• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.11
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• pp.1079-1088
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• 2001

A dynamic simulation model was developed to analyse the transient characteristics of a multi-inverter heat pump. The programs included a basic air conditioning system such as a evaporator, condenser, compressor, linear electronic expansion valve (LEV) and by-pass circuit. The theoretical model was derived from mass conservation and energy conservation equations to predict the performance of the multi-inverter heat pump at various operating conditions. Calculated results were compared with the values obtained from the experiments at different operation frequencies of compressor, area of the LEV and configuration of indoor units operation. The results of the simulation model showed a good agreement with the experimental ones, so that the model could be used as an efficient tool for thermodynamic design and control factor design of air-conditioners.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.1
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• pp.26-32
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• 2010

This paper is suggesting a new technology for refrigerant amount detection of a system air-conditioner installed under various installation conditions. System air-conditioner was introduced to domestic market first in 2000. It consists of one or a series of outdoor units and a number of indoor units connected with single pipe line to the outdoor unit. The system can vary the capacity from 2.0 kW to 186 kW. For the system Installed under long and high-elevated condition, about 100 kg of refrigerant is charged in the whole system. In this paper, the new technology RAD (Refrigerant Amount Detection) with edge technology of refrigerant cycle control and measurement of a system air conditioner was developed and investigated for its application for the various installation conditions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.397-400
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• 2007

Indoor air-conditioning system(IAS) using wireless sensor network serves to reduce the amount of pollution entering the room from outside and also the pollution that is generated indoor. Small-size and lower power wireless sensor node and sensor interface board was designed for indoor air-conditioning system in buildings of offices and industrial establishments. Many sensor nodes forms Ad-hoc network topology using simple forwarding routing to transmit polluting gas concentration data from different rooms to the indoor air-conditioning system. Sensor node analyzes pollution concentration in the each room and air-conditioning system performs to air-distribution and air-inhalation according to room's pollution by regulating the fan of indoor air-conditioning system. To reduce power consumption electrochemical gas sensor was used in the design. Thus the designed system can optimize state of indoor environment. Graphic user interface displays node sate, gas concentration and temperature of each room.

• Journal of the Korean Solar Energy Society
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• v.22 no.4
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• pp.85-96
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• 2002

Recently the number of auditoriums such as theaters, assembly halls, and concert halls is increasing in Korea. Auditoriums have generally large space volume, have a high density of occupancy per unit floor area, compared to other buildings. Since they have relatively high ceilings, some heat may stratify above the occupied zone. The under floor air conditioning system, which is set under seats, is frequently selected in an auditorium, because typical air conditioning system where air is supplied from ceilings often causes drafts and unequal temperature distribution. Therefore, this study aims to suggest basic data for air conditioning system design of a middle-sized auditorium. Features and problems of air conditioning system of an auditorium which has about 500 seats are investigated as a case study. In addition, indoor thermal comfort and cooling energy consumption are analyzed with a CFD program and an energy analysis program.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1225-1231
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• 2006

Recently, as the climate of temperature change has happened worldwide, To solve this problem, Kyoto protocol was taken to regulate global warming on Feb. 2005 and each country is making efforts to prevent global warming. In the automotive industry, R-134a refrigerant is widely used most these days because it has zero ODP(Ozone Depletion Potential). But R-134a GWP(Global Warming Potential) is so high. Therefore, replacement refrigerant desperately is needed as a alternative refrigerant. So, R-l52a is considered as one of the alternative refrigerants due to zero ODP and lower GWP against as required on Europe Committee. In this paper, performance of the air conditioning system between R-134a and R-152a is investigated experimentally. In the bench level, cooling capacity, condensing capacity, COP of automotive air conditioning system are ovaluated by means of air velocity entering the condenser and compressor revolution speed with optimized charge refrigerant quantity. Result of this study, R-152a refrigerant shows the possibility as alternative refrigerant of current R-134a in automotive air conditioning system.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.4
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• pp.129-134
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• 2009

The objectives of this paper are to study the effects of thermal and geometric conditions on the performance of indoor heat exchangers with R-410A for Gas Engine Driven Heat Pump (GHP) application and to find the optimum design conditions of indoor heat exchangers by parametric analysis for the key parameters. The key parameters are number of tube row, number of tube pipe, fin pitch and transverse tube pitch. In the air side, moisture out of the humid air condenses on the fin surface while the refrigerant (R-410A) boils inside the smooth tube. Therefore this study uses Log Mean Enthalpy Difference (LMHD) method to analyze the heat transfer from the humid air to the refrigerant. This study determines the heat exchanger size, air side/refrigerant side pressure drop and overall heat transfer coefficient. Optimum design conditions for the key parameters are also determined by the parametric analysis. The results show that number of rows and pipes, fin pitch have significant effect on the heat exchanger size. It is also found that the tube length of the louver fin is $17{\sim}30%$ shorter than that of the plate fin.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.10
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• pp.504-514
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• 2017

The insulation performance of aircaps has been recognized and various studies regarding the aircap as a solution to increased building energy consumption are being carried out. However, the aircap is not durable and therefore it cannot play the role of an independent finishing material. Accordingly, the purpose of this study is to suggest an aircap wall module with improved durability through the lamination of the aircap and verify its effectiveness by evaluating its energy saving performance for lighting and air conditioning through a full-scale testbed. The conclusions of this study are as follows. 1) The aircap wall module featuring a laminated aircap that is being proposed in this study can save lighting energy due to the permeability of the aircap in comparison to previous insulating materials. 2) The aircap wall module with a laminated aircap is effective in improving heating and air-conditioning energy saving when it is more than 15 cm-thick during summer and winter in comparison to a 5 cm-thick prefabricated panel. 3) The aircap wall module featuring a laminated aircap is effective in improving lighting and heating and air-conditioning energy saving when it is 10 cm- and 5 cm-thick during summer and winter, respectively, in comparison to a 5 cm-thick prefabricated panel.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.1002-1009
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• 2004

Direct contact air conditioning systems, in which heat and mass are transferred directly between air and water droplets, have many advantages over conventional indirect contact systems. The purpose of this research is to investigate the cooling and heating performances of direct contact air conditioning system for various inlet parameters such as air velocity, air temperature, water flow rate and water temperature. The experimental apparatus comprises a wind tunnel, water spray system, scrubber, demister, heater, refrigerator, flow and temperature controller, and data acquisition system. The inlet and outlet conditions of air and water are measured when the air contacts directly with water droplets as a counter flow in the spray section of the wind tunnel, and the heat and mass transfer rates between air and water are calculated. The droplet size of the water sprays is also measured using a Malvern Particle Analyzer. In the cooling conditions, the outlet air temperature and humidity ratio decrease as the water flow rate increases and as the water temperature, air velocity and temperature decrease. On the contrary, the outlet air temperature and humidity ratio increase in the heating conditions as the water flow rate and temperature increase and as the air velocity decreases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.7
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• pp.681-687
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• 2005

Experimental results for heat transfer characteristic and pressure gradients of HCs refrigerants R-290, R-600a, R-1270 and HCFC refrigerant R-22 during evaporating inside horizontal double pipe heat exchangers are presented. The test sections which has one tube diameter of 12.70 m with 0.86 mm wall thickness, another tube diameter of 9.52 mm with 0.76 mm wall thickness are used for this investigation. The local evaporating heat transfer coefficients of hydrocarbon refrigerants were higher than that of R-22. The average evaporating heat transfer coefficient increased with the increase of the mass flux. It showed the higher values in hydrocarbon refrigerants than R-22. Hydrocarbon refrigerants have higher pressure drop than R-22 in 12.7 mm and 9.52 mm. This results form the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air- conditioning systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.10
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• pp.548-554
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• 2013

A thermodynamic analysis of the R404A refrigeration system with an internal heat exchanger using R744 as a secondary refrigerant is presented in this paper to optimize the design for operating parameters of the system. The main results are summarized as follows: The COP increases with increasing subcooling and superheating degree of R404A, internal heat exchanger and compression efficiency of the R404A cycle and evaporating temperature of the R744 cycle and decreasing temperature difference of the cascade heat exchanger and condensing temperature of the R404A cycle. The mass flow ratio decreases with increasing evaporating temperature of the R744 cycle and internal heat exchanger efficiency of the R404A cycle and decreasing subcooling and superheating degree of the R744 cycle, temperature difference of the cascade heat exchanger and condensing temperature of the R404A cycle.