• Title/Summary/Keyword: low temperature heating

Search Result 961, Processing Time 0.034 seconds

Study on the Performance of a Variable Speed Cascade Heat Pump under Various Operating Conditions (운전조건에 따른 가변속 캐스케이드 열펌프의 성능 특성 연구)

  • Jeong, Kwangmoo;Choi, Jong Min
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
    • /
    • v.9 no.2
    • /
    • pp.1-7
    • /
    • 2013
  • Most researches done on heat pumps have been on heat pumps for refrigeration, cooling and heating. There is therefore the need for more research on hot water heat pumps, especially for high temperature. Even though the cascade heat pump cycle has a great potential more efficient hot water generation even at low evaporating temperatures, it has been researched least for this purpose. In this study, the heating performance of a variable speed cascade heat pump was investigated by varying operating conditions. For the same heating capacity values, it was found that increasing the low stage compressor speed was more suitable for enhancing the performance of the system to get a higher temperature.

A Study on Optimal Operation of Summer Season Cooling System with Numbers of Heat Pumps (다수의 히트펌프로 구성된 냉난방시스템에서 하절기 히트펌프의 최적운전에 관한 연구)

  • Shin, Kwan-Woo
    • The Transactions of the Korean Institute of Electrical Engineers P
    • /
    • v.55 no.1
    • /
    • pp.35-40
    • /
    • 2006
  • Heat-pump system has a special feature that provides heating operation in winter season and cooling operation in summer season with a single system. It also has a merit that absorbs and makes use of wastewater heat, terrestrial heat, and heat energy from the air. Because heat-pump system uses midnight electric power, it decreases power peak load and is very economical as a result. By using the property that energy source is converted to low temperature when losing the heat, high temperature energy source is used to provide heating water and low temperature energy source is used to provide cooling water simultaneously in summer season. This study made up a heat-pump system with 4 air heat sources and a water heat source and implemented the optimal operation algorithm that works with numbers of heat pumps to operate them efficiently. With the heat-pump system, we applied it to cooling and heating operation in summer season operation mode in a real building.

Effects of Viscosity Control by Induction Heating on Micro Cell in Forming Process of Foamed Aluminum (알루미늄 발포재의 성형공정에서 유도가열 법에 의한 점도 제어가 미세 기공에 미치는 영향)

  • Jeon, Yong-Pil;Kang, Chung-Gil
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.19 no.6
    • /
    • pp.136-144
    • /
    • 2002
  • Melting method has long been considered difficult to realize because of problems such as the low foamability of molten metal, the varying size of cellular structures and solidification shrinkage. The parameters to solve the problem in electric furnace were stirring temperature, stirring velocity, heating velocity and foaming temperature It is important to consider the effects of induction heating, because it brings about the inner flow by the temperature gradient. Aspect ratio also depends on the induction heating. Mechanical properties are dependent on cell sizes and aspect rations. Therefore, this paper presents the effects of these parameters on the cell sizes. For the sake of this, combined stirring process was used to fabricate aluminum foam materials by the above mentioned parameters. Image analysis was performed to calculate the cell sizes, distributions, and aspect ratioes at the cross section of feared aluminum in the direction of height.

Comparative Study on Performance of Wet-type and Dry-type Floor Heating Systems Using Geothermal Heat Pump (지열히트펌프를 이용한 습식.건식 바닥난방 성능평가 연구)

  • Lee, Byoung-Doo;Lee, Se-Jin;Lee, Dae-Woo;Oh, Sung-Hae;Nam, Woo-Dong
    • New & Renewable Energy
    • /
    • v.5 no.4
    • /
    • pp.60-65
    • /
    • 2009
  • The present study was conducted for a comparative evaluation of wet and dry floor heating systems using geothermal heat pump. We circulated hot water from geothermal heat pump which is $10{\sim}15^{\circ}C$ lower than that from boiler. In order to access indoor temperature ($25^{\circ}C$) it took 74 minutes for dry type and 247 minutes for wet type. Average floor temperature was $23.9^{\circ}C$ for wet type and $32.7^{\circ}C$ for dry type. Energy saving rate gradually increased by 66% after 138 minutes. As a result, in case of floor heating system using low temperature circulation water, dry type was more practicable for stable floor heating than wet type in terms of floor temperature and access time to indoor set temperature.

  • PDF

Heating and Cooling Effect of Portected Horticulture by Geothermal Heat Pump System with Horizontal Heat Exchanger (수평형 지열히트펌프 시스템의 시설원예 냉난방 실증 효과)

  • Ryou, Young-Sun;Kang, Youn-Ku;Kim, Young-Jung;Kang, Keun-Chun
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2008.05a
    • /
    • pp.630-633
    • /
    • 2008
  • Geothermal heat pump systems use the earth as a heat source in heating mode and a heat sink in cooling mode. These systems can be used for heating or cooling systems in farm facilities such as greenhouses for protected horticulture, cattle sheds, mushroom house and etc. A horizontal type means that a geothermal heat exchanger is laid in the trench buried in 1.2 to 1.8 m depth. Because a horizontal type has advantages of low installation, operation and maintenance costs compared to a vertical type, it is easy to be adopted to agriculture. In this study, to heat and cool farm facilities and obtain basic data for practical application of horizontal geothermal heat pump system in agriculture, a horizontal geothermal heat pump system of 10 RT was installed in greenhouse. Heating and cooling performance of this system was estimated. The horizontal geothermal heat pump used in this study had heating COP of 4.57 at soil temperature of $14^{\circ}C$ with depth of 1.75m and heating COP of 3.75 at soil temperature of $7^{\circ}C$ with the same depth. The cooling COP was 2.7 at ground temperature at 1.75m depth of $25.5^{\circ}C$ and 2.0 at the temperature of $33.5^{\circ}C$.

  • PDF

Optimum Design of the Heating Equipment by Influence of Wind Speed at Cryogenic Temperature (극저온에서 풍속의 영향에 따른 발열기자재의 최적설계)

  • Cho, Hyun Jun;Yun, Won Young
    • Journal of Korean Society for Quality Management
    • /
    • v.48 no.3
    • /
    • pp.463-479
    • /
    • 2020
  • Purpose: The purpose of this study is to evaluate the performance of heating equipments by implementing the extreme environment in which ships navigating the ice zone are exposed and to study and apply the experimental method to infer the optimized design for each factors. Methods: It is required to verify by analysis and experiment how the environment with low temperature and wind speed implemented through the test facility affects the heating walk-way and The optimum design of the heating walk-way in that extreme environment is derived using the Taguchi technique. Results: The results of this study are as follows; It was found the effect on the condition of each factor and derive optimized conditions that satisfy the performance condition of the heating walk-way in extreme use environment. Conclusion: Ships operating in Polar waters require reliable and durable facilities for all environments during sailing.

Evaluation of self-heating propensity and its relation with fuel properties of various coals (다양한 탄종별 자체발열 특성과 물성의 비교 분석)

  • Kim, Jungsoo;Lee, Yongwoon;Im, Hyeon Soo;Park, Hoyoung;Ryu, Changkook
    • 한국연소학회:학술대회논문집
    • /
    • 2013.06a
    • /
    • pp.83-85
    • /
    • 2013
  • With an increase in the use of low rank coals in power plants, various operational issues were raised in the fuel storage and supply, combustion, boiler and flue gas treatment systems. In the fuel storage and supply system, the main issue is the self-heating propensity of low rank coals leading to spontaneous combustion in yard storage, transport and pulverization. This study evaluated the reactivity of various sub-bituminous and bituminous coals with oxygen at low temperatures by analyzing the temperature increase characteristics of coals under a constant flow rate of oxygen supply. The results were quantified to a self-heating index and the relation with the fuel properties were evaluated.

  • PDF

Characterization of Indoor Temperature and Humidity in Low-income Residences over a Year in Seoul, Korea

  • Lee, Daeyeop;Lee, Kiyoung;Bae, Hyunjoo
    • Asian Journal of Atmospheric Environment
    • /
    • v.11 no.3
    • /
    • pp.184-193
    • /
    • 2017
  • People spend the majority of their time in indoor environments. Maintaining adequate indoor temperature and humidity is necessary to support health and improve quality of life. However, people with low incomes can be vulnerable because they may not be able to use effective cooling and heating systems in their homes. In this study, the indoor temperature and humidity in low-income residences over a year in Seoul, Korea was characterized. Indoor temperature and humidity were measured in three types of homes (12 rooftop residences, 16 basement residences, and 18 public rental apartments) occupied by low-income residents. Both differed significantly among the three types of residence, particularly during the summer and winter seasons. A regression model between indoor and outdoor temperature detected a heating threshold at $3.9^{\circ}C$ for rooftop residences, $9.9^{\circ}C$ for basement residences, and $17.1^{\circ}C$ for public rental apartments. During tropical nights and cold-wave advisory days, rooftop residences showed the most extreme indoor temperatures. This study demonstrates that people living in rooftop residences could be at risk from extreme hot and cold conditions.

Study on the Vinyl House Heating by Warm Air (농업용 비닐하우스의 온풍난방에 관한 기초적 연구)

  • 조진구;이근후
    • Magazine of the Korean Society of Agricultural Engineers
    • /
    • v.19 no.3
    • /
    • pp.4483-4491
    • /
    • 1977
  • The results obtained are as follows; 1. The variation of the temperature in a vinyl house without heating system is similar to that of air temperature in a day. The difference of maximum temperature and minimum one in a day is 27$^{\circ}C$ which is two times greater than the daily difference of air temperature. 2. When the length of the duct is increased, the high temperature zone is built up in the direction of warm air discharge from the duct, and the low temperature zone is built up in the opposite direction of warm air discharge. But, in case of the duct length is short (0.05 L), the temperature distrubution in a vinyl house become uniform. It is concluded that the shorter length of the duct, the better the distribution of the temperature in a vinyl house is. 3. When the duct is installed at high position, the high temperature zone is built up in the upper zone of the vinyl house and the low temperature zone is built up in the lower zone. And when the position of the duct is low, the rate of temperature variation along the vertical direction become high, and the direct contact of warm air with the plant in the house is occured. It is concluded that the duct should be installed at the position of slightly higher than the plant height. 4. When the fuel consumption rate is fixed at the 101/hr, the lowest temperature warming rate in the vinyl house is 5$^{\circ}C$ without regard to the air temperature.

  • PDF

Effect of Heating Rate and $V_2O_5$ Addition on Densification and Electrical Properties of $Pb(Mn_{1/3}Sb_{2/3})O_3-PZT$ Ceramics for Piezoelectirc Transformer (압전변압기용 $Pb(Mn_{1/3}Sb_{2/3})O_3-PZT$ 세라믹스에서 승온속도 및 $V_2O_5$ 첨가가 치밀화 및 전기적 특성에 미치는 영향)

  • 허수정;손준호;손정호;이준형;김정주;정우환;박명식;조상희
    • Journal of the Korean Ceramic Society
    • /
    • v.37 no.4
    • /
    • pp.295-301
    • /
    • 2000
  • The effect of V2O5 addition on the low temperature sintering of Pb(Mn1/3Sb2/3)O3-PZT ceramics, which is known as a prominent material for piezoelectric transformer application was studied, and the densification behavior and piezoelectric characteristics of the samples as a function of heating rate were also examined. V2O5 led the system to liquid phase sintering by forming liquid phase during sintering, which accelerated densification through the particle rearrangement in the early stage of sintering. The liquid phase mostly existed at grain boundaries retarded the evaporation of PbO, while the densification temperature and the weight loss of V2O5-free samples were higher than those of samples with V2O5. Faster heating improved the densification of the samples regardless of V2O5 addition. The low temperature sintering at 100$0^{\circ}C$ was achieved in PMS-PZT ceramics with high density and reasonable dielectric and piezoelectric characteristics. This result revealed optimistic way to the development of multi-layered piezoelectric transformers.

  • PDF