• Title, Summary, Keyword: Heat of sublimation

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A study on the Analogy between Heat Transfer and Mass Transfer (열전달과 물질전달의 유사성에 관한 연구)

  • 유성연;노종광;정문기
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.10
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    • pp.2624-2633
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    • 1993
  • Mass transfer experiment by naphthalene sublimation method has great advantages in measurement of local transfer coefficients in the region of a three dimensional flow or for a model of complex geometry, which is considered to be very difficult with conventional heat transfer measurements. Mass transfer data obtained by naphthalene sublimation technique are converted to the heat transfer data through heat/mass transfer analogy. This analogy is valid for a simple or laminar flow, but new insight is needed when applying to a turbulent flow or complex flow such as separation, reattachment and recirculation, The purpose of this research is to investigate how geometries and flow conditions incorporate heat/mass transfer analogy. Mass transfer experiments are performed using naphthalene sublimation technique for a flat plate, a circular cylinder, and rectangular cylinders. And mass transfer data are compared with earlier heat transfer measurements for the same geometries. Usefulness of analogy relation between heat and mass transfer is examined with these results.

Measurements of Heat (Mass) Transfer Coefficient on the Surface of a Turbine Blade with n High Turning Angle Using Naphthalene Sublimation Technique (큰 회전각을 가지는 터빈 블레이드 표면에서 나프탈렌승화법을 이용한 열(물질)전달계수 측정)

  • Gwon, Hyeon-Gu;Lee, Sang-U;Park, Byeong-Gyu
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.8
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    • pp.1077-1087
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    • 2002
  • The heat (mass) transfer characteristics on the blade surface of a high-turning first-stage turbine rotor for power generation has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is developed successfully for the measurements of local sublimation depth on the curved surface In the leading edge region, there is a good agreement between the present heat (mass) transfer data and the previous result on a turbine blade with a moderate turning angle, but some discrepancies are found in the mid-chord heat (mass) transfer between the two results. The local heat (mass) transfer on the present suction surface is greatly enhanced due to an earlier boundary transition, compared with that on a turbine blade with a moderate turning angle, meanwhile there is only a slight change in the pressure-side heat (mass) transfer between the two different turbine rotors. In general, the heat (mass) transfer augmentation by the endwall vortices is found much higher on the suction surface than on the pressure surface.

A Naphthalene Sublimation Study on Heat/Mass Transfer for Flow over a Flat Plate

  • Park, Jong-Hark;Yoo, Seong-Yeon
    • Journal of Mechanical Science and Technology
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    • v.18 no.7
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    • pp.1258-1266
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    • 2004
  • It is important to completely understand heat/mass transfer from a flat plate because it is a basic element of heat/mass transfer. In the present study, local heat/mass transfer coefficient is obtained for two flow conditions to investigate the effect of boundary layer using the naphthalene sublimation technique. Obtained local heat/mass transfer coefficient is converted to dimensionless parameters such as Sherwood number, Stanton number and Colburn j-factor. These also are compared with correlations of laminar and turbulent heat/mass transfer from a flat plate. According to experimental results, local Sherwood number and local Stanton number are in much better agreement with the correlation of turbulent region rather than laminar region, which means analogy between heat/mass transfer and momentum transfer is more suitable for turbulent boundary layer. But average Sherwood number and average Colburn j-factor representing analogy between heat/mass transfer and momentum transfer are consistent with the correlation of laminar boundary layer as well as turbulent boundary layer.

QSPR analysis for predicting heat of sublimation of organic compounds (유기화합물의 승화열 예측을 위한 QSPR분석)

  • Park, Yu Sun;Lee, Jong Hyuk;Park, Han Woong;Lee, Sung Kwang
    • Analytical Science and Technology
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    • v.28 no.3
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    • pp.187-195
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    • 2015
  • The heat of sublimation (HOS) is an essential parameter used to resolve environmental problems in the transfer of organic contaminants to the atmosphere and to assess the risk of toxic chemicals. The experimental measurement of the heat of sublimation is time-consuming, expensive, and complicated. In this study, quantitative structural property relationships (QSPR) were used to develop a simple and predictive model for measuring the heat of sublimation of organic compounds. The population-based forward selection method was applied to select an informative subset of descriptors of learning algorithms, such as by using multiple linear regression (MLR) and the support vector machine (SVM) method. Each individual model and consensus model was evaluated by internal validation using the bootstrap method and y-randomization. The predictions of the performance of the external test set were improved by considering their applicability to the domain. Based on the results of the MLR model, we showed that the heat of sublimation was related to dispersion, H-bond, electrostatic forces, and the dipole-dipole interaction between inter-molecules.

A study of the color reproducibility and color fastness of digital textile printing for nylon sublimation transfer (나일론 승화전사 디지털 프린팅의 컬러 재현성 및 견뢰도에 관한 연구)

  • Choi, Gyung-Me;Kim, Ki-Hoon
    • The Research Journal of the Costume Culture
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    • v.26 no.5
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    • pp.754-763
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    • 2018
  • This study examined the color reproducibility and color fastness of digital textile printing for nylon sublimation transfer. After measuring the temperature and time suited to nylon sublimation transfer, the researchers conducted various tests for comparison and analysis including polyester transfer paper on polyester fabric to check dyeing characteristics, color change, sharpness, and the rubbing fastness of the dyeing samples for nylon sublimation transfer. These tests produced the following results. At $185^{\circ}C$ and $187^{\circ}C$, the sublimation transfer dyeing characteristics of nylon were similar to those of polyester and the researchers even observed superior color development in some colors; at a low temperature of $180^{\circ}C$, the sample that was worked on had the lowest level of color development. The examination of color difference (${\Delta}E$), which compared $L^*a^*b^*$ values, showed that the ${\Delta}E$ value of magenta was 10.34, that of yellow was 24.70, and that of black was 15.28. These results highlight the important role of heat treatment temperature and time on color development in nylon sublimation transfer. Concerning sharpness, the samples subjected to higher temperature heat treatment exhibited fewer color spreading phenomena around lines. Thus, dyeing properties and fastness can be enhanced by elongating time at low temperatures and shortening time at high temperatures; however, considering production time constraints as well as the need to produce industrially marketable quantities, the findings of this study suggest that the heat treatment temperature most suitable for nylon sublimation transfer is $187^{\circ}C$ for a duration of 50 seconds.

A Study on the Mass Transfer from a Square Cylinder Using Naphthalene Sublimation Technique (나프탈렌승화법을 이용한 사각관 주위에서의 물질전달에 관한 연구)

  • 유성연
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1300-1310
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    • 1990
  • Naphthalene sublimation technique is employed to investigate the mass transfer processes from a square cylinder at various Reynolds numbers and various angles of attack. Distribution of the local mass transfer coefficients on each face of the cylinder changes dramatically with the angle of attack. Such variation of local mass transfer rates closely connected with the complex flow phenomena such as stagnation, acceleration, separation, reattachment and vortex shedding. The average Sherwood number has a minimum value at 12.deg.-13.deg., and a maximum value at a=20.deg.-25.deg. A comparison of present mass transfer measurement with other heat transfer measurements, using the heat/mass transfer analogy, shows good agreement in average transfer rates, same trend but notable differences in local values. Therefore, naphthalene sublimation technique can be adopted to explore heat transfer processes in the complex flow situations, which is considered to be hardly possible with the conventional heat transfer measurements.

Local and Overall Heat Transfer Characteristics of Fin- Flat Tube Heat Exchanger with Vortex Generators

  • Yoo, Seong-Yeon;Chung, Min-Ho;Park, Dong-Seong
    • International Journal of Air-Conditioning and Refrigeration
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    • v.11 no.3
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    • pp.150-157
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    • 2003
  • Local and overall heat transfer characteristics of fin-flat tube heat exchangers with and without vortex generators were investigated. Local heat transfer coefficients were measured with the heat exchanger model using naphthalene sublimation technique. In case of a fin-flat tube heat exchanger without vortex generators, only the horseshoe vortices formed around tubes augment the heat transfer. On the other hand, longitudinal vortices created artificially by vortex generators additionally enhance heat transfer in case of a fin-flat tube heat exchanger with vortex generators. Overall heat transfer coefficients were measured with the prototypes of the fin-flat tube heat exchanger with and without vortex generators in a wind tunnel and results were compared with those of a fin-circular tube heat exchanger with wavy fin. Friction losses for heat exchangers were also measured and compared. The fin-flat tube heat exchanger with vortex generators is found to be more effective than the fin-circular tube heat exchanger with wavy fin.

Measurements of Endwall Heat(Mass) Transfer Coefficient in a Linear Turbine Cascade Using Naphthalene Sublimation Technique (나프탈렌승화법을 이용한 터빈 익렬 끝벽에서의 열(물질)전달계수 측정)

  • Lee, Sang-U;Jeon, Sang-Bae;Park, Byeong-Gyu
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.3
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    • pp.356-365
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    • 2001
  • Heat (mass) transfer characteristics have been investigated on the endwall of a large-scale linear turbine cascade. Its profile is based on the mid-span of the first-stage rotor blade in a industrial gas turbine. By using the naphthalene sublimation technique, local heat (mass) transfer coefficients are measured for two different free-stream turbulence intensities of 1.3% and 4.7%. The results show that local heat (mass) transfer Stanton number is widely varied on the endwall, and its distribution depends strongly on the three-dimensional vortical flows such as horseshoe vortices, passage vortex, and corner vortices. From this experiment, severe heat loads are found on the endwall near the blade suction side as well as near the leading and trailing edges of the blade. In addition, the effect of the free-stream turbulence on the heat (mass) transfer is also discussed in detail.

An Experimental Study on Heat Transfer Enhancement of Cross Flow Heat Exchanger Using Screen (스크린을 이용한 직교류 열교환기의 열전달 촉진에 관한 연구)

  • Yoo, Seong-Yeon;Jang, Kwang-Il;Kwon, Hwa-Kil
    • Proceedings of the SAREK Conference
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    • pp.185-190
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    • 2007
  • For the successful design of heat exchangers, it is very important to understand local heat transfer characteristics on the circular cylinder of the cross flow heat exchangers. In this study, the heat exchanger using screen is developed to enhance heat transfer. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients in the heat exchanger. The experiments are performed for single circular tube, in-line array tube bank with and without heat transfer promoter. Local Nusselt numbers of single circular tube and tube bank with heat transfer promoter are investigated and compared to those of without heat transfer promoter.

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Heat Transfer Enhancement in Cross-flow Heat Exchanger Using Vortex Generator (와류발생기를 사용한 직교류 열교환기의 열전달 촉진)

  • Yoo, Seong-Yeon;Kwon, Hwa-Kil;Lee, Sang-Sub;Kim, Byeong-Chae;Park, Dong-Seong
    • Proceedings of the KSME Conference
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    • pp.61-66
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    • 2003
  • Fouling is very serious problem in heat exchanger because it rapidly deteriorates the performance of heat exchanger. Cross-flow heat exchanger with vortex generators is developed, which enhance heat transfer and reduce fouling. In the present heat exchanger, shell and baffle are removed from the conventional shell-and-tube heat exchanger. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients. The experiments are performed for single circular tube, staggered array tube bank and in-line array tube bank with and without vortex generators. Local and average Nusselt numbers of single tube and tube bank with vortex generator are investigated and compared to those of without vortex generator.

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