Analysis of Indoor Thermal Environment Characteristics by Heating Supply Systems in Apartment Houses

Dong woo Cho,Ki hyung Yu 국제온돌학회 2010 International Journal of Ondol Vol.2010 No.-

Recent apartment houses tend to expose the problems of unbalanced floor temperatures and real temperature due to changes in thermal performance arising from reinforced insulation and air tightness. In this study, the indoor thermal environment was analyzed against the apartment unit household in the type of individual heating, central heating, and District Heating methods in order to determine the operational status of indoor thermal environments and heating system by Heating supply systems. The temperature of hot water supplied at the time the indoor loads occurs to the maximum by Heating supply systems was found to rise in order to individual heating (70℃) , central heating(47℃) and District Heating (41℃). The hot water supply frequency showed variable changes in the range of 3 to 6 times per day in cases of individual heating while periodical changes was ranging from 3 or 4 times a day in the case of central heating and district heating. The width of variation of floor surface temperatures depending on the temperature of the supply water was found to be in order of Individual Heating, District Heating, and Central Heating. The average floor surface temperature appeared similar to the hot water supply temperature pattern in the order of 26.4 to 30.2℃ for Individual Heating, 28.2 to 28.6℃ for Central Heating, and 24.8 to 29.4℃for District Heating. In the case of non-heating where heating is not implemented, the temperature of the floor surface was 22.8℃ to 26.0℃ showing the same temperature as the indoor temperature. Heating supply appeared to be maintained in a stable manner overall in a sporadic manner ranging from 3 to 6 times a day, which was maintained in a stable manner on the whole regardless of the heating method.

히트파이프 배열을 갖는 태양열 축열시스템의 열전달 해석

정의국(Jung Eui-Guk),김종규(Kim Jong-Kyu),강용혁(Kang Yong-Heack),부준홍(Boo Joon-Hong) 한국태양에너지학회 2010 한국태양에너지학회 학술대회논문집 Vol.2010 No.4

Heat transfer analysis results were shown for the solar thermal storage system which used heat pipe array. The thermal storage system was composed of thermal storage tank and charging/discharging heat exchanger by connection with the heat pipes. Heat pipe heat exchanger was attached to system, and could carry out charging and discharging to thermal storage tank at the same time. Height of the thermal storage tank was 600 ㎜, and that of the charging/discharging heat exchanger was 400 ㎜. Length of the heat pipe was the same as the total height of thermal storage system, and outer and inner diameter were 25.4 ㎜(O.D.) and 21.4 ㎜(I.D.) respectively. Diameter of the circular was 43 ㎜(O.D.), and fin geometries were considered as the design parameters. High temperature phase change material(PCM), KNO₃ was charged to storage tank to adjust melting temperature. Energy relations between heat exchanger and thermal storage tank were defined by the thermal resistance and node temperature. Physical transient equations of the heat pipe heat exchanger/thermal storage and PCM was modeled with energy conservation. Furthermore, melting/solidification phase change interface radius were calculated based on latent and sensible heat. Thermal storage system sizes satisfying inlet and outlet conditions of the charging/discharging heat exchanger were predicted according to heat pipe fin pitch variation of the thermal storage. Maximum and minimum heat pipe row was predicted to 899 and 808 respectively.

다수의 히트펌프로 구성된 냉난방시스템에서 하절기 히트펌프의 최적운전에 관한 연구

申寬雨(Kwan-Woo Shin) 대한전기학회 2006 전기학회논문지 P Vol.55 No.1

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.

Heat transfer characteristics of the integrated heating system for cabin and battery of an electric vehicle under cold weather conditions

Seo, Jae-Hyeong,Patil, Mahesh Suresh,Cho, Chong-Pyo,Lee, Moo-Yeon Elsevier 2018 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.117 No.-

<P><B>Abstract</B></P> <P>The objective of this study is numerically to investigate the heat transfer characteristics of the integrated heating system considering the temperature of cabin and battery of an electric vehicle under the cold weather conditions. The integrated heating system consists of a burner to combust fuel, an integrated heat exchanger for CHE (coolant heat exchanger) and AHE (air heat exchanger). The heat transfer characteristics like the overall heat exchanger effectiveness, the heat transfer rate, the temperature distribution and the fluid flow characteristics like the pressure drop, velocity distribution of the investigated integrated heating system were considered and analyzed by varying the inlet mass flow rates and the inlet temperatures of the cold air and water, respectively. The average Nusselt numbers for the cold air side and the water side were increased 28.4% and 9.5%, respectively, with the increase of the cold air side Reynolds numbers from 15,677 to 72,664 and the water side Reynolds numbers from 4330 to 11,912. The numerical results showed good agreement within ±9.0% of the existed data and thus confirmed that the present model was valid. In addition, the proposed integrated heating system could be used as the thermal management of the cabin and the battery system of the electric vehicle under the cold weather conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> EVs have issues on cabin heating source and battery heating under cold weather. </LI> <LI> EVs suffer from a short driving range and shortage of cabin heating. </LI> <LI> Cabin air heating and battery thermal management for electric vehicle investigated. </LI> <LI> The considered system was investigated under various operating conditions. </LI> <LI> Integrated heating system suggested for cabin heating and battery thermal management. </LI> </UL> </P>

Heating performance characteristics of a dual source heat pump using air and waste heat in electric vehicles

Ahn, J.H.,Kang, H.,Lee, H.S.,Jung, H.W.,Baek, C.,Kim, Y. Applied Science Publishers 2014 APPLIED ENERGY Vol.119 No.-

A heat pump has been considered as an alternative to an electric heater to increase the efficiency of the heating unit in electric vehicles. However, the heating performance of a single source heat pump has yet to be improved at low outdoor temperatures. This study investigates the feasibility of a dual source heat pump using both air and waste heat in electric vehicles. The performance of the dual source heat pump was measured at various operation modes: air source-only, waste heat-only and dual heat source. The heating performance of the dual source heat pump was higher than those of the single source heat pumps. In addition, an alternating single mode operation of air source-only and waste heat-only modes was proposed to improve performance at low outdoor air temperatures.

Performance investigation of a novel calorimeter for a heat pump system according to flow loops

Kofi Owura Amoabeng,이광호,JONGMIN CHOI 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.4

Heat pumps cover a wide range of heating and cooling applications owing to their means of drawing out heat from ground, air and water at low temperature. In order to acquire performance data for heat pump certification and rating, the calorimeter is used in measuring the heat pump. In conventional approach of measuring the heat pump with standard test conditions, a great amount of energy is used in the calorimeter for cooling and heating. Using innovative ways to enhance the calorimeter performance is significant for energy and cost savings. Therefore, a novel calorimeter was developed for heat pump measurement. Two different flow loop configurations, specified as cases (1) and (2) were adopted. In the case (1), secondary fluid flow through the heat recovery unit was directly from heat pump test unit heat exchanger while in case (2), secondary fluid flow through heat recovery unit was from constant temperature water bath directly. The energy usage of the novel calorimeter based on the impact of each configuration was analyzed. Experiments were conducted using a water-to-water heat pump unit in heating and cooling approach with variation in operating conditions. Energy analyses based on test data indicated that energy reduction of the novel calorimeter was at least 72 % for heating and 69 % for cooling in relation to energy used in conventional calorimeter. Moreover, for novel calorimeter, case (1) resulted in energy savings of at least 9.1 % for cooling and 13 % for heating in relation to case (2). However, for heat pump units with very low capacities, tests measurements were executed using case (2) configuration because the tests in case (1) resulted in large thermal fluctuations such that the steady operating conditions of the water setpoint temperatures at inlet to the indoor and outdoor heat exchangers of the test unit were unattainable.

공동주택 공기열 멀티 히트펌프의 바닥난방 성능 평가

이철희,나환선,정훈,김강식 한국기계기술학회 2011 한국기계기술학회지 Vol.13 No.3

To analyze and evaluate the performance of developing air to water multi heat pump, the heat pump was installed and tested at low energy house in Daejeon, korea. Heating capacity of heat pump is 16.5KW and cooling capacity is 14.0KW. Space heating/cooling, floor heating and hot water is available. The results performance evaluation of heat pump in lab test showed that the coefficient of performance (cop) was 3.75,and heating capacity was 16.0KW in ambient temperature 7℃. Also at ambient temperature -15℃, the COP was 1.69. At a low energy house, floor heating is controled by a floor heating water temperature and a room temperature. The COP of heat pump is decreased with frequent on/off operation for controlling of floor heating water temperature.

수열원 열펌프시스템용 적산열량계의 냉방, 난방 성능특성에 관한 연구

강희정,이현수 한국기계기술학회 2019 한국기계기술학회지 Vol.21 No.2

In this study, the cooling and heating amount, temperature, flow rate of turbine type heat meter for water source heat-pump system were experimentally investigated at the standard operating conditions. The obtained cooling and heating capacity from the heat meter were deviated within 5.0%, 3.8% comparing with the precise values calculated from an accredited test facility. Even though the accumulated cooling and heating amount values of the heat meter had a small difference comparing with the precise values, the temperatures of heat meter showed greatly different values comparing with the precise temperature. Therefore, it is highly recommended to develop the heat meter which is appropriate for the water source heat pump systems.

Effects of Heating Temperature and Time on the Mechanical Properties of Heat-Treated Woods1

Kyung Rok Won,Nam Euy Hong,Han Min Park,Sun Ok Moon,Hee Seop Byeon 한국목재공학회 2015 목재공학 Vol.43 No.2

This study was performed to investigate the effects of heat treatment the on mechanical properties of two species of wood under different heating conditions including at 180℃ for 12 h and 24 h, and at 210℃ for 3 h and 6 h. Two species of wood, Pinus densiflora and Larix kaempferi, were exposed to different heat treatments to assess the effects on the volume change, bending properties in static and dynamic mode and compressive strength. The results showed heat treatment caused significant changes in mechanical properties such as the static and dynamic moduli of elasticity (MOEd and MOEs), and the modulus of rupture (MOR). The volume of the wood after heat treatment decreased as the heating temperature and time were increased. The bending strength performance of the wood after heat treatment decreased as the heating temperature and time were increased. The effect of heat treatment at a high temperature on the bending MOR was greater in both species than that for a long time. However, the compressive strengths of all the heat-treated samples were higher than the control sample. Furthermore, highly significant correlations between MOEd and MOR, and MOEs and MOR were found for all heating conditions.

태양열 공기가열 집열기에 의한 난방 실내공간의 열유동 특성 해석

양영준 ( Young-joon Yang ) 한국산업융합학회 2022 한국산업융합학회 논문집 Vol.25 No.2

The solar energy has been widely used to reduce the fossil fuel and prevent the environmental pollution. The renewable energy including solar heat tends to spread due to carbon neutrality for main country of the world. Targets of solar collector are usually acquisitions of hot water or hot air. Especially, air-heating collector using solar heat is known as the technology for obtaining hot air. This study aims to investigate of characteristics of thermal flow when the hot air by air-heating collector using solar heat flows inside of indoor space. The thermal flow of heating indoor space was simulated using ANSYS-CFX program and thus the behaviors of hot air in indoor space were evaluated with standard k-ε turbulence model. As the results, as the inlet velocity was increased, the behaviors of hot air became simple, and temperature range of 25∼75℃ had almost no effect on behavior of flow. As the inlet temperature was increased, the temperature curve of indoor space from bottom to top was changed from linear to quadratic. Furthermore, it was confirmed that inlet velocity as well as inlet temperature also should be considered to heat indoor space equally by air-heating collector using solar heat.