• Title/Summary/Keyword: Heating Cycle

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Experimental Study on Heating Performance by Operation Combination of Heat Pump with 3 Indoor-Units (3실 열펌프의 운전조합에 대한 난방성능 실험연구)

  • Kim, Ju-Hyung;Kim, Ki-Young;Kwon, Young-Chul;Park, Seung-Chul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.9
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    • pp.4197-4203
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    • 2013
  • In order to investigate the heating performance of multi-heat pump applying an inverter compressor, the experiment on heat pump with 3 indoor units was performed under the heating standard and heating low-temperature conditions. The performance data of heat pump with 3 indoor units were measured by the multi-psychrometric calorimeter. The operation characteristics and the behavior of the refrigerant cycle of the heat pump with 3 indoor units were understood from the heating capacity, heating COP, and P-h diagram by indoor-unit combination. The present experimental results show that the operating load and performance of the multi-heat pump depends on the indoor-unit combination. The heating capacity and heating COP of the low temperature condition were smaller than those of the standard one. Also the refrigerant cycles on indoor-unit combination were analyzed by using P-h diagram.

Simnlation of a Thermal Behavior in Solar Heating and Cooling System with respect to Demand Room Temperature (실내 설정온도에 따른 태양열 냉난방 시스템의 동적 거동 해석)

  • Jang, H.Y.;Lee, S.B.;Chung, K.T.;Suh, J.S.
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.3446-3451
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    • 2007
  • The thermal behavior of a building in response to heat input from an active solar space heating system is analysed to determine the effect of the variable storage tank temperature on the cycling rate, on and off temperature of a heating cycle and on the comfort characteristics of room air temperature. A computer simulation of the system behavior has been performed and verified by comparisons with various parameters. Especially, this study is focused on the effect of the system's performance when subjected to dynamic cooling loads. The heat input to the absorption system is provided by an array of solar collectors that coupled to a thermal storage tank.

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Single-Phase Current Source Induction Heater with Improved Efficiency and Package Size

  • Namadmalan, Alireza;Moghani, Javad Shokrollahi
    • Journal of Power Electronics
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    • v.13 no.2
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    • pp.322-328
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    • 2013
  • This paper presents a modified Current Source Parallel Resonant Push-pull Inverter (CSPRPI) for single phase induction heating applications. One of the most important problems associated with current source parallel resonant inverters is achieving ZVS in transient intervals. This paper shows that a CSPRPI with the integral cycle control method has dynamic ZVS. According to this method, it is the Phase Locked Loop (PLL) circuit that tracks the switching frequency. The advantages of this technique are a higher efficiency, a smaller package size and a low EMI in comparison with similar topologies. Additionally, the proposed modification results in a low THD of the ac-line current. It has been measured as less than %2. To show the validity of the proposed method, a laboratory prototype is implemented with an operating frequency of 80 kHz and an output power of 400 W. The experimental results confirm the validity of the proposed single phase induction heating system.

Performance Test for High Efficient Heat Pump System using Seawater Heat Source and Exhaust Energy (해수열원 및 폐열이용 고성능 열펌프 시스템 성능실험)

  • 최광일;오종택;오후규
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.12
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    • pp.979-986
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    • 2003
  • The performance characteristics of heating and cooling operation for a heat pump system using seawater heat source and exhaust energy are presented. The heat pump system is made of a waste heat recovery system and a vapor compression refrigeration system. The working fluid is R-22. The heat pump system COPs are measured during heating and cooling operation modes, and the resultant COPs were 9.7 and 7.9, respectively, which are three times higher than those of the heat pump itself. Therefore, the performance of the heat pump system using exhaust energy is excellent compared to that of a general heat pump. The experimental data can be effectively used for the design of the high efficient heat pump using a seawater heat source.

NUMERICAL STUDY OF UNSTEADY HEAT TRANSFER ON MICRO HEATER UNDER HALF-CYCLE SINUSOIDAL HEAT LOAD (마이크로히터에서 반주기 정현곡선의 열부하에 의한 비정상 열전달 연구)

  • Kim, M.J.;Lee, H.J.
    • Journal of computational fluids engineering
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    • v.19 no.4
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    • pp.1-7
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    • 2014
  • A numerical study of transient conjugate heat transfer on micro heater in a micro-channel substrate under a sinusoidal heat load was conducted. It was found that the time constant is not affected by the maximum heating magnitude of the sinusoidal heat load. However, the time constant increases with low duration of the sinusoidal heating period and low Reynolds number. Moreover, there is a threshold where a heater temperature do not reach to time constant at low thermal diffusivity, low flow rate, and low pulse duration of the sinusoidal heating. The time constant should be considered for transient convective heat transfer under transient sinusoidal heat load in a micro heat sink.

Optimization of District Heating Pipes Considering Thermal Fatigue Life (열피로 수명을 고려한 지역난방 배관의 최적화)

  • Ahn Min-Yong;Chang Yoon-Suk;Choi Jae-Boong;Kim Sang-Ho;Kim Youn-Hong;Kim Young-Jin
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.6 s.183
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    • pp.143-150
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    • 2006
  • Recently, in proportion to increased demand on environmentally-friendly heat source, efficient management of district heating(DH) system becomes one of important issue. The objectives of this paper are to systematize data processing of transition temperature, investigate the effect of temperature variations on thermal fatigue and find out a way to improve design fractures of Korean DH pipes. For this purpose, reliable fatigue lift evaluation procedures are examined and applied to quantify thermal fatigue lives. Also, as a prototypal optimization analysis results, mean value of original cross sectional area of selected pipes was reduced 18.6% sustaining their sufficient margins against fatigue failure. So, it is anticipated that the output of this research can be used as useful information of optimal design and operation in the future.

A New PWM Power Control Scheme of Class-D Inverter for Induction Heating Jar Application. (IH-Jar용 Class-D 인버터의 새로운 PWM 출력 제어 기법)

  • Choi Won-Suk;Park Nam-Ju;Lee Dong-Yun;Hyun Dong-Seok
    • Proceedings of the KIPE Conference
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    • 2004.07b
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    • pp.519-523
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    • 2004
  • In this paper, a simple power control scheme of Class-D inverter, which is varied duty cycle of fixed frequency to desired output power. It is more suitable and acceptable for high-frequency induction heating (IH) jar applications. The proposed control scheme has the advantages of not only wide power regulation range but also ease to control output power. Also it can achieve the stable and efficient Zero-Voltage-Switching (ZVS) in whole load range. The control principles of proposed method are described in detail and its validity is verified trough simulations results on 38.5kHz IGBT for induction heating rated on 1.6kW with constant frequency variable power.

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Simulation of Alcohol Absorption Heat Pumps for Heating Performance (알코올 흡수식 열펌프의 난방성능 예측)

  • Kim, Dong-Seon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.5
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    • pp.269-276
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    • 2015
  • Single-effect $CH_3OH-LiI-ZnBr_2$ and $C_2H_5OH-LiI$ absorption heat pumps are simulated to evaluate feasibility as heating device. These systems are predicted to give higher heating COPs in wide operating ranges compared to conventional systems. Among the two systems, the $C_2H_5OH-LiI$ system is found to be more advantageous for operating in extremely cold weather due to the large solubility of Lil in $C_2H_5OH$.

Examination of the Optimal Insulation Thickness of Exterior Walls for Climate Change (기후변화를 고려한 외벽 최적단열두께 검토)

  • Jung, Jae-Hoon
    • KIEAE Journal
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    • v.11 no.6
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    • pp.81-86
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    • 2011
  • By strengthening the insulation performance of a building, a great deal of energy can be saved and a comfortable indoor environment can be offered to people. On the other hand, the climate, which has a great influence on the indoor environment, is changed by global warming. Therefore, in planning building envelope structure and design, climate change should be considered. In this paper, the optimal insulation thickness of exterior walls was calculated by an economic assessment method using heating degree-days. Additionally, how much influence climate change has on planning building insulation was investigated. The examination showed that heating degree-days have decreased by about 10% due to climate change in the past few decades. It was also shown that the optimal insulation thickness of exterior walls was thin, at about 6%, in three representative Korean cities (Seoul, Daejeon, Jeju).

Selection of Working fluid for the Organic Rankine Cycle to Utilize Low-Temperature Waste Heat (저온 폐열을 이용하기 위한 유기랭킨 사이클의 작동유체 선정에 관한 연구)

  • Cho, Soo-Yong;Cho, Chong-Hyun
    • New & Renewable Energy
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    • v.10 no.4
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    • pp.36-46
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    • 2014
  • Low-grade heats are wasted even though an amount of their energy is huge. In the small and medium industrial complex sites, large amount of low-grade thermal energy generated during the manufacturing process is wasted if it is not used directly for building heating or air-conditioning. In order to utilize this waste thermal energy more efficiently, organic Rankine cycle (ORC) was adopted. The range of operating temperature of ORC was set to $60^{\circ}C$ from $30^{\circ}C$ applicable low-temperature waste heat. A study was conducted to select an appropriate organic working fluid based on these operating conditions. More than 60 working fluids were screened. Eleven working fluids were selected based on the requirements as working fluid for ORC such as environmentally friendly, safety, and good operation on the expander. Finally, six working fluids were selected by considering the operating temperature ranges. Then, a cycle analysis was conducted with these six working fluids. As a results, R-245fa and R-134a appeared as appropriate working fluids for ORC operating at low-temperature condition based on the system efficiency and the turbine output power.