• Title/Summary/Keyword: thermal response test

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Thermal Response Property of Grout Materials from In-situ Test and Temperature Variation of Ground Heat Exchanger (그라우트 재료별 열응답 특성 및 열교환기 운전온도 변화)

  • Kim, Kap-Duk;Lee, Soung-Ju;Yun, Yeo-Sang
    • Proceedings of the SAREK Conference
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    • 2008.06a
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    • pp.769-775
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    • 2008
  • The objective of this report is to determine the difference of thermal response that grouted two different materials, and compare the simulation result of the length of total ground heat exchanger length that using the ground thermal conductivity. And also to know heat exchange variation of ground heat exchanger temperature that measured with various test depth. The result shows that the test hole grouted with water permeable material got better thermal response than grouted with water impermeable material. However, with consideration of ingnore for the initial 12 hour data, the test hole grouted with impermeable material has larger thermal conductivity than the other. By former thermal conductivity, simulated data by engineering program shows only 3.4% difference or less. This result shows that ground thermal conductivity is not the main variables for the design program of ground heat exchanger. At the cooling or heating mode, base on the depth of -150m, the ground heat exchanger has best temperature at $-90{\sim}-60m$ and than getting worse because of entering water heat exchanged with leaving water in the same hole.

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An Experimental Study of Thermal Response of Sprinklers (스프링클러의 열응답성에 관한 실험적 연구)

  • 한용식;김명배
    • Proceedings of the Korea Institute of Fire Science and Engineering Conference
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    • 1996.11a
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    • pp.68-71
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    • 1996
  • The thermal response of sprinkler is characterized by the response time index(RTI). The RTI represents the product of the thermal time constant for the heat responsive element of a sprinkler and the square root of the hot air velocity at plunge test. A plunge test is adapted for measuring RTI, wherein a sprinkler is suddenly immersed in the steady flow in the test section of a hot air tunnel. The method of measurements of the response parameters is presented.

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Evaluation of Thermal Conductivity for Grout/Soil Formation Using Thermal Response Test and Parameter Estimation Models (열응답 시험과 변수 평가 모델을 이용한 그라우트/토양 혼합층의 열전도도 산정)

  • Sohn Byong Hu;Shin Hyun Jun;An Hyung Jun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.2
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    • pp.173-182
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    • 2005
  • The Performance of U-tube ground heat exchanger for geothermal heat Pump systems depends on the thermal properties of the soil, as well as grout or backfill materials in the borehole. In-situ tests provide a means of estimating some of these properties. In this study, in-situ thermal response tests were completed on two vertical boreholes, 130 m deep with 62 mm diameter high density polyethylene U-tubes. The tests were conducted by adding a monitored amount of heat to water over a $17\~18$ hour period for each vertical boreholes. By monitoring the water temperatures entering and exiting the loop and heat load, overall thermal conductivity values of grout/soil formation were determined. Two parameter estimation models for evaluation of thermal response test data were compared when applied on the same temperature response data. One model is based on line-source theory and the other is a numerical one-dimensional finite difference model. The average thermal conductivity deviation between measured data and these models is of the magnitude $1\%$ to $5\%$.

Evaluation of performance of closed-loop vertical ground heat exchanger by In-situ thermal response test (현장 열응답 시험을 통한 수직 밀폐형 지중열교환기의 성능 평가)

  • Lee, Chul-Ho;Park, Moon-Seo;Kwak, Tae-Hoon;Choi, Hang-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.03a
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    • pp.229-239
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    • 2010
  • Performing a series of in-situ thermal response tests, the effective thermal conductivity of six vertical closed-loop ground heat exchangers was experimentally evaluated and compared each other, which were constructed in a test bed in Wonju. To compare thermal efficiency of the ground heat exchangers in field, the six boreholes were constructed with different construction conditions: grouting materials (cement vs. bentonite), different additives (silica sand vs. graphite) and the shape of pipe-sections (general U-loop type vs. 3 pipe-type). From the test results, it can be concluded that cement grouting has a higher effective thermal conductivity than that of bentonite grouting, and the efficiency of graphite better performs over silica sand as a thermally-enhancing addictive. In addition, a new 3 pipe-type heat exchanger provides less thermal interference between the inlet and outlet pipe than the conventional U-loop type heat exchanger, which results in superior thermal performance.

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A study on thermal behavior of energy textile by performing in-situ thermal response test and numerical simulation (현장 열응답 시험과 수치해석을 통한 터널에 적용된 에너지 텍스타일의 열적 거동 연구)

  • Lee, Chul-Ho;Park, Moon-Seo;Min, Sun-Hong;Jeoung, Jae-Hyeung;Choi, Hang-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09a
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    • pp.325-335
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    • 2010
  • A new geothermal energy source obtained from a tunnel structure has been studied in this paper. The geothermal energy is extracted through a textile-type ground heat exchanger named "Energy Textile" that is installed between a shotcrete layer and a guided drainage geotexitle. A test bed was constructed in an abandoned railway tunnel to verify the geothermal heat exchanger system performed by the energy textile. To evaluate the applicability of the energy textile, we measured the thermal conductivity of shotcrete and lining samples which were prepared in accordance with a common mixture design. An overall performance of the energy textile installed in the test bed was evaluated by carrying out a series of in-situ thermal response test. In addition, a 3-D finite volume analysis (FLUENT) was adopted to simulate the operation of the ground heat exchanger being encased in the energy textile with the consideration of the effect of the shotcrete and lining thermal conductivity.

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Effect of initial ground temperature measurement on the design of borehole heat exchanger (초기 지중온도 측정이 지중 열교환기 설계에 미치는 영향)

  • Song, Yoon-ho;Kim, Seong-Kyun;Lee, Kang-Kun;Lee, Tae-Jong
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.600-603
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    • 2009
  • We compared relative importance of thermal conductivity and initial ground temperature in designing borehole heat exchanger network and also we test accuracy of ground temperature estimation in thermal response test using a proven 3-D T-H modeler. The effect of error in estimating ground temperature on calculated total length of borehole heat exchanger was more than 3 times larger than the case of thermal conductivity in maximum 20% error range. Considering 10% of error in estimating thermal conductivity is generally acceptable, we have to define the initial ground temperature within 5% confidence level. Utilizing the mean annual ground surface temperature and the geothermal gradient map compiled so far can be a economic way of estimating ground temperature with some caution. When performing thermal response test for estimating ground temperature as well as measuring thermal conductivity, minimum 100 minutes of ambient circulation is required, which should be even more in case of very cold and hot seasons.

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An Experimental Study on the Thermal Performance Measurement of Vertical Borehole Heat Exchanger(BHE) (수직형 지열 열교환기(BHE)의 열성능 측정에 관한 실험적 연구)

  • Lim Kyoung-Bin;Lee Sang-Hoon;Soung Nak-Won;Lee Chang-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.8 s.251
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    • pp.764-771
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    • 2006
  • Knowledge of ground thermal properties is most important for the proper design of large BHE(borehole heat exchanger) systems. Thermal response tests with mobile measurement devices were first introduced in Sweden and USA in 1995. Thermal response tests have so far been used primarily for in insitu determination of design data for BHE systems, but also for evaluation of grout material, heat exchanger types and ground water effects. The main purpose has been to determine insitu values of effective ground thermal conductivity, including the effect of ground-water flow and natural convection in the boreholes. Test rig is set up on a small trailer, and contains a circulation pump, a heater, temperature sensors and a data logger for recording the temperature data. A constant heat power is injected into the borehole through the pipe system of test rig and the resulting temperature change in the borehole is recorded. The recorded temperature data are analysed with a line-source model, which gives the effective insitu values of rock thermal conductivity and borehole thermal resistance.

Performance-based comparison of energy pile of various heat exchange pipe arrangement by in-situ thermal response test (현장 열응답 시험을 통한 에너지파일의 열교환파이프 배열 방식에 따른 성능 비교)

  • Min, Sunhong;Koh, Hyungseon;Yoo, Jaihyun;Jung, Kyoungsik;Lee, Youngjin;Choi, Hangseok
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.05a
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    • pp.196.1-196.1
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    • 2011
  • In this study, a test bed was constructed in order to evaluate thermal efficiency of the energy pile which carries out combined roles of a structural foundation and of a heat exchanger. The energy pile in this study is designed as a large-diameter drilled shaft equipped with the heat exchange pipes which configures a W-shape and an S-shape. The drilled shaft reached to the depth of 60 m whilst the heat exchange pipes were installed to about 30 m deep from the ground surface. The W-shaped and S-shaped heat exchange pipes were installed in the opposite sections of the same drilled shaft. In-situ thermal response tests were performed for both the shapes of heat exchange pipes. To avoid underestimating the thermal performance due to hydration heat of concrete inside the drilled shaft, the in-situ thermal response tests for the energy pile were performed after four weeks since the installation of the energy pile.

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Influences of Power Fluctuation on In-Situ Ground Thermal Response Testing (지중 열반응 현장시험에서 소비전력 변동의 영향)

  • Kim, Jin-Sang;Park, Keun-Woo
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.707-712
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    • 2006
  • Knowing the ground thermal conductivity is very importnat in designing ground heat exchangers. Knowledge of the ground soil and rock composition information dose not guarantee the prediction of accurate thermal information. In Situ testing of ground heat exchangers is becoming popular. However, in situ testing are performed at construction sites in real life. Adequate data collection and analysis are not easy mainly due to poor power quality. Power fluctuation also causes the fluctuation of received data. The power quality must be maintained during the entire in situ testing processes. To accurately analyse the test data, the understanding of the response of the power fluctuation is essential. Testing under the power quality varied by tester is very difficult. Analyzing power variation by numerical simulation is a realistic option. By varying power in a sinosuidal manner, its effects on predicting thermal conductivity from thermal response plots made from the test data are examined.

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Transient Heat Flux Evaluation of Underwear for Protective Clothing using Sweating Manikin (발한 마네킹을 이용한 보호복용 언더웨어의 동적(Transient) 열류량 평가)

  • Park, Hye-Jun;Kim, Hyun-Jung;Hong, Kyung-Hi
    • Journal of the Korean Society of Clothing and Textiles
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    • v.32 no.1
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    • pp.157-165
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    • 2008
  • Transient thermal response of five types of underwear(cotton jersey, wool jersey, nylon jersey, cotton mesh and polyester mesh) for a protective coverall is evaluated using a sweating thermal manikin. Experimental protocol for transient thermal response of the sweating thermal manikin was also proposed. As results, it was found that steady state thermal response from sweating thermal manikin was not sensitive enough to evaluate thermal comfort of the experimental garments. However, when half time is used as an index of the heat flux change in transient thermal response, difference was found among underwear materials. Half time of cotton was the shortest and heat transfer of cotton was the fastest followed by polyester mesh, cotton jersey, nylon jersey and wool jersey. Dynamic thermal response of wool underwear was quite different from that of cotton underwear. Wool shows quite less heat flow at the initial stage, however, moisture permeability of wool was higher than cotton at the later stage. It was difficult to distinguish surface temperature difference visually using thermogram taken right before the completion of dry and wet test in steady state thermal response.