• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.136-141
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• 2008

Due to environmental concerns $CO_2$ has been reintroduced as a potential candidate to replace HFCs in refrigeration systems since 1990s. In a refrigeration cycle, oil is utilized in lubricating a compressor. However, although oil separators are installed after a compressor oil is prone to leak to the whole system. The mixing of $CO_2$ and oil, even a small amount of oil, the heat transfer performance in heat exchanger deteriorated and the pressure drop inside tube increases. Therefore, it is needed to precisely estimate the mixture thermodynamic properties of $CO_2$-lubricant oil to correctly design a $CO_2$ refrigeration system. The commonly used method in estimating the mixture properties is the mole based weighting model. However, the accuracy of the method can not be assured. In the present study, $CO_2$-lubricant oil mixture properties including viscosity and density were estimated by using the mixture models, based on the equation of state (EOS).

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.782-787
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• 2008

The Kalina cycle simulation study was carried out for a preliminary design of a geothermal power generation system. The Kalina cycle system can be used for the utilization of a low-temperature heat sources such as geothermal and industrial waste heat that are not hot enough to produce steam. The sea/river water can be considered as a cooling media. A steady-state simulation model was developed to analyze and optimize its performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump were modelled by an isentropic efficiency, while a condenser, an evaporator and a regenerative heat exchanger were modeled by UA-LMTD method with a counter-flow assumption. The simulation results show that the power generation efficiency over 10% is expected when a heat source and sink inlet temperatures are $100^{\circ}C$ and $10^{\circ}C$ respectively.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.42-47
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• 2008

This paper reports the system performance of a hybrid plant, which combines a renewable energy plant of GSHP(Ground Source Heat Pump) with a conventional plant (screw water chiller). To find out operational cost and operating characteristics, the performance of the hybrid system was measured in a building located in Jeju island. Based on the measured data, the operating characteristics were analyzed and the operational cost was estimated by using payment table, which was provided by the Korea Electric Power Cooperation. Operating methods to save energy were recommended.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.801-806
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• 2008

The best plan is that the insulation performance should be improved because the insulation and airtight of building envelopes have an effect on the energy consumption basically. New insulation materials, which have the high performance and are above insulation standard, have been developed steadily. Because there are not studies on the building energy rating system and economic evaluation considering new insulation materials, these matters should be studied. In result alternatives, which applied 6 high performance material each, influence, reduce the annual heating energy and raise the building energy rating. Applying the vacuum insulation material(Case1,2) and vacuum or triple glazing can retrieves the investment with $120 and $$140{\sim}150$ per barrel each.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1406-1411
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• 2008

The percentage of apartment houses in residential buildings has increased every year, and it result in higher energy consumption of residential buildings. After the house law could be amended to legalize the remodeling of the balcony, buyers and contractors prefer to choose the balcony remodeling type when they choose a house for installment sale. Many construction companies design an apartment house considering balcony remodeling. So, this paper compares the balcony remodeling type with the basic type(prior to remodeling balcony) by using the building energy rating system tool. The balcony remodeling type consumes heating energies more than the basic type, and is unable to receive high rating. If the balcony is remodeled, it is required to improve the performance of wall and window and reduce the area of remodeling balcony.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.148-153
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• 2008

As the oil price is dramatically jumping up, the consumption of LNG is rapidly expanding and the size of LNG carriers becomes bigger. For LNG ships, the application of DF (Dual-Fuel) engines gradually increases because of high efficiency, which alternatively use diesel or BOG (Boil-Off Gas) from cargo tank as a fuel. The surplus BOG from LNG cargo tank should be exhausted by GCU or liquefied through the BOG reliquefaction system and returned back. This study focused into its operational characteristics through the process simulation using HYSYS and discussed details on the influence of the variations of some operational parameters such as a distribution ratio by the change of fuel mass flow into the DF engine.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.3-9
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• 2008

Recently, the plant industries are being activated and plant control systems use various technologies. Because the optimized design for the plants is very important for the reducing of operation and maintenance costs, automatic control systems become more important. Plant control systems consist of the master controller, the plant networks, the programming environment for engineering, monitoring software and the field devices. The control systems should have reliability, availability and safety. Modular architecture of hardware and software makes flexible configuration of the control systems. Each component should have diagnostic functions. It follows industrial standards and makes open systems. Open systems increase accessibility against the data which is distributed in the plants. The controllers including processor and communication modules use the up-to-date technology. They have real time and fault tolerant function by duplicating processors or networks. It also enables to make the distributed control systems. The distributed architecture makes more scalable main control system. Automatic control systems can be operated with better performance. In this paper, we analyzed the requirements of the seawater desalination plants and made some consideration facts for developing the optimized controller. Also we described the design concept of the main controller, which consists of several modules. We should validate and complement the design for the reliability and better performance.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.54-59
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• 2008

The poor maintenance and management of HVAC systems finally lead to the shortening of the life expectancy and result in the increase of operating costs and energy consumptions due to low efficiencies. Also, it is essential to try to develop ways to adequately maintain and to use the building facilities efficiently in order to preserve earth environment and the limited resource. In this study, an analysis on the maintenance and management cost for HVAC systems was carried out with the capacity of equipment. Besides, the LCC(Life Cycle Cost) based analysis was carried out to verify the effect of the doing maintenance and management. As the results, the case of the good maintenance and management is able to save LCC to 11 % than the case of the poor method.

• Journal of Power System Engineering
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• v.20 no.5
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• pp.72-77
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• 2016

The present study investigates noise and condensation characteristics of polyvinyl chloride (PVC), which is widely used for drainage piping materials, complex double structure by comparing to those of PVC single structure piping materials. In addition, effects of insulation on drainage noise has been measured experimentally. As the results of the experiments, noise reduction effect of PVC complex double structure is superior to that of PVC single structure in terms of elbow and vertical piping materials which are employed for drainage pipes of toilet bowls and bathtub. The insulation barely have effect on the noise reduction in case of the PVC single structure since there is almost no changes in noise occurrence even though the insulation is applied on both elbow and vertical piping materials. Temperature differences between inside and outside of the pipes have been measures for the PVC single and complex double structures as well. In consequence, outside temperature of the PVC complex double structure is higher than that of the PVC single structure. The condensation occurrence time of the PVC complex double structure shows a distinct difference from that of the PVC single structure, thus, the PVC complex double structure has outstanding effect on preventing the condensation.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.447-452
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• 1999

This paper describes the cycle performance of heat-pump system using R-22 and R-290. Experiments were performed in the smooth tube with inside diameter of 10.07mm and outside diameter of 12.07 mm and grooved inner tube having 75 fins with a height of 0.25mm Condensing temperatures were held constantly between 318K and 328 K while evaporating temperatures were varied from 257 K to 288 K mass velocities from 51 to $280 kg/m^2s$. From the experiments it was known that the evaporating temperature and condensing temperature had more affected by the compressor shaft power than the tube geometries. Cooling capacity of the R-22 and R-290 had similar values in the smooth and grooved inner tubes. The coefficient of performance(COP) was calculated using the compressor shaft power volumetric refrigeration capacity compression ratio and cooling capacity. The COP of the R-290 had slightly higher values than that of R-22 The major parameters affecting the heat pump cycle performance wee the refrigerant proper-ties and operating conditions rather than the geometric shapes of the heat exchanger