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.

축열식과 비축열식 바닥복사난방의 실내 열환경 특성 비교

최동호 ( Choi Dong-ho ) 대구가톨릭대학교 자연과학연구소 2019 자연과학연구논문집 Vol.17 No.1

This paper examines the characteristics of thermal storage floor heating system and compares the heating characteristics of thermal and non-thermal storage floor heating systems through field experiments. In addition, the heating energy consumption of the two heating systems were measured and used as the basis for performance evaluation. Our results are as follows: ① The two floor radiant heating systems showed extremely uniform temperature regardless of location and height of the indoor space, which effectively improved the thermal comfort of the room. ② Non-thermal storage floor heating systems were found to elicit relatively fast thermal responses and were thus effective for intermittent heating that requires a fast thermal response. ③ It was confirmed that the longer the heating operation time and the higher the set temperature of water, the higher the indoor globe temperature rose. ④ The initial long-wave radiation of non-thermal storage floor heating systems, which exhibits a relatively rapid rise of the bottom surface temperature, was high, but subsequently thermal storage floor heating systems showed higher long-wave radiation than that of non-thermal storage floor heating. ⑤ In this comparative experiment, non-thermal storage floor heating required only 27% of energy compared to its thermal storage counterpart.

호화점 이하에서 옴가열이 감자 전분의 열적특성에 미치는 영향

차윤환,Cha, Yun-Hwan 한국식품영양학회 2012 韓國食品營養學會誌 Vol.25 No.4

Ohmic heating uses electric resistance heat which occurs equally and rapidly inside of food when electrical current is flown into. In other study, we researched about soybean protein's characteristic changes by ohmic heating. Nevertheless treated same temperature, denaturation of soybean protein were accelerated by ohmic heating than conventional heating. In this time, we studied thermal property change of potato starch by ohmic heating besides conventional heating. For this purpose, potato starch was heated at same subgelatinization temperature by ohmic and conventional heating. And thermal properties were tested using DSC. Annealing of starch is heat treatment method that heated at 3~4% below the gelatinization point. DSC analysis results of this study, the $T_o$, $T_p$, $T_c$ of potato starch levels were increased, whereas $T_c{\sim}T_o$ was narrowed. This thermal property changes appear similar to annealing's result. It is thought the results shown in this study, because the heating from below the gelatinization point. 6, 12, 24, 72, and 120 hours heating at $55^{\circ}C$ for potato starch, $T_o$, $T_p$, $T_c$ values continue to increased with heating time increase. The gelatinization temperature of raw potato starch was $65.9^{\circ}C$ and the treated starch by conventional heating at $55^{\circ}C$ for 120 hr was $72^{\circ}C$, ohmic was $76^{\circ}C$. The gelatinization range of conventional (72 hr) was $10^{\circ}C$, ohmic was $8^{\circ}C$. In case of 24 hours heating at 45, 50, 55, 60, $65^{\circ}C$ for potato starch, the result was similar to before. $T_o$, $T_p$, $T_c$ values continue to increased and gelatinization range narrowed with heating temperature increase. In case of conventional heating at $60^{\circ}C$, the results of gelatinization temperature and range were $70.1^{\circ}C$ and $9.1^{\circ}C$. And ohmic were $74.4^{\circ}C$ and $7.5^{\circ}C$. When viewed through the results of the above, the internal structure of starch heated by ohmic heating was found that the shift to a more stable form and to increase the homology of the starch internal structure.

Pasteurization of fermented red pepper paste by ohmic heating

Cho, W.I.,Yi, J.Y.,Chung, M.S. Elsevier Science 2016 INNOVATIVE FOOD SCIENCE AND EMERGING TECHNOLOGIES Vol.34 No.-

<P>Ohmic heating was applied to a Korean traditional fermented food containing red pepper paste, called Gochujang with low thermal conductivity (0.458 W/m.K), by varying frequencies (40-20,000 Hz) and applied voltages (20-60 V). Contrary to conduction heating, the entire sample was heated uniformly, and the specific heating rate was found to be highly dependent on the frequency, peaking at 5 kHz and 60 V. The results showed that complex differential equation and the Runge-Kutta fourth-order method are suitable for simulating the temperature profile during ohmic heating. The deactivation of vegetable cells of Bacillus strains on fermented red pepper paste by ohmic heating was indicated by a 99.7% reduction, compared with conduction heating for 8 min at 100 degrees C producing a 81.9% reduction. The organoleptic and physicochemical qualities of the samples pasteurized by ohmic heating were nearly the same as those of raw samples, and higher than those of conventionally heated samples. Industrial relevance: The present study designed and implemented a novel sterilization process based on a static ohmic heating system with low-frequency AC at the laboratory scale for fermented red pepper paste with a low thermal conductivity (0.458 W/m.K). The developed system was used to investigate the mechanisms and characteristics underlying the induction of ohmic heating and then, tested the pasteurization effect against microorganisms in fermented red pepper paste. Comparing with conventional heating processes, ohmic heating could provide rapid and uniform heating, thereby is more suitable for pasteurization and sterilization of viscous foods as fermented red pepper paste on industrial thermal processing. (C) 2016 Elsevier Ltd. All rights reserved.</P>

온수배관을 이용한 시설딸기 부분난방기술 개발

문종필,강금춘,권진경,백이,이태석,오성식,남명현,Moon, Jongpil,Kang, Geum-Choon,Kwon, Jin-Kyung,Paek, Yee,Lee, Tae Seok,Oh, Sung-Sik,Nam, Myeong-Hyeon 한국농공학회 2016 한국농공학회논문집 Vol.58 No.5

The effects of spot heating for growing the strawberry cultivated in a plastic greenhouse during the winter that were estimated in Nonsan strawberry experiment station located in Chungnam. The temperature of water for heating was controlled by a electric hot water boiler and kept at the range of $22{\sim}24^{\circ}C$. Heating pipes were set up in root zone for root zone heating and very close to crown for crown heating. Spot heating effects were estimated by applying spot heating system in three test factors of heating root zone, crown only and crown plus root zone. The material for crown heating pipe was white low density polyethylene and the nominal diameter of that pipe was 16 mm. The material for root zone heating pipe was flexible stainless steel and the nominal diameter of that pipe was 15A. The flow rate of heating water circulation was 480 L/h and water circulation lasted for all day long. Temperatures, harvest yield by test beds were surveyed from Nov. 10, 2013 to Apr. 29, 2014. The temperature of crown spot for crown heating bed was at the range of $13.0{\sim}17.0^{\circ}C$ during the night and that of crown spot in control bed was at the range of $8.0{\sim}14.0^{\circ}C$. Also, the temperature of root zone for root zone heating bed was at the range of $18{\sim}21.0^{\circ}C$ and that of root zone in control bed was at the range of $13.0{\sim}15.0^{\circ}C$. The cumulative yield growth rate in earlier harvest period (from Dec. 20 to Mar. 15) of crown heating bed was 43% compared with that of control bed and the cumulative yield of crown plus root zone heating bed was 39 % and that of root zone heating bed was 39 %.

Conduction Heating of Boron Alloyed Steel in Application for Hot Stamping

Weikang Liang,Yong Liu,Bin Zhu,Minglin Zhou,Yisheng Zhang 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

In traditional hot stamping process, heating of the sheet by radiation heating occupies most of cycle time, which limits the application of hot stamping in automotive industry. Thus a faster heating method has great significance on the hot stamping. The conduction heating overcomes shortage of the radiation heating because of higher heating rate and greater energy efficiency. It attracts increasing attention in the application of heating blanks in hot stamping. In the present study, a movable conduction heating device on die was designed in terms of the Joule’s Law. Heating experiments of boron alloyed steel were performed using the developed device. Heating rate and uniform temperature region were investigated in the non-heat preservation condition (NHPC) and the heat preservation condition (HPC). The results revealed that in the HPC, the heating rate was improved by 13.1 °C/s. In addition, the length of the uniform temperature region was lengthened by 15 mm. It was demonstrated that the HPC was preferred. Furthermore, it was indicated that the mechanical properties of the blanks in uniform temperature region of the conduction heating were also superior to that of the radiation heating.

옴가열이 전분의 열적 특성과 흡수력에 미치는 영향

차윤환,Cha, Yun-Hwan 한국식품영양학회 2014 韓國食品營養學會誌 Vol.27 No.1

Ohmic heating uses electric resistance heat which occurs equally and rapidly inside food when the electrical current is transmitted into. Prior to the study, we have researched the potato starch's thermal property changes during ohmic heating. Comparing with conventional heating, the gelatinization temperature and the range of potato starch treated by ohmic heating are increased and narrowed respectively. Herein, we have studied thermal property changes of wheat, corn, potato and sweet potato starch by ohmic heating as well as conventional heating. And then we measure the water holding capacity of starches. Annealing of starch is a heat treatment method heated at 3~4% below the gelatinization point. This treatment changes the starch's thermal property. In the DSC analysis of this study, the $T_o$, $T_p$, $T_c$ of all starch levels have increased, and the $T_c$-$T_o$ narrowed. In the ohmic heating, the treatment sample is extensively changed but not with the conventional heating. From the ohmic treatment, increases from gelatinization temperature are potato ($8.3^{\circ}C$) > wheat ($5.3^{\circ}C$) > corn ($4.9^{\circ}C$) > sweet potato ($4.5^{\circ}C$), and gelatinization ranges are potato ($7.9^{\circ}C$), wheat ($7.5^{\circ}C$), corn ($6.1^{\circ}C$) and sweet potato ($6.8^{\circ}C$). In the case of conventional treatment, water holding capacity is not changed with increasing temperature but the ohmic heating is increased. Water holding capacity is related to the degree of gelatinization for starch. This result show that when treated with below gelatinization temperature, the starches are partly gelatined by ohmic treatment. When viewing the results of the above, ohmic treatment is enhanced by heating and generating electric currents to the starch structure.

Comparison of pH effects on ohmic heating and conventional heating for inactivation of Escherichia coli O157:H7, Salmonella enterica Serovar Typhimurium and Listeria monocytogenes in orange juice

Kim, S.S.,Kang, D.H. Academic Press, etc 2015 FOOD SCIENCE AND TECHNOLOGY -ZURICH- Vol.64 No.2

The objective of the current study is to identify the influence of acidity on ohmic heating compared to conventional heating for inactivation of food-borne pathogens in orange juice. For conventional heating, the heating rate was not significantly different (P > 0.05) regardless of pH and pathogens were inactivated more effectively at lower pH. However, different patterns were observed for ohmic heating. Although temperature and electrical conductivity were not greatly affected by lowering pH, temperature increased more rapidly with increasing pH due to higher electrical conductivity. Also, the inactivation patterns were significantly different (P < 0.05) from conventional heating. While Salmonella Typhimurium was inactivated most rapidly at pH 2.5, Escherichia coli O157:H7 and Listeria monocytogenes were inactivated most rapidly at pH 4.5. When pathogens were exposed to each heating method at a fixed temperature, additional effects of ohmic heating were not observed. Also, the overall quality of orange juice subjected to ohmic heating was not greatly affected at any pH level. Therefore, increasing as well as lowering pH can also be considered effective ways to optimize pasteurization of orange juice when using ohmic heating. The different characteristics of ohmic heating compared to conventional heating indicate the necessity of a new approach.

Electrical–Thermal–Mechanical Analysis of Focused Infrared Heating Process

Eun-Ho Lee,Woo-sung Kim 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.4

Demand of infrared (IR) heating technology has been increasing in industrial heat treatment processes to replace traditional heating methods because of this technology’s high energy efficiency. However, numerical analyses of IR heating have not been sufficiently reported. This work proposes a framework for electrical–thermal–mechanical analysis of a focused IR heating process using multi-physics analysis to obtain more information about the physical phenomenon. In the present model, the electrical-thermal analysis simulated the IR lamp converting electrical energy to infrared radiation, then the radiation heating and mechanical analyses of the target material was conducted. The temperature of the IR lamp in the simulation was 2357 °C (around 2600 K), which matches the well-known range of the temperatures (2500–3000 K) of IR lamps. For the radiation heating analysis, four simple models were proposed, based on geometrical-feature, to consider the distribution of IR radiation. With the present model, focused IR heating for a metal sheet was simulated and the results were compared to the experimental data. The normalized root mean square errors (RMSEs) of all of the proposed models were less than 10% for the central temperature, which is the most important heating position of the focused IR heating. The results show that the electrical–thermal–mechanical model provides good agreement with the measured data in predicting local heating eff ect of saving heating energy. In addition, this multi-physics simulation can provide information on the thermal expansion and stress distribution as well as the temperature field of the heated material.

파프리카 재배 벤로형 유리온실에서 난방에너지 절감 패키지 기술 적용효과

권진경(Jin Kyung Kwon),전종길(Jong Gil Jeon),김승희(Seung Hee Kim),김형권(Hyung Gweon Kim) (사)한국생물환경조절학회 2016 생물환경조절학회지 Vol.25 No.4

본 연구에서는 유리온실 경영비 절감을 위한 고효율 난방기술을 개발하기 위하여 지하수열원 히트펌프, 알루미늄 다겹보온커튼, 근권부 국소난방장치를 조합한 난방패키지 모델을 구성하고 파프리카 재배 벤로형 유리온실에 적용 시험을 수행하였다. 적용효과 분석을 위하여 관행 경유온수보일러와 일반 보온커튼을 설치한 대조구 온실과 비교시험을 통해 온실환경, 난방비용, 작물생육 등을 검토하였다. 알루미늄 다겹보온커튼과 일반 부직포 보온커튼을 설치한 온실에 대한 무가온 조건에서의 야간온도 비교시험에서 알루미늄 다겹보온커튼 설치 온실의 온도가 일반 부직포 보온커튼 설치 온실에 비해 평균 2.2℃ 더 높게 유지됨을 확인하였다. 또한 근권부 국소난방장치를 설치한 온실에서 미설치 온실에 비해 야간난방 중의 베드내부 근권온도가 4.7℃ 더 높게 유지됨을 확인하였다. 난방패키지를 구성하는 지하수열원 히트펌프의 난방성능을 분석한 결과 지하수를 직접 열원으로 이용하는 시스템 특성상 난방성능계수는 평균 3.7로 비교적 높게 나타났다. 난방패키지를 적용한 처리구 온실과 관행 난방의 대조구 온실에 대하여 연료소비량을 계측한 결과 10a(1,000㎡)당 대조구 온실은 경유 14,071L, 전력 364㎾h를 소비하였고, 처리구는 전력 35,082㎾h를 소비하여 난방비용 기준으로 대조구 온실의 비용 절감율은 87%로 나타났다. 처리구 및 대조구 온실의 작물생육을 비교한 결과 초장과 엽록소 함량에서 차이가 발생하였으나 두 온실의 난방온도가 거의 동일하므로 전체적인 생육은 큰 차이가 없는 것으로 분석되었다. 원예시설의 난방에너지 절감효과를 극대화하기 위해서는 본 연구의 난방패키지를 구성하는 개별 기술뿐 아니라 이미 개발된 고효율 공조기 이용기술, 보온성 향상기술, 온도관리 기술 등을 지역, 시설, 작목, 작형 등에 최적화하여 조합할 수 있는 추가적 패키지 모델의 개발 연구가 필요한 것으로 판단되었다. Glasshouse heating package technologies to improve energy usage efficiency in winter were developed. Heating package was composed of the ground water source heat pump with heating capacity of 105㎾, the aluminum multi-layer thermal curtain with six layers of different materials and the root zone local heater with XL pipes of φ 20㎜. Venlo type glasshouse(461㎡) with the heating package was compared with the same type and area control glasshouse with the light oil boiler, the usual non-woven fabric thermal curtain with respect to the glasshouse inside temperature, relative humidity, crop growth, and heating energy consumption. The results of test in paprika cultivation glasshouses showed that the air temperature inside glasshouse with aluminum multi-layer thermal curtain was maintained 2.2℃ higher than that of control glasshouse in un-heating night time and the temperature in bed with root zone local heating was 4.7℃ higher than that in bed without local heating. Average heating coefficient of performance(COP) of the ground water source heat pump used in paprika cultivation was 3.7 and the glasshouse inside temperature was maintained at 21℃ of heating set up temperature. The heating energy consumptions per 10a were measured at 14,071L of light oil and 364㎾h of electric power for the control glasshouse and 35,082㎾h for the glasshouse applied heating package. As results, the heating cost of the glasshouse applied heating package was 87 percent lower than that of control glasshouse. The growths of paprika in glasshouses of control and applied heating package did not show any significant difference.