP of this system. A multilinear regression analysis was employed in terms of subcooling, superheating, evaporating, condensing, and cascade heat exchanger temperature difference in order to develop mathematical expressions for maximum COP and an optimum evaporating temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.4
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• pp.297-302
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• 2005

Since the use of CFC and HCFC refrigerants are to be restricted due to the depletion of ozone layer, this experiment applies the $NH_3$ gas to study the performance characteristics of $NH_3$ refrigeration system by the superheat control for improving the energy efficiency. The experiments are carried out for the condensing pressure of refrigeration system from 1,500 kPa to 1,600 kPa and for degree of superheat from $0^{\circ}C\;to\;10^{\circ}C$ at each condensing pressure. As a result of experiment, when the degree of superheat is $0^{\circ}C$ at each condensing pressure, the refrigeration system has the highest performance.

• Journal of Energy Engineering
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• v.8 no.2
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• pp.333-340
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• 1999

A numerical study of turbulent condensing vapor jet submerged in subcooled liquids has been conducted. A physical model of the process is presented employing the locally homogeneous flow approximation of two phase flow in conjunction with a $\kappa$-$\varepsilon$-g model of turbulence properties. In this model the turbulence is represented by differential equations for its kinetic energy and dissipation. A differential equation for the concentration fluctuations is solved and a clipped normal probability distribution function is proposed for the mixture fraction. Effects of steam mass flux, pool temperature and nozzle internal diameter on the condensing vapor jet are also analyzed. The model is evaluated using existing data for turbulent condensing vapor jets. The agreement between the predictions and the available experimental data is good.

• Journal of Power System Engineering
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• v.21 no.3
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• pp.45-50
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• 2017

This paper presents the Coefficient of performance(COP) and mass flow ratio of cascade refrigeration system with respect to refrigerants appling to high temperature cycle. The operating parameters considered in this study include degree of superheating and subcooling, compressor efficiency, evaporating temperature, condensing temperature and internal heat exchanger effectiveness in high temperature cycle. The result of this study is as follows : The COP of cascade system increases with increasing degree of superheating and subcooling, compressor efficiency and internal heat exchanger effectiveness except increasing condensing temperature. The mass flow ratio of low and high temperature cycle increases with increasing evaporating temperature and condensing temperature, but decreases with increasing internal heat exchanger effectiveness, degree of superheating and subcooling. Also, the mass flow ratio has no correlation with compressor efficiency at high temperature cycle.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.3
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• pp.285-293
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• 1998

This paper presents an experimental study on condensing heat transfer characteristics of R-22 alternative refrigerants, R-290 and R-410a on water sources heat pump. The apparatus mainly consisted of vapor pump condenser used to the test section evaporator manual expansion valve and measuring device. Test section constructed a smoothed tube of 10.07 mm ID and 12.7mm OD with a total length 6,300 mm was horizontal double pipe counterflow condenser. The refrigerants R-22, R-290 and R-410a were cooled by a coolant circulated in a surrounding annulus. Experimental range of mass velocities was changed from about 100 to 300 kg/($m^2$.s) and inlet quality 1.0 The credibility of experimental apparatus was 6 percent between heating capacity and cooling capacity added to compressor shaft power. The condensing heat transfer coefficients were increased with increasing mass velocity. However in case of R-290 they were more increasing than those of R-410a and R-22 Comparing the heat transfer coefficient between the experimental data and other's data the Cavallini-Zecchin's data was revealed to more similar prediction of author's experimental results on the average heat transfer coefficients.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.1
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• pp.54-61
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• 2001

Condensing heat transfer coefficients of R-22 and R-134a were measured in smooth, horizontal copper tubes with inner diameters of 1.77mm, 3.36mm, and 5.35mm, respectively. The experiments were conducted in the closed loop, which was driven by a magnetic gear pump. Data are presented for the following range of variables : mass velocity from 200 to 500kg/$m^2$.s and quality from 0 to 1.0. The heat transfer coefficients in the small diameter tubes (ID < 7mm) were observed to be strongly affected by various diameters and the heat transfer characteristics in the small diameter tubes differed from those in the large diameter tubes. Heat transfer coefficients in the small diameter tubes are higher than those in the large diameter tubes at the same experimental condition. It was found that some well-known previous correlations(Shahs correlation and Cavallini-Zecchins correlation) were not suitable for small diameter tubes.