• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.627-636
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• 2008

The purpose of this study is to develop the new korean district heating system for apartment houses. The upper & lower side ondol system with multi sensing control system was developed as a new korean district heating system and evaluated in 2 mock-up laboratories last winter. As a result of field measurement, when the load differences between perimeter zone and central zone are increased, the ondol system divided in the upper and lower side can be evaluated as the new ondol system with a capability for suppling proper heating energy for each zone. The user can have the freedom for changing an upper zone and a lower zone and controlling each temperature according to their needs.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.1
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• pp.38-42
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• 2017

This study proposes an idea for energy saving in apartment machine rooms. A conventional district heating system is equipped with constant-flow pumps and bypass valves to regulate pump differential pressure. Each family unit is equipped with a constant-flow on/off valve. This leads to excessive hot water circulation and a high return temperature. To reduce energy loss, this study assumes that each family unit is renovated with a heating valve which regulates the return temperature at $35^{\circ}C$. The hot water supply pump is also replaced with a pump with an inverter to vary flow rate. Expected energy savings is then estimated from field test data. According to the results, pump electricity consumption was reduced by 6,100 kWh for a family unit building over about half a year. The supply temperature can also be lowered by $5^{\circ}C$, which can contribute to a production of electricity of 10.3 kWh/ton of hot water.

• Journal of Korean Institute of Industrial Engineers
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• v.4 no.2
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• pp.97-105
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• 1978

A mathematical model is developed in order to describe the network configuration and heating distribution to a Central District Heating System for an Urban Residential Community. The purpose of using this model is to optimize operating costs and to distribute heat to the Residential Community efficiently. In particular, because of the inherent nonlinearity and dual optimization of the problem a dyamic programming approach is taken. It is turned out that the optimal cost of the system is a strong non-linear function of the network. In particular, it is found that increasing N, the number of houses, may not necessarily imply increased costs. It is felt that past failure of producing economical systems may be due to the improper attention given to the network.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.183-192
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• 1996

This paper presents a numerical model of the optimal operation pattern of the CHP system built for duel-purpose of power generation and district heat production. The model can be differently formulated in accordance with the view of planner: society, electric utility or district-heating company. Here, the operation pattern of the system components and the effect of heat price are of major interest in the study. From the case study, it was found that the optimal use of auxiliary heating equipment is very important to achieve the minimum societal cost. And, the multi-step heat pricing scheme is desirable to induce the voluntary behavior of both companies towards the societal optimal pattern.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.4
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• pp.202-211
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• 2017

In this study, the exergy that can be reflected in the energetic and economic values was used to assess the heat tariff of a district heating (DH) system instead of the enthalpy. It is difficult to directly apply the exergy to the current heat-charge system because of the complicated calculation; therefore, the difference between the supply and return temperatures was converted to the exergy-temperature difference for the ease of the heat-amount calculation. As a result of the exergy analysis for a DH substation, the exergy-temperature difference did not affect the surrounding temperature and pressure loss. The supply temperature and the maximum difference between the supply temperature and the return temperature exerted the main effect on the exergy-temperature difference. The new heat charge of a DH user was slightly reduced in winter compared with the previous charge, but the heat charges in the other seasons are almost the same. It is concluded from the assessment of the heat tariff for which the exergy is used that this tariff is more feasible for both DH suppliers and consumers compared with enthalpy.

• Corrosion Science and Technology
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• v.19 no.6
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• pp.296-301
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• 2020

Failure analysis on the welded type 304 pipe used for cooling water piping in the district heating primary side was conducted. Inorganic elements and bacteria in the cooling water and in corrosion products were analyzed, and the weldment was inspected by microscopy and a sensitization test. Corrosion damages were observed in the heat-affected zone, on weld defects such as incomplete fusion or excessive penetration caused by improper welding, or/and at the 6 o'clock position along the pipe axial direction. However, the level of concentration of chloride in the cooling water as low as 80 ppm has been reported to be not enough for even a sensitized type 304 steel, meaning that the additional corrosive factor was required for these corrosion damages. The factor leading to these corrosion damages was drawn to be the metabolisms of the types of bacteria, which is proved by the detection of proton, sulfur containing species, biofilms, and both bacteria and corrosion product analyses.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.2
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• pp.10-16
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• 2019

In this study, the present regulation of heat metering for the ground source heat pump was investigated. The ground source heat pump has been adopting the heat metering system used in the district heating system for estimating the heating and cooling energy production amount. The accuracy of the present heat metering systems for a water to water ground source heat pump is low, because the system for district heating has a relatively high temperature range comparing with the ground source heat pump operating conditions. Even though the heat amount for the building side should be measured, the heat absorption and extraction amount from or to the ground was measured for the water to air ground source heat pump due to the difficulty of estimating the air side heating and cooling capacity in the present regulation. It is highly recommended to validate the heat metering system to have reliability for the ground source heat pump and develop the system to be applicable water to air ground source heat pump.

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.119-126
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• 2009

A district energy system plays very important role to fulfill energy demand in regional areas. This paper diagnoses the necessity of the development of an economical operation system for the efficient operation of district energy plants located in Seoul. The effect anticipated from the use of the optimal operation system is also analyzed. Production and consumption of energy are estimated for the district energy plants at Suseo, Bundang, Ilwon and Jungang located near in Seoul, Korea. The problem is formulated as a mixed integer linear programming(MILP) problem where the objective is to minimize the overall cost of the district energy system. From the results of numerical simulations we can see that the energy efficiency is improved due to the application of the optimal operation conditions provided by the proposed model.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.2
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• pp.86-90
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• 2014

It is important to select an optimal capacity for equipment, because the initial cost of new and renewable energy system is more expensive than that of exiting system. An optimal equipment and enhanced rate of operation can be selected, to analyze the cooling and heating load of buildings. In this study, seawater heat pump system in the Jeju area will be applied, by the heat source equipment of district heating. The loads of buildings are analyzed from existing researches, to select optimal capacity of equipment. Also, an optimal rate of building use will be set up, from a combination of buildings.

• Corrosion Science and Technology
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• v.23 no.4
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• pp.315-323
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• 2024

This work examined pitting corrosion failure of a copper heat-return pipe used in a district heating system. The copper pipe was corroded with a 48% reduction in thickness due to localized corrosion on the inner surface exposed to heating water of 20 ~ 40 ℃. Fe and Si elements as corrosion products were found around pits. Cl element was also observed, which accelerated oxidation of copper inside pits. Cu₂O deposits on the pit's bottom surface decreased the pH inside the pit. X-ray diffraction analysis revealed hematite, cuprite, malachite and brochantite as corrosion products. Chemical analysis demonstrated that Fe and Si elements did not exist in the copper, supply water, or heating water, indicating that Fe and Si species might have entered into the pipe from the exterior. These results indicated that pits were initiated due to ion concentration gradient near Fe and Si species. Moreover, the interior of pits had lower pH due to Cl^- concentration and Cu₂O reactions, which accelerated the pit's growth and led to formation of pinholes. Additionally, we confirmed that the type of pitting corrosion was a complex combination of types I and II based on the HCO₃^-/SO₄^2- ratio, pH, temperature, and corrosion products.