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보일러 용량과 온수온도에 따른 복사난방 시스템의 열효율 평가
장형문(Xinwen Zhang),최지수(Ji Su Choi),김상엽(Sang Yeop Kim),김찬희(Chan Hee Kim),박종호(Jong Ho Park),정근주(Gun Joo Jung) 대한설비공학회 2021 대한설비공학회 학술발표대회논문집 Vol.2021 No.6
With the building insulation system strengthened, the heating load of apartment building has been gradually reduced. Therefore, the capacities of the most domestic gas fired boilers are over-sized and the boilers will work for a long time under the part load condition. This leads to a decrease in heating system efficiency. This study aimed to evaluate the heating efficiency variation of radiant heating system under different heating load conditions. In this study, three types of boilers with different capacity were selected as heat source of heating system, and the boiler efficiency with different hot water temperature were analyzed with different heating load and hot water temperature conditions through mock-up experiments. The results showed that the boiler efficiency decreased when the part load ratio was reduced. In the same part load condition, the non-condensing gas boiler with small capacity resulted in the higher efficiency than that with large capacity. It was also found that the condensing boiler led to the higher efficiency than non-condensing boilers under part load conditions.
장형문(Xin Wen Zhang),이규남(Kyu Nam Rhee),정근주(Gun Joo Jung) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.4
Ground source heat pump(GSHP) as heating or cooling system in the building has high energy performance, because the heat sourse is stable geothermal temperature. In summer time, long time operation of GSHP cooling system can reduce the stable geothermal temperature. With the result that heat pump system’s coefficient of performance(COP) will be decreased. In order to improve the performance of the heat pump system, the GSHP cooling system combined with hot water heat pump system is put forward. This system uses the condensation heat from the heat pump cooling part as a heat source for hot water heat pump. Hot water heat pump can cool the higher outlet water temperature which comes from cooling heat pump. Therefore, the geothermal temperature will be balanced, and the performance of the system will be improved. In this study, the COPs of single cooling and hot water GSHP systems are compared with the compound GSHP system. As the result, COP of cooling part in the compound GSHP system is 34% higher than the single cooling GSHP system. The COP of hot water part is 30% higher than the single hot water GSHP system.
저에너지 공동주택 개별보일러의 출력범위 조절을 위한 난방 및 급탕부하 분석
김상엽(Kim, Sang-Yeop),장형문(Zhang, Xinwen),김찬희(Kim, Chan-Hee),최지수(Choi, Ji-Su),이규남(Rhee, Kyu-Nam),정근주(Jung, Gun-Joo) 대한건축학회 2021 대한건축학회논문집 Vol.37 No.11
In Korea, it is common to determine the capacity of individual gas-fired boilers based on the floor area or unit heating load of residential buildings. With this approach, the current tendency of heating load reduction can not be taken into account when sizing the individual gas-fired boilers for low-energy apartment buildings. Most of the low-energy apartment buildings might be equipped with over-sized boilers, which would cause the boiler to operate with low efficiency particularly under part load conditions. As the over-sized boilers can deteriorate the energy saving performance of low-energy apartment buildings, this study was conducted to suggest the necessity of adjusting the output range of individual gas-fired boilers. For this purpose, heating and domestic hot water load of apartment buildings were analyzed considering the historical change of energy saving design standards. The analyzed loads were compared with the output range of household gas-fired boilers currently available on the market. The results showed that the heating output of the boilers is over-sized, even though the heating load has been reduced by 53%. It was found that the part-load output of boilers was significantly higher than the heating load, which would lead to the reduced efficiency during the part load conditions. It was also found that the individual room control can increase the difference between the boiler part-load output and heating load. Therefore, it is necessary to adjust the output range of boilers by lowering the part-load output and to increase the turn-down ratio of boilers in order to improve the energy efficiency of low-energy apartment buildings.
수열원 히트펌프용 열가소성수지 코팅 STS주름관의 열관류 특성
정근주(Jung, Gun-Joo),이규남(Rhee, Kyu-Nam),장형문(Zhang, Xinwen) 한국건축친환경설비학회 2018 한국건축친환경설비학회 논문집 Vol.12 No.4
Recently, high density poly ethylene (HDPE) tube has been utilized in surface water source heat pump (SWSHP) as a surface water heat exchanger (SWHE). Stainless steel (STS) corrugated tube has much higher heat transfer coefficient (U value) than HDPE tube in SWHE. However, this material cannot be perfectly protected from corrosion when exposed to aggressive water environments. The goal of this work is to increase U value of SWHE when STS corrugated tube is perfectly protected from corrosion by covering polyolefin material on its corrugated surface. In order to verify the thermal performance of proposed tube, U values and friction factors of the proposed tube were compared with those of the HDPE tube. For the evaluation on possible applicability of proposed tube, the economic evaluation of the proposed tube was also performed based on the result from test bed experiments. The results show that the proposed tube leads to 4.65 times higher U value and 2 times higher friction factor than HDPE smooth tube. Despite with the increased friction loss and installation cost, it was revealed that the proposed tube can achieve COP due to enhanced heat transfer performance.