자연순환형 태양열 온수시스템 집열판의 열유동 특성분석을 위한 수치해석 연구

김철호(Chul-Ho Kim),이승현(Sung-Hyun Lee) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

Solar water heating system is one of the popular renewable energy collection systems supplying hot water in our daily life. The conventional solar hot water supply system applies a forced water circulation system to heat cold water up in the heating system, with an electric water pump and the forced solar water heat system has some operating problems with the fault of important parts; water pump, and automatic control system. In this numerical study, the performance of the model solar heat collector of a solar water heating system was tested to see the possibility of natural hot water circulation in the model solar water heating system. For a case study, a flat-type solar heat collector was used and its height, length is 2.7m, 1.98m respectively and the heat flux of the collector was fixed to 800watt/m2. From the research, it is found that the solar heat energy is good enough source to have water circulation in the solar heat energy collector. But a parametric study is needed to have higher efficiency of the heat energy collector. The thermal efficiency of the model heat energy collector is about 75% and the temperature increment of the water in the collector is only 20oC at the given operating condition.

부하를 고려한 태양열온수시스템의 일간 집열효율에 대한 실험적 분석

이경호(Lee Kyoung-Ho),주홍진(Joo Hong-Jin),윤응상(Yoon Eung-Sang),곽희열(Kwak Hee-Youl) 한국태양에너지학회 2012 한국태양에너지학회 논문집 Vol.32 No.2

This paper describes an experimental study on efficiency of solar collector in solar water heating system connected to hourly water heating load. In general, the functional form of solar efficiency is expressed as a function of fluid temperature entering solar collector, ambient temperature, and solar irradiance. When energy saving from solar heating of water heating system is analyzed on a long-term basis such as one year with given solar irradiance data, simplified analysis is more convenient than detailed system simulation for quick assessment. However, the functional form of the efficiency is not convenient for approximately simplified energy analysis because the inlet temperature can be obtained through a detailed system simulation. In the study, solar collector efficiency is obtained with various daily water heating loads and daily solar irradiance using experimental tests. The study also considers large residential buildings such as apartment buildings for application of solar water heating systems. From test results, it is found that daily solar collector efficiency is proportional to daily water heating loads and daily solar irradiance. The data obtained from the study can be utilized to find a functional relation between daily solar irradiance and daily heating load instead of collector inlet temperature for application of solar collector efficiency to long-term approximated energy analysis of solar heating system.

온수 급탕 및 난방을 위한 히트 펌프 태양열 시스템의 성능 분석

손진국(Sohn Jin-Gug) 한국태양에너지학회 2018 한국태양에너지학회 논문집 Vol.38 No.5

This study aims to analyze the performance of solar thermal system with heat pump for domestic hot water and heat supply. There are four types of system. Systems are categorized based on the existence of a heat pump and the ways of controlling the working fluid circulating from the collector. Working fluid is controlled by either temperature level (categorized as system 1 and 2) or sequential flow (system 3 and 4). Heat balance of the system, the solar fraction, hot water and heating supply rates, and performance of heat pump are analyzed using TRNSYS and TESS component programs. Technical specifications of the main facilities are as follow; the area of the collector to 25 ㎡, the volumes of the main tank and the buffer tank to 0.5 ㎥ and 0.8 ㎥, respectively. Heating capacity of the heat pump in the heating mode is set to 30,000 kJ / hr. Hot water supply set 65 liters per person each day, total heat transfer coefficient of the building to 1,500 kJ / kg.K. Indoor temperature is kept steadily around 22℃. The results are as follows; 6 months average solar fraction of system 1 turns out to be 39%, which is 6.7% higher than system 2 without the heat pump, indicating a 25% increase of solar fraction compared to that of system 2. In addition, the solar fraction of system 1 is 2% higher than that of system 3. Hot water and heating supply rate of system 1 are 93% and 35%, respectively. Considering the heat balance of the system, higher heat efficiency, and solar fraction, as whole, it can be concluded that system 1 is the most suitable system for hot water and heat supply.

A comparative investigation of solar-assisted heat pumps with solar thermal collectors for a hot water supply system

Kim, Taehoon,Choi, Byung-Il,Han, Yong-Shik,Do, Kyu Hyung Elsevier 2018 Energy conversion and management Vol.172 No.-

<P><B>Abstract</B></P> <P>The concept of a hybrid solar collector was newly proposed, which has a solar thermal receiver part and air-source receiver part that can operate as a fin-tube exchanger with fans when there is no solar radiation. This is the distinguishing feature of the hybrid solar collector. The solar-assisted heat pump system applying the hybrid solar collectors was also introduced. To analyze the proposed solar-assisted heat pump system, a simple thermodynamic model considering the electric power consumption for fans and circulation pumps was developed. The model results for the air-source heat gain were validated from the corresponding experimental data with the maximum error of 8.8%. Based on the parametric study, the increase of the collector area and the absorption coefficient led to the enhancement of the system performance of the solar-assisted heat pump with hybrid solar collectors. In addition, a comparative investigation was carried out for three different indirect solar-assisted heat pumps. Regarding of annual operation hour, the serial-type solar-assisted heat pump was worst at 3509 h over a year. On the other hand, the solar-assisted heat pump with hybrid solar collectors had the superior performance of 7036 h. If the efficiency of the hybrid solar collector was as superior as the conventional flat plate solar collector, the system COP of the suggested solar-assisted heat pump system in the winter season could be improved by 5.1% compared with that of the parallel-type solar-assisted heat pump system. Consequently, it clearly showed the feasibility of the suggested solar-assisted heat pump system as a standalone system for hot water supply due to the merits of significantly extending the annual operation hour, the simple system configuration, and the economic aspect with lower capital cost.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The concept of a hybrid solar collector was newly proposed. </LI> <LI> A thermodynamic model for the SAHP with hybrid solar collectors was developed. </LI> <LI> The model considered electric power consumption models for auxiliary components. </LI> <LI> A comparative study was done to predict the efficiency of the proposed SAHP. </LI> <LI> Numerical results show feasibility of the SAHP as a standalone for a DHW system. </LI> </UL> </P>

콤팩트형 태양열/지열히트펌프 하이브리드 냉난방 및 급탕 시스템 개발 및 성능분석

백남춘,정선영,윤응상,이경호 한국태양에너지학회 2012 한국태양에너지학회 논문집 Vol.32 No.5

In this study, the compact type solar thermal and ground coupled heat pump hybrid system for space heating/cooling and hot water supply has been developed. This hybrid system was installed in Zero Energy Solar House(ZeSH) in KIER for the demonstration. The thermal performance and operational characteristics of this hybrid system were analysed especially. The results are as follows. (1) This hybrid system was designed in order to address the existing disadvantages of solar thermal/ground coupled heat pump system. For this design, all parts except solar collector and ground coupled heat pump were integrated into a single product in a factory. The compact type unit includes two buffer tanks, an expansion tank, pumps, valves, a controller, etc. This system has an advantage of easy installation with simple plumbing work even in narrow space. (2) The thermal charging and discharging time of the buffer tanks and its characteristics by ground coupled heat pump, and heat pump COP according to geo-source temperature and buffer storage temperature have been studied. This system was found to meet well to the heat load without any other auxiliary heating equipment. (3) The operating hours of the ground coupled heat pump as a backup device of solar thermal can be reduced significantly by using solar heat. It was also found that the minimum heating water supply setting temperature and maximum cooling water supply setting temperature make an influence on the heat pump COP. The lower heating water and the higher cooling water temperature, the higher COP. In this respect, the hybrid system’s performance can be improved in ZeSH than conventional house.

단독주택용 태양열/지열 융복합시스템의 태양열 급탕성능 평가

백남춘(Namchoon Baek),한승현(Seunghyun Han),이왕제(Wang Je Lee),신우철(Ucheul Shin) 대한설비공학회 2015 설비공학 논문집 Vol.27 No.11

In this study, an analysis was performed on the performance of the solar water heating system with geo-thermal heat pump for a detached house. This system has a flat plate solar collector (8 ㎡) and a 3 RT heat pump. The heat pump acts as an auxiliary heater of the solar water heating system. These systems were installed at four individual houses with the same area of 100 ㎡. The monitoring results for one year are as follows. (1) The average daily operating time of the solar system appeared to be 313 minutes in spring (intermediate season), and 135 minutes and 76 minutes in winter and summer respectively. The reason for the short operating time in summer is the high storage temperature due to low water heating load. The high storage temperature is caused by a decrease in collecting efficiency as well as by overheating. (2) The geothermal heat pump as an auxiliary heater mainly operates on days of poor insolation during the winter season. (3) Despite controlling for total house area, hot water consumption varies greatly according to the number of people in the family, hot water usage habits, etc. (4) The yearly solar fraction was 69.8 to 91.5 percent, which exceeds the maximum value of 80% as recommended by ASHRAE. So the solar collector area of 8 ㎡ appeared to be somewhat greater for the house with an area of 100 ㎡. (5) The observed annual efficiency of solar systems was relatively low at 13.5 to 23.6%, which was analyzed to be due to the decrease in thermal efficiency and the overheating caused by a high solar fraction.

An Experimental Study on the Characteristic of tie Hot Water-Air Heating Generating System with a Solar Collector

Fatkhur Rokhman,Boo-Pyo Hong,Jin-Kwang You,Jung-In Yoon,Kwang-Hwan Choi 한국태양에너지학회 2012 한국태양에너지학회 학술대회논문집 Vol.2012 No.3

A solar air heating has low efficiency compared with the solar water heating because the heat capacity of the air is small. The heat received by solar collector plate is not fully transferred to the air and then a part of them became the losses to the environment through conduction and convection process. This research is focusing on a design of better combined multi-purposed system suggested by us and aims to secure the more efficient solar energy utilization by combining the hot water and air heating system. The result in this paper has shown that the proposed design has better thermal performance than that of the common design. Furthermore, it was found that the performance of the combined ai -water heating system increases the efficiency from 30% to 3%-40%.

난방 및 급탕 부하를 고려한 태양열 온수 급탕 시스템의 시뮬레이션 해석

장환영(H.Y. Jang),김병기(B.G. Kim),서정세(J.S. Suh) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

This paper is to simulate a solar water heating system under the several patterns of heat load by the dynamic simulation code(TRNSYS). This system consists of evacuated solar collector, a water-storage tank, an electronic heater, pump, controller, auxiliary heater and so on. The results of simulations will be presented on an annual data base for a Active Solar System, which provides domestic heating & hot water for a four-person family. The simulation model is used to evaluate the annual variation of annual energy performance, the solar fraction with respect to demand hot water temperature required, difference of space heating temperature and preset storage tank water temperature, and consumption profile of the domestic hot water demand.

난방 및 급탕 부하를 고려한 태양열 온수 급탕 시스템의 시뮬레이션 해석

장환영(H.Y. Jang),김병기(B.G. Kim),서정세(J.S. Suh) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

This paper is to simulate a solar water heating system under the several patterns of heat load by the dynamic simulation code(TRNSYS). This system consists of evacuated solar collector, a water-storage tank, an electronic heater, pump, controller, auxiliary heater and so on. The results of simulations will be presented on an annual data base for a Active Solar System, which provides domestic heating & hot water for a four-person family. The simulation model is used to evaluate the annual variation of annual energy performance, the solar fraction with respect to demand hot water temperature required, difference of space heating temperature and preset storage tank water temperature, and consumption profile of the domestic hot water demand.

접이식 유연재질의 태양열 집열 시스템 성능 평가

이승주(Seung Joo Lee),송주영(Joo Young Song),김윤정(Youn Jeong Kim),김성수(Sung Soo Kim),강용태(Yong Tae Kang) 대한설비공학회 2016 대한설비공학회 학술발표대회논문집 Vol.2016 No.6

In winter, it is important to maintain greenhouse with a constant temperature to cultivate crops. Owing to rise in gasoline prices, most of the rural residents spend approximately 30-40 % of their total running cost to pay heating bills. Water curtain system is an effective way to reduce the cost of the heating by using underground water instead of using fossil fuel. To operate water curtain system, however, excessive usage of the underground water is needed, causing the underground water depletion. In this paper, performance of the flexible solar driven collector system is studied, with the aim of collecting hot water from solar driven collector system to substitute the underground water used in water curtain system. Furthermore, performance of the heat pump driven by solar heat is examined compared to that driven by ambient air. It was found that the flexible solar driven collector system was able to collect 32 ℃ water in three hours of operation while COP and solar collecting efficiency was 28.5 and 28 % respectively. Finally, compared to the heat pump driven by ambient air, performance of heat pump driven by solar heat showed 37 % enhancement in COP.