			Home About us Contact

Heat Transfer Surface (heat + transfer_surface)

Distribution by Scientific Domains

Engineering	73%
Chemistry	26%

Selected Abstracts

A Method for Measuring the Strength of Scale Deposits on Heat Transfer Surfaces

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2005
J. Y. M. Chew
The technique of fluid dynamic gauging has been successfully applied to assess the adhesion characteristics of thin (< 1 mm) layers of calcium sulphate deposits serving as mimics of mineral scales often found on heat transfer surfaces. The shear strength of the scale layers increased on ageing; layers aged for more than 14 hours could not be removed by the gauging fluid flow. The shear stresses imposed by the gauging flow have been shown to be reliably estimated by an analytical result, provided that the flow rate is measured. [source]

Adhesion and detachment characteristics of a TBAB hydrate solid on a heat transfer surface (Effect of concentration of TBAB solutions)

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2009
Tadafumi Daitoku
Abstract In air-conditioning systems, it is desirable that the liquid,solid phase change temperature of a cool energy storage material be approximately 10°C, with respect to improving the coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize a large heat capacity of the working fluids. A solid that adheres to the heat transfer surface forms a thermal resistance layer and significantly reduces the rate of cold storage; therefore, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removal of the solid phase from the heat transfer surface was investigated. Tetra-n-butylammonium bromide (TBAB) clathrate hydrate was used as a cold storage material and the effect of the TBAB solution concentration on the scraping force required to detach the adhered TBAB hydrate solid from the heat transfer surface was experimentally examined. The TBAB hydrate solids were broadly categorized into two types, and the scraping force required for removal of these two types of TBAB hydrate solid was different. The scraping force required for removal of the solid increased due to the effect of increasing the concentration of the TBAB solution. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20254 [source]

An effect of scraper shapes on detachment of solid adhered to cooling surface for formation of clathrate hydrate slurry

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2007
Tadafumi Daitoku
Abstract In air-conditioning systems, it is desirable that the liquid, solid phase change temperature of a cool energy storage material is approximately 10°C from the perspective of improving the coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize large heat capacity of working fluids. Since the solid that adheres to the heat transfer surface forms a thermal resistance layer and remarkably reduces the rate of cold storage, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removing the solid phase from the heat transfer surface was studied. Tetra-n-butylammonium bromide (TBAB) clathrate hydrate was used as a cold storage material. The effect of the scraper shapes on the scraping force for detachment of the adhered solid of TBAB hydrate to the heat transfer surface was examined experimentally. The TBAB hydrate solids were categorized broadly into two kinds of solids. The scraping force of the TBAB hydrate solid on the heat transfer surface was different for the two kinds of the TBAB hydrate solids. And the scraping force of the TBAB hydrate solid formed after scraping was improved by the modifying the scraper shape. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 489, 500, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20179 [source]

Behaviors of micro-layer in micro-channel boiling system applying laser extinction method

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 1 2006
Yoshio Utaka
Abstract To elucidate the mechanism and characteristics of boiling heat transfer in a micro-channel vaporizer, the experimental investigation of the micro-layer thickness that formed between the heating surface and vapor generated was important. The micro-layer thickness was measured applying the laser extinction method for channel gap sizes of 0.5, 0.3, and 0.15 mm. It was clarified that the gap size, the rate of bubble growth, and the distance from the incipient bubble site have an effect on the micro-layer thickness in a micro-channel boiling system. The initial micro-layer thickness grew with an increase of the velocity of bubble forefront to moderate the value of the velocity. In the region of greater velocity, the thickness was constant for each gap. The distributions of the initial thickness of micro-layer on the heat transfer surface were shown. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(1): 35,46, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20096 [source]

Boiling heat transfer in a narrow space controlled by punched interference plate

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2004
Ryohachi Shimada
Abstract An experiment on pool boiling in methanol was performed for a case in which the boiling space was controlled by an interference plate with many holes. The narrow space, 0.12 mm in thickness, between the heat transfer surface and the interference plate was hermetically sealed at the perimeter. Therefore, the vapor and liquid were only exchanged through the holes in the interference plate. The degree of superheat at the onset of boiling was 0.7 K without overshoot at 10-mm plate thickness, 1-mm hole diameter, and 3.85-mm hole pitch. The critical heat flux obtained was the same value without the interference plate mentioned above. The interference plate disturbed free convection and a superheat layer was provided under small heat flux on the heat transfer surface. The critical bubble diameter for the onset of boiling was decreased as the temperature of the superheat layer was increased. Thus, the degree of superheat at the onset of boiling was decreased. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(7): 462,471, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20028 [source]

An investigation of liquid film thickness during solutal Marangoni condensation using a laser absorption method: Absorption property and examination of measuring method

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2003
Yoshio Utaka
Abstract The objective of the study is to establish a method for measuring the thickness of thin condensates of liquid mixtures using a laser light absorption method during the process of water,ethanol Marangoni dropwise condensation. First, the extinction property of the test material, with unknown properties related to infrared laser light having a wavelength of 3.39µm, was measured. Next, measurements were made of the variations in condensate film thickness after the sweeping of the heat transfer surface by departing drops in the Marangoni dropwise condensation cycle. The precision of this method was investigated on the basis of the extinction coefficient of the test material and the thickness of the liquid film. Results showed that this method provides good precision and is applicable to the measurement of other similar materials. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(8): 700,711, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10124 [source]

Micro-bubble emission boiling from horizontal and vertical surfaces to subcooled parallel flow water

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 2 2003
Satoshi Kumagai
Abstract Heat removal of more than 10 MW/m2 in heat flux has been required in high-heat-generation equipment in nuclear fusion reactors. In some conditions of water subcooling and velocity, there appears an extraordinary high heat flux boiling in the transition boiling region. This boiling regime is called micro-bubble emission boiling (MEB) because many micro-bubbles are spouted from the heat transfer surface accompanying a huge sound. The study intent is to obtain heat transfer performance of MEB in horizontal and vertical heated surfaces to parallel flow of subcooled water, comparing with CHF of this system. Three types of MEB with different heat transfer performance and bubble behavior are observed according to the flow velocity and liquid subcooling. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(2): 130,140, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10077 [source]

Pool boiling on a superhydrophilic surface

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2003
Y. Takata
Abstract Titanium Dioxide, TiO2, is a photocatalyst with a unique characteristic. A surface coated with TiO2 exhibits an extremely high affinity for water when exposed to UV light and the contact angle decreases nearly to zero. Inversely, the contact angle increases when the surface is shielded from UV. This superhydrophilic nature gives a self-cleaning effect to the coated surface and has already been applied to some construction materials, car coatings and so on. We applied this property to the enhancement of boiling heat transfer. An experiment involving the pool boiling of pure water has been performed to make clear the effect of high wettability on heat transfer characteristics. The heat transfer surface is a vertical copper cylinder of 17 mm in diameter and the measurement has been done at saturated temperature and in a steady state. Both TiO2 -coated and non-coated surfaces were used for comparison. In the case of the TiO2 -coated surface, it is exposed to UV light for a few hours before experiment and it is found that the maximum heat flux (CHF) is about two times larger than that of the uncoated surface. The temperature at minimum heat flux (MHF) for the superhydrophilic surface is higher by 100 K than that for the normal one. The superhydrophilic surface can be an ideal heat transfer surface. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Comparison of performance of heat regenerators: Relation between heat transfer efficiency and pressure drop

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2001
Françoise Duprat
Abstract Heat regenerators transfer heat from one gas to another, with an intermediate storage in solids. The heat transfer surface for gas flow application should provide at the same time high surface area and low friction factor. Three geometries of heat transfer surface, monolith, stack of woven screens and bed of spheres, have been compared. Their performance was evaluated from the pressure drop of the heat regenerator working at a given heat transfer efficiency. The comparison was performed using numerical simulation and published measurements of heat transfer and flow friction characteristics. By adjusting the length and the period of the exchanger, it is possible to obtain the same heat transfer efficiency with the three geometries. Beds of spheres give very short and compact heat regenerators, working at high pressure drop. At the opposite, monoliths form long regenerators working at low pressure drop. Stacks of woven screens cover a wide range of performance: low porosity woven screens give high heat transfer efficiency and high pressure drop, while high porosity woven screens offer performance similar to that of the monoliths. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Experimental and Numerical Simulation Study of Heat Transfer Due to Confined Impinging Circular Jet

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2007
L. Chang-geng
Abstract An experimental and numerical simulation study of heat transfer due to a confined impinging circular jet is presented. In this research, a stainless steel foil heated disk was used as the heat transfer surface of a simulated chip, and the thermocouples were mounted symmetrically along the diameter of the foil to measure the temperature distribution on the surface. Driven by a small pump, a circular air jet (1.5,mm and 1,mm in diameter) impinged on the heat-transfer surface with middle and low Reynolds numbers. The parameters, such as Reynolds number and ratio of height-to-diameter, were changed to investigate the radial distribution of the Nusselt number and the characteristics of heat transfer in the stagnation region. Numerical computations were performed by using several different turbulence models. In wall bounded turbulent flows, near-wall modeling is crucial. Therefore, the turbulence models enhanced wall treatment, such as the RNG ,-, model, may be superior for modeling impingement flows. The numerical results showed reasonable agreement with the experimental data for local heat transfer coefficient distributions. The impinging jet may be an effective method to solve the cooling problem of high power density electronic packaging. [source]

Method of calculation of heat transfer coefficient of the heater in a circulating fluidized bed furnace

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2002
J.F. Lu
Abstract Knowledge of heat transfer coefficients is important in the design and operation of CFB boilers. It is the key to determining the area and the layout of the heat transfer surfaces in a CFB furnace. Local bulk density has a close relationship to the local heat transfer coefficient. Using a heat flux probe and bulk density sampling probe, the local bed to wall heat transfer coefficient in the furnace of a 75 t/h CFB boiler was measured. According to the experimental results and theoretical analysis of the facts that influence the heat transfer, the heat transfer coefficient calculation method for the CFB furnace was developed. The heat transfer surface configuration, heating condition, and the material density are considered in this method. The calculation method has been used in the design of CFB boilers with a capacity from 130 t/h to 420 t/h. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(7): 540,550, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10056 [source]

Experimental investigation into cavity-type inertial separators,a novel technique for development of subcompact circulating fluidized bed boilers

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2005
Animesh Dutta
Abstract Cavity-type inertial separators developed by GRI (Patent no. 2, 159, 949, Canada, 2002) were tested in a semi-industrial size circulating fluidized bed pilot plant operated at room temperature. Three rows of separators were hung from the roof of the pilot plant where one row was kept inside the riser and the others were kept in the primary separation chamber, located between the back-pass and the riser. Parameters measured were axial pressure drops along the height of the riser, vertical solids flux on the separator walls, lateral outwards solids flux in the riser with and without separator and local temperatures on the separator walls. A net downwards solids flux is on the inner wall of the separators; however, no downwards solids flux is on the outer walls of the separators. Heat transfer coefficients on the outer wall are found higher than those on the inner walls of the separator. It is also found that the presence of inertial separators not only provides additional heat transfer surfaces but also indirectly increases the heat transfer coefficients on the riser wall. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Impact of deposit ageing on thermal fouling: Lumped parameter model

AICHE JOURNAL, Issue 2 2010
Edward.
Abstract The thermal and hydraulic performance of heat exchangers can be seriously impaired by the formation of fouling deposits on the heat transfer surfaces. The thermal effect of fouling can be complicated when the deposit is subject to ageing, represented here as a change in deposit thermal conductivity (but not thickness) over time. In this article, we revisit the ageing concept for crude oil fouling proposed by Nelson (Refiner Nat Gas Manufacturer. 1934;13:271,276, 292,298), using a numerical model incorporating first order kinetics to generate quantitative comparisons of different ageing rates. Results are reported for lumped parameter systems (which also simulate point measurement methods commonly used in laboratory testing) that demonstrate that ageing can have a substantial influence on the rate of heat transfer and hence on the surface temperature and rate of fouling. Rapid ageing (compared with the rate of deposition) does not pose problems, but slow ageing, or the use of constant heat fluxes in experiments, can lead to modified thermal fouling behavior. It is concluded that deposit ageing dynamics should be considered alongside deposition rate dynamics when interpreting experimental fouling data and when modeling fouling behavior in support of heat exchanger design or operation. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]