Heat Transfer Analysis of Fin Tube
Energy Technology Data Exchange (ETDEWEB)
Jeon, Woo-Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Choi, Cheng-Ryul [ELSOLTEC Co., Yongin (Korea, Republic of)
2015-10-15
This paper describes a preliminary numerical analysis of fin tube used for a heat exchanger of the air-water cooling system. The internal flow in a fin tube is steam and the external of the fin is cooled by air. Cooling system in a nuclear power plant can be divided into two categories; 1) active pump driven system powered by alternating current and 2) passive cooling system drived by natural circulation phenomena. After the accident in Hukushima Nuclear Power Plants, the importance of the passive cooling system that can provide a long-term cooling of reactor decay heat during station blackout condition is emphasized. However, the effectiveness of passive cooling system based on cooling water is limited by the capacity of water storage tank. To overcome the limit due to the exhaustion of the cooling water, an natural convection air cooling system is proposed. As the air operated cooling system utilizes natural circulation phenomena of air, it does not require cooling water. However, the heat transfer area of the air operated cooling system should be increased much as the heat removal capacity per unit area is much lower than that of water cooling system. The air-water combined cooling system can resolve this excess increase of the heat transfer area in the air operated cooling system. This air-water cooling system can be also used in the passive containment cooling system. The effect of design parameters such as fin tube arrangement, the fin height, and pitch has been analyzed and the chimney effect on the simulation of heat transfer in a heat exchanger is evaluated. The internal flows in a fin tube heat exchanger for natural circulation flow condition and forced convection (suction) condition were investigated.
Flow and heat transfer enhancement in tube heat exchangers
Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.
2015-11-01
The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.
Heat transfer and thermal stress analysis in grooved tubes
Indian Academy of Sciences (India)
The maximum thermal stress ratio positions inside the tube have been indicated as MX for all investigated cases. In the light of the thermal stress values, various designs can be applied to reduce thermal stress in grooved tubes. Keywords. Heat transfer; thermal stress; grooved tubes. 1. Introduction. Heat transfer in pipe flow ...
Heat transfer and fluid friction in bundles of twisted tubes
Dzyubenko, B. V.; Dreitser, G. A.
1986-06-01
The results of heat-transfer and friction studies in bundles of twisted tubes and rods with spiral wire-wrap spacers are analyzed, and recommendations are given for calculating the heat-transfer coefficient in heat exchangers using twisted tubes.
Heat transfer and thermal stress analysis in grooved tubes
Indian Academy of Sciences (India)
Heat transfer and thermal stresses, induced by temperature differencesin the internally grooved tubes of heat transfer equipment, have been analysed numerically. The analysis has been conducted for four different kinds of internally grooved tubes and three different mean inlet water velocities. Constant temperature was ...
A novel investigation of heat transfer characteristics in rifled tubes
Jegan, C. Dhayananth; Azhagesan, N.
2017-12-01
The experimental investigation of heat transfer of water flowing in a rifled tube was explored at different pressures and at various operating conditions in a rifled tube heat exchanger. The specifications for the inner and outer diameters of the inner tube are 25.8 and 50.6 mm, respectively. The working fluids used in shell side and tube side are cold and hot water. The rifled tube was made of the stainless steel with 4 ribs, 50.6 mm outer diameter, 0.775 mm rib height, 58o helix angle and the length 1500 mm. The effect of pressure, wall heat flux and friction factor were discussed. The results confirm that even at low pressures the rifled tubes has an obvious enhancement in heat transfer compared with smooth tube. Results depicts that the Nusselt number increases with Reynolds number and the friction factor decreases with increase in Reynolds number and the heat transfer rate is higher for the rifled tube when compared to smooth tube, because of strong swirl flow due to centrifugal action. It also confirms that, the friction factor obtained from the rifled tube is significantly higher than that of smooth tube.
Heat transfer enhancement of a single row of tube
Directory of Open Access Journals (Sweden)
Tsutsui Takayuki
2017-01-01
Full Text Available A rod was positioned upstream of a circular cylinder to enhance its heat transfer and reduce its drag in air stream. The results are increasing the overall heat transfer by 40% over and reducing the drag by 30% the value for a single circular cylinder. In the present, this technique applied to a single row of tubes. Heat transfer enhancement and drag reduction are important factor for multi-tube heat exchanger. The present study investigated the heat transfer and surface pressure characteristics of each tube for single row of tubes under various numbers of tubes, pitch and Reynolds number. The tube diameter, D, was 20 mm, and the rod diameter was 5 mm. The distance between the center axes of the rod and the tube was 30mm. The Reynolds number based on D ranged from 5.3×103 to 2.1×104. The result is that this technique is effective for heat transfer enhancement and drag reduction of row of tube.
Local Heat Transfer for Finned-Tube Heat Exchangers using Oval Tubes
Energy Technology Data Exchange (ETDEWEB)
O' Brien, James Edward; Sohal, Manohar Singh
2000-08-01
This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with either a circular tube or an elliptical tube in crossflow. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.56 x 10-3 to 15.6 x 10-3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 630 – 6300 with a duct height of 1.106 cm and a duct width-toheight ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. The elliptical tube had an aspect ratio of 3:1 and a/H equal to 4.33. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of circular and oval tubes and their relationship to the complex horseshoe vortex system that forms in the flow stagnation region. Fin surface stagnation-region Nusselt numbers are shown to be proportional to the square-root of Reynolds number.
Heat transfer enhancement in two-start spirally corrugated tube
Directory of Open Access Journals (Sweden)
Zaid S. Kareem
2015-09-01
Full Text Available Various techniques have been tested on heat transfer enhancement to upgrade the involving equipment, mainly in thermal transport devices. These techniques unveiled significant effects when utilized in heat exchangers. One of the most essential techniques used is the passive heat transfer technique. Corrugations represent a passive technique. In addition, it provides effective heat transfer enhancement because it combined the features of extended surfaces, turbulators and artificial roughness. Therefore, A Computational Fluid Dynamics was employed for water flowing at low Reynolds number in spiral corrugated tubes. This article aimed for the determination of the thermal performance of unique smooth corrugation profile. The Performance Evaluation Criteria were calculated for corrugated tubes, and the simulation results of both Nusselt number and friction factor were compared with those of standard plain and corrugated tubes for validation purposes. Results showed the best thermal performance range of 1.8–2.3 for the tube which has the severity of 45.455 × 10−3 for Reynolds number range of 100–700. The heat transfer enhancement range was 21.684%–60.5402% with friction factor increase of 19.2–36.4%. This indicated that this creative corrugation can improve the heat transfer significantly with appreciably increasing friction factor.
Laminar fluid flow and heat transfer in a fin-tube heat exchanger with vortex generators
Energy Technology Data Exchange (ETDEWEB)
Yanagihara, J.I.; Rodriques, R. Jr. [Polytechnic School of Univ. of Sao Paolo, Sao Paolo (Brazil). Dept. of Mechanical Engineering
1996-12-31
Development of heat transfer enhancement techniques for fin-tube heat exchangers has great importance in industry. In recent years, heat transfer augmentation by vortex generators has been considered for use in plate fin-tube heat exchangers. The present work describes a numerical investigation about the influence of delta winglet pairs of vortex generators on the flow structure and heat transfer of a plate fin-tube channel. The Navier-Stokes and Energy equations are solved by the finite volume method using a boundary-fitted coordinate system. The influence of vortex generators parameters such as position, angle of attack and aspect ratio were investigated. Local and global influences of vortex generators in heat transfer and flow losses were analyzed by comparison with a model using smooth fin. The results indicate great advantages of this type of geometry for application in plate fin-tube heat exchangers, in terms of large heat transfer enhancement and small pressure loss penalty. (author)
Double tube heat exchanger with novel enhancement: part II—single phase convective heat transfer
Tiruselvam, R.; Chin, W. M.; Raghavan, Vijay R.
2012-08-01
The study is conducted to evaluate the heat transfer characteristics of two new and versatile enhancement configurations in a double tube heat exchanger annulus. The novelty is that they are usable in single phase forced convection, evaporation and condensation. Heat transfer coefficients are determined by the Wilson Plot technique in laminar and turbulent flow and correlations are proposed for Nusselt numbers. Comparisons are then made between heat transfer and flow friction.
Suggestion of a New Empirical Correlation to predict Pool Boiling Heat Transfer on Tandem Tubes
Energy Technology Data Exchange (ETDEWEB)
Kang, Myeong-Gie [Andong National Univ., Andong (Korea, Republic of)
2014-10-15
Most studies were focused on the bundles consisting of many tubes for application to a flooded evaporator. Along with the tube spacing, its location is also of interest. Many researchers have been investigated the effect of tube spacing on heat transfer for the tube bundles and the tandem tubes. The heat transfer on the upper tube of the tubes is enhanced compared with the single tube. However, the maximum heat transfer coefficient of the upper tube decreases, increases, or negligible with increasing tube pitch ( P ) in pool boiling. According to Ribatski et al. the spacing effects on the heat transfer became relevant as the tubes come closer to each other at the low heat fluxes. The effect of tube array on heat transfer enhancement was also studied for application to the flooded evaporators. Since the source of the convective flow in pool boiling is the lower heated tube, the heat transfer change due to the heat flux of the lower tube ( q{sub L}) is of interest. Kumar et al. carried an experimental study and developed a model to predict the heat transfer coefficient of individual tube in a multi-tube row and the bundle heat transfer coefficient. Ustinov et al. investigated effects of the heat flux of lower tube on pool boiling of the upper tube. They used microstructure-R134a or FC-3184 combinations and identified that the increase in the heat flux of the lower tube decreased the superheat (T{sub sat} ) of the upper tube. Summarizing the previous results it can be stated that heat transfer coefficients are highly dependent on the tube geometry and the heat flux of the lower tube. As shown in Table 1 most published studies were for the tandem tubes in a vertical column arrangement. In general, tubes are not in a vertical plane. Therefore, the present study is focused on the quantification of the combined effects of the tube pitch and the elevation angle of the tubes and the heat flux of the lower tube on pool boiling heat transfer on tandem tubes. To the present
Turbulent Heat Transfer Behavior of Nanofluid in a Circular Tube Heated under Constant Heat Flux
Directory of Open Access Journals (Sweden)
Shuichi Torii
2010-01-01
Full Text Available The aim of the present study is to disclose the forced convective heat transport phenomenon of nanofluids inside a horizontal circular tube subject to a constant and uniform heat flux at the wall. Consideration is given to the effect of the inclusion of nanoparticles on heat transfer enhancement, thermal conductivity, viscosity, and pressure loss in the turbulent flow region. It is found that (i heat transfer enhancement is caused by suspending nanoparticles and becomes more pronounced with the increase of the particle volume fraction, (ii its augmentation is affected by three different nanofluids employed here, and (iii the presence of particles produces adverse effects on viscosity and pressure loss that also increases with the particle volume fraction.
Development of Empirical Correlation to Calculate Pool Boiling Heat Transfer of Tandem Tubes
Energy Technology Data Exchange (ETDEWEB)
Kang, Myeong-Gie [Andong National University, Andong (Korea, Republic of)
2015-10-15
The heat exchanging tubes are in vertical alignment. For the cases, the upper tube is affected by the lower tube. Since heat transfer is closely related to the conditions of tube surface, bundle geometry, and liquid, lots of studies have been carried out for the several decades to investigate the combined effects of those factors on pool boiling heat transfer. One of the most important parameters in the analysis of a tube array is the pitch ( P ) between tubes. Many researchers have been investigated its effect on heat transfer enhancement for the tube bundles and the tandem tubes. The effect of a tube array on heat transfer enhancement was also studied for application to the flooded evaporators. Cornwell and Schuller studied the sliding bubbles by high speed photography to account the enhancement of heat transfer observed at the upper tubes of a bundle. The study by Memory et al. shows the effects of the enhanced surface and oil adds to the heat transfer of tube bundles. They identified that, for the structured and porous bundles, oil addition leads to a steady decrease in performance. The flow boiling of n-pentane across a horizontal tube bundle was investigated experimentally by Roser et al. They identified that convective evaporation played a significant part of the total heat transfer. The fouling of the tube bundle under pool boiling was also studied by Malayeri et al. They identified that the mechanisms of fouling on the middle and top heater substantially differ from those at the bottom heater.
Heat Transfer Enhancement for Finned-tube Heat Exchangers with Winglets
Energy Technology Data Exchange (ETDEWEB)
O' Brien, James Edward; Sohal, Manohar Singh
2000-11-01
This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with a circular tube and/or a delta-winglet pair. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.51 x 10-3 to 14.0 x 10-3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 670 – 6300 with a duct height of 1.106 cm and a duct width-toheight ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of a circular tube, a delta-winglet pair, and a combination of a circular tube and a delta-winglet pair. Comparisons of local and average heat transfer distributions for the circular tube with and without winglets are provided. Overall mean finsurface Nusselt-number results indicate a significant level of heat transfer enhancement associated with the deployment of the winglets with the circular cylinder. At the lowest Reynolds numbers (which correspond to the laminar operating conditions of existing geothermal air-cooled condensers), the enhancement level is nearly a factor of two. At higher Reynolds numbers, the enhancement level is close to 50%.
Effects of Angle of Rotation on Pool Boiling Heat Transfer of V-shape Tube Bundle
Energy Technology Data Exchange (ETDEWEB)
Kang, Myeong-Gie [Andong National University, Andong (Korea, Republic of)
2016-10-15
The most important facility for the systems is a passive heat exchanger that transfers core decay heat to the cold water in a water storage tank under atmospheric pressure. Since the space for the installation of the heat exchanger is usually limited, developing more efficient heat exchangers is important. In general, pool boiling is generated on the surface of the heat exchanging tube. The major design parameter of the heat exchanger is a tube arrangement. The upper tube is affected by the lower tube and the enhancement of the heat transfer on the upper tube is estimated by the bundle effect. Since heat transfer is related to the conditions of a tube surface, bundle geometries, and a liquid type, lots of studies have been carried out for the combinations of those parameters. An experimental study was performed to investigate the effects of the angle of rotation on pool boiling heat transfer of a V-shape tube bundle. For the test, two smooth stainless steel tubes of 19 mm outside diameter and the water at atmospheric pressure were used. The enhancement of the heat transfer is clearly observed when the angle becomes to 90° where the upper tube has the maximum region of influence by the lower tube. The convective flow and liquid agitation enhance heat transfer while the coalescence of the bubbles deteriorates heat transfer.
Directory of Open Access Journals (Sweden)
Yoshinori Itaya
2017-06-01
Full Text Available Heat and mass transfer of a LiBr/water absorption heat pump system (AHP was experimentally studied during working a heating-up mode. The examination was performed for a single spiral tube, which was simulated for heat transfer tubes in an absorber. The inside and outside of the tube were subjected to a film flow of the absorption liquid and exposed to the atmosphere, respectively. The maximum temperature of the absorption liquid was observed not at the entrance but in the region a little downward from the entrance in the tube. The steam absorption rate and/or heat generation rate in the liquid film are not constant along the tube. Hence the average convective heat transfer coefficient between the liquid film flowing down and the inside wall of the tube was determined based on a logarithmic mean temperature difference between the tube surface temperature and the film temperature at the maximum temperature location and the bottom. The film heat and mass transfer coefficients rose with increasing Reynolds number of the liquid film stream. The coefficients showed opposite trend to the empirical correlation reported for laminar film flow on a straight smooth tube in a refrigeration mode in the past work. The fact can be caused due to a turbulent promotion effect of the liquid in a spiral tube.
Flow and heat transfer investigations in swirl tubes for gas turbine blade cooling
Biegger, Christoph
2017-01-01
A swirl tube is a very effective cooling technique for high thermal loaded components like gas turbine blades. Such a tube consists of one or more tangential inlet jets, which induce a highly 3D swirling flow. This swirling flow is characterized by large velocities near the wall and an enhanced turbulence in the tube which both increase the convective heat transfer. In the present work, the flow phenomena and the heat transfer in swirl tubes are studied experimentally and numerically. Therefo...
Measurement of Heat Transfer Coefficients in an Agitated Vessel with Tube Baffles
M. Dostál; Petera, K.; Rieger, F.
2010-01-01
Cooling or heating an agitated liquid is a very common operation in many industrial processes. A classic approach is to transfer the necessary heat through the vessel jacket. Another option, frequently used in the chemical and biochemical industries is to use the heat transfer area of vertical tube baffles. In large equipment, e.g. fermentor, the jacket surface is often not sufficient for large heat transfer requirements and tube baffles can help in such cases. It is then important to know th...
Jiao, Anjun; Zhang, Yuwen; Ma, Hongbin; Critser, John
2010-01-01
Heat and mass transfer in a circular tube subject to the boundary condition of the third kind is investigated. The closed form of temperature and concentration distributions, the local Nusselt number based on the total external heat transfer and convective heat transfer inside the tube, as well as the Sherwood number were obtained. The effects of Lewis number and Biot number on heat and mass transfer were investigated. PMID:20862211
Numerical Study on the Effect of Tube Rows on the Heat Transfer Characteristic of Dimpled Fin
Directory of Open Access Journals (Sweden)
Xuehong Wu
2014-09-01
Full Text Available The dimpled fin has excellent heat transfer performance and has attracted a lot of attention to apply on the fin and tube heat exchanger. A study presents to investigate the effects of number of tube rows on the air-side heat transfer characteristics of dimpled fin for velocity ranging from 1 to 3 m/s. The Q/ΔP and Q/((ΔP × V are used to evaluate the heat transfer performance of the heat exchanger. The results show that the dimpled arrangement can change the mainstream direction, increase the disturbance, and enhance the heat transfer. With the increase of the number of tube rows, the average Nusselt number decreases and Q/ΔP and Q/((ΔP × V increase gradually. Compared with the multipipe tube rows, the performance of two-row tube is better.
Air-side heat transfer characteristics of spiral-type circular fin-tube heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Lee, Mooyeon; Kang, Taehyung; Kim, Yongchan [Department of Mechanical Engineering, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-713 (Korea)
2010-03-15
The objective of this study is to investigate the air-side heat transfer characteristics of spiral-type circular fin-tube heat exchangers used as evaporators in household refrigerators. The j-factors of the tested heat exchangers under non-frosting conditions were measured by varying the fin pitch, number of tube rows, and fin alignment. The j-factors of the spiral-type circular fin-tube heat exchangers were analyzed as a function of heat exchanger geometries and then compared with those of the flat plate fin-tube heat exchangers with discrete fins. Two empirical correlations of the j-factors were developed separately for the inline and the staggered fin alignment as a function of the Reynolds number, number of tube rows, and dimensionless fin pitch normalized by the hydraulic diameter. The mean deviation of the predictions using the present correlations from the measured data was 4.78% for the inline fin alignment and 6.02% for the staggered fin alignment. (author)
Energy Technology Data Exchange (ETDEWEB)
Melnikov, I.A., E-mail: corpuskula@gmail.com; Sviridov, E.V.; Sviridov, V.G.; Razuvanov, N.G.
2016-11-15
Highlights: • Local and averaged heat transfer coefficient are measured. • Free convection influence on MHD-flow is investigated. • The region with the free convection effect of MHD-heat transfer is found. • Temperature low-frequency fluctuations of abnormally high amplitude are detected. • Analysis of the MHD-heat transfer experimental data is performed. - Abstract: The article is devoted to the results of experimental investigation of heat transfer for a downward mercury flow in a vertical round tube in the presence of a transverse magnetic with non-uniform heat flux along the tube circumference.
Bizzy, Irwin; Setiadi, Rachmat
2013-01-01
To reduce production costs, the design of heat exchanger is very effective in advance of buying a ready-made exchanger. The design of a calculation of the dimensions of heat exchanger shell and tube type using computerized analysis method Heat Transfer Research Inc.. (HTRI) and manual calculation methods of analysis. Dimensional calculation of heat exchanger is intended to determine the quality of a heat exchanger based on the overall heat transfer coefficient, fouling factors, and pressure d...
Simple heat transfer correlations for turbulent tube flow
Directory of Open Access Journals (Sweden)
Taler Dawid
2017-01-01
Full Text Available The paper presents three power-type correlations of a simple form, which are valid for Reynolds numbers range from 3·103 ≤ Re ≤ 106, and for three different ranges of Prandtl number: 0.1 ≤ Pr ≤ 1.0, 1.0 < Pr ≤ 3.0, and 3.0 < Pr ≤ 103. Heat transfer correlations developed in the paper were compared with experimental results available in the literature. The comparisons performed in the paper confirm the good accuracy of the proposed correlations. They are also much simpler compared with the relationship of Gnielinski, which is also widely used in the heat transfer calculations.
Local heat transfer in an in-line tube bundle with asymmetrical flow
DEFF Research Database (Denmark)
Meyer, Knud Erik
1999-01-01
Measurements of the local heat transfer in themiddle of a small in-line tube bundle with longitudinal to transverse pitches of $1.5\\times 1.8$ are performed at a Reynolds number of $30\\,000$. Asymmetrical distributions of the local heat transfer are found. The distributions are in good agreement...... with earlier flow measurements. The mean heat transfer rate is only little affected bythe asymmetrical conditions....
The report gives results of an evaluation of the heat transfer performance of pure hydrofluorocarbon (HFC)-236ea for high performance enhanced tubes which had not been previously used in Navy shipboard chillers. Shell-side heat transfer coefficient data are presented for condensa...
Heat transfer of alumina-deionized water nanofluids in concentric tube heat exchanger
Alias, Hajar; Ani, Muhamad Fahmi Che; Sa'ad, Siti Fatimah; Ngadi, Norzita
2017-12-01
This research studied the characteristics of nanofluids in a concentric tube heat exchanger. The objectives of this research are to prepare the stable nanofluids with addition of surfactant and to investigate the stability, properties, and heat transfer of nanofluids in concentric tube heat exchanger. Aluminium oxide (Al2O3) was added to base fluid deionized water (DW) with addition of polyvinylpyrrolidone (PVP) as surfactant by two-step method. First, the best stability ratio of nanofluids to surfactant PVP was determined by preparing several samples of 0.50 wt% nanofluids with addition of different weight fraction of surfactant. Thus, each sample has different ratio and being observed for one week by visual observation. Then, nanofluids samples (0.25, 0.50, 0.75 and 1.00 wt%) were prepared based on the best stability ratio. The properties and heat transfer of nanofluids were analyzed at different concentration of nanofluids and at different temperatures (room temperature, 40 °C, 50 °C, 60 °C and 70 °C). From the observation, the alumina nanofluids was stable with the addition of surfactant at ratio 1:2. The thermal conductivity of nanofluids are higher than base fluid and increased as the temperature and concentration increased. Viscosity of nanofluids was highest at 1.00 wt% and at room temperature. The heat transfer performance of heat exchanger increased by using nanofluids. Nanofluids absorbed more heat than base fluid and the highest percentage drop of hot stream is 120% at 70 °C by using 1.00 wt% nanofluids.
Chen, Ting; Bae, Kyung Jin; Kwon, Oh Kyung
2018-02-01
In this paper, heat transfer characteristics of fin-tube heat exchanger and primary surface heat exchanger (PSHE) used in waste heat recovery were investigated experimentally. The flow in the fin-tube heat exchanger is cross flow and in PSHE counter flow. The variations of friction factor and Colburn j factor with air mass flow rate, and Nu number with Re number are presented. Various comparison methods are used to evaluate heat transfer performance, and the results show that the heat transfer rate of the PSHE is on average 17.3% larger than that of fin-tube heat exchanger when air mass flow rate is ranging from 1.24 to 3.45 kg/min. However, the PSHE causes higher pressure drop, and the fin-tube heat exchanger has a wider application range which leads to a 31.7% higher value of maximum heat transfer rate compared to that of the PSHE. Besides, under the same fan power per unit frontal surface, a higher heat transfer rate value is given in the fin-tube heat exchanger.
Kumar, Anil; Maithani, Rajesh; Suri, Amar Raj Singh
2017-12-01
In this study, numerical and experimental investigation has been carried out for a range of system and operating parameters in order to analyse the effect of dimpled rib on heat and fluid flow behaviours in heat exchanger tube. Tube has, stream wise spacing ( x/ d d ) range of 15-35, span wise spacing ( y/ d d ) range of 15-35, ratio of dimpled depth to print diameter ( e/ d d ) of 1.0 and Reynolds number ( Re n ) ranges from 4000 to 28,000. Simulations were carried out to obtain heat and fluid flow behaviour of smooth and rough tube, using commercial CFD software, ANSYS 16.0 (Fluent). Renormalization k - ɛ model was employed to assess the influence of dimpled on turbulent flow and velocity field. Simulation results show that, the enhancement of 3.18 times in heat transfer and 2.87 times enhancement in thermal hydraulic performance as a function of stream wise direction ( x/ d d ) of 15 and span wise direction ( y/ d d ) of 15 respectively. Comparison between numerical and experimental simulation results showed that good agreement as the data fell within ±10% error band.
Energy Technology Data Exchange (ETDEWEB)
Huh, Seon Jeong; Lee, Hee Joon [Kookmin University, Seoul (Korea, Republic of); Kim, Myoung Jun; Moon, Joo Hyung; Bae, Youngmin; Kim, Young-In [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2016-10-15
Recently emergency cooldown tank(ECT) is a great concern of passive cooling system for the safety of nuclear reactor. After the operation of a conventional passive cooling system for an extended period, however, the water level falls as a result of the evaporation from the ECT, as steam is emitted from the open top of the tank. In this study, the effect of heat transfer area at the air cooled condensing heat exchanger was investigated by changing 5×5 tube banks into 4×4 and 3×3. Moreover, each of air-side natural convective heat transfer coefficient of tube banks was compared to existing correlations. This study presents the effect of heat transfer area at air-cooled condensing heat exchanger. As heat transfer area decreased, the temperature of outlet increased. In other words, the cooling performance got lower with the decrease of heat transfer area. In addition, the average natural convective heat transfer coefficient was 15.3 W/m{sup 2}/K from the 4×4 tube banks, and 4.92 W/m{sup 2}/K from the 3×3 tube banks, which had quite a large error more than 46% especially with the value of 4×4 tube banks compared to the value from correlation equation. Therefore, according to this result, it is needed to measure the local heat transfer coefficient of vertical cylinder more elaborately in further study.
Stability of coaxial jets confined in a tube with heat and mass transfer
Mohanta, Lokanath; Cheung, Fan-Bill; Bajorek, Stephen M.
2016-02-01
A linear temporal stability of coaxial confined jets in a vertical tube involving heat and mass transfer at the interface is presented in this paper. A potential flow analysis that includes the effect of viscosity at the interface is performed in analyzing the stability of the system. Film boiling in a vertical tube gives rise to the flow configuration explored in this work. The effects of various non-dimensional parameters on the growth rate and the neutral curve are discussed. The heat transfer at the interface has been characterized by introducing a heat flux ratio between the conduction heat flux and the evaporation heat flux. Viscous forces and the heat and mass transfer at the interface are found to stabilize the flow both in the capillary instability region and Kelvin-Helmholtz instability region. Increasing heat and mass transfer at the interface stabilizes the flow to small as well as very large wave numbers.
Correlation for the Prediction of Flow Boiling Heat Transfer in Small Diameter Tubes
Miyata, Kazushi; Mori, Hideo; Hamamoto, Yoshinori
The objective of the present study is to develop a correlation applicable to a prediction of an axially local heat transfer coefficient in flow boiling within small diameter tubes. From experimental data of authors obtained previously, it was found that, for the accurate prediction of the heat transfer in small diameter tubes, it was necessary to evaluate precisely the contribution of evaporation heat transfer of thin liquid film around vapor plugs in slug flow, adding to the forced convection heat transfer and nucleate boiling heat transfer. There are, however, only conventional heat transfer correlations which consider any two of the three contributions; forced convection and nucleate boiling in most cases. In this study, a new correlation considering all of three contributions was developed based on data of R 410A by authors and data of other Freons, water and CO2 by other researchers. In the new correlation, the liquid film evaporation heat transfer is evaluated using liquid film thickness correlated with the Capillary number, the forced convection heat transfer is calculated by use of the Dittus-Boelter correlation and the Lockhart-Martinelli parameter, and the nucleate boiling heat transfer is predicted from the Stephan-Abdelsalam correlation with the suppression factor. The new correlation showed higher prediction performance compared with conventional heat transfer correlations.
Directory of Open Access Journals (Sweden)
Zeki ARGUNHAN
2006-02-01
Full Text Available This paper examines the effect of turbulance creators on heat transfer and pressure drop used in concentric heat exchanger experimentaly. Heat exchanger has an inlet tube with 60 mm in diameter. The angle of swirl generators wings is 55º with each wing which has single, double, three and four holes. Swirl generators is designed to easily set to heat exchanger entrance. Air is passing through inner tube of heat exhanger as hot fluid and water is passing outer of inner tube as cool fluid.
Flow boiling heat transfer of carbon dioxide inside a small-sized microfin tube
Energy Technology Data Exchange (ETDEWEB)
Dang, Chaobin; Haraguchi, Nobori; Hihara, Eiji [Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa-shi, Chiba 277-8563 (Japan)
2010-06-15
This study investigated the flow boiling heat transfer of carbon dioxide inside a small-sized microfin tube (mean inner diameter: 2.0 mm; helix angle: 6.3 ) at a saturation temperature of 15 C, and heat and mass flux ranges of 4.5-18 kW m{sup -2} and 360-720 kg m{sup -2} s{sup -1}, respectively. Although, experimental results indicated that heat flux has a significant effect on the heat transfer coefficient, the coefficient does not always increase with mass flux, as in the case of conventional refrigerants such as HFCs or HCFCs. Under certain conditions, the heat transfer coefficient at a high mass flux was lower than that at a lower mass flux, indicating that convective heat transfer had a suppression effect on nucleate boiling. The heat transfer coefficients in the microfin tubes were 1.9{proportional_to}2.3 times the values in smooth tubes of the same diameter under the same experimental conditions, and the dryout quality was much higher, ranging from 0.9 to 0.95. The experimental results indicated that using microfin tubes may considerably increase the overall heat transfer performance. (author)
Kido, Osao; Uehara, Haruo
The empirical correlation to predict the evaporation heat transfer coefficient inside an internally grooved horizontal tube was proposed using previous experimental data studied by other researchers. Parameters in the correlation were selected by refering to the correlation for rectangular channnel. The correlation for rectangular channnel was proposed by taking weighted average of heat transfer coefficients on upper and lower grooved surfaces inside a rectangular channnel to applicate to the internally grooved tube. Effects of parameters in the correlation for grooved tube are corresponding to those in the correlation for rectangular chaannel, and increasing the modified bond number, the heat transfer coefficient decreases. For rectangular channel, the maximum heat transfer coefficient is obtained on the grooved surface with 2 × 10-3 of the modified bond number.
Hashimoto, Katsumi; Kiyotani, Akihiro; Sasaki, Naoe
The CO2 heat pump water heater ”ECO CUTE” which was commercialized in 2001 has a high potential for energy conservation and greenhouse abatement. The most important element apparatus is always the evaporator in order to develop smaller and higher performance equipment. In this paper, an experimental study has been conducted to measure the pure CO2 flow boiling heat transfer coefficient (99.999 % purity, without oil) in a horizontal smooth tube (outer diameter 6 mm, thickness 0.4 mm). The measured mean heat transfer coefficients are compared with calculated value with using previous experimental heat transfer correlation equations. These two values are different from each other. Mean heat transfer coefficients are measured with varying mass velocity, pressure and heat transfer lengths. The tube length is varied to 3.0 m, 4.0 m and 5.0 m, to distinguish the influence of mass velocity and that of heat flux to the heat transfer coefficient. The test conditions were: CO2 mass velocity from about 150 to about 700 kg⁄(m2s) (heat flux from about 10 to about 40 kW⁄m2), quality at inlet of test section is 0.17, CO2 super heat at outlet of test section is 5 K and saturation temperature of CO2 ranges from 0 to 10 °C. As a result, it has been understood that heat flux has a greater influence on the heat transfer coefficient.
Analysis of Tube Bank Heat Transfer In Downward Directed Foam Flow
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Jonas Gylys
2004-06-01
Full Text Available Apparatus with the foam flow are suitable to use in different technologies like heat exchangers, food industry, chemical and oil processing industry. Statically stable liquid foam until now is used in technologic systems rather seldom. Although a usage of this type of foam as heat transfer agent in foam equipment has a number of advantages in comparison with one phase liquid equipment: small quantity of liquid is required, heat transfer rate is rather high, mass of equipment is much smaller, energy consumption for foam delivery into heat transfer zone is lower. The paper analyzes the peculiarities of heat transfer from distributed in staggered order and perpendicular to foam flow in channel of rectangular cross section tube bundle to the foam flow. It was estimated the dependence of mean gas velocity and volumetric void fraction of foam flow to heat transfer in downward foam flow. Significant difference of heat transfer intensity from front and back tubes of tube row in laminar foam flow was noticed. Dependence of heat transfer on flow velocity and volumetric void fraction of foam was confirmed and estimated by criterion equations.
Measurement of Heat Transfer Coefficients in an Agitated Vessel with Tube Baffles
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M. Dostál
2010-01-01
Full Text Available Cooling or heating an agitated liquid is a very common operation in many industrial processes. A classic approach is to transfer the necessary heat through the vessel jacket. Another option, frequently used in the chemical and biochemical industries is to use the heat transfer area of vertical tube baffles. In large equipment, e.g. fermentor, the jacket surface is often not sufficient for large heat transfer requirements and tube baffles can help in such cases. It is then important to know the values of the heat transfer coefficients between the baffles and the agitated liquid. This paper presents the results of heat transfer measurements using the transient method when the agitated liquid is periodically heated and cooled by hot and cold water running through tube baffles. Solving the unsteady enthalpy balance, it is possible to determine the heat transfer coefficient. Our results are summarized by the Nusselt number correlations, which describe the dependency on the Reynolds number, and they are compared with other measurements obtained by a steady-state method.
Heat transfer and fluid flow behaviors in a five-start spiral corrugated tube
Promthaisong, Pitak; Jedsadaratanachai, Withada; Chuwattanakul, Varesa; Eiamsa-ard, Smith
2017-08-01
This paper presented a numerical investigation on turbulent periodic flow, heat transfer, pressure loss and thermal enhancement factor in a 3D five-start spiral corrugated tube. Air was used as the working fluids through the tube for Reynolds numbers of about 5000-20,000. In the current studied, the five-start spiral corrugated tube with six relative pitch ratios (p/D, PR=1.0, 1.5, 2.0, 2.5, 3.0 and 3.5) with constant depth ratio (e/D, DR=0.06). The numerical results reveal that the five-start spiral corrugated tube can generated a swirl flow, main swirl flow and five-secondary swirl flow. This behavior lead to the major change of temperature in transverse plane, reduced thermal layer thickness and enhanced heat transfer on the tube wall. The five-start spiral corrugated tube in range investigated provided the heat transfer rate and friction factor up to 2.02 and 6.12 times, respectively, over the straight circular tube. The thermal enhancement factor of the five-start spiral corrugated tube in the range of 0.89-1.16 where its maximum found as the optimum point is at PR=2.0.
Energy Technology Data Exchange (ETDEWEB)
Boscary, J. [CEA Centre d`Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Direction des Sciences de la Matiere]|[Association Euratom-CEA, Centre d`Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee
1997-03-01
The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author) 197 refs.
Energy Technology Data Exchange (ETDEWEB)
Boscary, J.
1995-10-01
The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author). 198 refs., 126 figs., 21 tabs.
Energy Technology Data Exchange (ETDEWEB)
Rao, Bala Bhaskara [Dept. of Mechanical Engineering, SISTAM College, JNTU, Kakinada (India); Raju, V. Ramachandra [Dept. of Mechanical Engineering, JNTU, Kakinada (India); Deepak, B. B V. L. [Dept. of Industrial Design, National Institute of Technology, Rourkela (India)
2017-01-15
Most thermal/chemical industries are equipped with heat exchangers to enhance thermal efficiency. The performance of heat exchangers highly depends on design modifications in the tube side, such as the cross-sectional area, orientation, and baffle cut of the tube. However, these parameters do not exhibit a specific relation to determining the optimum design condition for shell and tube heat exchangers with a maximum heat transfer rate and reduced pressure drops. Accordingly, experimental and numerical simulations are performed for a heat exchanger with varying tube geometries. The heat exchanger considered in this investigation is a single-shell, multiple-pass device. A Generalized regression neural network (GRNN) is applied to generate a relation among the input and output process parameters for the experimental data sets. Then, an Artificial immune system (AIS) is used with GRNN to obtain optimized input parameters. Lastly, results are presented for the developed hybrid GRNN-AIS approach.
Directory of Open Access Journals (Sweden)
Sarvari Seyed
2011-01-01
Full Text Available Abstract Laminar mixed convection of a nanofluid consisting of water and Al2O3 in an inclined tube with heating at the top half surface of a copper tube has been studied numerically. The bottom half of the tube wall is assumed to be adiabatic (presenting a tube of a solar collector. Heat conduction mechanism through the tube wall is considered. Three-dimensional governing equations with using two-phase mixture model have been solved to investigate hydrodynamic and thermal behaviours of the nanofluid over wide range of nanoparticle volume fractions. For a given nanoparticle mean diameter the effects of nanoparticle volume fractions on the hydrodynamics and thermal parameters are presented and discussed at different Richardson numbers and different tube inclinations. Significant augmentation on the heat transfer coefficient as well as on the wall shear stress is seen.
Experimental Investigation of Heat Transfer Coefficient in Vertical Tube Rising Film Evaporator
Syed Naveed Ul Hasan; Sultan Ali
2011-01-01
This paper reports the experimental evaluation of the heat transfer coefficient (U) in a VRF (Vertical Tube Rising Film Evaporator). The aim is to describe the variation of U against different process parameters. Experiments were carried out for laminar flow conditions. The experimental unit is a floor standing tubular framework for a rising film evaporation system. There are many parameters affecting heat transfer coefficient in evaporators, but it was not possible to consider all of them, s...
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Adnan M. Hussein
2013-01-01
Full Text Available The additives of solid nanoparticles to liquids are significant enhancement of heat transfer and hydrodynamic flow. In this study, the thermal properties of three types of nanoparticles (Al2O3, TiO2, and SiO2 dispersed in water as a base fluid were measured experimentally. Forced convection heat transfer turbulent flow inside heated flat tube was numerically simulated. The heat flux around flat tube is 5000 W/m2 and Reynolds number is in the range of 5×103 to 50×103. CFD model by finite volume method used commercial software to find hydrodynamic and heat transfer coefficient. Simulation study concluded that the thermal properties measured and Reynolds number as input and friction factor and Nusselt number as output parameters. Data measured showed that thermal conductivity and viscosity increase with increasing the volume concentration of nanofluids with maximum deviation 19% and 6%, respectively. Simulation results concluded that the friction factor and Nusselt number increase with increasing the volume concentration. On the other hand, the flat tube enhances heat transfer and decreases pressure drop by 6% and −4%, respectively, as compared with circular tube. Comparison of numerical analysis with experimental data available showed good agreement with deviation not more than 2%.
Evaporation heat transfer of carbon dioxide at low temperature inside a horizontal smooth tube
Yoon, Jung-In; Son, Chang-Hyo; Jung, Suk-Ho; Jeon, Min-Ju; Yang, Dong-Il
2017-05-01
In this paper, the evaporation heat transfer coefficient of carbon dioxide at low temperature of -30 to -20 °C in a horizontal smooth tube was investigated experimentally. The test devices consist of mass flowmeter, pre-heater, magnetic gear pump, test section (evaporator), condenser and liquid receiver. Test section is made of cooper tube. Inner and outer diameter of the test section is 8 and 9.52 mm, respectively. The experiment is conducted at mass fluxes from 100 to 300 kg/m2 s, saturation temperature from -30 to -20 °C. The main results are summarized as follows: In case that the mass flux of carbon dioxide is 100 kg/m2 s, the evaporation heat transfer coefficient is almost constant regardless of vapor quality. In case of 200 and 300 kg/m2 s, the evaporation heat transfer coefficient increases steadily with increasing vapor quality. For the same mass flux, the evaporation heat transfer coefficient increases as the evaporation temperature of the refrigerant decreases. In comparison of heat transfer correlations with the experimental result, the evaporation heat transfer correlations do not predict them exactly. Therefore, more accurate heat transfer correlation than the previous one is required.
Evaporation flow pattern and heat transfer of R-22 and R-134a in small diameter tubes
Oh, Hoo-Kyu; Son, Chang-Hyo
2011-06-01
The flow patterns and heat transfer coefficients of R-22 and R-134a during evaporation in small diameter tubes were investigated experimentally. The evaporation flow patterns of R-22 and R-134a were observed in Pyrex sight glass tubes with 2 and 8 mm diameter tube, and heat transfer coefficients were measured in smooth and horizontal copper tubes with 1.77, 3.36 and 5.35 mm diameter tube, respectively. In the flow patterns during evaporation process, the annular flows in 2 mm glass tube occurred at a relatively lower vapor quality compared to 8 mm glass tube. The flow patterns in 2 mm glass tube did not agree with the Mandhane's flow pattern maps. The evaporation heat transfer coefficients in the small diameter tubes ( d i heat transfer coefficients of 1.77 mm tube were higher than those of 3.36 mm and 5.35 mm tube. Most of the existing correlations failed to predict the evaporation heat transfer coefficient in small diameter tubes. Therefore, based on the experimental data, the new correlation is proposed to predict the evaporation heat transfer coefficients of R-22 and R-134a in small diameter tubes.
Energy Technology Data Exchange (ETDEWEB)
Kim, Kyoo Woan; Chien, Nguyen Ba; Choi, Kwang Il; Oh, Jong Taek [Chonnam National University, Yeosu (Korea, Republic of)
2014-10-15
We report experimental data of boiling heat transfer of R-1234yf in horizontal small tubes. The experimental data obtained in the horizontal circular small tubes of 1.5 and 3.0 mm inner diameter, the lengths of 1000 and 2000 mm, the mass flux range from 200 - 650 kg/m{sup 2}s, the heat flux range from 5-40 kW/m{sup 2}and saturation temperature of 10 and 15 .deg. C, was used to develop a modified correlation for the heat transfer coefficient. The flow pattern of the experimental data was mapped and analyzed with existing flow pattern maps. The heat transfer coefficient was also compared with some well-known correlations.
Heat transfer enhancement with elliptical tube under turbulent flow TiO2-water nanofluid
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Hussein Adnan M.
2016-01-01
Full Text Available Heat transfer and friction characteristics were numerically investigated, employing elliptical tube to increase the heat transfer rate with a minimum increase of pressure drop. The flow rate of the tube was in a range of Reynolds number between 10000 and 100000. FLUENT software is used to solve the governing equation of CFD (continuity, momentum and energy by means of a finite volume method (FVM. The electrical heater is connected around the elliptical tube to apply uniform heat flux (3000 W/m2 as a boundary condition. Four different volume concentrations in the range of 0.25% to 1% and different TiO2 nanoparticle diameters in the range of 27 nm to 50 nm, dispersed in water are utilized. The CFD numerical results indicate that the elliptical tube can enhance heat transfer and friction factor by approximately 9% and 6% than the circular tube respectively. The results show that the Nusselt number and friction factor increase with decreasing diameters but increasing volume concentrations of nanoparticles.
The Influence of the Lubricant Mixture into a Refrigerant on the Condensation Heat Transfer in Tube
Katsuta, Masafumi; Miyai, Ryo; Komatsu, Tomohiro; Kawai, Akinari
In a refrigerator and an air conditioner, it is a well-known fact that the contamination of lubricant into a pure refrigerant has a great influence on the heat transfer characteristics and two-phase flow behavior at the condenser and evaporator. However, up to now, in the most of heat exchanger design, the refrigerant has been regarded as a pure one. On the other hand, a recent condenser tube diameter tends to be fine to overcome the various demands on the compactness and the high performance, especially required for the alternative refrigerant. Unfortunately, quantitative studies of the tube less than 6 mm in diameter were insufficient, moreover, only few studies have been made including the effect of the oil contamination on the condensation heat transfer. In this study, we employed HFC134a as a refrigerant and PAG-oil as a lubricant and experiments with a flat tube and three kinds of circular tube which has different diameters were made. By using the flow visualization data, a new flow pattern map being applicable both of a pure and oil-lubricant mixture was proposed. Moreover, by examining the local heat transfer coefficient and pressure drop, the most sensitive flow pattern affected by contamination of lubricant was specified and the detailed discussion on the quantitative effect of oil contamination on condensation heat transfer including the effect of tube geometry was carried out. Finally, based on these results, new correlation for heat transfer and pressure drop was suggested, and it predicted our data successfully well up to a mass flux of 150kg/(m2•s.)
One-dimensional model for heat transfer to a supercritical water flow in a tube
Sallevelt, J.L.H.P.; Withag, J.A.M.; Bramer, Eduard A.; Brilman, Derk Willem Frederik; Brem, Gerrit
2012-01-01
Heat transfer in water at supercritical pressures has been investigated numerically using a one-dimensional modeling approach. A 1D plug flow model has been developed in order to make fast predictions of the bulk-fluid temperature in a tubular flow. The chosen geometry is a vertical tube with an
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Y.K.Sklifus
2012-12-01
Full Text Available The article presents the calculation of heat transfer coefficient during condensation of steam, the mathematical model of temperature distribution in the gas and liquid phases of the coolant and the model of the formation of the condensate film on the walls of the tubes.
New Correlation Methods of Evaporation Heat Transfer in Horizontal Microfine Tubes
Makishi, Osamu; Honda, Hiroshi
A stratified flow model and an annular flow model of evaporation heat transfer in horizontal microfin tubes have been proposed. In the stratified flow model, the contributions of thin film evaporation and nucleate boiling in the groove above a stratified liquid were predicted by a previously reported numerical analysis and a newly developed correlation, respectively. The contributions of nucleate boiling and forced convection in the stratified liquid region were predicted by the new correlation and the Carnavos equation, respectively. In the annular flow model, the contributions of nucleate boiling and forced convection were predicted by the new correlation and the Carnavos equation in which the equivalent Reynolds number was introduced, respectively. A flow pattern transition criterion proposed by Kattan et al. was incorporated to predict the circumferential average heat transfer coefficient in the intermediate region by use of the two models. The predictions of the heat transfer coefficient compared well with available experimental data for ten tubes and four refrigerants.
Heat transfer to immersed horizontal tubes in gas fluidized bed dryers
Energy Technology Data Exchange (ETDEWEB)
Jonassen, Ola
1999-07-01
The main objective of this study was to construct heat pump fluidized bed dryers of the FHT type with improved dewatering capacity for a given size of the dryer. The use of heat exchangers immersed in the fluidized bed drying chambers is an important part of the FHT (Fluidized Bed High Temperature Heat Pump Dryer) concept. A pilot plant FHT dryer was built and successfully tested on fish meal raw material and seaweed. The plant included two fluidized bed drying chambers with immersed heat exchangers. The gain in water vapor of the drying air through the chambers was increased up to four times that of adiabatic drying. The energy saving concept was retained as a SMER ratio of 3.5 to 4.7 was measured in the same tests. Therefore optimization of the immersed heat exchangers was considered the most important single objective for this work. The optimization study of the heat exchangers was confined to the actual operating conditions for the dryers using: (1) Bubbling gas fluidized beds were used, (2) air as the only type of fluidizing gas,(3) beds at atmospheric pressure, (4) bed temperatures below 100 {sup o}C, (5) fluidized particles of Geldart classes B and D, (6) horizontal tube banks for the immersed heat exchanger and the influence of radiation heat transfer was ignored. The heat transfer study was confined to the fluidized bed side of the heat exchanger surface. It was concluded early in this work that the bubbles play a major role in generating the particle circulation inside the bed and hence also in heat transfer. Publications describing the most important bubble induced mechanisms contributing to high rates of heat transfer were found to be limited. Therefore the first part of this study was aimed at establishing a method for locating and measuring the size and rise velocity of bubbles inside the bed. The method established through this work using differential pressure measurements from two static pressure probes was used later in the study of heat transfer
Heat transfer to immersed horizontal tubes in gas fluidized bed dryers
Energy Technology Data Exchange (ETDEWEB)
Jonassen, Ola
1999-10-01
The main objective of this study was to construct heat pump fluidized bed dryers of the FHT type with improved dewatering capacity for a given size of the dryer. The use of heat exchangers immersed in the fluidized bed drying chambers is an important part of the FHT (Fluidized Bed High Temperature Heat Pump Dryer) concept. A pilot plant FHT dryer was built and successfully tested on fish meal raw material and seaweed. The plant included two fluidized bed drying chambers with immersed heat exchangers. The gain in water vapor of the drying air through the chambers was increased up to four times that of adiabatic drying. The energy saving concept was retained as a SMER ratio of 3.5 to 4.7 was measured in the same tests. Therefore optimization of the immersed heat exchangers was considered the most important single objective for this work. The optimization study of the heat exchangers was confined to the actual operating conditions for the dryers using: (1) Bubbling gas fluidized beds were used, (2) air as the only type of fluidising gas, (3) beds at atmospheric pressure, (4) bed temperatures below 100 {sup o}C, (5) fluidized particles of Geldart classes B and D, (6) horizontal tube banks for the immersed heat exchanger, and the influence of radiation heat transfer was ignored. The heat transfer study was confined to the fluidized bed side of the heat exchanger surface. It was concluded early in this work that the bubbles play a major role in generating the particle circulation inside the bed and hence also in heat transfer. Publications describing the most important bubble induced mechanisms contributing to high rates of heat transfer were found to be limited. Therefore the first part of this study was aimed at establishing a method for locating and measuring the size and rise velocity of bubbles inside the bed. The method established through this work using differential pressure measurements from two static pressure probes was used later in the study of heat transfer
CFD investigation of flow and heat transfer of nanofluids in isoflux spirally fluted tubes
Salama, Amgad
2012-01-01
In this work, the problem of flow and heat transfer of nanofluids in spirally fluted tubes is investigated numerically using the CFD code Fluent. The tube investigated in this work is characterized by the existence of helical ridging which is usually obtained by embossing a smooth tube. A tube of diameter of 15 mm, 1.5 mm groove depth and a single helix with pitch of 64 mm is chosen for simulation. This geometry has been chosen for simulation because it has been investigated experimentally for pure fluids and would, therefore, provide a verification framework with our CFD model. The result of our CFD investigation compares very well with the experimental work conducted on this tube geometry. Interesting patterns are highlighted and investigated including the existence of flow swirl as a result of the existence of the spirally enhanced ridges. This swirl flow enhances heat transfer characteristics of this system as reported in the literatures. This study also shows that further enhancement is achieved if small amount of nanoparticles are introduced to the fluid. These nanoparticles (metallic-based nanoparticles) when introduced to the fluid enhances its heat transfer characteristics.
Turbulent flow regime in coiled tubes: local heat-transfer coefficient
Bozzoli, F.; Cattani, L.; Mocerino, A.; Rainieri, S.
2017-08-01
Wall curvature represents a widely adopted technique for enhancing heat transfer: the fluid flowing inside a coiled pipe experiences the centrifugal force and this phenomenon induces local maxima in the velocity distribution that locally increase the temperature gradients at the wall by enhancing the heat transfer both in the laminar and in the turbulent flow regime. Consequently, the distribution of the velocity field over the cross-section of the tube is strongly uneven thus leading to significant variations along the circumferential angular coordinate of the convective heat-transfer coefficient at the wall internal surface: in particular, it shows higher values at the outer bend side of the coil than at the inner bend side. The aim of the present work is to estimate experimentally the local convective heat-transfer coefficient at the fluid wall interface in coiled tubes when turbulent flow regime occurs. In particular, the temperature distribution maps on the external coil wall are employed as input data of the inverse heat conduction problem in the wall and a solution approach based on the Tikhonov regularisation is implemented. The results, obtained with water as working fluid, are focused on the fully developed region in the turbulent flow regime in the Reynolds number range of 5000 to 12,000. For the sake of completeness, the overall efficiency of the coiled tubes under test is assessed under a first-law performance evaluation criterion.
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Ponnusamy Selvaraj
2016-01-01
Full Text Available This paper reports experimental studies on friction factor, Nusselt number, and thermal hydraulic performance of a tube equipped with the classic three modified internally grooved tubes. Heat transfer and friction factor characteristics and pres- sure drop results have been obtained experimentally for a fully developed water flow in a grooved tube is also reported. Tests were performed for Reynolds number ranges from 5000-13500 for different geometric grooved tubes (circular, square, and rapezium. The ratio of length-to-diameter is 38.69 D. Among the grooved tubes, heat transfer enhancement obtained up to 47% for circular grooved tube, 31% for square grooved tube, and 52% for trapezoidal grooved tube in comparison with the smooth tube. It has been observed that the friction factor high in the case of square grooved tube than those of other tubes.
Numeric Simulation of Heat Transfer from a Single Round Tube Shielded with Wire Mesh
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Dymo B.V.
2015-08-01
Full Text Available This paper presents the results of development and investigation of heat transfer at transverse flow of round tube with wire screen using the software ANSYS Fluent 3D-model. Selection of optimal parameters of the finite element model, in particular, transition shear stress transport model as well and boundary conditions are realized. Instructed and combined net is used at numerical calculations. This net is built with the help of generators grid-torus ANSYS CFX Mesh 14.0. The problem of verification of conformity of the numerical model of the heat transfer of a single screen-covered round tubes according to physical experiment for the same tubes in the range of Reynolds numbers Re = (5000...35000 was studied. We established that discrepancy between physical experiments and numerical simulation results not exceeds 5% with respect to the data of physical experiment.
The evaluation of energy efficiency of convective heat transfer surfaces in tube bundles
Grigoriev, B. A.; Pronin, V. A.; Salohin, V. I.; Sidenkov, D. V.
2017-11-01
When evaluating the effectiveness of the heat exchange surfaces in the main considered characteristics such as heat flow (Q, Watt), the power required for pumps (N, Watt), and surface area of heat transfer (F, m2). The most correct comparison provides a comparison “ceteris paribus”. Carried out performance comparison “ceteris paribus” in-line and staggered configurations of bundles with a circular pipes can serve as a basis for the development of physical models of flow and heat transfer in tube bundles with tubes of other geometric shapes, considering intertubular stream with attached eddies. The effect of longitudinal and transverse steps of the pipes on the energy efficiency of different configurations would take into account by mean of physical relations between the structure of shell side flow with attached eddies and intensity of transfer processes of heat and momentum. With the aim of energy-efficient placement of tubes, such an approach opens up great opportunities for the synthesis of a plurality of tubular heat exchange surfaces, in particular, the layout of the twisted and in-line-diffuser type with a drop-shaped pipes.
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim
2017-01-01
type is chosen and investigated at different angles of attack 0 , ??10 and ??20 with the flow direction. Three-dimensional numerical model is developed and simulations are performed for a Reynolds number range 5000 Re 11000 taking conjugate heat transfer into account. The heat transfer and pressure...... loss characteristics are determined and analyzed for an in-line configuration of a fin and tube heat exchanger. In order to evaluate the enhancement in the performance on an equitable basis, the heat exchanger with plain fin surface is considered as a reference design. Results show that the angle...... of attack of a vortex generator has a significant impact on the volume goodness factor, and enhance the thermal performance of a fin and tube heat exchanger in comparison to the design with plain fin. The vortex generator at an angle of attack ??10 is found to perform superior over the Reynolds number range...
Heat transfer and visualization of falling film evaporation on a tube bundle
Energy Technology Data Exchange (ETDEWEB)
Christians, M.
2010-07-01
Horizontal falling film evaporators have the potential of displacing flooded evaporators in industry, due to advantages such as lower required refrigerant charge and lower pressure drop. However, there is a need to improve the understanding of falling film evaporation mechanisms to provide accurate thermal design methods. In this work, the existing LTCM falling film facility was utilized to perform falling film evaporation measurements on a single tube, a vertical row of horizontal tubes and a small tube bundle. Two enhanced boiling tubes, namely the Wolverine Turbo-B5 and the Wieland Gewa-B5, were tested using R-134a and R-236fa. The tests were carried out at a constant saturation temperature of T{sub sat} = 5 °C, liquid film Reynolds numbers ranging from 0 to 3000, and heat fluxes between 15 and 90 kW/m{sup 2} in pool boiling and falling film configurations. A visualization study was performed under adiabatic and diabatic conditions (in both single-array and bundle configurations) to study the flow. The physical phenomena governing the falling film evaporation process have been studied, and insight into their effects on the performance of tube bundles has been gained. Measurements of the local heat transfer coefficient were obtained and utilized to generate new prediction methods, including a method for predicting the onset-of-dryout film flow rate during falling film evaporation, local pool boiling and falling film heat transfer prediction methods and a falling film multiplier prediction method. (author)
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Lin Wei
2015-01-01
Full Text Available Heat recovery unit (HRU is a heat exchange device in drying process. In HRU, room air is preheated by waste hot air and then transported to drying oven to remove moisture, which helps to save both energy and time. The main purpose of this paper is to build a heat transfer model of HRU and study its characteristics. A numerical method based on fluid-solid coupling was used to calculate the heat transfer between tube and fluids, and the actual structure was simplified to improve computation efficiency. The results were validated by theoretical calculation and experiments. Effects of Reynolds number (Re on outlet temperature, Nusselt number, and pressure drop were investigated. It was found that the thermal resistance of shell side is large, by reducing which the total heat transfer coefficient can be improved. The difference between finned tube and smooth tube is in the shell side. Larger Re of shell side leads to good heat transfer performance but also larger pressure drop which increases the flow resistance.
Shibahara, Makoto; Fukuda, Katsuya; Liu, Qiusheng; Hata, Koichi
2018-02-01
The heat transfer characteristics of forced convection for subcooled water in small tubes were clarified using the commercial computational fluid dynamic (CFD) code, PHENICS ver. 2013. The analytical model consists of a platinum tube (the heated section) and a stainless tube (the non-heated section). Since the platinum tube was heated by direct current in the authors' previous experiments, a uniform heat flux with the exponential function was given as a boundary condition in the numerical simulation. Two inner diameters of the tubes were considered: 1.0 and 2.0 mm. The upward flow velocities ranged from 2 to 16 m/s and the inlet temperature ranged from 298 to 343 K. The numerical results showed that the difference between the surface temperature and the bulk temperature was in good agreement with the experimental data at each heat flux. The numerical model was extended to the liquid sublayer analysis for the CHF prediction and was evaluated by comparing its results with the experimental data. It was postulated that the CHF occurs when the fluid temperature near the heated wall exceeds the saturated temperature, based on Celata et al.'s superheated layer vapor replenishment (SLVR) model. The suggested prediction method was in good agreement with the experimental data and with other CHF data in literature within ±25%.
Heat and mass transfer and friction resistance of forced superheated vapor flow in tubes
Energy Technology Data Exchange (ETDEWEB)
Grebennikov, V.N.
This paper describes a procedure used for calculating the heat/mass transfer and friction resistance of a forced superheated vapor flow in tubes of separators-vapor superheaters and direct-flow vapor generators under equilibrium conditions and also under conditions where the flow is in a thermodynamic nonequilibrium state. Using the Reynolds analogy-based concept, an analysis of the process is carried out. Recommendations for calculating the heat/mass transfer and the hydraulic characteristics of vapor- superheating sections in separators-vapor superheaters and direct-flow vapor generators are made.
Green's function solution to heat transfer of a transparent gas through a tube
Frankel, J. I.
1989-01-01
A heat transfer analysis of a transparent gas flowing through a circular tube of finite thickness is presented. This study includes the effects of wall conduction, internal radiative exchange, and convective heat transfer. The natural mathematical formulation produces a nonlinear, integrodifferential equation governing the wall temperature and an ordinary differential equation describing the gas temperature. This investigation proposes to convert the original system of equations into an equivalent system of integral equations. The Green's function method permits the conversion of an integrodifferential equation into a pure integral equation. The proposed integral formulation and subsequent computational procedure are shown to be stable and accurate.
Heat transfer to throat tubes in a square-chambered rocket engine at the NASA Lewis Research Center
Nesbitt, James A.; Brindley, William J.
1989-01-01
A gaseous H2/O2 rocket engine was constructed at the NASA-Lewis to provide a high heat flux source representative of the heat flux to the blades in the high pressure fuel turbopump (HPFTP) during startup of the space shuttle main engines. The high heat flux source was required to evaluate the durability of thermal barrier coatings being investigated for use on these blades. The heat transfer, and specifically, the heat flux to tubes located at the throat of the test rocket engine was evaluated and compared to the heat flux to the blades in the HPFTP during engine startup. Gas temperatures, pressures and heat transfer coefficients in the test rocket engine were measured. Near surface metal temperatures below thin thermal barrier coatings were also measured at various angular orientations around the throat tube to indicate the angular dependence of the heat transfer coefficients. A finite difference model for a throat tube was developed and a thermal analysis was performed using the measured gas temperatures and the derived heat transfer coefficients to predict metal temperatures in the tube. Near surface metal temperatures of an uncoated throat tube were measured at the stagnation point and showed good agreement with temperatures predicted by the thermal model. The maximum heat flux to the throat tube was calculated and compared to that predicted for the leading edge of an HPFTP blade. It is shown that the heat flux to an uncooled throat tube is slightly greater than the heat flux to an HPFTP blade during engine startup.
Momoki, Satoru; Arima, Hirofumi; Yamaguchi, Tomohiko; Shigechi, Toru
This paper presents the experimental results on flow boiling heat transfer of ammonia inside a horizontal internally spirally grooved steel tube with 12mm in averaged inner diameter. Experimental conditions are 40 to 80kg/(m2s) in mass velocity, about 0.7MPa in pressure, and 0 to 20 kW/m2 in heat flux. Measured values on frictional pressure drop in adiabatic condition were correlated by Higashiiue's correlation, which was developed based on the experimental results with fluorocarbon refrigerants. On the measured heat transfer coefficients, very little significant effect of heat flux was found even in the small mass velocity condition, and also smaller influence of mass flux was observed than expected from the forced convection heat transfer theory. The measured heat transfer coefficients were compared with the predicted values by the author's previously developed correlation for fluorocarbon refrigerants,and this equation could not predict heat transfer coefficients of ammonia well. The trends of circumferential distribution of wall temperature in high quality region were different from those observed in the case of fluorocarbon refrigerants. In high quality region, annular mist flow regime appears instead of ordinary annular flow regime.
DEFF Research Database (Denmark)
Hærvig, Jakob; Condra, Thomas Joseph; Sørensen, Kim
Even though the corrugated tube is a widely used technique to enhance transfer heat, the exact heat transfer enhancing mechanism remains relatively un-documented. Most studies attribute the favourable heat transfer characteristics to a swirling flow being present at higher corrugation....... In this study, a systematic approach relying on Computational Fluid Dynamics (CFD) is used to study and compare the heat transfer characteristics with the detailed flow field in the spirally corrugated tubes. By comparing the flow in 12 different spirally corrugated tubes at a fixed Reynolds number of 5000......, this study compares the flow field with the surface averaged Nusselt number to gain valuable insight into which flow phenomena causes favourable heat transfer characteristics. While the flow at low corrugations approximates the non-corrugated tube, higher corrugations of h/D creates a significant tangential...
Jafarimoghaddam, Amin; Aberoumand, Sadegh; Javaherdeh, Kourosh; Arani, Ali Akbar Abbasian; Jafarimoghaddam, Reza
2017-10-01
In this work, an experimental study on nanofluid preparation stability, thermo-physical properties, heat transfer performance and friction factor of Al/ Oil nanofluids has been carried out. Electrical Explosion Wire (E.E.W) which is one of the most reliable one-step techniques for nanofluids preparation has been used. An annular tube has been considered as the test section in which the outer tube was subject to a uniform heat flux boundary condition of about 204 W. The utilized nanofluids were prepared in three different volume concentrations of 0.011%, 0.044% and 0.171%. A wide range of parameters such as Reynolds number Prandtl number, viscosity, thermal conductivity, density, specific heat, convective heat transfer coefficient, Nusselt number and the friction factor have been studied. The experiment was conducted in relatively low Reynolds numbers of less than 160 and within a hydrodynamically fully-developed regime. According to the results, thermal conductivity, density and viscosity increased depending on the volume concentrations and working temperatures while the specific heat declined. More importantly, it was observed that convective heat transfer coefficient and Nusselt number enhanced by 28.6% and 16.4%, respectively, for the highest volume concentration. Finally, the friction factor (which plays an important role in the pumping power) was found to be increased around 18% in the volume fraction of 0.171%.
Evaporation Heat Transfer and Pressure Drop of HCFC 22 Inside an Internally Grooved Horizontal Tube
Kido, Osao; Taniguchi, Mitsunori; Taira, Teruhiko; Uehara, Haruo
The evaporation heat heat transfer and pressure drop inside seven kinds of grooved horizontal tubes with 7.0 mm outside diameter and 60 to 100 grooves with 0.15 to 0.21 mm in height and 3 to 18 degree of lead angle, were obtained. The test section, 300 mm in length, was heated by condensing CFC 114 vapor on the outside of tube. HCFC 22 was used as a working fluid. Evaporating pressure was 0.49MPa, heat flux was 9.3 kW/ m2, vapor quality was varied from 0.1 to 0.9, and mass velocity was varied from 86 to 345 kg/(m2s). The empirical correlations to predict heat transfer coefficient and pressure drop were proposed. Increasing the modified bond number, the heat transfer coefficient decreases in the range of the modified bond number experimented. Pressure drop isn't influenced by the groove geometries except for lead angle.
Heat Transfer Correlations for Flow Boiling of Hydrocarbon Mixtures inside Horizontal Tubes
Zou, X.; Gong, M. Q.; Wu, J. F.; Chen, G. F.
The hydrocarbons and its mixtures are suitable for environment-friendly refrigerant alternatives because of their good environmental criteria and high thermodynamic performances. Based on the experimental results of the hydrocarbon mixtures, a correlation was developed earlier by Zou (2010) to predict saturated flow boiling heat transfer coefficients inside horizontal smooth tubes. In this article, the proposed correlation is extended to predict evaporation of some more mixtures (such as R50/R170) inside a horizontal tube by evaluating the mixture factor for that fluid. The comparisons of the present model and other classic models with the previous experimental data are made to evaluate the mean deviation for the hydrocarbon mixtures. It reveals that the new model is better to predict the flow boiling heat transfer for the hydrocarbon mixtures.
Improvement of heat transfer by means of ultrasound: Application to a double-tube heat exchanger.
Legay, M; Simony, B; Boldo, P; Gondrexon, N; Le Person, S; Bontemps, A
2012-11-01
A new kind of ultrasonically-assisted heat exchanger has been designed, built and studied. It can be seen as a vibrating heat exchanger. A comprehensive description of the overall experimental set-up is provided, i.e. of the test rig and the acquisition system. Data acquisition and processing are explained step-by-step with a detailed example of graph obtained and how, from these experimental data, energy balance is calculated on the heat exchanger. It is demonstrated that ultrasound can be used efficiently as a heat transfer enhancement technique, even in such complex systems as heat exchangers. Copyright © 2012 Elsevier B.V. All rights reserved.
Peng, Y.; Zhang, S. J.; Shen, F.; Wang, X. B.; Yang, X. R.; Yang, L. J.
2017-11-01
The air-cooled heat exchanger plays an important role in the field of industry like for example in thermal power plants. On the other hand, it can be used to remove core decay heat out of containment passively in case of a severe accident circumstance. Thus, research on the performance of fins in air-cooled heat exchangers can benefit the optimal design and operation of cooling systems in nuclear power plants. In this study, a CFD (Computational Fluid Dynamic) method is implemented to investigate the effects of inlet velocity, fin spacing and tube pitch on the flow and the heat transfer characteristics of flat fins constructed of various materials (316L stainless steel, copper-nickel alloy and aluminium). A three dimensional geometric model of flat finned tube bundles with fixed longitudinal tube pitch and transverse tube pitch is established. Results for the variation of the average convective heat transfer coefficient with respect to cooling air inlet velocity, fin spacing, tube pitch and fin material are obtained, as well as for the pressure drop of the cooling air passing through finned tube. It is shown that the increase of cooling air inlet velocity results in enhanced average convective heat transfer coefficient and decreasing pressure drop. Both fin spacing and tube pitch engender positive effects on pressure drop and have negative effects on heat transfer characteristics. Concerning the fin material, the heat transfer performance of copper-nickel alloy is superior to 316L stainless steel and inferior to aluminium.
Boiling on a tube bundle: heat transfer, pressure drop and flow patterns
Energy Technology Data Exchange (ETDEWEB)
Royen Van, E.
2011-11-15
The complexity of two-phase flow boiling on a tube bundle presents many challenges to the understanding of the physical phenomena taking place. It is important to quantify these numerous heat flow mechanisms in order to better describe the performance of tube bundles as a function of the operational conditions. In the present study, the bundle boiling facility at the Laboratory of Heat and Mass Transfer (LTCM) was modified to obtain high-speed videos to characterise the two-phase regimes and some bubble dynamics of the boiling process. It was then used to measure heat transfer on single tubes and in bundle boiling conditions. Pressure drop measurements were also made during adiabatic and diabatic bundle conditions. New enhanced boiling tubes from Wolverine Tube Inc. (Turbo-B5) and the Wieland-Werke AG (Gewa-B5) were investigated using R134a and R236fa as test fluids. The tests were carried out at saturation temperatures T{sub sat} of 5 °C and 15 °C, mass flow rates from 4 to 35 kg/m{sup 2}s and heat fluxes from 15 to 70 kW/m{sup 2}, typical of actual operating conditions. The flow pattern investigation was conducted using visual observations from a borescope inserted in the middle of the bundle. Measurements of the light attenuation of a laser beam through the intertube two-phase flow and local pressure fluctuations with piezo-electric pressure transducers were also taken to further help in characterising the complex flow. Pressure drop measurements and data reduction procedures were revised and used to develop new, improved frictional pressure drop prediction methods for adiabatic and diabatic two-phase conditions. The physical phenomena governing the enhanced tube evaporation process and their effects on the performance of tube bundles were investigated and insight gained. A new method based on a theoretical analysis of thin film evaporation was used to propose a new correlating parameter. A large new database of local heat transfer coefficients were obtained
Experimental Investigation of Heat Transfer Coefficient in Vertical Tube Rising Film Evaporator
Directory of Open Access Journals (Sweden)
Syed Naveed Ul Hasan
2011-10-01
Full Text Available This paper reports the experimental evaluation of the heat transfer coefficient (U in a VRF (Vertical Tube Rising Film Evaporator. The aim is to describe the variation of U against different process parameters. Experiments were carried out for laminar flow conditions. The experimental unit is a floor standing tubular framework for a rising film evaporation system. There are many parameters affecting heat transfer coefficient in evaporators, but it was not possible to consider all of them, so parameters including, Reynolds Number (NRe, Temperature Difference (DT, Feed Temperature (Tf and Re-circulation Ratio (R were investigated while other factors were kept constant. The experimental results obtained showed that heat transfer coefficient increased with the increase in Reynolds number, feed temperature and temperature difference. The increase in re-circulation ratio also increased the heat transfer coefficient but up to the value of 0.85 and after this the heat transfer coefficient started decreasing slowly and then remained almost constant. An experimental correlation has been developed to relate the Nusselt number and the parameters investigated during the research work.
Interaction of two cavitation bubbles in a tube and its effects on heat transfer
Liu, Bin; Cai, Jun; Tao, Yuequn; Huai, Xiulan
2017-02-01
When two cavitation bubbles exist in a confined space, the interaction between the bubbles significantly affects the characteristics of bubble dynamic behaviors. In this paper, a three-dimensional (3D) model is established to study the growth and collapse of two cavitation bubbles in a heated tube and its effects on heat transfer. The liquid and gas phases throughout the calculation domain are solved by a set of Navier-Stokes equations. It is assumed that the gas inside the bubble is compressible vapor, and the surrounding liquid is incompressible water. The mass transfer between two phases is ignored. The calculated bubble profiles were compared to the available experimental data, and a good agreement has been achieved. Then, the relationship among the bubble motion, flow field and pressure distributions was analyzed. On this basis, the effects of bubble interaction on the heat transfer between the wall surface and sounding liquid were discussed. It is found that heat transfer in the centre wall region is enhanced owing to the vortex flow and micro-jet induced by the bubble contraction and collapse. In contrast, the highest surface temperature appears in the surrounding region, which is mainly attributed to the thermal resistance induced by the bubble. The present study is helpful to understand the heat transfer phenomenon with cavitation in the liquid.
Convective heat transfer in foams under laminar flow in pipes and tube bundles.
Attia, Joseph A; McKinley, Ian M; Moreno-Magana, David; Pilon, Laurent
2012-12-01
The present study reports experimental data and scaling analysis for forced convection of foams and microfoams in laminar flow in circular and rectangular tubes as well as in tube bundles. Foams and microfoams are pseudoplastic (shear thinning) two-phase fluids consisting of tightly packed bubbles with diameters ranging from tens of microns to a few millimeters. They have found applications in separation processes, soil remediation, oil recovery, water treatment, food processes, as well as in fire fighting and in heat exchangers. First, aqueous solutions of surfactant Tween 20 with different concentrations were used to generate microfoams with various porosity, bubble size distribution, and rheological behavior. These different microfoams were flowed in uniformly heated circular tubes of different diameter instrumented with thermocouples. A wide range of heat fluxes and flow rates were explored. Experimental data were compared with analytical and semi-empirical expressions derived and validated for single-phase power-law fluids. These correlations were extended to two-phase foams by defining the Reynolds number based on the effective viscosity and density of microfoams. However, the local Nusselt and Prandtl numbers were defined based on the specific heat and thermal conductivity of water. Indeed, the heated wall was continuously in contact with a film of water controlling convective heat transfer to the microfoams. Overall, good agreement between experimental results and model predictions was obtained for all experimental conditions considered. Finally, the same approach was shown to be also valid for experimental data reported in the literature for laminar forced convection of microfoams in rectangular minichannels and of macrofoams across aligned and staggered tube bundles with constant wall heat flux.
Critical heat flux and boiling heat transfer to water in a 3-mm-diameter horizontal tube.
Energy Technology Data Exchange (ETDEWEB)
Yu, W.; Wambsganss, M. W.; Hull, J. R.; France, D. M.
2000-12-04
Boiling of the coolant in an engine, by design or by circumstance, is limited by the critical heat flux phenomenon. As a first step in providing relevant engine design information, this study experimentally addressed both rate of boiling heat transfer and conditions at the critical point of water in a horizontal tube of 2.98 mm inside diameter and 0.9144 m heated length. Experiments were performed at system pressure of 203 kPa, mass fluxes in range of 50 to 200 kg/m{sup z}s, and inlet temperatures in range of ambient to 80 C. Experimental results and comparisons with predictive correlations are presented.
Boiling Heat Transfer and Pressure Drop of Non-Azeotropic Mixtures Inside a Horizontal Grooved Tube
Kajikawa, Satoru; Ayukawa, Kyozo; Sogo, Motosuke; Okita, Yuji
The evaporation of HCFC141b, HFC152a and HFC23, and non-azeotropic refrigerant mixture used at the very low temperature refrigeration system is experimentally studied in a horizontal spirally grooved tube with corrugation. The experiments were conducted at 0.03 to 0.47MPa of boiling pressure, 100 kg/(m2s) of mass flux, 1 to 15 kW/ m2 of heat flux, -26 to 21 °C of refrigerant temperature and 11.4 mm of average inner diameter. It is concluded that boiling heat transfer coefficients of single-refrigerant are higher than these of non-azeotropic refrigerant mixture. And dimensionless correlation of the heat transfer coefficirnts, i.e. Lockhart-Martinelli parameters agreed with equation (10) within the limit of ±40 percent. Pressure drops of these refrigerant mixture depend on its liquid density and flow pattern.
The effect of the removal of steam generator tube ID deposits of heat transfer
Energy Technology Data Exchange (ETDEWEB)
Klimas, S.J.; Miller, D.G.; Semmler, J.; Turner, C.W
1998-12-01
The thermal resistance of boiler primary-side tube deposits from the Gentilly-2 Nuclear Generating Station (Hydro-Quebec) was evaluated by an experimental comparison of the heat-transfer rates between fouled samples and identical, factory-new, 'clean' tubing. The deposits were subsequently removed using either a chemical decontamination process (CAN-DEREM Plus) or a mechanical cleaning process (Siemens SIVABLAST) in two stages. After each removal, the thermal resistance of the remaining deposit was remeasured. The 90- to 150-{mu}m-thick deposits on the inside diameter of steam generator cold-leg tubes were found to pose significant resistance to heat transfer (0.05 to 0.06 m{sup 2}{center_dot}K/kW at 210 degrees C). However, the 10- to 30-{mu}m-thick dense layers remaining on the tubes after the decontamination were found to have no measurable effect on the heat transfer. The thin, 2-{mu}m tube deposit on the steam generator hot leg slightly enhanced heat transfer. The measured thermal resistance results in a calculated thermal conductivity of 1.5 W/m{center_dot}K for the 90-{mu}m-thick deposit. The 150-{mu}m-thick deposits were found to consist of two layers: an outer surface layer having an average porosity of 50% and a conductivity of 2.3 W/m{center_dot}K, and an inner layer having an average porosity of 5% and a conductivity of >3.0 W/m{center_dot}K. The previous best estimate of the thermal conductivity was 1.4 W/m.K for the porous magnetite deposits that had formed with a thickness <90 {mu}m on the primary side of nuclear steam generators. This work confirms this number, but also demonstrates that it is applicable only for porous, unconsolidated deposits. The conductivity increases for thicker deposits because of increasing deposit consolidation, particularly at the innermost layer adjacent to the tube metal. (author)
Energy Technology Data Exchange (ETDEWEB)
Hirata, T. (Faculty of Engineering, Shinshu Univ. (JP)); Hanaoka, C. (Nihon Tabaco Sangyo Co., Ltd. (JP))
1990-01-01
Laminar-flow heat transfer and ice formation phenomena in a horizontal tube with freezing have been examined experimentally. The effect of flow acceleration accompanied by ice growth on local ice thickness was studied, and it was found that the ice thickness can be correlated in terms of a flow acceleration parameter. The effect of natural convection in a horizontal tube with internal freezing on the heat transfer is also investigated. It is shown that the average Nusselt number in a horizontal tube with internal freezing is correlated with a modified form of Oliver's empirical formula for a horizontal tube without ice.
Directory of Open Access Journals (Sweden)
A. O. Morais
2015-06-01
Full Text Available AbstractEnhanced heat transfer in tubes under laminar flow conditions can be found in coils or corrugated tubes or in the presence of high wall relative roughness, curves, pipe fittings or mechanical vibration. Modeling these cases can be complex because of the induced secondary flow. A modification of the Graetz problem for non-Newtonian power-law flow is proposed to take into account the augmented heat transfer by the introduction of an effective radial thermal diffusivity. The induced mixing was modeled as an increased radial heat transfer in a straight tube. Three experiments using a coiled tube and a tubular heat exchanger with high relative wall roughness are presented in order to show how this parameter can be obtained. Results were successfully correlated with Reynolds number. This approach can be useful for modeling laminar flow reactors (LFR and tubular heat exchangers available in the chemical and food industries.
Fernández-Torrijos, María; Marugán-Cruz, Carolina; Sobrino, Celia; Santana, Domingo
2017-06-01
In this work, a molten salt test loop to study the heat transfer process in external molten salt receivers is described. The experimental installation is formed by a cylindrical molten salt tank, a pump, a flow meter, and an induction heater to generate the heat flux, which is applied in a small rectangular region of the tube surface. In central tower plants, the external receiver pipe is considered to be under unilateral concentrated solar radiation, because only one side of the pipe receives high heat flux. The main advantage of using an induction heater is the control of heating in different areas of the tube. In order to measure the effects of a non-homogenous and unsteady heat flux on the wall temperature distribution a series of experiments have been carried out. 4 K-type thermocouples have been welded at different axial and azimuthal positions of the pipe to obtain the wall temperature distribution. Different temperature measurements have been made varying the heat flux and water velocity to study their effects on the heat transfer process.
Investigation of boiling heat transfer of binary mixture from vertical tube embedded in porous media
Mo, Hailong; Ma, Tongze; Zhang, Zhengfang
1996-07-01
Ethanol-water binary mixtures with 7 different mole fractions of ethanol ranging from 0 to 1 were adopted as testing liquids in the experiment. The vertical heating tube was inserted in porous matrix composed of five well sorted glass beads whose diameters range from 0.5 to 4.3 mm. Due to the effect of composition, the trend of combination of vapor bubbles was reduced, resulting in the increase of peak heat flux of binary mixture. With the increase of ethanol mole fraction, 0.5 mm diameter bead had lower value of peak heat flux, while for pure liquid the critical state is difficult to appear. With given diameter of glass bead, there existed an optimum value of mole fraction of ethanol, which was decreased with the increase of bead diameter. A dimensionless heat transfer coefficient was predicted through the introduction of a dimensionless parameter of porous matrix, which agreed with the experimental results satisfactorily.
Prediction of the heat transfer rate of a single layer wire-on-tube type heat exchanger using ANFIS
Energy Technology Data Exchange (ETDEWEB)
Hayati, Mohsen [Electrical Engineering Department, Faculty of Engineering, Razi University, Tagh-E-Bostan, Kermanshah 67149 (Iran); Computational Intelligence Research Center, Razi University, Tagh-E-Bostan, Kermanshah 67149 (Iran); Rezaei, Abbas; Seifi, Majid [Electrical Engineering Department, Faculty of Engineering, Razi University, Tagh-E-Bostan, Kermanshah 67149 (Iran)
2009-12-15
In this paper, we applied an Adaptive Neuro-Fuzzy Inference System (ANFIS) model for prediction of the heat transfer rate of the wire-on-tube type heat exchanger. Limited experimental data was used for training and testing ANFIS configuration with the help of hybrid learning algorithm consisting of backpropagation and least-squares estimation. The predicted values are found to be in good agreement with the actual values from the experiments with mean relative error less than 2.55%. Also, we compared the proposed ANFIS model to an ANN approach. Results show that the ANFIS model has more accuracy in comparison to ANN approach. Therefore, we can use ANFIS model to predict the performances of thermal systems in engineering applications, such as modeling heat exchangers for heat transfer analysis. (author)
Directory of Open Access Journals (Sweden)
Yonghui Xie
2015-01-01
Full Text Available Flow characteristics and heat transfer performances in rectangular tubes with protrusions are numerically investigated in this paper. The thermal heat transfer enhancement of composite structures and flow resistance reduction of non-Newtonian fluid are taken advantage of to obtain a better thermal performance. Protrusion channels coupled with different CMC concentration solutions are studied, and the results are compared with that of smooth channels with water flow. The comprehensive influence of turbulence effects, structural effects, and secondary flow effects on the CMC’s flow in protrusion tubes is extensively investigated. The results indicate that the variation of flow resistance parameters of shear-thinning power-law fluid often shows a nonmonotonic trend, which is different from that of water. It can be concluded that protrusion structure can effectively enhance the heat transfer of CMC solution with low pressure penalty in specific cases. Moreover, for a specific protrusion structure and a fixed flow velocity, there exists an optimal solution concentration showing the best thermal performance.
Directory of Open Access Journals (Sweden)
Yanhong Wang
2014-11-01
Full Text Available In order to obtain a deeper understanding of the regenerative cooling process of scramjet engines, in this paper, a numerical investigation on the supercritical convective heat transfer of n-decane in horizontal circular tubes was conducted, based on a complete set of conservation equations and the Renormalization group (RNG k–ε turbulence model with enhanced wall treatment. The present study mainly focuses on the heat transfer deterioration (HTD phenomenon, including the mechanism and critical conditions for the onset of HTD. Moreover, the applicability of some conventional heat transfer empirical correlations was analyzed and compared, thus providing guidance for the Nusselt number predictions in the cooling channels. Results indicate that under the compositive conditions of low pressure and high heat flux, two types of HTD phenomena could occur when the wall and bulk fluid temperatures are near the pseudo-critical temperature, owing to the abnormal distributions of near-wall turbulent kinetic energy and radial velocity, respectively. Increasing the pressure would effectively alleviate and eliminate the HTD. A comparison of numerical results with those obtained with different empirical expressions shows that the Bae-Kim expression provides the best agreement, especially when HTD occurs. Furthermore, a new correction for critical heat flux of HTD has been successfully developed.
Directory of Open Access Journals (Sweden)
Jiang Yuguang
2016-01-01
Full Text Available Hydrocarbon fuel has been widely used in air-breathing scramjets and liquid rocket engines as coolant and propellant. However, possible heat transfer deterioration and threats from local high heat flux area in scramjet make heat transfer enhancement essential. In this work, 2-D steady numerical simulation was carried out to study different schemes of heat transfer enhancement based on a partially filled porous media in a tube. Both boundary and central layouts were analyzed and effects of gradient porous media were also compared. The results show that heat transfer in the transcritical area is enhanced at least 3 times with the current configuration compared to the clear tube. Besides, the proper use of gradient porous media also enhances the heat transfer compared to homogenous porous media, which could help to avoid possible over-temperature in the thermal protection.
Prediction of Heat Transfer Coefficient for Refrigerants Flowing in Horizontal Evaporator Tubes
Yoshida, Suguru; Mori, Hideo; Hong, Haiping; Matsunaga, Takashi
The objective of the present study is to develop a method which is generally applicable to the prediction of the axially local heat transfer coefficient for refigerants flowing in horizontal evaporator tubes. Existing correlations were compared with a data base, which was established from a large number of sources of measurements, covering a wide range of conditions. For an annular flow regime, correlations by Jung et al. and Takamatsu et al. had best accuracies of prediction but they were less accurate in the region of high Boiling number. No correlation was found to be generally applicable in a separated flow regime. A new general prediction method was, therefore, developed for both regimes. The correlation obtained for the annular flow regime has a good precision even in the region of high Boiling number. The prediction method proposed for the separated flow rigime, which takes account of the effect of circumferential heat conduction in the tube wall, is generally applicable irrespective of the tube material, its geometrical parameters and its heated conditions.
Research of heat transfer of staggered horizontal bundles of finned tubes at free air convection
Novozhilova, A. V.; Maryna, Z. G.; Samorodov, A. V.; Lvov, E. A.
2017-11-01
The study of free-convective processes is important because of the cooling problem in many machines and systems, where other ways of cooling are impossible or impractical. Natural convective processes are common in the steam turbine air condensers of electric power plants located within the city limits, in dry cooling towers of circulating water systems, in condensers cooled by air and water, in radiators cooling oil of power electric transformers, in emergency cooling systems of nuclear reactors, in solar power, as well as in air-cooling of power semiconductor energy converters. All this makes actual the synthesis of the results of theoretical and experimental research of free convection for heat exchangers with finned tube bundles. The results of the study of free-convection heat transfer for two-, three- and four-row staggered horizontal bundles of industrial bimetallic finned tubes with finning factor of 16.8 and equilateral tubes arrangement are presented. Cross and diagonal steps in the bundles are the same: 58; 61; 64; 70; 76; 86; 100 mm, which corresponds to the relative steps: 1.042; 1.096; 1.152; 1.258; 1.366; 1.545; 1.797. These steps are standardized for air coolers. An equation for calculating the free-convection heat transfer, taking into account the influence of geometrical parameters in the range of Rayleigh number from 30,000 to 350,000 with an average deviation of ± 4.8%, has been obtained. The relationship presented in the article allows designing a wide range of air coolers for various applications, working in the free convection modes.
Hibler, Susanne; Wagner, Christophe; Gieseler, Henning
2012-03-01
In order to optimize a freeze-drying cycle, information regarding the heat transfer characteristics of the container system is imperative. Two most recently developed tubing (TopLyo™) and molded (EasyLyo™) vial designs were compared with a standard serum tubing and molded vial, a polymer vial (TopPac™), and an amber molded EasyLyo™. In addition, the impact of methodology on the determination of reliable vial heat transfer coefficient (K(v) ) data is examined in detail. All K(v) s were gravimetrically determined by sublimation tests with pure water at 50, 100, 200, and 400 mTorr. In contrast to the traditional assumption that molded vials exhibit inefficient heat transfer characteristics, these vials showed a very similar performance compared with their serum tubing counterparts in the relevant pressure range for freeze-drying. At 100 mTorr, the TopLyo™ center vials show only 4% higher K(v) values than the EasyLyo™ center vials. All glass vials outmatch the polymer vial in terms of heat transfer, up to 30% elevated heat transfer for the TopLyo™ center vials at 400 mTorr. Sublimation tests have demonstrated to be a valuable tool to investigate the heat transfer characteristics of vials, but results are dependent on methodology. New developments in molded vial manufacturing lead to improved heat transfer performance. Copyright © 2011 Wiley Periodicals, Inc.
Heat Transfer Experiments with Supercritical CO{sub 2} in a Vertical Circular Tube (9.0 mm)
Energy Technology Data Exchange (ETDEWEB)
Yoo, Tae Ho; Kim, Hwan Yeol [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Sim, Woo Gun; Bae, Yoon Yeong [Hannam University, Daejeon (Korea, Republic of)
2008-10-15
Heat transfer test facility, SPHINX(Supercritical Pressure Heat transfer Investigation for NeXt generation), has been operated at KAERI for an investigation of the thermal-hydraulic behaviors of supercritical CO{sub 2} at several test sections with a different geometry. The loop uses CO{sub 2} because it has critical pressure and temperature which is much lower than water. Experimental study of heat transfer to supercritical CO{sub 2} in a vertical circular tube with and inner diameter of 9.0mm has been performed. CO{sub 2} flows downward through the vertical circular tube for the simulation of the water rod which may be used for a moderation of the reactor. The heat transfer characteristics were analyzed and compared with the upward flow test results previously performed at the same test section at KAERI.
Miyata, Kazushi; Mori, Hideo; Ohishi, Katsumi; Tanaka, Hirokazu
Experiments were performed on boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically downward in a copper smooth tube of 1.0 mm inside diameter for the development of a high-performance heat exchanger using small diameter tubes for air conditioning systems. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200 kg/(m2•s), heat fluxes from 1 to 16 kW/m2 and quality from 0.1 to over 1 at evaporation temperature of 10°C. Pressure drops were measured and flow patterns were observed at mass fluxes from 30 to 200 kg/(m2•s) and quality from 0.1 to 0.9. The characteristics of frictional pressure drop, heat transfer coefficient and dryout qualities were clarified by comparing the measurements with the data for the vertically upward flow previously obtained.
Higashiiue, Shinya; Momoki, Satoru; Shigechi, Toru; Mori, Hideo; Yamaguchi, Tomohiko
This paper presents a prediction method of flow regimes during evaporation of pure refrigerants in a horizontal spirally grooved steel tube with 12mm in average inner diameter. Circumferential temperature distributions on the external surface of the tube and boiling heat transfer coefficients were obtained through the experiments on the flow boiling heat transfer using two kinds of fluorocarbon refrigerants, HCFC123 and HCFC22. Based on the temperature distributions and the characteristics of heat transfer coefficient against vapor quality, we discussed the conditions of liquid film formed on the heat transfer surface. The experimental data were classified into four kinds of flow regimes according to the viewpoint on the liquid film conditions and heat transfer characteristics: annular flow, annular flow with liquid meniscus, separated flow with liquid meniscus and separated flow with dry surface. In order to predict the transition quality from separated flow to annular flow, we developed the correlation for border angle of well-wetted perimeter for the present grooved tube based on the Mori et al. correlation proposed for smooth tubes. The correlation for the transitional quality between separated flow with dry surface and separated flow with liquid meniscus was developed empirically as well as the correlation for the transient transitional quality between annular flow and annular flow with liquid meniscus.
Makarova, M. S.; Lushchik, V. G.
2017-11-01
Using a differential turbulence model, a numerical simulation of turbulent flow in a tube is carried out and the dependences of the flow and heat transfer characteristics on the intensity of the coolant injection through permeable walls are obtained. It is shown that the coefficients of friction and heat transfer decrease with increasing of injection rate. The comparison of calculation results reflecting the main features of rather complicated processes of flow in tube under gas injection with well-known experimental data over a wide range of the Reynolds number and the intensity of injection show their satisfactory agreement.
Liu, Song; Jin, Hua; Song, KeWei; Wang, LiangChen; Wu, Xiang; Wang, LiangBi
2017-10-01
The heat transfer performance of the tube bank fin heat exchanger is limited by the air-side thermal resistance. Thus, enhancing the air-side heat transfer is an effective method to improve the performance of the heat exchanger. A new fin pattern with flow redistributors and curved triangular vortex generators is experimentally studied in this paper. The effects of the flow redistributors located in front of the tube stagnation point and the curved vortex generators located around the tube on the characteristics of heat transfer and pressure drop are discussed in detail. A performance comparison is also carried out between the fins with and without flow redistributors. The experimental results show that the flow redistributors stamped out from the fin in front of the tube stagnation points can decrease the friction factor at the cost of decreasing the heat transfer performance. Whether the combination of the flow redistributors and the curved vortex generators will present a better heat transfer performance depends on the size of the curved vortex generators. As for the studied two sizes of vortex generators, the heat transfer performance is promoted by the flow redistributors for the fin with larger size of vortex generators and the performance is suppressed by the flow redistributors for the fin with smaller vortex generators.
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Hu, Haitao; Ding, Guoliang; Wei, Wenjian; Huang, Xiangchao; Wang, Zhence [Institute of Refrigeration and Cryogenics, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai 200240 (China)
2010-08-15
Two-phase heat transfer characteristics of R410A-POE oil mixture and R22-mineral oil mixture flow boiling inside a horizontal C-shape curved smooth tube with an outside diameter of 7.0 mm and a curvature ratio of 60 were investigated experimentally. The test results show that the curvature of C-shape curved smooth tube deteriorates the flow boiling heat transfer, and the ratios of the heat transfer coefficients in C-shape curved smooth tube to those in straight smooth tube for R410A-oil mixture and R22-oil mixture are within 0.46-0.74 and 0.74-0.90, respectively. A correlation to predict the heat transfer coefficients of refrigerant-oil mixtures flow boiling inside C-shape curved smooth tube was developed based on mixture properties of refrigerant-oil, and it could agree with 96% of the experimental data within a deviation of {+-}20%. (author)
Mori, Hideo; Yoshida, Suguru; Kakimoto, Yasushi; Ohishi, Katsumi
The authors had previously proposed a prediction method of the local heat transfer coefficient for pure refrigerants flowing in horizontal smooth evaporator tubes. This method was compared with new experimental data, and found not to be accurately applicable to refrigerants of a large vapor density and/or flow in a tube of small diameter, particularly in the separated flow regime1nthis prediction method, the separation angle is a primary factor, and correlation of this angle is used not only to classify the flow regime into the annular flow and the separated flow, but also to determine the ratio of the wet perimeter to the whole perimeter f the tube for the separated flow. Based on the new experimental data of the separation angle obtained for refrigerants of a large vapor density and in a small diameter tube, the correlation for the separation angle was reformed so that the predicted heat transfer coefficient agrees well also with the new experimental values.
Large-scale heat transfer experiments with supercritical R134a flowing upward in a circular tube
Energy Technology Data Exchange (ETDEWEB)
Feuerstein, Florian; Coelho Silva, Alexandre; Klingel, Denis; Cheng, Xu [KIT Karlsruhe Institute of Technology (Germany). Inst. of Fusion and Reactor Technology
2017-02-15
Heat transfer experiments with supercritical Freon R134a flowing upward in a circular tube with inner diameter of 10 mm and a heating length of 2,495 mm were conducted with a wide range of parameters: mass fluxes of 300 to 2,000 kg/m2s, heat fluxes of 10 to 200 kW/m2, bulk fluid temperature of 50 to 124 C and pressures of 4.22 to 5.51 MPa. Effects of heat flux, mass flux, pressure and inlet temperature on heat transfer behavior are analyzed. Significant heat transfer deterioration is observed above a critical heat flux to mass flux ratio. Six representative correlations were selected and compared with the test data.
Energy Technology Data Exchange (ETDEWEB)
Obot, N. T.; Das, L.; Rabas, T. J.
2000-11-14
The objectives of this presentation are two-fold: first, to demonstrate the connection between the attainable coefficients and transition to turbulent flow by using the transition-based corresponding states method to generalize results obtained with smooth tubes and enhanced tubes, and second, to provide guidelines on the calculation of heat transfer coefficients from pressure-drop data and vice versa by using the transition concept or the functional law of corresponding states.
Directory of Open Access Journals (Sweden)
Siddharth Shankar Bhatt
2016-01-01
Full Text Available This mathematical study is related to heat transfer under peristaltic flow of fractional second-grade fluid through nonuniform cylindrical tube with permeable walls. The analysis is performed under low Reynolds number and long wavelength approximation. The analytical solution for pressure gradient, friction force, and temperature field is obtained. The effects of appropriate parameters such as Grashof number, nonuniformity of tube, permeability of tube wall, heat source/sink parameter, material constant, fractional time derivative parameter and amplitude ratio on pressure rise, friction force, and temperature distribution are discussed. It is found that an increase in amplitude ratio and material constant causes increase in pressure but increase in nonuniformity of the tube causes decrease in pressure. It is also observed that variation of friction force against flow rate shows opposite behavior to that of pressure. Increase in temperature is also observed due to increase in heat source/sink parameter at inlet as well as downstream.
Havlik, Jan; Dlouhy, Tomas
This article deals with the experimental determination of heat transfer coefficients. The calculation of heat transfer coefficients constitutes a crucial issue in design and sizing of heat exchangers. The Wilson plot method and its modifications based on measured experimental data utilization provide an appropriate tool for the analysis of convection heat transfer processes and the determination of convection coefficients in complex cases. A modification of the Wilson plot method for shell-and-tube condensers is proposed. The original Wilson plot method considers a constant value of thermal resistance on the condensation side. The heat transfer coefficient on the cooling side is determined based on the change in thermal resistance for different conditions (fluid velocity and temperature). The modification is based on the validation of the Nusselt theory for calculating the heat transfer coefficient on the condensation side. A change of thermal resistance on the condensation side is expected and the value is part of the calculation. It is possible to improve the determination accuracy of the criterion equation for calculation of the heat transfer coefficient using the proposed modification. The criterion equation proposed by this modification for the tested shell-and-tube condenser achieves good agreement with the experimental results and also with commonly used theoretical methods.
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Junxia Zhang
2017-05-01
Full Text Available Field synergy characteristics in condensation heat transfer with non-condensable gas (NCG over a horizontal tube were numerically simulated. Consequently, synergy angles between velocity and pressure or temperature gradient fields, gas film layer thickness, and induced velocity and shear stress on gas–liquid interface were obtained. Results show that synergy angles between velocity and temperature gradient fields are within 73.2°–88.7° and ascend slightly with the increment in mainstream velocity and that the synergy is poor. However, the synergy angle between velocity and pressure gradient fields decreases intensively with the increase in mainstream velocity at θ ≤ 30°, thereby improving the pressure loss. As NCG mass fraction increases, the gas film layer thickness enlarges and the induced velocity and shear stress on gas–liquid interface decreases. The synergy angles between velocity and temperature gradient fields increase, and the synergy angles between velocity and pressure gradient fields change at θ = 70°, decrease at θ 70°. When the horizontal tube circumference angle increases, the synergy angles between velocity and temperature or pressure gradient fields decrease, the synergy between velocity and pressure fields enhances, and the synergy between velocity and temperature fields degrades.
Miyata, Kazushi; Mori, Hideo; Ohishi, Katsumi; Tanaka, Hirokazu
In the present study, experiments were performed to examine characteristics of flow boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically upward in a copper smooth tube with 1.0 mm inside diameter for the development of a high-performance heat exchanger using small diameter tubes for air conditioning systems. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200 kg/(m2•s), heat fluxes from 1 to 16 kW/m2 and qualities from 0.1 to over 1 at evaporation temperature of 10°C, and pressure drops were also measured at mass fluxes of 100 and 200 kg/(m2•s) and qualities from 0.1 to 0.9. Three types of flow pattern were observed in the tube: A slug, a slug-annular and an annular flow. Based on the measurements, the characteristics of frictional pressure drop, heat transfer coefficient and dryout qualities were clarified. The measured pressure drop and heat transfer coefficient were compared with correlations.
Condensation heat transfer and pressure drop of R-410A in flat aluminum multi-port tubes
Kim, Nae-Hyun
2018-02-01
Brazed heat exchangers with aluminum flat multi-port tubes are being used as condensers of residential air-conditioners. In this study, R-410A condensation tests were conducted in four multi-port tubes having a range of hydraulic diameter (0.78 ≤ Dh ≤ 0.95 mm). The test range covered the mass flux from 100 to 400 kg/m2 s and the heat flux at 3 kW/m2, which are typical operating conditions of residential air conditioners. Results showed that both the heat transfer coefficient and the pressure drop increased as the hydraulic diameter decreased. The effect of hydraulic diameter on condensation heat transfer was much larger than the predictions of existing correlations for the range of investigation. Comparison of the data with the correlations showed that some macro-channel tube correlations and mini-channel tube correlations reasonably predicted the heat transfer coefficient. However, macro-channel correlations highly overpredicted the pressure drop data.
Energy Technology Data Exchange (ETDEWEB)
Benmachiche, Abdelmoumene Hakim [University of Biskra, Department of Mechanics, Biskra (Algeria); Bougriou, Cherif [University of Batna, LESEI FSI Department of Mechanics, Batna (Algeria); Abboudi, Said [UTBM, Department of Mechanical Engineering, SET Laboratory, Belfort (France)
2010-12-15
In this work, we present the numerical results of the average heat transfer coefficients, h{sub {phi}}, over a circular plane fin in a finned-tube bundle for both aligned and staggered arrangements as well as the fin efficiency and the heat flux dissipated from the whole fin. The study covers a wide range of Reynolds number (2 x 10{sup 3}-3 x 10{sup 4}), for three different positions of the finned tube inside the heat exchanger. The temperature distribution on the fins surfaces was obtained experimentally using infrared thermography technique. The predicted values of the heat transfer coefficient were obtained numerically using the finite element method in conjunction with the conjugate gradient algorithm and the measured temperatures. (orig.)
Promthaisong, Pitak; Jedsadaratanachai, Withada; Chuwattanakul, Varesa; Eiamsa-ard, Smith
2017-08-01
The article presents a numerical analysis of turbulent periodic flow and heat transfer characteristics in a five-start spiral corrugated tube combined with five-channel twisted tape. Influences of the five-channel twisted tape with tape width ratio, w/D=0.10, 0.20, 0.30, 0.40 and 0.44 at constant the twisted length ratio, y/D=2.0 were described. The results were reported in term of flow structure, temperature distribution, TKE field, local Nusselt number distribution on the wall, Nusselt number ratio, friction factor ratio and thermal enhancement factor. The five-start spiral corrugated tube combined with five-channel twisted tape showed a main swirl flow and secondary swirl flow along the tube due to the induction of the spiral groove while the smooth circular tube appeared the straight only and the five-start spiral corrugated tube with the five-channel twisted tape at w/D=0.44 appeared the main swirl flow only. The swirl flow help to increase fluid mixing and increase in heat transfer rate over the smooth circular tube. The increase in the w/D lead to the rise of Nusselt number and friction factor. The result showed that the optimum thermal enhancement factor of about 1.16was found at the five-start spiral corrugated tube without the five-channel twisted tape and at w/D=0.44.
Momoki, Satoru; Higashiiue, Shinya; Shigechi, Toru; Mori, Hideo; Yamaguchi, Tomohiko
This paper presents a prediction method for evaporating heat transfer coeffcient of refrigerants fowing in a horizontal spirally grooved tube with consideration of flow regimes. The experimental data employed for development of the correlation equation were measured at pressures 0.2-1.1 MPa, mass velocities 100-300kg/(m2s), heat fluxes5-25 kW/m2 and vapor qualities 0.1-0.8 with HCFC123 and HCFC22 using a spirally grooved steel tube with 12mm in average inner diameter, 32 in number of groove, 0.4 mm in depth of groove and 15 degree in helix angle. In the previous paper, the authors showed that the flow patterns of evaporating refrigerant inside a horizontal spirally grooved tube could be classified into four types : annular flow, annular flow with liquid meniscus, separated flow with liquid meniscus and separated flow with dry surface, and proposed the correlations for the borders of each flow regime. In the present paper the correlation equations for heat transfer coeffcient were developed for each flow regime. The calculated heat transfer coefficient showed good agreement with the experimental data for all flow regimes. The mean deviation between the calculated and the measured heat transfer coefficient is ±12.6% for the all present experimental data.
Directory of Open Access Journals (Sweden)
Alexey G. Abramov
2015-12-01
Full Text Available Results of the numerical simulation of turbulent flow field and heat transfer of liquid metal in cross-flow over inline tube bundles consisting of smooth round tubes are presented. Computations have been performed with CFD-code ANSYS Fluent on the base of a two-dimensional unsteady RANS formulation using the SST turbulence model by Menter and assuming constant physical properties of a fluid with the Prandtl number equal to 0.023. The Reynolds number ranged from 26,200 to 52,400. Instantaneous and time-averaged velocity and temperature fields obtained for bundles of different intertube spacing with a variation of the bundle width (number of tube rows in the cross direction were analyzed. Integral characteristics of heat transfer were compared with the experimental data.
Energy Technology Data Exchange (ETDEWEB)
Welty, J. R.
1984-01-01
The project involved two parts: analytical and experimental. The progression of work includes the following major divisions: analytical studies involving studies of heat transfer, hydrodynamics of gas flow within the bed, and some considerations of bubble and adjacent tube influences on the heat transfer; experimental apparatus including the instrumented tubes for heat transfer measurements, digital data acquisition, and the high temperature fluidized bed test facility; experimental results; and experimental validation of the analytical model.
Directory of Open Access Journals (Sweden)
Kadhim S. K.
2016-01-01
Full Text Available The aim of this work is to investigate experimentally the effect of the forced vibrations on the free convection heat transfer coefficient using heated longitudinally finned cylinder made of Aluminium. The effect of the vibration frequency ranged from 2 to16 Hz with various heat fluxes ranged from 500-1500 W/m2. It was found that, the relation between the heat transfer coefficient and amplitude of vibration increased for all inclination angles from (0°-45°, while the increment of inclination angle decreases the values of convection heat transfer coefficient. The results show that the heat transfer coefficient ratio (hv/ho of longitudinal finned cylinders in (0° angle was (8% and (30% greater than those for the (30° and (45° respectively.
Wang, Liang-Bi; Zhang, Qiang; Li, Xiao-Xia
2009-01-01
This paper aims to contribute to a better understanding of convective heat transfer. For this purpose, the reason why thermal diffusivity should be placed before the Laplacian operator of the heat flux, and the role of the velocity gradient in convective heat transfer are analysed. The background to these analyses is that, when the energy…
Federal Laboratory Consortium — The Heated Tube Facility at NASA GRC investigates cooling issues by simulating conditions characteristic of rocket engine thrust chambers and high speed airbreathing...
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim
2017-01-01
Vortex generator is considered as an effective device for augmentation of the thermal-hydraulic performance of a heat exchanger. The aim of present study is to examine the influence of vortex generators on a double fin and tube heat exchanger performance. Vortex generator of rectangular winglet...... loss characteristics are determined and analyzed for an in-line configuration of a fin and tube heat exchanger. In order to evaluate the enhancement in the performance on an equitable basis, the heat exchanger with plain fin surface is considered as a reference design. Results show that the angle...... of attack of a vortex generator has a significant impact on the volume goodness factor, and enhance the thermal performance of a fin and tube heat exchanger in comparison to the design with plain fin. The vortex generator at an angle of attack ??10 is found to perform superior over the Reynolds number range...
坂口, 勝次; 鈴木, 康太郎; サカグチ, カツジ; スズキ, コウタロウ; Katsuji, SAKAGUCHI; Kotaro, SUZUKI
2006-01-01
To attempt the heat transfer enhancement, the experimental study of convective heat transfer around a horizontal circular cylinder across the oscillatory flow was carried out in the closed resonance tube. The oscillatory flow was occurred from the resonance of air column produced by a piston type pump in which a piston was reciprocated as an oscillator. The frequency was changed in the range of 10 to 22.5Hz under the constant amplitude. The velocity and pressure in the oscillatory flow were m...
Suri, Amar Raj Singh; Kumar, Anil; Maithani, Rajesh
2018-01-01
The present work deals with experimental investigation of heat transfer and fluid flow characteristics of multiple square perforated twisted tape with wing inserts in a heat exchanger tube. The range of selected geometrical parameters are, perforation width ratio (a/WT) of 0.083-0.333, twist ratio (TL/WT) of 2.0-3.5, wing depth ratio (Wd/WT) of 0.042-0.167 and number of twisted tapes (TP) of 4. The Reynolds number (Ren) selected for experimentation ranges from 5000 to 27,000. The maximum heat transfer and friction factor enhancement was found to be 6.96 and 8.34 times that of plane tube, respectively. The maximum heat transfer enhancement is observed at a a/WT of 0.250, TL/WT of 2.5, and Wd/WT of 0.167.
Terekhov, V. I.; Bogatko, T. V.
2017-03-01
The results of a numerical study of the influence of the thicknesses of dynamic and thermal boundary layers on turbulent separation and heat transfer in a tube with sudden expansion are presented. The first part of this work studies the influence of the thickness of the dynamic boundary layer, which was varied by changing the length of the stabilization area within the maximal extent possible: from zero to half of the tube diameter. In the second part of the study, the flow before separation was hydrodynamically stabilized and the thermal layer before the expansion could simultaneously change its thickness from 0 to D1/2. The Reynolds number was varied in the range of {Re}_{{{{D}}1 }} = 6.7 \\cdot 103 {{to}} 1.33 \\cdot 105, and the degree of tube expansion remained constant at ER = ( D 2/ D 1)2 = 1.78. A significant effect of the thickness of the separated boundary layer on both dynamic and thermal characteristics of the flow is shown. In particular, it was found out that with an increase in the thickness of the boundary layer the recirculation zone increases and the maximal Nusselt number decreases. It was determined that the growth of the heat layer thickness does not affect the hydrodynamic characteristics of the flow after separation but does lead to a reduction of heat transfer intensity in the separation area and removal of the coordinates of maximal heat transfer from the point of tube expansion. The generalizing dependence for the maximal Nusselt number at various thermal layer thicknesses is given. Comparison with experimental data confirmed the main trends in the behavior of heat and mass transfer processes in separated flows behind a step with different thermal prehistories.
Ice slurry flow and heat transfer during flow through tubes of rectangular and slit cross-sections
Directory of Open Access Journals (Sweden)
Niezgoda-Żelasko Beata
2014-09-01
Full Text Available The paper presents the results of experimental research of pressure drop and heat transfer coefficients of ice slurry during its flow through tubes of rectangular and slit cross-sections. Moreover, the work discusses the influence of solid particles, type of motion and cross-section on the changes in the pressure drop and heat transfer coefficient. The analysis presented in the paper allows for identification of the criterial relations used to calculate the Fanning factor and the Nusselt number for laminar and turbulent flow, taking into account elements such as phase change, which accompanies the heat transfer process. Ice slurry flow is treated as a generalized flow of a non-Newtonian fluid.
Gomez, C. F.; Mireles, O. R.; Stewart, E.
2016-01-01
The Space Capable Cryogenic Thermal Engine (SCCTE) effort considers a nuclear thermal rocket design based around a Low-Enriched Uranium (LEU) design fission reactor. The reactor core is comprised of bundled hexagonal fuel elements that directly heat hydrogen for expansion in a thrust chamber and hexagonal tie-tubes that house zirconium hydride moderator mass for the purpose of thermalizing fast neutrons resulting from fission events. Created 3D steady state Hex fuel rod model with 1D flow channels. Hand Calculation were used to set up initial conditions for fluid flow. The Hex Fuel rod uses 1D flow paths to model the channels using empirical correlations for heat transfer in a pipe. Created a 2-D axisymmetric transient to steady state model using the CFD turbulent flow and Heat Transfer module in COMSOL. This model was developed to find and understand the hydrogen flow that might effect the thermal gradients axially and at the end of the tie tube where the flow turns and enters an annulus. The Hex fuel rod and Tie tube models were made based on requirements given to us by CSNR and the SCCTE team. The models helped simplify and understand the physics and assumptions. Using pipe correlations reduced the complexity of the 3-D fuel rod model and is numerically more stable and computationally more time-efficient compared to the CFD approach. The 2-D axisymmetric tie tube model can be used as a reference "Virtual test model" for comparing and improving 3-D Models.
Energy Technology Data Exchange (ETDEWEB)
Roko, K.; Shiraha, M. (Kawasaki Heavy Industries Ltd., Akashi, Hyogo (Japan). Technical Inst.)
1980-09-01
Importance of the problem of post-dryout heat transfer is increasing in the field of the new technologies being developed lately. This is because the correct understanding of post-dryout heat transfer characteristics together with the position of dryout point is important in designing steam generators and evaluating their safety. By this experiment, the data on the post-dryout heat transfer coefficient in vapor/water system in a vertical straight tube by sodium heating were obtained in the ranges of pressure from 8.2 to 14.3 MPa and mass flow from 240 to 550 kg/m/sup 2/s, for the straight tube steam generators for fast breeder reactors. Based on the result, the investigation by the comparison with the existing correlating equations showed that all equations except the Remizov's equation gave considerably higher values than the experimental value, and the difference was larger as the pressure and flow rate were lower. Next, from the viewpoint that the thermal non-equilibrium of droplets and vapor basically governs the post-dryout heat transfer, the initial diameter of droplets was arranged in the form of a correlating equation after establishing an analytical model and determining the diameter capable of evaluating the experimental values most reasonably. Comparison of the calculated value of heat transfer coefficient by this equation with this experimental value and with the experimental value obtained by electric heating in the region including high flow rate range of 5200 kg/m/sup 2/s or less by Bennett showed good agreement.
Energy Technology Data Exchange (ETDEWEB)
Kang, Deog Ji
2008-02-15
The SCWR(Super Critical Water-cooled Reactor) is one of the feasible options for the 4th generation nuclear power plant, which is being pursued by an international collaborative organization, the Gen IV International Forum(GIF). The major advantages of the SCWR include a high thermal efficiency and a maximum use of the existing technologies. In the SCWR, the coolant(water) of a supercritical pressure passes the pseudo-critical temperature as it flows upward through the sub-channels of the fuel assemblies. At certain conditions a heat transfer deterioration occurs near the pseudo-critical temperature and it may cause an excessive rise of the fuel surface temperature. Therefore, an accurate estimation of the heat transfer coefficient is necessary for the thermal-hydraulic design of the reactor core. A test facility, SPHINX(Supercritical Pressure Heat Transfer Investigation for the Next Generation), dedicated to produce heat transfer data and study flow characteristics, uses supercritical pressure CO{sub 2} as a surrogate medium to take advantage of the relatively low critical temperature and pressure: and similar physical properties with water. The produced data includes the temperature of the heating surface and the heat transfer coefficient at varying mass fluxes, heat fluxes, and operating pressures. The test section is a circular tube of ID 6.32 mm: it is almost the same as the hydraulic diameter of the sub-channel in the conceptional design presented by KAERI. The test range of the mass flux is 285 to 1200 kg/m{sup 2}s and the maximum heat flux is 170 kW/m{sup 2}. The tests were mainly performed for an inlet pressure of 8.12 MPa which is 1.1 times of critical pressure. With the test results of the wall temperature and the heat transfer coefficient, effects of mass flux, heat flux, inlet pressure, and the tube diameter on the heat transfer were studied. And the test results were compared with the existing correlations of the Nusselt number. In addition, New
Energy Technology Data Exchange (ETDEWEB)
Turner, C.W.; Klimas, S.J.; Brideau, M.G
2000-02-01
Degradation of the thermal performance of steam generators(SGs) is a serious problem in nuclear power stations throughout the world (Lovett and Dow, 1991). In pressurized-heavy-water reactors (PWHRs), the reduced thermal performance of the SGs is manifested by an increase of the primary coolant reactor inlet header temperature (RIHT). In pressurized-light-water reactors(PWRs), which operate with fixed primary coolant temperature, the loss of thermal performance is manifested by a reduction of the steam pressure. Degradation mechanisms that may contribute to the loss of SG thermal performance include: fouling of the boiler tube inner surfaces (primary-side fouling); fouling of the boiler tube outer surfaces (secondary-side fouling); divider and thermal plate leakage that causes the coolant to bypass either the SG or the integral preheater and fouling of the steam separators. The relative contribution of these various degradation mechanisms to the overall loss of thermal performance is still under investigation. Soulard et al. (1990) examined the relative contributions of tube bundle fouling, divider plate leakage, and thermal plate leakage to the increase in RIHT at the Point Lepreau Generating Station, and concluded that tube fouling contributes to a significant fraction of the loss of thermal performance. Corrosion products deposit on both the inner and outer surfaces of the boiler tubes. Thus a complete understanding of the reasons fro the loss of thermal performance and the development of strategies to mitigate this loss requires a knowledge of the thermal resistance of tube deposits under primary and secondary side heat transfer conditions. We present here the results of measurements of the thermal resistance of primary-side and secondary-side boiler tube deposits performed under single-phase forced convection and flow-boiling conditions, respectively. The results are discussed in terms of the physical properties of the deposit and the mode of heat transfer.
DEFF Research Database (Denmark)
Hærvig, Jakob; Sørensen, Kim; Condra, Thomas Joseph
2017-01-01
in the ranges 0–0.16 and 0–2.0 respectively. The 3D Unsteady Reynolds-averaged Navier–Stokes (URANS) equations combined with the transition SST turbulence model are solved using the finite volume method to obtain the fully-developed flow field in a repeatable section of the heat exchangers at a constant wall......A numerical study has been carried out to investigate heat transfer enhancing flow field in 28 geometrically different sinusoidally, spirally corrugated tubes. To vary the corrugation, the height of corrugation e/D and the length between two successive corrugated sections p/D are varied...
Directory of Open Access Journals (Sweden)
Amnart Boonloi
2015-01-01
Full Text Available 3D numerical investigations are performed to study the heat transfer, friction factor, and thermal performance of a fin-and-oval heat exchanger with punched delta wings for a range of 500 ≤ Re ≤ 2500 (based on the hydraulic diameter. The influences of the punched angles, 20°, 30°, and 45°, flow directions, wing tips pointing downstream and upstream, and pitch ratios, 2, 3, 4, 5, and 6, are investigated. The results show that the use of the punched delta wings in the fin-and-oval-tube heat exchanger leads to an enhancement in the heat transfer and friction loss as compared to the plain fin for all cases (Nu/Nu0 and f/f0 higher than 1. The enhancements of the heat transfer and friction factor are around 1.01–1.22 and 1.37–2.65 times higher than the base case, respectively. The punched delta wings create the vortex flows through the test section that helps enhance the strength of the impinging flow on the tube walls. The impingement of the fluid flow is an important key to augment the heat transfer rate and thermal performance in the heat exchanger.
Senhaji, S.; Feddaoui, M.; Mediouni, T.; Mir, A.
2009-03-01
A numerical study of the evaporation in mixed convection of a pure alcohol liquid film: ethanol and methanol was investigated. It is a turbulent liquid film falling on the internal face of a vertical tube. A laminar flow of dry air enters the vertical tube at constant temperature in the downward direction. The wall of the tube is subjected to a constant and uniform heat flux. The model solves the coupled parabolic governing equations in both phases including turbulent liquid film together with the boundary and interfacial conditions. The systems of equations obtained by using an implicit finite difference method are solved by TDMA method. A Van Driest model is adopted to simulate the turbulent liquid film flow. The influence of the inlet liquid flow, Reynolds number in the gas flow and the wall heat flux on the intensity of heat and mass transfers are examined. A comparison between the results obtained for studied alcohols and water in the same conditions is made.
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Hori, M.; Tsumita, Y.; Nakamura, S. (Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan))
1992-01-01
The mechanism of rifled tube for the DNB improvement was studied to reflect the superior characteristics to the practical design and to get the quantitative data. Now, the application of the rifled tube to evaporator tube is studied. The pressure drop of two-phase flow could be derived by using the pressure drop of single phase flow and an emperical formula was derived from the experimental results. In addition, the two-phase DNB predicting method of rifled tube which provides a flow disturbing effect based on the knowledge of two-phase flow of smooth tube. This predicting formula enabled the prediction of DNB in both areas where the DNB improving effect was recognized and the DNB improving effect was not recognized. The behavior of DNB characteristics of rifled tube which had been fragmentary was analyzed by simulating experiments using freon. As a result, it was found that the area showing the large DNB improving effect transferred to higher mass velocity side and the area showing few DNB improving effect spread by the increase of pressure and heat flux. 9 refs., 14 figs., 1 tab.
Directory of Open Access Journals (Sweden)
Thamir K. Jassem
2015-02-01
Full Text Available An experimental forced laminar study was presented in this research for an air flowing through a circular channel for different angles ( ,30o,45o,60o, the channel was heated at constant heat flux , the channel also was packed with steel and glass spheres respectively . The tests were done for three values of Peclets number (2111.71,3945.42,4575.47 with changing the heat flux for each case and five times for each number.The results showed that the dimensionless temperature distribution will decrease with increasing the dimensionless channel length for all cases with changing Peclet number, heat flux and inclination angles, and its lowest value will be for glass spheres at highest flux, while at lower flux for , and the decreasing in dimensionless temperature was closed for both types of packed at other inclination angles.The study declared that the local Nusselt number decreases with increasing the dimensionless length of the channel for both packeds and for different applied heat flux, also through this study it was declared that the average Nusselt increases as Peclet number increases for both packed. Its value for the glass spheres is greater than the steel spheres with percentage (98.3% at small Peclet, and percentage (97.2% at large Peclet number for the horizontal tube, and (98.3% at small Peclet number and (97.8% at large Peclet number at .Through this study its was found that average Nusselt number increases along the channel as the heat flux increases, because the bulk temperature will increase as the flow proceeds toward the end of the channel , so the heat transfer coefficient will increase. It was declared from this study that in the case of the steel packed the heat transfer will occur mainly by conduction, while in the case of glass packed the heat transfer will occur mainly by laminar forced convection, where the lowest Nusselt number (Nu=3.8 was found when the pipe is horizontal and lowest heat flux and lowest Peclet number.
Qi, Cong; Li, Chunyang; Wang, Guiqing
2017-09-01
The flow and heat transfer characteristics of TiO2-water nanofluids with different nanoparticle mass fractions in a spirally fluted tube and a smooth tube are experimentally investigated at different Reynolds numbers. The effects of pH values and doses of dispersant agent on the stability of TiO2-water nanofluids are discussed. The effects of nanoparticle mass fractions and Reynolds numbers on Nusselt numbers and frictional resistance coefficients in the spirally fluted tube and the smooth tube are also investigated. It is found that TiO2-water nanofluids in the spirally fluted tube have a larger enhancement than that in the smooth tube. The heat transfer enhancement and the increase in frictional resistance coefficients of TiO2-water nanofluids in the spirally fluted tube and the smooth tube for laminar flow and turbulent flow are compared. It is found that there are a larger increase in heat transfer and a smaller increase in frictional resistance coefficients for turbulent flow than that for laminar flow of TiO2-water nanofluids in the spirally fluted tube. The comprehensive evaluations for the thermo-hydraulic performance of TiO2-water nanofluids in the smooth tube and spirally fluted tube are also discussed.
Directory of Open Access Journals (Sweden)
Okbaz Abdulkerim
2017-01-01
Full Text Available In this study 3-D numerical simulations on heat transfer and pressure drop characteristics for a typical louver fin-and- double-row tube heat exchanger were carried out. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles, fin pitch and Reynolds number, and reported in terms of Colburn j-factor and Fanning friction factor f. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles between 20° ≤Ө≤ 30°, louver pitch of Lp=3.8 mm and frontal velocities of U between 1.22 m/s - 3 m/s. In addition, flow visualization of detailed flow features results, such as velocity vectors, streamlines and temperature counters have been shown to understand heat transfer enhancement mechanism. The present results indicated that louver angle and fin pitch noticeably affected the thermal and hydraulic performance of heat exchanger. It has been seen that increasing louver angle, increases thermal performance while decreasing hydraulic performance associated to pressure drop for fin pitches of 3.2 mm and 2.5 mm. Fin pitch determines the flow behaviour that for fin pitch of 2 mm, increasing louver angle decreased heat transfer and pressure drop. Velocity vectors and streamlines give considerable information about the flow whether it is duct directed or louver directed. For all conditions the flow is louver directed.
Energy Technology Data Exchange (ETDEWEB)
Takeda, Takeshi; Furusawa, Takayuki [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Miyamoto, Satoshi [Japan Atomic Power Company, Tokyo (Japan)
2001-07-01
Heat transfer tubes of a primary pressurized water cooled (PPWC) in the high temperature engineering test reactor (HTTR) form the reactor pressure boundary of the primary coolant, therefore are important from the viewpoint of safety. To establish inspection techniques for the heat transfer tubes of the PPWC, an automatic inspection system was developed. The system employs a bobbin coil probe, a rotating probe for eddy current testing (ECT) and a rotating probe for ultrasonic testing (UT). Nondestructive test of a half of the heat transfer tubes of the PPWC was carried out by the automatic inspection system during reactor shutdown period of the HTTR (about 55% in the maximum reactor power in this paper). The nondestructive test results showed that the maximum signal-to-noise ratio was 1.8 in ECT. Pattern and phase of Lissajous wave, which were obtained for the heat transfer tube of the PPWC, were different from those obtained for the artificially defected tube. In UT echo amplitude of the PPWC tubes inspected was lower than 20% of distance-amplitude calibration curve. Thus, it was confirmed that there was no defect in depth, which was more than the detecting standard of the probes, on the outer surface of the heat transfer tubes of the PPWC inspected. (author)
Yang, Dong; Shen, Zhi; Chen, Tingkuan; Zhou, Chenn Q.
2013-07-01
The characteristics of flow boiling heat transfer and pressure drop of organic fluid with high saturation temperature in a vertical porous coated tube are experimentally studied in this paper. The experiments are performed at evaporation pressure of 0.16-0.31MPa, mass flux of 390-790kg/m2s, and vapor quality of 0.06-0.58. The variations of heat transfer coefficient and pressure drop with vapor quality are measured and compared to the results of smooth tube. Boiling curves are generated at mass flux of 482 and 675kg/m2s. The experimental results indicate that the heat transfer coefficients of the porous tube are 1.8-3.5 times those of smooth tube, and that the frictional pressure drops of the porous tube are 1.1-2.9 times those of smooth tube. The correlations for heat transfer coefficient and frictional pressure drop are derived, in which the effect of fluid molecular weight is included. The experiments show that significant heat transfer enhancement is accompanied by a little pressure drop penalty, the application of the porous coated tube is promising in the process industries.
Simulations of Special Interior Ballistic Phenomena with and without Heat Transfer to Gun Tube Wall.
1986-05-01
34Catlcurlion of Heat Trarsfer to the Gun Barrel WaLt ," J. Ballistics 6 (3), pp. 1518-1524, 1982. 7 Barlett , E.P., Anderson, L.W., Kendall, L.:!., ’Time...34Calculation of Heat Transfer to the Gun Barrel Wall," J. Ballistics 6 (3), pp. 1518-1524, 1982. 7. Barlett , E.P., Anderson, L.W., Kendall, R.M., "Time...47 HQS Santa Monica CA Only) Washington, DC 20505 90401-3297 I Foster Miller Associates General Applied Sciences Lab ATTN: A. Erickson ATTN: J. Erdos
Directory of Open Access Journals (Sweden)
P. Shahmohammadi
2016-01-01
Full Text Available The effect of γ-Al2O3 nanoparticles on heat transfer rate, baffle spacing and pressure drop in the shell side of small shell and tube heat exchangers was investigated numerically under turbulent regime. γ-Al2O3-water nanofluids and pure water were used in the shell side and the tube side of heat exchangers, respectively. Since the properties of γ-Al2O3-water nanofluids were variable, they were defined using the user define function. The results revealed that heat transfer and pressure drop were increased with mass flow rate as well as baffle numbers. Adding nanoparticles to the based fluid did not have a significant effect on pressure drop in the shell side. The best heat transfer performance of heat exchangers was for γ-Al2O3-water 1 vol.% and higher nanoparticles concentration was not suitable. The suitable baffle spacing was 43.4% of the shell diameter, showing a good agreement with Bell-Delaware method.
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Cho, Yong Jin; Ahn, Seung Hoon; Kim, Kap; Kim, Hho Jung [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)
2009-07-01
TRACE assessment was performed to investigate local condensation heat transfer coefficients in the presence of a noncondensable gas inside a vertical tube. The data obtained from pure steam and steam/nitrogen mixture condensation experiments were compared to study the effects of noncondensable nitrogen gas on the annular film condensation phenomena. The condenser tube had a small inner diameter of 13mm (about 1/2-in.) and this experiment had been performed to prove the effectiveness of the a Passive Residual Heat Removal System (PRHRS) of SMART (System-integrated Modular Advanced ReacTor), which is a small modular integral-type pressurized water reactor that is developed for the dual purposes of seawater desalination and small-scaled power generation. In the case of nitrogen presence, TRACE results show the converged results but the prediction is different from experimental data. The candidate reasons can be focused on several models, such as the film thickness calculation, surface area, and condensation heat transfer correlations, etc. In the case of pure steam condensation case, TRACE results shows large oscillations and do not converge. This should be investigated in detail to identify the reason. Until now, the oscillation in thermal hydraulic parameters results from the film thickness calculation and surface area calculation. For future works, the whole sets of the experiment will be assessed and the improvement of TRACE will be performed.
Grabski, Jakub Krzysztof; Kołodziej, Jan Adam
2016-06-01
In the paper an analysis of fluid flow and heat transfer of a power-law fluid in an internally finned tube with different fin length is conducted. Nonlinear momentum equation of a power-law fluid flow and nonlinear energy equation are solved using the Picard iteration method. Then on each iteration step the solution of inhomogeneous equation consists of two parts: the general solution and the particular solution. Firstly the particular solution is obtained by interpolation of the inhomogeneous term by means of the radial basis functions and monomials. Then the general solution is obtained using the method of fundamental solutions and by fulfilling boundary conditions.
REVIEW ON SHELL AND TUBE HEAT EXCHANGER USING NANOFLUIDS
Nitheesh Krishnan M C*, B Suresh Kumar
2017-01-01
Different types of heat exchangers are extensively used in various industries to transfer the heat between cold and hot fluids. The key role of the heat exchanger is to transfer heat at maximum rate .Shell and Tube heat exchangers are having special importance in boilers, oil coolers, condensers, pre-heaters. Shell and Tube heat exchanger is one such heat exchanger, provides more area for heat transfer between two fluids in comparison with other type of heat exchanger. To intensify heat trans...
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Huang, Xiangchao; Ding, Guoliang; Hu, Haitao; Zhu, Yu.; Peng, Hao [Institute of Refrigeration and Cryogenics, Shanghai Jiaotong University, Shanghai 200240 (China); Gao, Yifeng [International Copper Association Shanghai Office, Shanghai 200020 (China); Deng, Bin [Institute of Heat Transfer Technology, Golden Dragon Precise Copper Tube Group Inc., Shanghai 200135 (China)
2010-01-15
The influence of oil on condensation heat transfer of R410A inside 4.18 mm and 1.6 mm inner diameter horizontal smooth tubes is investigated experimentally. The experimental condensing temperature is 40 C, and nominal oil concentration range is from 0% to 5%. The test results indicate that the presence of oil deteriorates the heat transfer, and the deterioration effect becomes obvious with the increase of oil concentration. At oil concentration of 5%, the heat transfer coefficient decreases by maximum 24.9% and 28.5% for 4.18 mm and 1.6 mm tubes, respectively. A new correlation for heat transfer coefficients of R410A-oil mixture flow condensation inside smooth tubes is proposed, which agrees with all the experimental data within a deviation of -30% {proportional_to} +20%. (author)
Heat transfer, pressure drop and void fraction in two- phase, two-component flow in a vertical tube
Sujumnong, Manit
1998-09-01
There are very few data existing in two-phase, two- component flow where heat transfer, pressure drop and void fraction have all been measured under the same conditions. Such data are very valuable for two-phase heat-transfer model development and for testing existing heat-transfer models or correlations requiring frictional pressure drop (or wall shear stress) and/or void fraction. An experiment was performed which adds markedly to the available data of the type described in terms of the range of gas and liquid flow rates and liquid Prandtl number. Heat transfer and pressure drop measurements were taken in a vertical 11.68-mm i.d. tube for two-phase (gas-liquid) flows covering a wide range of conditions. Mean void fraction measurements were taken, using quick- closing valves, in a 12.7-mm i.d. tube matching very closely pressures, temperatures, gas-phase superficial velocities and liquid-phase superficial velocities to those used in the heat-transfer and pressure-drop experiments. The gas phase was air while water and two aqueous solutions of glycerine (59 and 82% by mass) were used as the liquid phase. In the two-phase experiments the liquid Prandtl number varied from 6 to 766, the superficial liquid velocity from 0.05 to 8.5 m/s, and the superficial gas velocity from 0.02 to 119 m/s. The measured two-phase heat-transfer coefficients varied by a factor of approximately 1000, the two-phase frictional pressure drop ranged from small negative values (in slug flow) to 93 kPa and the void fraction ranged from 0.01 to 0.99; the flow patterns observed included bubble, slug, churn, annular, froth, the various transitions and annular-mist. Existing heat-transfer models or correlations requiring frictional pressure drop (or wall shear stress) and/or void fraction were: tested against the present data for mean heat-transfer coefficients. It was found that the methods with more restrictions (in terms of the applicable range of void fraction, liquid Prandtl number or liquid
Flow boiling heat transfer coefficient of R-134a/R-290/R-600a mixture in a smooth horizontal tube
Directory of Open Access Journals (Sweden)
Balakrishnan Raja
2008-01-01
Full Text Available An investigation on in-tube flow boiling heat transfer of R-134a/R-290/R-600a (91%/4.068%/4.932% by mass refrigerant mixture has been carried out in a varied heat flux condition using a tube-in-tube counter-flow test section. The boiling heat transfer coefficients at temperatures between -5 and 5°C for mass flow rates varying from 3 to 5 g/s were experimentally arrived. Acetone is used as hot fluid, which flows in the outer tube of diameter 28.57 mm, while the test fluid flows in the inner tube of diameter 9.52 mm. By regulating the acetone flow rate and its entry temperature, different heat flux conditions between 2 and 8 kW/m2 were maintained. The pressure of the refrigerant was maintained at 3.5, 4, and 5 bar. Flow pattern maps constructed for the considered operating conditions indicated that the flow was predominantly stratified and stratified wavy. The heat transfer coefficient was found to vary between 500 and 2200 W/m2K. The effect of nucleate boiling prevailing even at high vapor quality in a low mass and heat flux application is high-lighted. The comparison of experimental results with the familiar correlations showed that the correlations over predict the heat transfer coefficients of this mixture.
Chindyakov, A. A.; Smirnov, Yu B.; Mikhailova, E. V.
2017-11-01
In the present work experimental data on heat transfer are obtained for the condensation of almost immobile pure steam and water-ethanol vapor mixture on three copper horizontal finned tubes with a cooled length of 100 mm. The fins are rectangular in shape, their height and thickness are 1 mm, and the spacing between fins 1.3, 2.0 and 3.0 mm. The experiments were carried out at pressures of 0.12…0.15 MPa, the vapor-to-surface temperature difference varied from 5 to 35 K. The mass concentration of ethanol in the vapor phase varied from 8.7 to 14.5%. The experimental data are presented in the form of the dependences of heat transfer coefficient on the vapor-to-wall temperature difference. The heat transfer coefficients for the condensation of pure steam are in good agreement with the calculations by the method of Srinivasan et al. According to experimental data for the condensation of the vapor mixture, diffusion thermal resistance and thermal resistance of the liquid phase at various ethanol concentrations and the spacing between fins were calculated.
Deissler, Robert G
1955-01-01
The expression for eddy diffusivity from a previous analysis was modified in order to account for the effect of kinematic viscosity on the turbulence in the region close to a wall. By using the modified expression, good agreement was obtained between predicted and experimental results for heat and mass transfer at Prandtl and Schmidt numbers between 0.5 and 3000. The effects of length-to-diameter ratio and of variable viscosity were also investigated for a wide range of Prandtl numbers.
Simulation of heat transfer in combustion chamber waterwall tubes of supercritical steam boilers
Directory of Open Access Journals (Sweden)
Grądziel Sławomir
2016-06-01
Full Text Available The paper presents the results of numerical computations performed for the furnace chamber waterwalls of a supercritical boiler with a steam output of 2400 × 103 kg/h. A model of distributed parameters is proposed for the waterwall operation simulation. It is based on the solution of equations describing the mass, momentum and energy conservation laws. The aim of the calculations was to determine the distribution of enthalpy, mass flow and fluid pressure in tubes. The balance equations can be brought to a form where on the left-hand side space derivatives, and on the right-hand side – time derivatives are obtained. The time derivatives on the right-hand side were replaced with backward difference quotients. This system of ordinary differential equations was solved using the Runge-Kutta method. The calculation also takes account of the variable thermal load of the chamber along its height. This thermal load distribution is known from the calculations of the heat exchange in the combustion chamber. The calculations were carried out with the zone method.
Energy Technology Data Exchange (ETDEWEB)
Belghazi, M.; Signe, J.C.; Marvillet, C. [Commissariat a l' Energie Atomique, Grenoble (France). Groupement pour la Recherche sur les Echangeurs Thermiques; Bontemps, A. [Universite Joseph Fourier, Grenoble (France)
2001-12-01
The condensation of pure HFC134a and different zeotropic mixtures with pure HFC134a and HFC23 on the outside of a bundle of smooth tubes was studied. The local heat transfer coefficient for each row was experimentally determined using a test section composed by a 13x3 staggered bundle of smooth copper tubes, measuring cooling water temperature in the inlet and the outlet of each tube, and measuring the vapour temperature along the bundle. All data were taken at the inlet vapour temperature of 40{sup o}C with a wall subcooling ranging from 4 to 26 K. The heat flux was varied from 5 to 30 kW/m{sup 2} and the cooling water flow rate from 120 to 300 1/h for each tube. The visualisation of the HFC134a condensate flow by means of transparent glass tubes reveals specific flow patterns and explains the difference between the measured values of the heat transfer coefficient and the calculated values from Nusselt's theory. On the other hand, the experimental heat transfer data with the binary mixtures HFC23-HFC134a show the important effects of temperature glide and the strong decrease of the heat transfer coefficient in comparison with the pure HFC134a data. The measured values with the different zeotropic mixtures were compared with the data calculated with the classical condensation model based on the equilibrium model. An improvement of this model is proposed. (author)
Balunov, B. F.; Il'in, V. A.; Shcheglov, A. A.; Lychakov, V. D.; Alekseev, S. B.; Kuhtevich, V. O.; Svetlov, S. V.; Sidorov, V. G.
2017-01-01
Results of experimental determination of the average heat transfer coefficient upon condensation of pure steam αc and steam from air-steam mixture αas.m in tubes of a large-scale model of the emergency cooling heat exchanger in the system of passive heat removal through steam generators of AES-2006 project at Leningrad II NPP are presented. The model contained 16 parallel tubes with a diameter of 16 × 2 mm and a length of 2.9 m connected to the upper steam distributing and lower condensate gathering horizontal collectors; the distance between their axes was 2.28 m. The tube segments were vertical, horizontal, or inclined. The internal diameter of the collectors was 40 or 60 mm. The model was placed in the lower part of a tank with a height of 6.5 m and a volume of 5.85 m3 filled with boiling water at atmospheric pressure. The experimental parameters were as follows: pressure range 0.43-7.77 MPa, condensate Reynolds number Ref = (0.87-9.3) × 103, and average air volume fraction at the segment with air-steam mixture 0.18-0.85. The studies showed that nonuniformity of static pressure distribution along the steam-distributing collector strongly influences the reduction of αc value (ejecting effect). The agreement between experimental and calculated according to statutory guidelines values of αc for vertical tubes is achieved if the dynamic head of the steam flow at the input of the steam-distributing collector does not exceed 1 kPa. Equations for calculation of the diffusion heat transfer coefficient at steam condensation from the air-steam mixture αas.m on the internal tube surface are proposed. In the considered conditions, air is completely displaced by steam flow from the upper to the lower part of the tubes. The boundary between these regions is characterized by an average reduced steam velocity through this cross section of 1.6 ± 0.4 m/s. Above the boundary cross section, it is recommended to calculate αc. according to [1].
Energy Technology Data Exchange (ETDEWEB)
Yoo, Tae Ho; Kim, Hwan Yeol; Bae, Yoon Yeong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2009-05-15
Pressure of coolant flowing through a SCWR core subchannel is supercritical and the heat transfer behavior is known to be quite different from those at a subcritical pressure. Therefore the heat transfer study in a supercritical pressure is required for the acquisition of a reliable heat transfer correlation. A downward flow as well as an upward flow occurs in a multi-pass reactor core. The heat transfer at a supercritical pressure in downward channel has been known to result in a quite different behavior from an upward flow. An experiment for a supercritical CO{sub 2} flowing vertically downward in circular tubes with inner diameters of 6.32 mm and 9 mm was performed by using SPHINX(Supercritical Pressure Heat transfer Investigation for NeXt generation) at KAERI. The obtained test results are compared with the estimations from the existing correlations and an empirical formula for a downward flow is suggested.
Energy Technology Data Exchange (ETDEWEB)
Yamagishi, Y.; Sugano, T. [Daido Hoxan Inc., Hokkaido (Japan); Takeuchi, H.; Pyatenko, A. [Hokkaido National Industrial Research Institute Sapporo (Japan)
1998-01-01
An experimental study using a slurry of micro-encapsulated phase change material (MCPCM) in water is conducted in order to investigate the increase in convection heat transfer coefficients of slurry flows as well as the increase in thermal capacity of a slurry by using the latent heat from a solid-liquid phase change material (PCM). Experiments were done for turbulent, hydrodynamically fully developed flows in a circular tube with constant wall heat flux. Local convective heat transfer coefficients were measured along the heating test section in order to study the effects of the melting phenomena inside MCPCMs. Experimental data are presented for various particle concentrations, slurry flow rates, and heating rates. Results show that an increase in the local convective heat transfer coefficient is found when the MCPCMs melted. Enhancement of heat transfer due to phase change is affected to varying degrees by Reynolds numbers of slurry flows, the fraction of PCM which is solid phase and heating rates. This paper provides and presents an explanation of the physical mechanism of the convective heat transfer enhancement due to the phase change of MCPCMs and a set of data available for the adjustments of system operating conditions for optimum heat transfer performance. 15 refs., 11 figs., 4 tabs.
Energy Technology Data Exchange (ETDEWEB)
Obot, N. T.; Das, L.; Rabas, T. J.
2000-11-14
An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics in laminar, transitional, and turbulent flow through one smooth tube and twenty-three enhanced tubes. The working fluids for the experiments were air, water, ethylene glycol, and ethylene glycol/water mixtures; Prandtl numbers (Pr) ranged from 0.7 to 125.3. The smooth-tube experiments were carried out with Pr values of 0.7, 6.8, 24.8, 39.1, and 125.3; Pr values of 0.7, 6.8, and 24.8 were tested with enhanced tubes. Reynolds number (Re) range (based on the maximum internal diameter of a tube) was 200 to 55,000, depending on Prandtl number and tube geometry. The results are presented and discussed in this paper.
Park, Chang Yong
Carbon dioxide (CO2) has been seriously considered as an alternate refrigerant for HCFC and HFC fluids, due to the increasing interest of environmentally safe refrigerants in air-conditioning and refrigeration systems. In this study, CO2 flow boiling heat transfer coefficients and pressure drop are measured in macro-scale (6.1 and 3.5 mm) tubes at evaporation temperatures of -15 and -30°C. The measured results show that the nucleate boiling is a main heat transfer mechanism in the 6.1 mm tube and the contribution of convective boiling becomes greater with the decrease of tube diameters and the increase of mass fluxes. The surface roughness of the 6.1 and 3.5 mm tube are presented by SEM and AFM images and surface profiles, and it is shown that the rougher surface of the 6.1 mm tube can affect the flow boiling heat transfer. The CO2 heat transfer coefficients and pressure drop are measured in a mini-scale (0.89 mm) multi-ported tube at the evaporation temperature of -30°C. Also, R410A and R22 flow boiling heat transfer coefficients and pressure drop in a macro-scale (6.1 mm) tube were measured, and they are compared with CO2. This comparison presents that the CO2 flow boiling heat transfer coefficients are higher than R410A and R22 at low vapor qualities, and CO2 pressure drop is significantly lower than R410A and R22. This advantageous characteristic for CO2 could be explained by properties such as surface tension, reduced pressure, and the density ratio of liquid to vapor. The prediction of heat transfer coefficients and pressure drop was performed by general correlations and the calculation results are compared with measured values. Two-phase flow patterns were visualized for CO2 and R410A in the 6 and 3 mm glass tubes, and they are compared with the Weisman et al. and the Wojtan et al. flow pattern maps. The flow pattern maps can determine the flow patterns relatively well, except the transition from intermittent to annular flow.
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Ismael Fernando Meza Castro
2017-07-01
Full Text Available Introduction: This project carried out an experimental research with the design, assembly, and commissioning of a convection heat transfer test bench. Objective: To determine new statistical correlations that allow knowing the heat transfer coefficients by air convection with greater accuracy in applications with different heating geometry configurations. Methodology: Three geometric configurations, such as flat plate, cylinders and tube banks were studied according to their physical properties through Reynolds and Prandtl numbers, using a data transmission interface using Arduino® controllers Measured the air temperature through the duct to obtain real-time data and to relate the heat transferred from the heating element to the fluid and to perform mathematical modeling in specialized statistical software. The study was made for the three geometries mentioned, one power per heating element and two air velocities with 10 repetitions. Results: Three mathematical correlations were obtained with regression coefficients greater than 0.972, one for each heating element, obtaining prediction errors in the heat transfer convective coefficients of 7.50% for the flat plate, 2.85% for the plate Cylindrical and 1.57% for the tube bank. Conclusions: It was observed that in geometries constituted by several individual elements, a much more accurate statistical adjustment was obtained to predict the behavior of the convection heat coefficients, since each unit reaches a stability in the surface temperature profile with Greater speed, giving the geometry in general, a more precise measurement of the parameters that govern the transfer of heat, as it is in the case of the geometry of the tube bank.
Simulation of heat transfer in combustion chamber waterwall tubes of supercritical steam boilers
Grądziel Sławomir; Majewski Karol
2016-01-01
The paper presents the results of numerical computations performed for the furnace chamber waterwalls of a supercritical boiler with a steam output of 2400 × 103 kg/h. A model of distributed parameters is proposed for the waterwall operation simulation. It is based on the solution of equations describing the mass, momentum and energy conservation laws. The aim of the calculations was to determine the distribution of enthalpy, mass flow and fluid pressure in tubes. The balance equations can be...
New data on two-phase two-component heat transfer and hydrodynamics in a vertical tube
Rezkallah, K. S.; Sims, G. E.
1987-06-01
In forced-convective two-phase, two component (gas-liquid) flow, experimental data for mean heat-transfer coefficients, pressure drop and flow patterns were taken simultaneously for the flow in a 1.17-cm i.d. electrically heated vertical tube using three liquids: water, glycerine and water and silicone liquid with air as the gas phase. The combination of silicone liquid and the glycerine and water solution provided a set of data in which the surface tension changed by a factor of 3.4 (being lower for the silicone liquid) with a rough matching of other hydrodynamic properties and a precise matching of the Prandtl number (63 at 25 C). The flow-pattern results showed a significant change in the bubble-slug boundary for the silicone liquid compared with the glycerine and water solution, while the pressure drop results for silicone-air, in the range of V(SL) between 0.277 and 0.690 m/s at high V(SC) showed a sudden drop in Delta/P(tot) followed by a subsequent increase.
А.V. Melnyk; Zhelezny, V. P.
2015-01-01
Experimental results of local heat transfer coefficients for the boiling of real working fluids (solutions of R600a with mineral naphthenic oil ISO VG 15) in smooth tube with small diameter (5.4 mm) are presented. The tests were carried out for the inlet pressure in the range from 71.1 kPa to 77.9 kPa, heat flux was 3800 W/m2, and mass velocity of working fluid was from 14.75 to 18.36 kg/(m2s). The quantitative estimation in reduction of heat transfer coefficient of the wetted surfa...
Energy Technology Data Exchange (ETDEWEB)
Blom, Elisabet; Ivarsson, Christofer
2007-11-15
The aim of the project is to develop a method for detecting soot on the transferring tubes by measuring the Eigen frequency of the tubes as a function of the soot deposit growth. The project is a pilot study independent of boiler type and it is applicable to all boilers where soot deposit on transferring tubes is a repeating issue. The report is supposed to answer two major questions. Is it possible to make use of Eigen frequencies in order to trace soot deposit on transferring tubes? What governing parameters are related to the Eigen frequency of transferring tubes? By today, soot blowing is executed after recommendations from the manufacturer in terms of number of soot blowing per time unit. The fuel type as well as boiler type has great influence on the soot deposit growth. The objective of the project is to investigate whether the mechanical properties of the transferring tube can be used to detect soot deposit. The project is divided into a theoretical and a practical part. The theoretical part covers the design of the probe and the change of its mechanical properties when soot deposit is present. Practical experiments were then carried out in a laboratory were the probes mechanical properties with and without soot deposit were investigated. It was shown that the Eigen frequency of the probe decreased with an increased mass due to soot deposit. A test was also made in a boiler at SAKAB but difficulties in attaching the probe to the inspection hatch. The results varied and the interpretation of the results become difficult. However, it was obvious that the mechanical properties of the probe changed with the amount of soot deposit. It was concluded that detection of soot deposit by studying the mechanical properties of the transferring tubes is possible. Yet, using a probe is no optimal solution, instead measurements should be done directly on the heat transferring tubes. In addition, a strategy for controlling the soot deposit has to be developed
Karagoz, Sendogan; Afshari, Faraz; Yildirim, Orhan; Comakli, Omer
2017-09-01
In this experimental and numerical study an attempt to enhance the heat transfer rate by cylindrical blade that form turbulence flow inside the exchanger pipe is carried out. The effects of the blade geometry are also examined to investigate heat transfer rate in experimented tube inserts. Experiments are performed in different blade spacing (Sy1,2,3 = 101-216-340 mm) and various blade angles (α1,2,3 = 0°-45°-90°). The water flow rate inside the tube is adjusted in three different ranges to approach intended Reynolds numbers (Re1,2,3 = 6000-11,000-17,000). Nusselt number, Reynolds number and effect of friction factor are investigated separately. For all experiments, the increase in Nu number due to used tube inserts is recorded and compared to each other and plain tube in the related profiles. It is concluded that installed tube inserts in the heat exchanger tube, led to a significant increase in Nu number and energy saving. Among different experimented cases, using mean value in various Re numbers, the highest Nusselt number was obtained at Sy1 = 101 mm which was 24% more than that of plain tube. This value was 18.7 and 8.3% for Sy2 = 216 and Sy3 = 340 mm respectively. By this way, according results for friction factor were 0.30, 0.19 and 0.14. The presented study has been simulated by ANSYS Fluent 16 software to analyze flow behavior and heat transfer characteristics.
1980-12-01
provides additional protection from contamination. After the strainer, the steam proceeds through a 31.75 mm. diameter line which provides for two...the system was tested for air-tightness and found to be secure. In addition , it was believed that the velocity of steam passing through the test...REFERENCES 1. Standards for Steam Surface Condensers, 6th ed., Heat Exchange Institue, 1970. 2. Standards of Tubular Exchanger Manifacturers Association
Directory of Open Access Journals (Sweden)
K. Petera
2017-10-01
Full Text Available Heat transfer at the bottom of a cylindrical vessel impinged by a flow with tangential velocity component generated by an axial-flow impeller in a draft tube was measured using the electrodiffusion experimental method. Local values of the Nusselt numbers along the radial coordinate of the heat transfer surface and corresponding mean values are presented for relatively small distances of the draft tube from the impinged surface (0.25 ≤ h/d ≤ 1. Such small distances are typical for mixing of liquids, which ensures good homogenization and increases the intensity of heat and mass transfer in many industrial operations. Results are compared with literature data for unconfined impinging jets with no tangential velocity components. The additional tangential velocity component generated by the rotating impeller significantly influences the hydrodynamics of the impinging jet and decreases the heat transfer intensity in the case of small distances from the impinged surface. A correlation describing the mean Nusselt number at the vessel bottom is proposed. It can be used in a design of a real industrial piece of equipment with heat transfer situated at the bottom.
Energy Technology Data Exchange (ETDEWEB)
Trp, Anica; Lenic, Kristian; Frankovic, Bernard [Faculty of Engineering, University of Rijeka, Vukovarska 58, HR-51000 Rijeka (Croatia)
2006-11-15
A transient heat transfer phenomenon during charging and discharging of the shell-and-tube latent thermal energy storage system has been analysed in this paper. The mathematical model, regarding the conjugate problem of transient forced convection and solid-liquid phase change heat transfer based on the enthalpy formulation, has been presented. A fully implicit two-dimensional control volume FORTRAN computer code has been developed for solving governing equations with initial and boundary conditions. The numerical model is validated with experimental data obtained by experimental investigations that have been performed on the test unit with technical grade paraffin as the phase change material (PCM) and water as the heat transfer fluid (HTF). Numerical predictions match the experimental results. This pointed out that the presented numerical procedure could be accurately used for transient heat transfer simulation. A series of numerical calculations have been done in order to analyse the influence of several HTF operating conditions and several geometric parameters on the heat transfer process inside the water-paraffin shell-and-tube latent thermal energy storage (LTES) unit. Numerical results, which could be used for operating conditions and geometry optimization, provide guidelines for the design of the latent thermal energy storage system. (author)
Directory of Open Access Journals (Sweden)
Sami D. Salman
2013-01-01
Full Text Available This paper presents the application of a mathematical model for simulation of the swirling flow in a tube induced by elliptic-cut and classical twist tape inserts. Effects of the twist ratio (y=2.93, 3.91, and 4.89 and cut depth (w=0.4, 0.8, and 1.4 cm on heat transfer enhancement (Nu and friction factor (f in laminar flow are numerically investigated. The simulation is carried out using commercial CFD package (FLUENT-6.3.26 to grasp the physical behaviour of the thermal and fluid flows of a constant heat-fluxed tube fitted with elliptic-cut twist tape in the laminar flow regime for the Reynolds number ranging from 200 to 2100. The simulated results matched the literature correlations of plain tube for validation with 8% variation for Nusselt number and 10% for friction factor. The results show that the heat transfer rate and friction factor in the tube equipped with elliptic-cut twist tape (ECT are significantly higher than those fitted with classical twist tape (CTT. Moreover the results also reveal that the Nusselt number and the friction factor in the tube with elliptic-cut twisted tape (ECT increase with decreasing twist ratios (y and cut depths (w.
Energy Technology Data Exchange (ETDEWEB)
Zikanov, Oleg [University of Michigan - Dearborn, MI 48128-1491 (United States); Listratov, Yaroslav [Moscow Power Engineering Institute, 14 Karsnokazarmennaya St., Moscow 111250 (Russian Federation)
2016-12-15
Numerical simulations of the flow of a liquid metal in a vertical pipe are performed. The configuration reproduces the test section of the recent experiment . The mean flow is directed downward, a half of the pipe's wall is heated, and a strong horizontal magnetic field perpendicular to the temperature gradient is imposed. The simulations produce results in good agreement with the experiment and lead us to an explanation of the observed phenomenon of anomalous high-amplitude temperature fluctuations. The fluctuations are caused by growth and quasi-periodic breakdown of the pairs of ascending and descending jets related to the elevator-mode thermal convection. Implications for operation of liquid metal blankets with poloidal ducts are discussed.
Energy Technology Data Exchange (ETDEWEB)
Raush, G.; Rigola, J.; Morales-Ruiz, S.; Oliva, A.; Perez-Segarra, C.D. [Centre Tecnologic de Transferencia de Calor (CTTC), Universitat Politecnica de Catalunya (UPC), ETSEIAT, C. Colom 11, 08222 Terrassa (Barcelona) (Spain)
2009-11-15
A methodology for analysing the influence of the heat transfer and friction factor correlations in the prediction of the two-phase flows inside horizontal ducts under evaporation phenomena is presented. An experimental unit based on single stage vapor compression refrigerating system with two parallel evaporation devices has been built to work under real refrigeration conditions. The first evaporation device consists of a double pipe evaporator which allows determining the heat flux through the pipe. The second device is an electrically heated pipe evaporator with uniformly distributed temperature and pressure sensors along the fluid path. The experimental data of temperature and pressure distribution along the smooth heated duct is compared with a selected set of heat transfer and friction factor correlations through a detailed numerical evaporation model. The aim of this paper is to determine possible criteria to select the most suitable heat transfer and friction factor correlations available. (author)
Er. Shivesh Kumar; Dr. Amit Kumar
2016-01-01
Since centuries steam is being used in power generating system. The steam leaving the power unit is reconverted into water in a condenser designed to transfer heat from the steam to the cooling water as rapidly and as efficiently as possible. The efficiency of condenser depends on rate of condensation and mode of condensation of steam in the condenser. The increase in efficiency of the condenser enhances the heat transfer co-efficient which in turn results in economic design of condenser and ...
Barron, Randall F
2016-01-01
Cryogenic Heat Transfer, Second Edition continues to address specific heat transfer problems that occur in the cryogenic temperature range where there are distinct differences from conventional heat transfer problems. This updated version examines the use of computer-aided design in cryogenic engineering and emphasizes commonly used computer programs to address modern cryogenic heat transfer problems. It introduces additional topics in cryogenic heat transfer that include latent heat expressions; lumped-capacity transient heat transfer; thermal stresses; Laplace transform solutions; oscillating flow heat transfer, and computer-aided heat exchanger design. It also includes new examples and homework problems throughout the book, and provides ample references for further study.
Directory of Open Access Journals (Sweden)
А.V. Melnyk
2015-08-01
Full Text Available Experimental results of local heat transfer coefficients for the boiling of real working fluids (solutions of R600a with mineral naphthenic oil ISO VG 15 in smooth tube with small diameter (5.4 mm are presented. The tests were carried out for the inlet pressure in the range from 71.1 kPa to 77.9 kPa, heat flux was 3800 W/m2, and mass velocity of working fluid was from 14.75 to 18.36 kg/(m2s. The quantitative estimation in reduction of heat transfer coefficient of the wetted surface in evaporator at high oil concentration in the mixture is made. The influence of mass velocities of the working fluid on the values of the local heat transfer coefficients are analyzed. Based on the results obtained it was observed that increasing mass velocity leads to increase the local heat transfer coefficient of RWF both on side of wetted perimeter and vapor phase. The equation for the modeling of the local heat transfer coefficient for boiling of isobutane/compressor oil solution flow in the pipe is suggested.
Fischer, W.
1986-11-01
Botany Facility tests were performed in an environmental laboratory in order to determine the heat transfer at the glass disk of the breadboard model and the temperature distribution in the fluorescent tube under different environmental conditions. The test objects, test facility, instrumentation, environmental conditions, and test procedures are described. The tests were successful since all data needed were obtained with the required accuracy. The extent of the data was substantially increased during the tests, allowing safe predictions.
Heat transfer, insulation calculations simplified
Energy Technology Data Exchange (ETDEWEB)
Ganapathy, V.
1985-08-19
Determination of heat transfer coefficients for air, water, and steam flowing in tubes and calculation of heat loss through multilayered insulated surfaces have been simplified by two computer programs. The programs, written in BASIC, have been developed for the IBM and equivalent personal computers.
Komarov, I. I.; Rostova, D. M.; Vegera, A. N.
2017-11-01
This paper presents the results of study on determination of degree and nature of influence of operating conditions of burner units and flare geometric parameters on the heat transfer in a combustion chamber of the fire-tube boilers. Change in values of the outlet gas temperature, the radiant and convective specific heat flow rate with appropriate modification of an expansion angle and a flare length was determined using Ansys CFX software package. Difference between values of total heat flow and bulk temperature of gases at the flue tube outlet calculated using the known methods for thermal calculation and defined during the mathematical simulation was determined. Shortcomings of used calculation methods based on the results of a study conducted were identified and areas for their improvement were outlined.
Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants
Yoshida, Suguru; Fujita, Yasunobu
The current state of knowledge on heat transfer to boiling refrigerants (halogenated hydrocarbons) in a pool and flowing inside a horizontal tube is reviewed with an emphasis on information relevant to the design of refrigerant evaporators, and some recommendations are made for future research. The review covers two-phase flow pattern, heat transfer characteristics, correlation of heat transfer coefficient, influence of oil, heat transfer augmentation, boiling from tube-bundle, influence of return bend, burnout heat flux, film boiling, dryout and post-dryout heat transfer.
Directory of Open Access Journals (Sweden)
Sami D. Salman
2013-01-01
Full Text Available This paper reports numerical investigations of heat transfer and friction factor characteristics in swirling flow conditions using CFD simulation. A commercial CFD package, FLUENT 6.3.26, was used in this study. 3D models for circular tube fitted with classical and quadrant-cut twisted tape (QCT inserts with three twist ratios (y = 2.93, 3.91, and 4.89 and different cut depths (w = 0.5, 1.0, and 1.5 cm were generated for the simulation. The data obtained from the CFD simulation were verified with the literature correlations of plain tube with the discrepancy of less than ±8% for Nusselt number and ±10% for friction factor. The results show that there was a significant increase in heat transfer coefficient and friction factor in the tube fitted with quadrant-cut twisted tape (QCT with decreasing of twist ratio (y and cut depth (w. Furthermore, the configuration of QCT insert with a twist ratio of y = 2.93 and a cut depth of w = 0.5 cm offered higher heat transfer rate and friction factor than other twist ratios.
Salman, Sami D; Kadhum, Abdul Amir H; Takriff, Mohd S; Mohamad, Abu Bakar
2013-01-01
Numerical investigation of the heat transfer and friction factor characteristics of a circular fitted with V-cut twisted tape (VCT) insert with twist ratio (y = 2.93) and different cut depths (w = 0.5, 1, and 1.5 cm) were studied for laminar flow using CFD package (FLUENT-6.3.26). The data obtained from plain tube were verified with the literature correlation to ensure the validation of simulation results. Classical twisted tape (CTT) with different twist ratios (y = 2.93, 3.91, 4.89) were also studied for comparison. The results show that the enhancement of heat transfer rate induced by the classical and V-cut twisted tape inserts increases with the Reynolds number and decreases with twist ratio. The results also revealed that the V-cut twisted tape with twist ratio y = 2.93 and cut depth w = 0.5 cm offered higher heat transfer rate with significant increases in friction factor than other tapes. In addition the results of V-cut twist tape compared with experimental and simulated data of right-left helical tape inserts (RLT), it is found that the V-cut twist tape offered better thermal contact between the surface and the fluid which ultimately leads to a high heat transfer coefficient. Consequently, 107% of maximum heat transfer was obtained by using this configuration.
Glass heat pipe evacuated tube solar collector
McConnell, Robert D.; Vansant, James H.
1984-01-01
A glass heat pipe is adapted for use as a solar energy absorber in an evacuated tube solar collector and for transferring the absorbed solar energy to a working fluid medium or heat sink for storage or practical use. A capillary wick is formed of granular glass particles fused together by heat on the inside surface of the heat pipe with a water glass binder solution to enhance capillary drive distribution of the thermal transfer fluid in the heat pipe throughout the entire inside surface of the evaporator portion of the heat pipe. Selective coatings are used on the heat pipe surface to maximize solar absorption and minimize energy radiation, and the glass wick can alternatively be fabricated with granular particles of black glass or obsidian.
Directory of Open Access Journals (Sweden)
Can Cai
2017-11-01
Full Text Available Due to its distinct capability to improve the efficiency of shale gas production, supercritical carbon dioxide (SC-CO2 fracturing has attracted increased attention in recent years. Heat transfer occurs in the transportation and fracture processes. To better predict and understand the heat transfer of SC-CO2 near the critical region, numerical simulations focusing on a vertical flow pipe were performed. Various turbulence models and turbulent Prandtl numbers (Prt were evaluated to capture the heat transfer deterioration (HTD. The simulations show that the turbulent Prandtl number model (TWL model combined with the Shear Stress Transport (SST k-ω turbulence model accurately predicts the HTD in the critical region. It was found that Prt has a strong effect on the heat transfer prediction. The HTD occurred under larger heat flux density conditions, and an acceleration process was observed. Gravity also affects the HTD through the linkage of buoyancy, and HTD did not occur under zero-gravity conditions.
Lopez Belchi, D. Alejandro
Heat exchanger developments are driven by energetic efficiency increase and emissionreduction. To reach the standards new system are required based on mini-channels. Mini-channels can be described as tubes with one or more ports extruded in aluminiumwith hydraulic diameter are in the range of 0.2 to 3 mm. Its use in refrigeration systemsfor some years ago is a reality thanks to the human ability to made micro-scale systems.Some heat exchanger enterprises have some models developed specially for their use inautomotive sector, cooling sector, and industrial refrigeration without having a deepknowledge of how these reduced geometries affect the most important parameters suchas pressure drop and the heat transfer coefficient. To respond to this objective, an exhaustive literature review of the last two decades hasbeen performed to determinate the state of the research. Between all the publications,several models have been selected to check the predicting capacities of them becausemost of them were developed for single port mini-channel tubes. Experimentalmeasurements of heat transfer coefficient and frictional pressure drop were recorded inan experimental installation built on purpose at the Technical University of Cartagena.Multiple variables are recorded in this installation in order to calculate local heattransfer coefficient in two-phase condensing flow within mini-channels. Both pressure drop and heat transfer coefficient experimental measurements arecompared to the previously mentioned models. Most of them capture the trend correctlybut others fail predicting experimental data. These differences can be explained by theexperimental parameters considered during the models development. In some cases themodels found in the literature were developed specific conditions, consequently theirpredicting capacities are restricted. As main contributions, this thesis provides new modelling tools for mini-channelscondensing pressure drop and heat transfer coefficient
Withag, J.A.M.; Sallevelt, J.L.H.P.; Brilman, Derk Willem Frederik; Bramer, Eduard A.; Brem, Gerrit
2012-01-01
Heat transfer to water at supercritical pressures has been numerically investigated using a two-dimensional modeling approach. The simulations in a two-dimensional domain have been performed using the low-Reynolds k–ϵ turbulence model, and the IAPWS-IF97 formulation to describe the properties of
Akbar, Noreen Sher; Raza, M; Ellahi, R
2016-07-01
The peristaltic flow of a copper oxide water fluid investigates the effects of heat generation and magnetic field in permeable tube is studied. The mathematical formulation is presented, the resulting equations are solved exactly. The obtained expressions for pressure gradient, pressure rise, temperature, velocity profile are described through graphs for various pertinent parameters. It is found that pressure gradient is reduce with enhancement of particle concentration and velocity profile is upturn, beside it is observed that temperature increases as more volume fraction of copper oxide. The streamlines are drawn for some physical quantities to discuss the trapping phenomenon. Copyright © 2016. Published by Elsevier Ireland Ltd.
Nucleate boiling heat transfer
Energy Technology Data Exchange (ETDEWEB)
Saiz Jabardo, J.M. [Universidade da Coruna (Spain). Escola Politecnica Superior], e-mail: mjabardo@cdf.udc.es
2009-07-01
Nucleate boiling heat transfer has been intensely studied during the last 70 years. However boiling remains a science to be understood and equated. In other words, using the definition given by Boulding, it is an 'insecure science'. It would be pretentious of the part of the author to explore all the nuances that the title of the paper suggests in a single conference paper. Instead the paper will focus on one interesting aspect such as the effect of the surface microstructure on nucleate boiling heat transfer. A summary of a chronological literature survey is done followed by an analysis of the results of an experimental investigation of boiling on tubes of different materials and surface roughness. The effect of the surface roughness is performed through data from the boiling of refrigerants R-134a and R-123, medium and low pressure refrigerants, respectively. In order to investigate the extent to which the surface roughness affects boiling heat transfer, very rough surfaces (4.6 {mu}m and 10.5 {mu}m ) have been tested. Though most of the data confirm previous literature trends, the very rough surfaces present a peculiar behaviour with respect to that of the smoother surfaces (Ra<3.0 {mu}m). (author)
SUNDÉN, B
2012-01-01
Presenting the basic mechanisms for transfer of heat, Introduction to Heat Transfer gives a deeper and more comprehensive view than existing titles on the subject. Derivation and presentation of analytical and empirical methods are provided for calculation of heat transfer rates and temperature fields as well as pressure drop. The book covers thermal conduction, forced and natural laminar and turbulent convective heat transfer, thermal radiation including participating media, condensation, evaporation and heat exchangers.
Energy Technology Data Exchange (ETDEWEB)
Nakagawa, Futahiko; Ikaruda, Kunihiro; Abe, Yoshio; Arai, Norio
1999-06-05
Combustion thermal process using the radiant heat transfer tube has widely been applied as a heating method which separates the combustion atmosphere from the heating-e atmosphere in various heating furnace such as iron and steel industry. In this thermal process, in order to burn the fuel in tight space in radiant heat transfer service area, radiant heat transfer tube and burner life were short under high temperature and high-load combustion, and there was a problem that that and, burning characteristic such as NO{sub x} generation rate are improved was difficult. In this study, large temperature distribution by the combustion in the radiant heat transfer tube clarified that the life of the radiant heat transfer tube was shortened by elasto-plasticity creep analysis of the radiant heat transfer tube. Then, two steps combustion burner of the exhaust gas self recycling type was developed as a method for reducing the NO{sub x} generation rate, while the temperature distribution of the radiant heat transfer tube was equalized. As the result, it was possible to reduce over 20% in comparison with conventional two steps combustion burner, while radiant heat transfer tube and life of the burner are extended over the conventional double, in respect of the NO{sub x} generation rate. (translated by NEDO)
Directory of Open Access Journals (Sweden)
WANG Fang
2017-04-01
Full Text Available Aimed to insufficient heat transfer of heat exchanger, research the influence on the heat transfer coefficient impacted by velocity and heat transfer temperature difference of tube heat exchanger. According to the different heat transfer temperature difference and gas velocity，the experimental data were divided into group. Using the control variable method，the above two factors were analyzed separately. K一△T and k一:fitting curve were clone to obtain empirical function. The entire heat exchanger is as the study object，using numerical simulation methods，porous media，k一￡model，second order upwind mode，and pressure一velocity coupling with SIMPLE algorithm，the entire heat exchanger temperature field and the heat transfer coefficient distribution were given. Finally the trend of the heat transfer coefficient effected by the above two factors was gotten.
Energy Technology Data Exchange (ETDEWEB)
Rosa, Juan Carlos de la [Department of Chemical and Nuclear Engineering, Institute of Energetic Engineering, Polytechnic University of Valencia, Camino de Vera, 14, 46022 Valencia (Spain)], E-mail: juadela3@upvnet.upv.es; Munoz-Cobo, Jose L.; Escriva, Alberto [Department of Chemical and Nuclear Engineering, Institute of Energetic Engineering, Polytechnic University of Valencia, Camino de Vera, 14, 46022 Valencia (Spain)
2008-01-15
Some contributions have been stated in order to improve the modeling of concurrent downflow condensation in presence of non-condensables inside vertical tubes. In particular, the influence of non-condensables over the liquid side heat transfer has been considered. The new proposed mechanistic models solve explicitly the real interface temperature by means of a cubic or a fourth order equation. As these models have a non-iterative nature, they can avoid the weakest point of the traditional mechanistic models, which is the slowdown computation if the model had to be implemented in a code. Moreover, as the main non-condensables effects can be accounted for in the heat and mass transfer processes, the new models will be more realistic. The models have been validated with the Vierow experimental data, obtaining a total average relative error, for the fourth order equation method model, of 21% for 268 points.
Venkitaraj, K. P.; Suresh, S.; Alwin Mathew, T.; Bibin, B. S.; Abraham, Jisa
2017-10-01
Nanofluids are advanced heat transfer fluids that exhibit thermal properties superior than that of the conventional fluids such as water, oil etc. This paper reports the experimental study on convective heat transfer characteristics of water based titanium dioxide nanofluids in fully developed flow through a uniformly heated pipe heat exchanger fitted with modified butterfly inserts. Nanofluids are prepared by dispersing TiO2 nanoparticles of average particle size 29 nm in deionized water. The heat transfer experiments are performed in laminar regime using nanofluids prepared with 0.1% and 0.3% volume fractions of TiO2 nanoparticles. The thermal performance characteristics of conventional butterfly inserts and modified butterfly inserts are also compared using TiO2 nanofluid. The inserts with different pitches 6 cm, 9 cm and 12 cm are tested to determine the effect of pitch distance of inserts in the heat transfer and friction. The experimental results showed that the modification made in the butterfly inserts were able to produce higher heat transfer than conventional butterfly inserts.
Heat transfer direction dependence of heat transfer coefficients in annuli
Prinsloo, Francois P. A.; Dirker, Jaco; Meyer, Josua P.
2017-11-01
In this experimental study the heat transfer phenomena in concentric annuli in tube-in-tube heat exchangers at different annular Reynolds numbers, annular diameter ratios, and inlet fluid temperatures using water were considered. Turbulent flow with Reynolds numbers ranging from 15,000 to 45,000, based on the average bulk fluid temperature was tested at annular diameter ratios of 0.327, 0.386, 0.409 and 0.483 with hydraulic diameters of 17.00, 22.98, 20.20 and 26.18 mm respectively. Both heated and cooled annuli were investigated by conducting tests at a range of inlet temperatures between 10 °C to 30 °C for heating cases, and 30 °C to 50 °C for cooling cases. Of special interest was the direct measurement of local wall temperatures on the heat transfer surface, which is often difficult to obtain and evasive in data-sets. Continuous verification and re-evaluation of temperatures measurements were performed via in-situ calibration. It is shown that inlet fluid temperature and the heat transfer direction play significant roles on the magnitude of the heat transfer coefficient. A new adjusted Colburn j-factor definition is presented to describe the heating and cooling cases and is used to correlate the 894 test cases considered in this study.
Tan, Yunkai; He, Zhenbin; Xu, Tao; Fang, Xiaoming; Gao, Xuenong; Zhang, Zhengguo
2017-09-01
An aqueous solution of Xanthan Gum (XG) at a weight fraction as high as 0.2% was used as the base liquid, the stable MWCNTs-dispersed non-Newtonian nanofluids at different weight factions of MWCNTs was prepared. The base fluid and all nanofluids show pseudoplastic (shear-thinning) rheological behavior. Experiments were performed to compare the shell-side forced convective heat transfer coefficient and pressure drop of non-Newtonian nanofluids to those of non-Newtonian base fluid in an integrally helical baffle heat exchanger with low-finned tubes. The experimental results showed that the enhancement of the convective heat transfer coefficient increases with an increase in the Peclet number and the nanoparticle concentration. For nanofluids with 1.0, 0.5 and 0.2 wt% of multi-walled carbon nanotubes (MWCNTs), the heat transfer coefficients respectively augmented by 24.3, 13.2 and 4.7% on average and the pressure drops become larger than those of the base fluid. The comprehensive thermal performance factor is higher than one and increases with an increasing weight fraction of MWCNTs. A remarkable heat transfer enhancement in the shell side of helical baffle heat exchanger with low-finned tubes can be obtained by adding MWCNTs into XG aqueous solution based on thermal resistance analysis. New correlations have been suggested for the shell-side friction coefficient and the Nusselt numbers of non-Newtonian nanofluids and give very good agreement with experimental data.
Kakac, Sadik; Pramuanjaroenkij, Anchasa
2014-01-01
Intended for readers who have taken a basic heat transfer course and have a basic knowledge of thermodynamics, heat transfer, fluid mechanics, and differential equations, Convective Heat Transfer, Third Edition provides an overview of phenomenological convective heat transfer. This book combines applications of engineering with the basic concepts of convection. It offers a clear and balanced presentation of essential topics using both traditional and numerical methods. The text addresses emerging science and technology matters, and highlights biomedical applications and energy technologies. What’s New in the Third Edition: Includes updated chapters and two new chapters on heat transfer in microchannels and heat transfer with nanofluids Expands problem sets and introduces new correlations and solved examples Provides more coverage of numerical/computer methods The third edition details the new research areas of heat transfer in microchannels and the enhancement of convective heat transfer with nanofluids....
Bacon, D H
2013-01-01
Basic Heat Transfer aims to help readers use a computer to solve heat transfer problems and to promote greater understanding by changing data values and observing the effects, which are necessary in design and optimization calculations.The book is concerned with applications including insulation and heating in buildings and pipes, temperature distributions in solids for steady state and transient conditions, the determination of surface heat transfer coefficients for convection in various situations, radiation heat transfer in grey body problems, the use of finned surfaces, and simple heat exc
Pisano, Alessandro; Martinez-Ballester, Santiago; Corberán, José M.; Hidalgo Monpeán, Fernando; Illán Gómez, Ferdando; García Cascales, J-Ramón
2014-01-01
As already demonstrated by others authors, when the performance of a heat exchanger is analyzed, a semi-empirical model allows getting good prediction of the experimental results provided that it is accompanied by the application of the suitable correlations for calculating heat transfer coefficients (HTC) and pressure drop (PD) in both refrigerant and air side. Many correlations for calculating these coefficients are available in literature, therefore choose the more suitable of them turns o...
Dmitrenko, Artur V.
2017-05-01
The stochastic equations of continuum are used for determining the heat transfer coefficients. As a result, the formulas for Nusselt (Nu) number dependent on the turbulence intensity and scale instead of only on the Reynolds (Peclet) number are proposed for the classic flows of a nonisothermal fluid in a round smooth tube. It is shown that the new expressions for the classical heat transfer coefficient Nu, which depend only on the Reynolds number, should be obtained from these new general formulas if to use the well-known experimental data for the initial turbulence. It is found that the limitations of classical empirical and semiempirical formulas for heat transfer coefficients and their deviation from the experimental data depend on different parameters of initial fluctuations in the flow for different experiments in a wide range of Reynolds or Peclet numbers. Based on these new dependences, it is possible to explain that the differences between the experimental results for the fixed Reynolds or Peclet numbers are caused by the difference in values of flow fluctuations for each experiment instead of only due to the systematic error in the experiment processing. Accordingly, the obtained general dependences of Nu for a smooth round tube can serve as the basis for clarifying the experimental results and empirical formulas used for continuum flows in various power devices. Obtained results show that both for isothermal and for nonisothermal flows, the reason for the process of transition from a deterministic state into a turbulent one is determined by the physical law of equivalence of measures between them. Also the theory of stochastic equations and the law of equivalence of measures could determine mechanics which is basis in different phenomena of self-organization and chaos theory.
Dmitrenko, Artur V.
2017-11-01
The stochastic equations of continuum are used for determining the heat transfer coefficients. As a result, the formulas for Nusselt (Nu) number dependent on the turbulence intensity and scale instead of only on the Reynolds (Peclet) number are proposed for the classic flows of a nonisothermal fluid in a round smooth tube. It is shown that the new expressions for the classical heat transfer coefficient Nu, which depend only on the Reynolds number, should be obtained from these new general formulas if to use the well-known experimental data for the initial turbulence. It is found that the limitations of classical empirical and semiempirical formulas for heat transfer coefficients and their deviation from the experimental data depend on different parameters of initial fluctuations in the flow for different experiments in a wide range of Reynolds or Peclet numbers. Based on these new dependences, it is possible to explain that the differences between the experimental results for the fixed Reynolds or Peclet numbers are caused by the difference in values of flow fluctuations for each experiment instead of only due to the systematic error in the experiment processing. Accordingly, the obtained general dependences of Nu for a smooth round tube can serve as the basis for clarifying the experimental results and empirical formulas used for continuum flows in various power devices. Obtained results show that both for isothermal and for nonisothermal flows, the reason for the process of transition from a deterministic state into a turbulent one is determined by the physical law of equivalence of measures between them. Also the theory of stochastic equations and the law of equivalence of measures could determine mechanics which is basis in different phenomena of self-organization and chaos theory.
Thermal radiation heat transfer
Howell, John R; Siegel, Robert
2016-01-01
Further expanding on the changes made to the fifth edition, Thermal Radiation Heat Transfer, 6th Edition continues to highlight the relevance of thermal radiative transfer and focus on concepts that develop the radiative transfer equation (RTE). The book explains the fundamentals of radiative transfer, introduces the energy and radiative transfer equations, covers a variety of approaches used to gauge radiative heat exchange between different surfaces and structures, and provides solution techniques for solving the RTE.
Hata, K.; Fukuda, K.; Masuzaki, S.
2017-10-01
Twisted-tape-induced swirl-flow heat transfer due to exponentially increasing heat inputs with various exponential periods (Q = Q 0 exp(t/τ), τ = 6.04 to 23.07 s) and twisted-tape-induced pressure drop was systematically measured for various mass velocities (G = 4115 to 13,656 kg/m2 s), inlet liquid temperatures (T in = 285.88 to 299.09 K), and inlet pressures (P in = 847.45 to 943.29 kPa) using an experimental water loop flow. Measurements were made over a 59.2-mm effective length and three sections (upper, middle, and lower positions), within which four potential taps were spot-welded onto the outer surface of a 6-mm-inner-diameter, 69.6-mm-heated length, 0.4-mm-thickness platinum circular test tube. Type SUS304 twisted tapes with a width w = 5.6 mm, a thickness δ T = 0.6 mm, a total length l = 372 mm, and twist ratios y = 2.39 and 4.45 were employed in this study. The RANS equations (Reynolds Averaged Navier-Stokes Simulation) with a k-ɛ turbulence model for a circular tube 6 mm in diameter and 636 mm in length were numerically solved for heating of water with a heated section 6 mm in diameter and 70 mm in length using the CFD code, under the same conditions as the experimental ones and considering the temperature dependence of the thermo-physical properties concerned. The theoretical values of surface heat flux q on the circular tubes with twisted tapes with twist ratios y of 2.39 and 4.45 were found to be almost in agreement with the corresponding experimental values of heat flux q, with deviations of less than 30% for the range of temperature difference between the average heater inner surface temperature and the liquid bulk mean temperature ΔT L [ = T s,av - T L , T L = (T in + T out )/2] considered in this study. The theoretical values of the local surface temperature T s , local average liquid temperature T f,av , and local liquid pressure drop ΔP x were found to be within almost 15% of the corresponding experimental ones. The thickness of the
Chindyakov, A. A.; Smirnov, Yu B.; Vinogradov, A. A.; Mikhailova, E. V.
2017-11-01
In the present study experimental heat transfer data on condensation of almost immobile water-ethanol and water-isopropanol vapor mixtures on the vertical smooth copper tube 100 mm long with an outer diameter of 12.0 mm were obtained. Experiments for water-ethanol mixture were carried out at mass concentrations of ethanol from 0.4 to 16% in the vapor phase, and for a water-isopropanol mixture - from 0.6 to 8.4%. The pressure was 0.12…0.13 MPa, vapor-to-surface temperature difference varied from 2 to 40K. The experimental data are represented as dependency of heat transfer coefficient and heat flux on the vapor-to-surface temperature difference. The results of high-speed photography of the condensation process are discussed. It is noted that the transition from film mode to pseudo-dropwise condensation occurs when vapor-to-surface temperature difference is close to dew point - bubble point temperature difference for a given composition of the mixture. According to experimental data, the diffusion thermal resistance and thermal resistance of the liquid phase at different concentrations of the mixture were calculated.
Energy Technology Data Exchange (ETDEWEB)
Ferrouillat, Sebastien, E-mail: sebastien.ferrouillat@ujf-grenoble.f [Universite Joseph Fourier, LEGI, BP 53X, 38041 Grenoble cedex (France); Bontemps, Andre [Universite Joseph Fourier, LEGI, BP 53X, 38041 Grenoble cedex (France); Ribeiro, Joao-Paulo; Gruss, Jean-Antoine; Soriano, Olivier [CEA/LITEN/DTS/LETH, 17, Avenue des martyrs, 38052 Grenoble cedex (France)
2011-04-15
The convective heat transfer of SiO{sub 2}/water colloidal suspensions (5-34 wt.%) is investigated experimentally in a flow loop with a horizontal tube test section whose wall temperature is imposed. Experiments were performed at different inlet temperatures (20, 50, 70 {sup o}C) in cooling and/or heating conditions at various flow rates (200 < Re < 10,000). The Reynolds and Nusselt numbers were deduced by using thermal conductivity and viscosity values measured with the same temperature conditions as those in the tests. Results indicate that the heat transfer coefficient values are increased from 10% to 60% compared to those of pure water. They also show that the general trend of standard correlations is respected. The problem of suspension stability at the highest temperatures is discussed. In order to evaluate the benefits provided by the enhanced properties of the nanofluids studied, an energetic performance evaluation criterion (PEC) is defined. This PEC decreases as the nanoparticle concentration is increased. This process is also discussed in this paper.
Miyara, A.; Kariya, K.; Ali, Md. H.; Selamat, S. B.; Jalaluddin
2017-01-01
Three kinds of vertical-type ground heat exchangers, U-tube; double-tube; multi-tube, and two kinds of horizontal-type ground heat exchangers, standing Slinky; reclined Slinky, were experimentally and numerically investigated in order to clarify their heat transfer characteristics. Experiments and simulations were carried out under two operation conditions which are continuous operation mode and discontinuous operation mode and effects of temperature recovery and thermal storage on the heat transfer rate were shown. Differences of the heat transfer rate between standing Slinky and reclined Slinky were also indicated.
REA, The Editors of
1988-01-01
REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Heat Transfer II reviews correlations for forced convection, free convection, heat exchangers, radiation heat transfer, and boiling and condensation.
Hartnett, James P; Cho, Young I; Greene, George A
2001-01-01
Heat transfer is the exchange of heat energy between a system and its surrounding environment, which results from a temperature difference and takes place by means of a process of thermal conduction, mechanical convection, or electromagnetic radiation. Advances in Heat Transfer is designed to fill the information gap between regularly scheduled journals and university-level textbooks by providing in-depth review articles over a broader scope than is allowable in either journals or texts.
Bejan, Adrian
2013-01-01
Written by an internationally recognized authority on heat transfer and thermodynamics, this second edition of Convection Heat Transfer contains new and updated problems and examples reflecting real-world research and applications, including heat exchanger design. Teaching not only structure but also technique, the book begins with the simplest problem solving method (scale analysis), and moves on to progressively more advanced and exact methods (integral method, self similarity, asymptotic behavior). A solutions manual is available for all problems and exercises.
Lunin, V. P.; Zhdanov, A. G.; Chegodaev, V. V.; Stolyarov, A. A.
2015-05-01
The problem of defining the criterion for blanking off heat-transfer tubes in the steam generators at nuclear power plants on the basis of signals obtained from the standard multifrequency eddy-current examination is considered. The decision about blanking off one or another tube is presently made with reference to one parameter of the relevant signal at the working frequency, namely, with reference to its phase, which directly depends on the depth of the flaw being detected, i.e., a crack in the tube. The crack depth equal to 60% of the tube wall thickness is regarded to be the critical one, at which a decision about withdrawing such a tube out from operation (blanking off) must be taken. However, since mechanical tensile rupture tests of heat-transfer tubes show the possibility of their further use with such flaws, the secondary parameter of the signal, namely, its amplitude, must be used for determining the blanking-off criterion. The signals produced by the standard flow-type transducers in response to flaws in the form of a longitudinal crack having the depth and length within the limits permitted by the relevant regulations were calculated using 3D finite-element modeling. Based on the obtained results, the values of the eddy-current signal amplitude were determined, which, together with the signal phase value, form a new amplitude-phase criterion for blanking off heat-transfer tubes. For confirming the effectiveness of this technique, the algorithm for revealing the signal indications satisfying the proposed amplitude-phase criterion was tested on real signals obtained from operational eddy-current examination of the state of steam generator heat-transfer tubes carried out within the framework of planned preventive repair.
Energy Technology Data Exchange (ETDEWEB)
Hata, Koichi, E-mail: hata@iae.kyoto-u.ac.j [Institute of Advanced Energy, Kyoto Univ., Gokasho, Uji, Kyoto 611-0011 (Japan); Masuzaki, Suguru, E-mail: masuzaki@LHD.nifs.ac.j [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292 (Japan)
2009-12-15
The subcooled boiling heat transfer and the steady-state critical heat fluxes (CHFs) in a short vertical SUS304-tube for the flow velocities (u = 17.28-40.20 m/s), the inlet liquid temperatures (T{sub in} = 293.30-362.49 K), the inlet pressures (P{sub in} = 842.90-1467.93 kPa) and the exponentially increasing heat input (Q = Q{sub 0} exp(t/tau), tau = 8.5 s) are systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test tubes of inner diameters (d = 3 and 6 mm), heated lengths (L = 33 and 59.5 mm), effective lengths (L{sub eff} = 23.3 and 49.1 mm), L/d (=11 and 9.92), L{sub eff}/d (=7.77 and 8.18), and wall thickness (delta = 0.5 mm) with average surface roughness (Ra = 3.18 mum) are used in this work. The inner surface temperature and the heat flux from non-boiling to CHF are clarified. The subcooled boiling heat transfer for SUS304 test tube is compared with our Platinum test tube data and the values calculated by other workers' correlations for the subcooled boiling heat transfer. The influence of flow velocity on the subcooled boiling heat transfer and the CHF is investigated into details and the widely and precisely predictable correlation of the subcooled boiling heat transfer for turbulent flow of water in a short vertical SUS304-tube is given based on the experimental data. The correlation can describe the subcooled boiling heat transfer obtained in this work within 15% difference. Nucleate boiling surface superheats for the SUS304 test tube become very high. Those at the high flow velocity are close to the lower limit of Heterogeneous Spontaneous Nucleation Temperature. The dominant mechanisms of the flow boiling CHF in a short vertical SUS304-tube are discussed.
Modest, Michael F
2013-01-01
The third edition of Radiative Heat Transfer describes the basic physics of radiation heat transfer. The book provides models, methodologies, and calculations essential in solving research problems in a variety of industries, including solar and nuclear energy, nanotechnology, biomedical, and environmental. Every chapter of Radiative Heat Transfer offers uncluttered nomenclature, numerous worked examples, and a large number of problems-many based on real world situations-making it ideal for classroom use as well as for self-study. The book's 24 chapters cover the four major areas in the field: surface properties; surface transport; properties of participating media; and transfer through participating media. Within each chapter, all analytical methods are developed in substantial detail, and a number of examples show how the developed relations may be applied to practical problems. It is an extensive solution manual for adopting instructors. Features: most complete text in the field of radiative heat transfer;...
1980-03-01
C-1) allows the isolation of the test condenser hotwell for condensate measurement. Since house steam was used as the steam supply system, the...Dans in Faiscean Tubulaire Horizontal," Department of Transfer and Conversion of Energy Service of Thermic Transfers, France, 1978. 13. Kline, S. J
Micro tube heat exchangers for Space Project
National Aeronautics and Space Administration — Mezzo fabricates micro tube heat exchangers for a variety of applications, including aerospace, automotive racing, Department of Defense ground vehicles, economizers...
Directory of Open Access Journals (Sweden)
Amin Jafarimoghaddam
Full Text Available The present study aims to experimentally investigate heat transfer performance of rectangular and semicircular tubes in the presence of Ag / water nanofluids. The nanoparticles of Ag (silver were used in seven different volume concentrations of 0.03%, 0.07%, 0.1%, 0.2%, 0.4%, 1% and 2%. The experiment was conducted in relatively low Reynolds numbers of 301 to 740. A heater with the power of 200 W was used to keep the outer surface of the tubes under a constant heat flux condition. In addition, the rectangular tube has been designed within the same length as the semicircular one and also within the same hydraulic diameter. Moreover, the average nanoparticles size was 20 nm. The outcome results of the present empirical work indicate that, for all the examined Reynolds numbers, the semicircular tube has higher convective heat transfer coefficient for all the utilized volume concentrations of Ag nanoparticles. The possible reasons behind this advantage are discussed through the present work mainly by taking the boundary effect on Brownian motions into account. Coming to this point that the conventional design for cooling system of photovoltaic cells is a heat sink with the rectangular graves, it is discussed that using a semicircular design may have the advantage over the rectangular one in convective heat transfer coefficient enhancement and hence a better cooling performance for these solar cells.
Jafarimoghaddam, Amin; Aberoumand, Sadegh
2017-01-01
The present study aims to experimentally investigate heat transfer performance of rectangular and semicircular tubes in the presence of Ag / water nanofluids. The nanoparticles of Ag (silver) were used in seven different volume concentrations of 0.03%, 0.07%, 0.1%, 0.2%, 0.4%, 1% and 2%. The experiment was conducted in relatively low Reynolds numbers of 301 to 740. A heater with the power of 200 W was used to keep the outer surface of the tubes under a constant heat flux condition. In addition, the rectangular tube has been designed within the same length as the semicircular one and also within the same hydraulic diameter. Moreover, the average nanoparticles size was 20 nm. The outcome results of the present empirical work indicate that, for all the examined Reynolds numbers, the semicircular tube has higher convective heat transfer coefficient for all the utilized volume concentrations of Ag nanoparticles. The possible reasons behind this advantage are discussed through the present work mainly by taking the boundary effect on Brownian motions into account. Coming to this point that the conventional design for cooling system of photovoltaic cells is a heat sink with the rectangular graves, it is discussed that using a semicircular design may have the advantage over the rectangular one in convective heat transfer coefficient enhancement and hence a better cooling performance for these solar cells.
Han, Je-Chin
2012-01-01
… it will complete my library … [and] complement the existing literature on heat transfer. It will be of value for both graduate students and faculty members.-Bengt Sunden, Lund University, Sweden
Elementary heat transfer analysis
Whitaker, Stephen; Hartnett, James P
1976-01-01
Elementary Heat Transfer Analysis provides information pertinent to the fundamental aspects of the nature of transient heat conduction. This book presents a thorough understanding of the thermal energy equation and its application to boundary layer flows and confined and unconfined turbulent flows. Organized into nine chapters, this book begins with an overview of the use of heat transfer coefficients in formulating the flux condition at phase interface. This text then explains the specification as well as application of flux boundary conditions. Other chapters consider a derivation of the tra
Lienhard, John H
2011-01-01
This introduction to heat transfer offers advanced undergraduate and graduate engineering students a solid foundation in the subjects of conduction, convection, radiation, and phase-change, in addition to the related topic of mass transfer. A staple of engineering courses around the world for more than three decades, it has been revised and updated regularly by the authors, a pair of recognized experts in the field. The text addresses the implications, limitations, and meanings of many aspects of heat transfer, connecting the subject to its real-world applications and developing students' ins
Karwa, Rajendra
2017-01-01
This textbook presents the classical treatment of the problems of heat transfer in an exhaustive manner with due emphasis on understanding of the physics of the problems. This emphasis is especially visible in the chapters on convective heat transfer. Emphasis is laid on the solution of steady and unsteady two-dimensional heat conduction problems. Another special feature of the book is a chapter on introduction to design of heat exchangers and their illustrative design problems. A simple and understandable treatment of gaseous radiation has been presented. A special chapter on flat plate solar air heater has been incorporated that covers thermo-hydraulic modeling and simulation. The chapter on mass transfer has been written looking specifically at the needs of the students of mechanical engineering. The book includes a large number and variety of solved problems with supporting line diagrams. The author has avoided duplicating similar problems, while incorporating more application-based examples. All the end-...
Study of heat and mass transfer in evaporative coolers
Perez-Blanco, H.; Bird, W. A.
1982-06-01
Evaporative coolers are generally considered efficient and economical devices for rejecting waste heat. In these coolers, a hot fluid circulates inside tubes, rejecting heat to a mixture of air and water. Water is sprayed on the tubes and flows downward while air circulates upward; thus, latent and sensible heat is transferred from the water to the air. Commercially available coolers are of the horizonal tube type; a vertical tube evaporative cooler is studied because it is possible to enhance condensing heat transfer coefficients by using vertical fluted tubes. A mathematical model describing the performance of a single tube is formulated which can predict performance for varied inlet conditions, thereby eliminating the need for extensive testing. The validity of the model rests on the accuracy of the controlling heat and mass transfer coefficients used, so these coefficients are measured experimentally in a single tube cooler and found to agree with existing empirical correlations.
Thermal radiation heat transfer
Howell, John R; Mengüç, M Pinar
2011-01-01
Providing a comprehensive overview of the radiative behavior and properties of materials, the fifth edition of this classic textbook describes the physics of radiative heat transfer, development of relevant analysis methods, and associated mathematical and numerical techniques. Retaining the salient features and fundamental coverage that have made it popular, Thermal Radiation Heat Transfer, Fifth Edition has been carefully streamlined to omit superfluous material, yet enhanced to update information with extensive references. Includes four new chapters on Inverse Methods, Electromagnetic Theory, Scattering and Absorption by Particles, and Near-Field Radiative Transfer Keeping pace with significant developments, this book begins by addressing the radiative properties of blackbody and opaque materials, and how they are predicted using electromagnetic theory and obtained through measurements. It discusses radiative exchange in enclosures without any radiating medium between the surfaces-and where heat conduction...
Baehr, Hans Dieter
2011-01-01
This comprehensive textbook provides a solid foundation of knowledge on the principles of heat and mass transfer and shows how to solve problems by applying modern methods. The basic theory is developed systematically, exploring in detail the solution methods to all important problems. The thoroughly revised 3rd edition includes an introduction to the numerical solution of Finite Elements. A new section on heat and mass transfer in porous media has also been added. The book will be useful not only to upper-level and graduate students, but also to practicing scientists and engineers, offering a firm understanding of the principles of heat and mass transfer, and showing how to solve problems by applying modern methods. Many completed examples and numerous exercises with solutions facilitate learning and understanding, and an appendix includes data on key properties of important substances.
EFFECT OF TUBE PITCH ON HEAR TRANSFER IN SPRINKLED TUBE BUNDLE
Directory of Open Access Journals (Sweden)
Petr Kracík
2015-10-01
Full Text Available Water flowing on a sprinkled tube bundle forms three basic modes: the Droplet mode (the liquid drips from one tube to another, the Jet mode (with an increasing flow rate, the droplets merge into a column and the Membrane (Sheet mode (with a further increase in the flow rate of the falling film liquid, the columns merge and create sheets between the tubes. With a sufficient flow rate, the sheets merge at this stage, and the tube bundle is completely covered by a thin liquid film. There are several factors influencing both the individual modes and the heat transfer. Beside the above-mentioned falling film liquid flow rate, these are for instance the tube diameters, the tube pitches in the tube bundle, or the physical conditions of the falling film liquid. This paper presents a summary of data measured at atmospheric pressure, with a tube bundle consisting of copper tubes of 12 millimetres in diameter, and with a studied tube length of one meter. The tubes are situated horizontally one above another at a pitch of 15 to 30 mm, and there is a distribution tube placed above them with water flowing through apertures of 1.0mm in diameter at a 9.2mm span. Two thermal conditions have been tested with all pitches: 15 °C to 40 °C and 15 °C to 45 °C. The temperature of the falling film liquid, which was heated during the flow through the exchanger, was 15 °C at the distribution tube input. The temperature of the heating liquid at the exchanger input, which had a constant flow rate of approx. 7.2. litres per minute, was 40 °C, or alternatively 45 °C.
Vapor chamber with hollow condenser tube heat sink
Ong, K. S.; Haw, P. L.; Lai, K. C.; Tan, K. H.
2017-04-01
Heat pipes are heat transfer devices capable of transferring large quantities of heat effectively and efficiently. A vapor chamber (VC) is a flat heat pipe. A novel VC with hollow condenser tubes embedded on the top of it is proposed. This paper reports on the experimental thermal performance of three VC devices embedded with hollow tubes and employed as heat sinks. The first device consisted of a VC with a single hollow tube while the other two VCs had an array of multi-tubes with different tube lengths. All three devices were tested under natural and force air convection cooling. An electrical resistance heater was employed to provide power inputs of 10 and 40 W. Surface temperatures were measured with thermocouple probes at different locations around the devices. The results show that temperatures increased with heater input while total device thermal resistances decreased. Force convection results in lower temperatures and lower resistance. Dry-out occurs at high input power and with too much condensing area. There appears to be an optimum fill ratio which depended upon dimensions of the VC and also heating power.
Thermal radiation heat transfer.
Siegel, R.; Howell, J. R.
1972-01-01
A comprehensive discussion of heat transfer by thermal radiation is presented, including the radiative behavior of materials, radiation between surfaces, and gas radiation. Among the topics considered are property prediction by electromagnetic theory, the observed properties of solid materials, radiation in the presence of other modes of energy transfer, the equations of transfer for an absorbing-emitting gas, and radiative transfer in scattering and absorbing media. Also considered are radiation exchange between black isothermal surfaces, radiation exchange in enclosures composed of diffuse gray surfaces and in enclosures having some specularly reflecting surfaces, and radiation exchange between nondiffuse nongray surfaces. The use of the Monte Carlo technique in solving radiant-exchange problems and problems of radiative transfer through absorbing-emitting media is explained.
Energy Technology Data Exchange (ETDEWEB)
Zhao, Chen-Ru; Zhang, Zhen [Institute of Nuclear and New Energy Technology of Tsinghua University, Advanced Nuclear Energy Technology Cooperation Innovation Centre, Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 100084 (China); Jiang, Pei-Xue, E-mail: jiangpx@tsinghua.edu.cn [Beijing Key Laboratory of CO_2 Utilization and Reduction Technology/Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Bo, Han-Liang [Institute of Nuclear and New Energy Technology of Tsinghua University, Advanced Nuclear Energy Technology Cooperation Innovation Centre, Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 100084 (China)
2017-03-15
Highlights: • Understanding of the mechanism of buoyancy effect on supercritical heat transfer. • Turbulence related parameters in upward and downward flows were compared. • Turbulent Prandtl number affected the prediction insignificantly. • Buoyancy production was insignificant compared with shear production. • Damping function had the greatest effect and is a priority for further modification. - Abstract: Heat transfer to supercritical pressure fluids was modeled for normal and buoyancy affected conditions using several low Reynolds number k-ε models, including the Launder and Sharma, Myong and Kasagi, and Abe, Kondoh and Nagano, with the predictions compared with experimental data. All three turbulence models accurately predicted the cases without heat transfer deterioration, but failed to accurately predict the cases with heat transfer deterioration although the general trends were captured, indicating that further improvements and modifications are needed for the low Reynolds number k-ε turbulence models to better predict buoyancy deteriorated heat transfer. Further investigations studied the influence of various aspects of the low Reynolds number k-ε turbulence models, including the turbulent Prandtl number, the buoyancy production of turbulent kinetic energy, and the damping function to provide guidelines for model development to more precisely predict buoyancy affected heat transfer. The results show that the turbulent Prandtl number and the buoyancy production of turbulent kinetic energy have little influence on the predictions for cases in this study, while new damping functions with carefully selected control parameters are needed in the low Reynolds number k-ε turbulence models to correctly predict the buoyancy effect for heat transfer simulations in various applications such as supercritical pressure steam generators (SPSGs) in the high temperature gas cooled reactor (HTR) and the supercritical pressure water reactor (SCWR).
Energy Technology Data Exchange (ETDEWEB)
Cho, Jin Min; Kim, Min Soo [School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-744 (Korea); Kim, Yong Jin [School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States)
2010-08-15
Heat transfer characteristics show different tendency according to the tube orientations such as horizontal, vertical, and inclined positions. In this study, evaporative heat transfer characteristics and pressure drop of CO{sub 2} and CO{sub 2}/propane mixtures flowing upward are investigated in inclined smooth and micro-fin tubes. Smooth and micro-fin tubes with outer diameter of 5 mm and length of 1.44 m with inclination angle of 45 were chosen as test tubes. Average inner diameters of test tubes are 4.0 mm (smooth tube) and 4.13 mm (micro-fin tube). The tests were conducted at mass fluxes from 212 to 656 kg/m{sup 2} s, saturation temperatures from -10 to 30 C and heat fluxes from 15 to 60 kW/m{sup 2} for CO{sub 2}. In addition, for CO{sub 2}/propane mixtures, the test was carried out at inlet temperatures from -10 to 30 C for several compositions (75/25, 50/50, 25/75 wt%) with the same mass fluxes, heat fluxes applied for CO{sub 2}. Heat transfer coefficients in inclined tube are approximately 1.8-3 times higher than those in horizontal tube and the average pressure drop of inclined tube exists between that of horizontal and vertical tubes. (author)
Energy Technology Data Exchange (ETDEWEB)
Bhattacharyya, A.
1965-11-15
This report contains descriptions of various analogues utilised to study different steady-state and unsteady-state heat transfer problems. The analogues covered are as follows: 1 . Hydraulic: a) water flow b) air flow 2. Membrane 3. Geometric Electrical: a) Electrolytic-tank b) Conducting sheet 4. Network; a) Resistance b) R-C A comparison of the different analogues is presented in the form of a table.
Performance study of a fin and tube heat exchanger with different fin geometry
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
2016-01-01
This study analyses the effect of different fin geometries on the heat transfer and pressure loss characteristics of a fin and tube heat exchanger. A numerical investigation is carried out on liquid–gas type double-finned tube heat exchanger under cross-flow condition. Three different cross...
Rathakrishnan, Ethirajan
2012-01-01
1 Basic Concepts and Definitions1.1 Introduction1.1.1 Driving Potential1.2 Dimensions and Units1.2.1 Dimensional Homogeneity1.3 Closed and Open Systems1.3.1 Closed System (ControlMass)1.3.2 Isolated System1.3.3 Open System (ControlVolume)1.4 Forms of Energy1.4.1 Internal Energy1.5 Properties of a System1.5.1 Intensive and Extensive Properties1.6 State and Equilibrium1.7 Thermal and Calorical Properties1.7.1 Specific Heat of an Incompressible Substance1.7.2 Thermally Perfect Gas 1.8 The Perfect Gas1.9 Summary1.10 Exercise ProblemsConduction Heat Transfer2.1 Introduction2.2 Conduction Heat Trans
Heat transfer characteristics of rotating triangular thermosyphon
Ibrahim, E.; Moawed, M.; Berbish, N. S.
2012-09-01
An experimental investigation is carried out to study heat transfer characteristics of a rotating triangular thermosyphon, using R-134a refrigerant as the working fluid. The tested thermosyphon is an equilateral triangular tube made from copper material of 11 mm triangular length, 2 mm thickness, and a total length of 1,500 mm. The length of the evaporator section is 600 mm, adiabatic section is 300 mm, and condenser section is 600 mm. The effects of the rotational speed, filling ratio, and the evaporator heat flux on each of the evaporator heat transfer coefficient, he, condenser heat transfer coefficient, hc, and the overall effective thermal conductance, Ct are studied. Experiments are performed with a vertical position of thermosyphon within heat flux ranges from 11 to 23 W/m2 for the three selected filling ratios of 10, 30 and 50 % of the evaporator section volume. The results indicated that the maximum values of the tested heat transfer parameters of the rotational equilateral triangular thermosyphon are obtained at the filling ratio of 30 %. Also, it is found that the heat transfer coefficient of the condensation is increased with increasing the rotational speed. The tested heat transfer parameters of the thermosyphon are correlated as a function of the evaporator heat flux and angular velocity.
Heat Transfer Performance for Evaporator of Absorption Refrigerating Machine
Kunugi, Yoshifumi; Usui, Sanpei; Ouchi, Tomihisa; Fukuda, Tamio
An experiment was conducted to check the heat transfer performance of evaporators with grooved tubes for absorption refrigerating machines. Heat transfer rate of evaporators were 35kW and 70kW. The range of the flow rate of the sprayed refrigerant per unit length Γ was 1 to 50kg/hm, and the outside diameters of the tubes, D0 were 16 and 19.6 mm. About 80 to 100 % increase of heat transfer rate over a plane surfaced tube is obtained by using grooved tube. The heat transfer coefficients for evaporation are correlated by the equation αE0=(Γ/D0)1/2. The substantial surface area, which is about three times larger than that of plane surfaced tube, is used in the above correlation.
Heat Transfer Characteristics of Tubular Thermal Reactor
Energy Technology Data Exchange (ETDEWEB)
Yang, Hei Cheon; Park, Sang Kyoo [Chonnam National Univ., Yeosu (Korea, Republic of); Ra, Beong Yeol [Sinsung Plant company, Ansan (Korea, Republic of)
2007-07-01
Heat transfer augmentation based on the process intensification concept in heat exchangers and thermal reactors has received much attention in recent years, mainly due to energy efficiency and environmental considerations. The concept consists of the development of novel apparatuses and techniques that, compared to those commonly used today, are expected to bring dramatic improvements in manufacturing and processing, substantially decreasing equipment size, energy consumption, and ultimately resulting in cheaper, sustainable technologies. The objective of this paper was to investigate the heat transfer characteristics of tubular thermal reactor using static mixing technology. Glycerin and water were used as the test fluids and water was used as the heating source. The results for heat transfer rate were strongly influenced by tube geometry and flow conditions.
Measuring of heat transfer coefficient
DEFF Research Database (Denmark)
Henningsen, Poul; Lindegren, Maria
Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure...... the heat transfer coefficient for a wide range of interface conditions in hot and warm forging processes. Subtask 3.4.2 Measurement of heat transfer coefficient The objective of subtask 3.4.2 is to determine heat transfer values for different interface conditions reflecting those typically operating in hot...
An experimental investigation of turbulent flow heat transfer through ...
African Journals Online (AJOL)
An experimental investigation has been carried out to study the turbulent flow heat transfer and to determine the pressure drop characteristics of air, flowing through a tube with insert. An insert of special geometry is used inside the tube. The test section is electrically heated, and air is allowed to flow as the working fluid ...
Wen, Fei; Khera, Eshita
2016-01-01
Despite the instinctive perception of mass and heat transfer principles in daily life, productive learning in this course continues to be one of the greatest challenges for undergraduate students in chemical engineering. In an effort to enhance student learning in classroom, we initiated an innovative active-learning method titled…
A Compact Remote Heat Transfer Device for Space Cryocoolers
Yan, T.; Zhao, Y.; Liang, T.
In this paper a compact remote heat transfer device (CRHD) for cryocoolers is proposed. This device is especially attractive in cases where cryocoolers are not easy to set near the heat source, generally the infrared sensor. The CRHD is designed on basis of the concept of loop heat pipes, while the primary evaporator is located near the cryocooler cold head and a simple tube-in-tube secondary evaporator is remotely located and thermally connected with the heat source for cooling. With such a device a cooling power of 1 W is achieved across a heat transfer distance of about 2 m. The major problem of this device is the low heat transfer efficiency (1 W of net cooling power at the cost of about 7 W of cooling power from the cryocooler), and in the future a secondary wicked evaporator will be used instead of the tube-in-tube evaporator in order to improve the efficiency.
De Vos, Wouter Philip
2006-01-01
Due to the phase-out of all refrigerants with ozone depletion potential, a large void is left in the refrigeration market. This void was caused due to a lack of new, ozone friendly, pure refrigerants with similar thermodynamic properties to those of the banned refrigerants. As a result mixtures of refrigerants are used to create replacement refrigerants. These new mixtures have to be experimentally evaluated to derive correlations for the prediction of the heat transfer coeffic...
Kaviany, Massoud
2014-01-01
This graduate textbook describes atomic-level kinetics (mechanisms and rates) of thermal energy storage, transport (conduction, convection, and radiation), and transformation (various energy conversions) by principal energy carriers. The approach combines the fundamentals of molecular orbitals-potentials, statistical thermodynamics, computational molecular dynamics, quantum energy states, transport theories, solid-state and fluid-state physics, and quantum optics. The textbook presents a unified theory, over fine-structure/molecular-dynamics/Boltzmann/macroscopic length and time scales, of heat transfer kinetics in terms of transition rates and relaxation times, and its modern applications, including nano- and microscale size effects. Numerous examples, illustrations, and homework problems with answers that enhance learning are included. This new edition includes applications in energy conversion (including chemical bond, nuclear, and solar), expanded examples of size effects, inclusion of junction quantum tr...
Energy Technology Data Exchange (ETDEWEB)
Ramadhan, Anwar Ilmar, E-mail: anwar.ilmar@ftumj.ac.id; Diniardi, Ery, E-mail: ery.diniardi@ftumj.ac.id [Mechanical Engineering Department, Faculty of Engineering, Universitas Muhammadiyah Jakarta Jl. Cempaka Putih Tengah 27 Jakarta 10510 Indonesia (Indonesia); Dermawan, Erwin, E-mail: erwin.dermawan@ftumj.ac.id [Electrical Engineering Department, Faculty of Engineering, Universitas Muhammadiyah Jakarta Jl. Cempaka Putih Tengah 27 Jakarta 10510 Indonesia (Indonesia)
2016-06-03
Heating or cooling fluid is a major requirement in the industrial sector, including transport, energy and production needs of the field and the field of electronics. It is known that the thermal properties of the working fluid hold an important role in the development of energy efficiency of heat transfer equipment. The cooling system can be improved either by replacing conventional cooling fluid from the fluid into the fluid of water mixed with nanoparticles (nanofluid). The method of this research is to analyze the calculations and numerical simulations of the nanofluid Al{sub 2}O{sub 3}− Water with the volume fraction of 1% and 3% coolant fluid using CFD Codes. The results of this research show the rate of heat transfer at the increasing velocity of fluid flow, with the velocity of 5 [m/s]. Whereas the 3% nanofluid have greater value than the 1% nanofluid and water, as well as for the velocity of 10 [m/s] which has almost the same pattern. Shown that the concentration of nanofluid has a value effective for improving heat release along the fluid flow rate.
Test bench HEATREC for heat loss measurement on solar receiver tubes
Márquez, José M.; López-Martín, Rafael; Valenzuela, Loreto; Zarza, Eduardo
2016-05-01
In Solar Thermal Electricity (STE) plants the thermal energy of solar radiation is absorbed by solar receiver tubes (HCEs) and it is transferred to a heat transfer fluid. Therefore, heat losses of receiver tubes have a direct influence on STE plants efficiency. A new test bench called HEATREC has been developed by Plataforma Solar de Almería (PSA) in order to determinate the heat losses of receiver tubes under laboratory conditions. The innovation of this test bench consists in the possibility to determine heat losses under controlled vacuum.
Gas turbine heat transfer and cooling technology
Han, Je-Chin; Ekkad, Srinath
2012-01-01
FundamentalsNeed for Turbine Blade CoolingTurbine-Cooling TechnologyTurbine Heat Transfer and Cooling IssuesStructure of the BookReview Articles and Book Chapters on Turbine Cooling and Heat TransferNew Information from 2000 to 2010ReferencesTurbine Heat TransferIntroductionTurbine-Stage Heat TransferCascade Vane Heat-Transfer ExperimentsCascade Blade Heat TransferAirfoil Endwall Heat TransferTurbine Rotor Blade Tip Heat TransferLeading-Edge Region Heat TransferFlat-Surface Heat TransferNew Information from 2000 to 20102.10 ClosureReferencesTurbine Film CoolingIntroductionFilm Cooling on Rotat
Pool boiling of distilled water over tube bundle with variable heat flux
Swain, Abhilas; Mohanty, Rajiva Lochan; Das, Mihir Kumar
2017-08-01
The experimental investigation of saturated pool boiling heat transfer of distilled water over plain tube bundle, under uniform and varying heat flux condition along the height are presented in this article. Experiments are carried out under various heat flux configurations applied to rows of tube bundles and pitch distance to diameter ratios of 1.25, 1.6 and 1.95. The wall superheats and pool boiling heat transfer coefficients over individual rows are determined. The pool boiling heat transfer coefficients for variable heat flux and uniform heat flux conditions are compared. The results indicate that the bundle effect is found to exist for uniform as well as variable heat flux under all operating conditions in the present investigation. The variable heat flux resulted in range of wall superheat being highest for decreasing heat flux from bottom to top and lowest for increasing heat flux from bottom to top.
Avoid heat transfer equipment vibration
Energy Technology Data Exchange (ETDEWEB)
Ganapathy, V.
1987-06-01
Tube bundles in heat exchangers, boilers, superheaters and heaters are often subject to vibration and noise problems. Vibration can lead to tube thinning and wear, resulting in tube failures. Excessive noise can be a problem to plant operating personnel. Large gas pressure drop across the equipment is also a side effect, which results in large operating costs. With the design checks presented in this paper, one can predict during design if problems associated with noise and vibration are likely to occur in petroleum refineries.
Heat Transfer Basics and Practice
Böckh, Peter
2012-01-01
The book provides an easy way to understand the fundamentals of heat transfer. The reader will acquire the ability to design and analyze heat exchangers. Without extensive derivation of the fundamentals, the latest correlations for heat transfer coefficients and their application are discussed. The following topics are presented - Steady state and transient heat conduction - Free and forced convection - Finned surfaces - Condensation and boiling - Radiation - Heat exchanger design - Problem-solving After introducing the basic terminology, the reader is made familiar with the different mechanisms of heat transfer. Their practical application is demonstrated in examples, which are available in the Internet as MathCad files for further use. Tables of material properties and formulas for their use in programs are included in the appendix. This book will serve as a valuable resource for both students and engineers in the industry. The author’s experience indicates that students, after 40 lectures and exercises ...
Convective Heat Transfer in Acoustic Streaming Flows
Gopinath, Ashok
1992-01-01
Convective heat transfer due to acoustic streaming has been studied in the absence of an imposed mean flow. The work is motivated by the need to design and control the thermal features of a suitable experimental rig for the containerless processing of materials by heat treatment of acoustically levitated alloy samples at near zero-gravity. First the problem of heat transfer from an isolated sphere (in a standing sound field) is explored in detail. The streaming Reynolds number, Rs, which characterizes the resulting steady flows, is determined from the acoustic signal. A scale analysis is used to ascertain the importance of buoyancy and viscous dissipation. The steady velocity and temperature fields are determined using asymptotic techniques and numerical methods for the limiting cases of RsKundt tube (supporting a plane axial standing sound wave) with insulated side-wall and isothermal end-walls. Analytical solution techniques are used to determine the steady fields close to the tube walls. For the steady recirculatory transport in the core, the numerical solver PHOENICS is adopted for the solution of the complete elliptic form of the governing equations. A study of the effects of a range of acoustic and geometric parameters on the flow and heat transfer is performed and Nusselt number correlations are obtained for air. PHOENICS is also used to study the effects of variable fluid properties and axial side-wall conduction (coupled with radiation). The role of normal/reduced gravity is assessed and suggestions made for terrestrial testing of the levitation apparatus. Finally, with the sample located at a node in the levitation chamber, the effect of the interaction of the streaming flows (on the sphere and the tube walls) is estimated. Representative calculations for the sample heating/cooling rates are presented and compared with existing data in the literature.
Blind vortex tube as heat-rejecting heat exchanger for pulse tube cryocooler
Mitchell, M. P.; Fabris, D.; Sweeney, R. O.
2002-05-01
This project integrated several unusual design features in a coaxial pulse tube cooler driven by a G-M compressor. Design objectives were simplification of construction and validation of innovative components to replace screens. The MS*2 Stirling Cycle Code was used to develop the thermodynamic design of the cooler. The primary innovation being investigated is the vortex tube that serves as both the orifice and the heat-rejecting heat exchanger at the warm end of the pulse tube. The regenerator is etched stainless steel foil with a developmental etch pattern. The cold heat exchanger is a copper cup with axial slits in its wall. Flow straightening in the cold end of the pulse tube is accomplished in traditional fashion with screens, but flow in the warm end of the pulse tube passes through a diffuser nozzle that is an extension of the cold throat of the vortex tube. The G-M compressor is rated at 2 kW. The custom-built rotary valve permits operation at speeds up to about 12 Hz. A series of adjustments over a period of about 7 months improved cooling performance by an average of almost 20 K per month. A no-load temperature of 65 K has been achieved. Experimental apparatus and results of this patented device [1,2] are described.
Heat transfer, diffusion, and evaporation
Nusselt, Wilhelm
1954-01-01
Although it has long been known that the differential equations of the heat-transfer and diffusion processes are identical, application to technical problems has only recently been made. In 1916 it was shown that the speed of oxidation of the carbon in iron ore depends upon the speed with which the oxygen of the combustion air diffuses through the core of gas surrounding the carbon surface. The identity previously referred to was then used to calculate the amount of oxygen diffusing to the carbon surface on the basis of the heat transfer between the gas stream and the carbon surface. Then in 1921, H. Thoma reversed that procedure; he used diffusion experiments to determine heat-transfer coefficients. Recently Lohrisch has extended this work by experiment. A technically very important application of the identity of heat transfer and diffusion is that of the cooling tower, since in this case both processes occur simultaneously.
Jang, Jin Yong; Jeong, Ji Hwan
2016-04-01
A multiple mini-tube (MMT) heat exchanger was considered as an internal heat exchanger of vapor-injection cycle heat pump. Heat transfer and pressure drop in multiple mini-tube heat exchangers were numerically and experimentally investigated. Results show that the best performance of the MMT heat exchanger can be obtained when the intermediate-pressure two-phase refrigerant is supplied to the shell-side and this refrigerant reaches a saturated vapor state at the exit of the heat exchanger.
Analytical and Numerical Design Analysis of Concentric Tube Heat Exchangers – A Review
Silaipillayarputhur, Karthik; Mughanam, Tawfiq Al; Mojil, Abdulaziz Al; Dhmoush, Mohammed Al
2017-12-01
This paper considers an analytical and a numerical approach in the design of a concentric tube heat exchanger. Sensible heat transfer is considered in the analysis and the heat exchanger is developed for actual operating conditions in a chemical plant. The heat exchanger is a concentric tube heat exchanger where hot oil exchanges heat with hot water. Hot oil is in the inner pipe and the heating medium, hot water, is in the outer pipe (annular side) of the heat exchanger. An analytical model employing effectiveness-number of transfer units (ε-NTU) approach and log mean temperature difference (LMTD) approach were employed in the design of the concentric tube heat exchanger. In the design process, performance charts were developed for concentric tube heat exchanger. Performance charts describe the performance of the heat exchanger in terms of crucial dimensionless parameters. Performance charts help to select the right number of transfer units (NTU) for the given heat exchanger. Both parallel and counter flow configurations were considered for the design analysis. Likewise, a numerical model was also considered in the design of the heat exchanger. The results from the analysis are presented and compared. From the results it can be seen that both numerical and analytical approaches produce the exact same results. The designer certainly has the flexibility to choose an appropriate design methodology based on the available inputs and requirements.
Directory of Open Access Journals (Sweden)
Qiming Men
2014-01-01
Full Text Available Aiming at the heat transfer calculation of the Passive Residual Heat Removal Heat Exchanger (PRHR HX, experiments on the heat transfer of C-shaped tube immerged in a water tank were performed. Comparisons of different correlation in literatures with the experimental data were carried out. It can be concluded that the Dittus-Boelter correlation provides a best-estimate fit with the experimental results. The average error is about 0.35%. For the tube outside, the McAdams correlations for both horizontal and vertical regions are best-estimated. The average errors are about 0.55% for horizontal region and about 3.28% for vertical region. The tank mixing characteristics were also investigated in present work. It can be concluded that the tank fluid rose gradually which leads to a thermal stratification phenomenon.
Enhanced boiling heat transfer in horizontal test bundles
Energy Technology Data Exchange (ETDEWEB)
Trewin, R.R.; Jensen, M.K.; Bergles, A.E.
1994-08-01
Two-phase flow boiling from bundles of horizontal tubes with smooth and enhanced surfaces has been investigated. Experiments were conducted in pure refrigerant R-113, pure R-11, and mixtures of R-11 and R-113 of approximately 25, 50, and 75% of R-113 by mass. Tests were conducted in two staggered tube bundles consisting of fifteen rows and five columns laid out in equilateral triangular arrays with pitch-to-diameter ratios of 1.17 and 1.5. The enhanced surfaces tested included a knurled surface (Wolverine`s Turbo-B) and a porous surface (Linde`s High Flux). Pool boiling tests were conducted for each surface so that reference values of the heat transfer coefficient could be obtained. Boiling heat transfer experiments in the tube bundles were conducted at pressures of 2 and 6 bar, heat flux values from 5 to 80 kW/m{sup 2}s, and qualities from 0% to 80%, Values of the heat transfer coefficients for the enhanced surfaces were significantly larger than for the smooth tubes and were comparable to the values obtained in pool boiling. It was found that the performance of the enhanced tubes could be predicted using the pool boiling results. The degradation in the smooth tube heat transfer coefficients obtained in fluid mixtures was found to depend on the difference between the molar concentration in the liquid and vapor.
Advances in heat transfer enhancement
Saha, Sujoy Kumar; Sundén, Bengt; Wu, Zan
2016-01-01
This Brief addresses the phenomena of heat transfer enhancement. A companion edition in the SpringerBrief Subseries on Thermal Engineering and Applied Science to three other monographs including “Critical Heat Flux in Flow Boiling in Microchannels,” this volume is idea for professionals, researchers, and graduate students concerned with electronic cooling.
Directory of Open Access Journals (Sweden)
Xin Wen Zhang
2015-07-01
Full Text Available Surface water source heat pump system is an energy-efficient heat pump system. Surface water heat exchanger is an important part of heat pump system that can affect the performance of the system. In order to enhance the performance of the system, the overall heat transfer coefficient (U value of the water exchanger using a 32A square copper coiled high-density polyethylene tube was researched. Comparative experiments were conducted between the performance of the coiled high-density polyethylene tube and the 32A smooth high-density polyethylene tube. At the same time, the coefficient of performance of the heat pump was investigated. According to the result, the U value of the coiled tube was 18% higher than that of the smooth tube in natural convection and 19% higher in forced convection. The coefficient of performance of the heat pump with the coiled tube is higher than that with the smooth tube. The economic evaluation of the coiled tube was also investigated.
Radius ratio effects on natural heat transfer in concentric annulus
DEFF Research Database (Denmark)
Alipour, M.; Hosseini, R.; Kolaei, Alireza Rezania
2013-01-01
This paper studies natural convection heat transfer in vertical and electrically heated annulus. The metallic cylinders mounted concentrically in a parallel tube. Measurements are carried out for four input electric powers and three radius ratios with an apparatus immersed in stagnant air...
Optimization research of sextant fan baffle curvature radius in shell and tube heat exchanger
Jin, M.; Liu, H. J.; Wang, X. Y.
2017-09-01
For a high shell side pressure drop of the conventional segmental baffles in shell and tube heat exchanger, a novel sextant fan baffle was put forward. To research the influence of baffle curvature radius of the sextant fan baffled shell and tube heat exchanger (SFTHX) on the shell side pressure drop, the heat transfer coefficient and the comprehensive heat transfer performance, six different curvature radius baffles were numerically simulated and experimental studied in this paper. Based on the numerically simulation results, under the same inlet flow conditions, a better comprehensive heat transfer performance can be found in SFTHX with the baffle curvature radius of 1 D, which is higher by 0.84-6.85% more than that of the others. Moreover, the experimental investigation data of SFTHX with baffle curvature radius of 1 D indicates that the numerically simulation can well predict the flow and heat transfer characteristics with the experiment.
Performance study of a fin and tube heat exchanger with different fin geometry
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
2016-01-01
This study analyses the effect of different fin geometries on the heat transfer and pressure loss characteristics of a fin and tube heat exchanger. A numerical investigation is carried out on liquid–gas type double-finned tube heat exchanger under cross-flow condition. Three different cross......-sections namely: a) Rectangular, b) Trapezoidal, c) Triangular are adopted to define the fin geometry. The CFD simulations are performed to incorporate coupled steady state conjugate heat transfer with the turbulent flow phenomenon for the Reynolds number in the range of 5000-13000. Dimensionless heat transfer...... models show that triangular fin geometry can provide higher heat transfer performance in comparison to the fins with rectangular and trapezoidal geometry with lower pressure loss and a bonus of 7.27% reduction in weight under similar operating conditions....
Heat transfer enhancement with nanofluids
Bianco, Vincenzo; Nardini, Sergio; Vafai, Kambiz
2015-01-01
Properties of NanofluidSamuel Paolucci and Gianluca PolitiExact Solutions and Their Implications in Anomalous Heat TransferWenhao Li, Chen Yang and Akira NakayamaMechanisms and Models of Thermal Conductivity in NanofluidsSeung-Hyun Lee and Seok Pil JangExperimental Methods for the Characterization of Thermophysical Properties of NanofluidsSergio Bobbo and Laura FedeleNanofluid Forced ConvectionGilles RoyExperimental Study of Convective Heat Transfer in NanofluidsEhsan B. Haghighi, Adi T. Utomo, Andrzej W. Pacek and Björn E. PalmPerformance of Heat Exchangers Using NanofluidsBengt Sundén and Za
Fundamental principles of heat transfer
Whitaker, Stephen
1977-01-01
Fundamental Principles of Heat Transfer introduces the fundamental concepts of heat transfer: conduction, convection, and radiation. It presents theoretical developments and example and design problems and illustrates the practical applications of fundamental principles. The chapters in this book cover various topics such as one-dimensional and transient heat conduction, energy and turbulent transport, forced convection, thermal radiation, and radiant energy exchange. There are example problems and solutions at the end of every chapter dealing with design problems. This book is a valuable int
3-D NUMERICAL STUDY AND COMPARISON OF ECCENTRIC AND CONCENTRIC ANNULAR-FINNED TUBE HEAT EXCHANGERS
Directory of Open Access Journals (Sweden)
FAROUK TAHROUR
2015-11-01
Full Text Available The use of 3-D computational fluid dynamics (CFD is proposed to simulate the conjugate conduction-convection of heat transfer problems in eccentric annularfinned tube heat exchangers. The numerical simulation results allow us to evaluate the heat transfer coefficient over fin surfaces, the fin efficiency and the pressure drop. The aim of the present paper is to determine the optimum tube position in the circular fin that maximizes heat dissipation and minimizes pressure drop. In addition, this study analyzes the effects of fin spacing and fin tube diameter on heat transfer and flow characteristics for a range of Reynolds numbers, 4500≤Re≤22500. A satisfactory qualitative and quantitative agreement was obtained between the numerical predictions and the results published in the literature. For small fin spacings, the eccentric annular finned tube is more efficient than the concentric one. Among the cases examined, the average heat transfer coefficient of the eccentric annular-finned tube, for a tube shift St =12 mm and a Reynolds number Re = 9923, was 7.61% greater than that of the concentric one. This gain is associated with a 43.09% reduction in pressure drop.
Heat transfer. Basics and practice
Energy Technology Data Exchange (ETDEWEB)
Wetzel, Thomas [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany); Boeckh, Peter von
2012-07-01
The book provides an easy way to understand the fundamentals of heat transfer. The reader will acquire the ability to design and analyze heat exchangers. Without extensive derivation of the fundamentals, the latest correlations for heat transfer coefficients and their application are discussed. The following topics are presented - Steady state and transient heat conduction - Free and forced convection - Finned surfaces - Condensation and boiling - Radiation - Heat exchanger design - Problem-solving After introducing the basic terminology, the reader is made familiar with the different mechanisms of heat transfer. Their practical application is demonstrated in examples, which are available in the Internet as MathCad files for further use. Tables of material properties and formulas for their use in programs are included in the appendix. This book will serve as a valuable resource for both students and engineers in the industry. The author's experience indicates that students, after 40 lectures and exercises of 45 minutes based on this textbook, have proved capable of designing independently complex heat exchangers such as for cooling of rocket propulsion chambers, condensers and evaporators for heat pumps. (orig.)
Fluid heating by current injection tubes; Chauffage de fluides par tubes a passage de courant
Energy Technology Data Exchange (ETDEWEB)
Schroeder, L.S. [Societe Parmilleux (France)
1999-04-01
Current injection tube technology may be applied in compact fluid heating installation with a very low level of thermal inertia. The technology is particularly suitable for heating heat-sensitive fluids or those with a tendency to foul other types of installations. Specific advantages of current injection tubes include the elimination of cold spots and their reduced volume requirements. (author)
Energy Technology Data Exchange (ETDEWEB)
Graber, H. [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires
1969-04-01
By introducing an additional parameter F{sub 0}, the processes known hitherto for calculating heat transfer are extended to the heat flux distributions following an exponential law q{sub w} = exp(mx) which give a heat transfer coefficient, independent of position for laminar and turbulent flow with a linear pressure drop. For laminar flow along a semi-infinite plate, the heat flux distribution in accordance with the law qw = x{sup m} leads to the Nusselt number, regardless of the position. Nu is then determined by the thickness of the thermal boundary layer. For the annular space, the equations for explicit calculation of the temperature field will be given, as well as the Nusselt number in laminar flow and constant heat flux. In turbulent flow, the laws of distribution of eddy diffusivity for momentum in a tube, established by H. Reichardt, adapted for the annular space and the tube bundle, give the velocity field and the coefficient of friction and thus permit solution of the heat transfer equations. The results of the numerical calculation are given in the tables and diagrams for an extended range of the various parameters and compared with the experimental results. A simple process to determine the lower limit of the thermal entry length will be described. (author) [French] Par l'introduction d'un parametre supplementaire F{sub 0}, les procedes connus jusqu'a present pour le calcul du transfert de chaleur sont etendus aux repartitions exponentielles q{sub w} = exp(mx) du flux de chaleur qui indiquent un coefficient de transfert de chaleur independant de l'endroit pour l'ecoulement laminaire ou turbulent avec chute de pression lineaire. Pour l'ecoulement laminaire le long d'une plaque plane, la repartition du flux de chaleur selon la loi q{sub w} = x{sup m} conduit au nombre de Nusselt independant de l'endroit. Nu est alors determine par l'epaisseur de la couche limite thermique. Pour l'espace annulaire, seront
Nuclear reactor fuel element having improved heat transfer
Garnier, J.E.; Begej, S.; Williford, R.E.; Christensen, J.A.
1982-03-03
A nuclear reactor fuel element having improved heat transfer between fuel material and cladding is described. The element consists of an outer cladding tube divided into an upper fuel section containing a central core of fissionable or mixed fissionable and fertile fuel material, slightly smaller in diameter than the inner surface of the cladding tube and a small lower accumulator section, the cladding tube being which is filled with a low molecular weight gas to transfer heat from fuel material to cladding during irradiation. A plurality of essentially vertical grooves in the fuel section extend downward and communicate with the accumulator section. The radial depth of the grooves is sufficient to provide a thermal gradient between the hot fuel surface and the relatively cooler cladding surface to allow thermal segregation to take place between the low molecular weight heat transfer gas and high molecular weight fission product gases produced by the fuel material during irradiation.
Annaratone, Donatello
2010-01-01
This book is a generalist textbook; it is designed for anybody interested in heat transmission, including scholars, designers and students. Two criteria constitute the foundation of Annaratone's books, including the present one. The first one consists of indispensable scientific rigor without theoretical exasperation. The inclusion in the book of some theoretical studies, even if admirable for their scientific rigor, would have strengthened the scientific foundation of this publication, yet without providing the reader with further applicable know-how. The second criterion is to deliver practi
Essentials of radiation heat transfer
Balaji
2014-01-01
Essentials of Radiation Heat Transfer is a textbook presenting the essential, fundamental information required to gain an understanding of radiation heat transfer and equips the reader with enough knowledge to be able to tackle more challenging problems. All concepts are reinforced by carefully chosen and fully worked examples, and exercise problems are provided at the end of every chapter. In a significant departure from other books on this subject, this book completely dispenses with the network method to solve problems of radiation heat transfer in surfaces. It instead presents the powerful radiosity-irradiation method and shows how this technique can be used to solve problems of radiation in enclosures made of one to any number of surfaces. The network method is not easily scalable. Secondly, the book introduces atmospheric radiation, which is now being considered as a potentially important area, in which engineers can contribute to the technology of remote sensing and atmospheric sciences in general, b...
Thermal performance of evacuated tube heat pipe solar collector
Putra, Nandy; Kristian, M. R.; David, R.; Haliansyah, K.; Ariantara, Bambang
2016-06-01
The high fossil energy consumption not only causes the scarcity of energy but also raises problems of global warming. Increasing needs of fossil fuel could be reduced through the utilization of solar energy by using solar collectors. Indonesia has the abundant potential for solar energy, but non-renewable energy sources still dominate energy consumption. With heat pipe as passive heat transfer device, evacuated tube solar collector is expected to heat up water for industrial and home usage without external power supply needed to circulate water inside the solar collector. This research was conducted to determine the performance of heat pipe-based evacuated tube solar collector as solar water heater experimentally. The experiments were carried out using stainless steel screen mesh as a wick material, and water and Al2O3-water 0.1% nanofluid as working fluid, and applying inclination angles of 0°, 15°, 30°, and 45°. To analyze the heat absorbed and transferred by the prototype, water at 30°C was circulated through the condenser. A 150 Watt halogen lamp was used as sun simulator, and the prototype was covered by an insulation box to obtain a steady state condition with a minimum affection of ambient changes. Experimental results show that the usage of Al2O3-water 0.1% nanofluid at 30° inclination angle provides the highest thermal performance, which gives efficiency as high as 0.196 and thermal resistance as low as 5.32 °C/W. The use of nanofluid as working fluid enhances thermal performance due to high thermal conductivity of the working fluid. The increase of the inclination angle plays a role in the drainage of the condensate to the evaporator that leads to higher thermal performance until the optimal inclination angle is reached.
A review on improving thermal-hydraulic performance of fin-and-tube heat exchangers
Nickolas, N.; Moorthy, P.; Oumer, A. N.; Ishak, M.
2017-10-01
Fin-and-tube heat exchangers are one of the most common type of heat exchangers that are normally used in sectors that require small size and light weight but high heat transfer capabilities. Compact fin-and-tube heat exchangers experiences high convective thermal resistance at the air-side due to the thermo-physical properties of air. Thus, the purpose of this paper is to provide an overview of research works that are relevant to improving thermalhydraulic performance at the air-side of fin-and-tube heat exchangers. This paper covers a variety of parameters such as tube parameters like tube arrangement, tube shapes and tube inclination angles; extended surfaces such as different shapes of fins and different parameters of vortex generators like attack angles, shapes and locations. Overall, for most modifications there was increment in heat transfer but accompanied with a pressure drop penalty. However, this varies for different combinations of parameters thus this review is to help understand how every mentioned parameters influences the thermal-hydraulic performance.
Energy Technology Data Exchange (ETDEWEB)
Kiessling, Leif; Haegerstedt, Lars-Erik [AaF-Energi och Miljoe AB, Stockholm (Sweden)
2005-06-01
refrigerator. The deposits decrease the tube heat transfer. This may give a higher investment cost, but that has to be compared to a longer service life. Tubes partially without fins at the baffle plates are recommended. Upgraded materials should be chosen for new tubes in tube heat exchangers if ammonia or chlorides are present in the heat source. Special attention shall be paid to vibrations and self-oscillation that will cause rapid wear and fatigue cracking of the tube bundle. Eddy Current Testing is the most common method of testing of tubes in heat pump heat exchangers. The tests shall always bee preceded by a calibration against identical sized specimens and, if possible, identical defects. Finned tubes shall be calibrated against identical sized specimens with measurements against length and sizes as measured from the bottom of the fins. It is also of importance that some tubes with indicated defects are subtracted and examined in connection with the test to get an impression of the correspondence between measurement and result. The report gives recommendations regarding i.a. choice of material and tests.
Mills, A F
1999-01-01
The Second Edition offers complete coverage of heat transfer with broad up-to-date coverage that includes an emphasis on engineering relevance and on problem solving. Integrates software to assist the reader in efficiently calculations. Carefully orders material to make book more reader-friendly and accessible. Offers an extensive introduction to heat exchange design to enhance the engineering and design content of course to satisfy ABET requirements. For professionals in engineering fields.
Kareem, Rashid
2017-10-01
Optimization of double pipe helical coil heat exchanger with various optimizing parameters and its comparison with double pipe straight tube are the prime objectives of this paper. Numerical studies were performed with the aid of a commercial computational fluid dynamics package ANSYS FLUENT 14. In this paper the double pipe helical coil is analysed under turbulent flow conditions for optimum heat exchanger properties. The parameters used for optimization are cross-sectional shape and taper angles. Optimization analysis is being carried out for finding best cross sectional shape of heat exchanger coils by using rectangular, square, triangular and circular cross-sections. The tapered double pipe helical coil is then analysed for best heat transfer and pressure drop characteristics by varying the angle of taper. Finally, an optimum coil on the basis of all the analysis is selected. This optimized double pipe helical coil is compared with double pipe straight tube of equivalent cross-sectional area and length as that of unwounded length of double pipe helical coil.
Effect of tube-support interaction on the dynamic responses of heat exchanger tubes. [LMFBR
Energy Technology Data Exchange (ETDEWEB)
Shin, Y.S.; Jendrzejczyk, J.A.; Wambsganss, M.W.
1977-01-01
Operating heat exchangers have experienced tube damages due to excessive flow-induced vibration. The relatively small inherent tube-to-baffle hole clearances associated with manufacturing tolerances in heat exchangers affect the tube vibrational characteristics. In attempting a theoretical analysis, questions arise as to the effects of tube-baffle impacting on dynamic responses. Experiments were performed to determine the effects of tube-baffle impacting in vertical/horizontal tube orientation, and in air/water medium on the vibrational characteristics (resonant frequencies, mode shapes, and damping) and displacement response amplitudes of a seven-span tube model. The tube and support conditions were prototypic, and overall length approximately one-third that of a straight tube segment of the steam generator designed for the CRBR. The test results were compared with the analytical results based on the multispan beam with ''knife-edge'' supports.
Advances and Outlooks of Heat Transfer Enhancement by Longitudinal Vortex Generators
He, Ya-Ling
2016-01-01
In the last several decades, heat transfer enhancements using extended surface (fins) has received considerable attentions. A new heat transfer enhancement technique, longitudinal vortex generators (LVG), has received significant attention since the 1990s. It is activated by a special type of extended surface that can generate vortices with axes parallel to the main flow direction. The vortices result from strong swirling secondary flow caused by flow separation and friction. The state-of-the-art on research and applications of LVG are described here. The topical coverage includes heat transfer enhancement in straight channels and in heat exchangers. Among the latter are plate and wavy fin-and-tube heat exchangers, fin-and-oval-tube heat exchangers, and fin-and-tube heat exchangers with multiple rows of tubes. The trends and future directions of heat transfer enhancement by means of LVG are discussed.
Thermal performance analysis for heat exchangers having a variable overall heat transfer coefficient
Conklin, J. C.; Granryd, E.
The classic, conventional analysis for the thermal performance of heat exchangers is based on three assumptions: constant fluid flow rate, constant specific heat fluids, and constant overall heat transfer coefficient. Our analysis describes a general approach for analyzing the thermal performance of heat exchangers in which the overall heat transfer coefficient varies as a function of enthalpy, with the other two basic assumptions of constant mass flow rates and constant specific heats unchanged. Many heat exchangers have an overall heat transfer coefficient that is not constant. The conventional heat exchanger thermal performance analysis is correct as long as a true, area-weighted mean value is used. In many applications, however, fluids undergo a change in phase, and the heat transfer coefficient is a function of the local quality or enthalpy; hence, the true, area-weighted, mean heat transfer coefficient will be a function of the heat flux distribution. Examples are presented that illustrate the variation in overall heat transfer coefficient for an evaporation process. We present a general method for computing a true, area-weighted mean overall heat transfer coefficient that permits use of a local overall heat transfer coefficient that is an arbitrary function of enthalpy. This method allows a simple yet accurate analysis of the effects of a variable overall heat transfer coefficient to be made without the use of a large mainframe computer. We then investigate: (1) linear variation of local overall heat transfer coefficient with respect to enthalpy; and (2) two heat transfer correlations applicable to flow-boiling inside a tube.
Fouling-the silent heat transfer thief
Energy Technology Data Exchange (ETDEWEB)
Ganapathy, V. (ABCO Industries, Inc., Abilene, TX (United States))
1992-10-01
Boilers or heat recovery steam generators perform efficiently under clean conditions. Their performance is significantly affected by fouling either on the tube or gas side whether it is a fire tube or water tube exchanger. In addition to reduced duty, steam side cleanliness impacts the tube wall temperature leading to its overheating and failure in the long run. This paper reports that good water chemistry is an easy, efficient way to reduce the effects of steam-side fouling on boiler performance and tube wall temperature. Water tube waste heat recovery boilers will be used as examples. The concept applies to fired water tube or fire tube boilers and heat recovery steam generators also.
Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel
Sullivan, John P.; Schneider, Steven P.; Liu, Tianshu; Rubal, Justin; Ward, Chris; Dussling, Joseph; Rice, Cody; Foley, Ryan; Cai, Zeimin; Wang, Bo;
2012-01-01
This project developed quantitative methods for obtaining heat transfer from temperature sensitive paint (TSP) measurements in the Mach-6 quiet tunnel at Purdue, which is a Ludwieg tube with a downstream valve, moderately-short flow duration and low levels of heat transfer. Previous difficulties with inferring heat transfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heat transfer that occurs during the unusually long tunnel startup and shutdown, (2) the non-uniform thickness of the insulating coating, (3) inconsistencies and imperfections in the painting process and (4) the low levels of heat transfer observed on slender models at typical stagnation temperatures near 430K. Repeated measurements were conducted on 7 degree-half-angle sharp circular cones at zero angle of attack in order to evaluate the techniques, isolate the problems and identify solutions. An attempt at developing a two-color TSP method is also summarized.
Experimental study of heat transfer to falling liquid films
Fagerholm, N. E.; Kivioja, K.; Ghazanfari, A. R.; Jaervinen, E.
1985-12-01
This project was initiated in order to obtain more knowledge about thermal design of falling film heat exchangers and to find methods to improve heat transfer in film flow. A short literature survey of film flow characteristics and heat transfer is presented. An experimental apparatus designed and built for studying falling film evaporation is described. The first experiments were made with smooth Cu tube 25/22 mm and refrigerant R114 as evaporating liquid. A significant amount of droplet entrainment was observed during the tests. The measured average heat transfer coefficient varied from 1000 to 1800 W/m K when Re=1300 to 11000 respectively and when the transfer mode is surface evaporation. This could be predicted accurately with the experimental correlation of Chun and Seban. When nucleate boiling is dominant the heat transfer could be predicted well with pool boiling correlation of VDI-84.
Process heat transfer principles, applications and rules of thumb
Serth, Robert W
2014-01-01
Process Heat Transfer is a reference on the design and implementation of industrial heat exchangers. It provides the background needed to understand and master the commercial software packages used by professional engineers in the design and analysis of heat exchangers. This book focuses on types of heat exchangers most widely used by industry: shell-and-tube exchangers (including condensers, reboilers and vaporizers), air-cooled heat exchangers and double-pipe (hairpin) exchangers. It provides a substantial introduction to the design of heat exchanger networks using pinch technology, the mos
Automated liquid-helium transfer tube lifting system
Kato, Kiyonori; Suzui, Mitsukazu
1990-07-01
An automatic liquid-helium transfer tube lifting system has been developed, in which the transfer tube can be raised or lowered very slowly by remote control. This system relieves the operator of considerable manual labor, and protects the O-ring seals from damage at low temperature.
Heat transfer to the adsorbent in solar adsorption cooling device
Pilat, Peter; Patsch, Marek; Papucik, Stefan; Vantuch, Martin
2014-08-01
The article deals with design and construction of solar adsorption cooling device and with heat transfer problem in adsorber. The most important part of adsorption cooling system is adsorber/desorber containing adsorbent. Zeolith (adsorbent) type was chosen for its high adsorption capacity, like a coolant was used water. In adsorber/desorber occur, at heating of adsorbent, to heat transfer from heat change medium to the adsorbent. The time required for heating of adsorber filling is very important, because on it depend flexibility of cooling system. Zeolith has a large thermal resistance, therefore it had to be adapted the design and construction of adsorber. As the best shows the tube type of adsorber with double coat construction. By this construction is ensured thin layer of adsorbent and heating is quick in all volume of adsorbent. The process of heat transfer was experimentally measured, but for comparison simulated in ANSYS, too.
Lionel Druette; Christian Inard; Pierre Peigné
2013-01-01
This paper presents a new air-heating system concept for energy-efficient dwellings. It is a system designed to heat a low-energy building by coupling a heat-recovery ventilation system with a three-fluid heat exchanger located on the chimney of a wood-pellet stove. The proposed work focuses on the heat transfer that occurs between flue gases, the ventilation air and the combustion air within a triple concentric tube heat exchanger with no insulation at its outer surface. The main objective i...
Heat transfer in aerospace propulsion
Simoneau, Robert J.; Hendricks, Robert C.; Gladden, Herbert J.
1988-01-01
Presented is an overview of heat transfer related research in support of aerospace propulsion, particularly as seen from the perspective of the NASA Lewis Research Center. Aerospace propulsion is defined to cover the full spectrum from conventional aircraft power plants through the Aerospace Plane to space propulsion. The conventional subsonic/supersonic aircraft arena, whether commercial or military, relies on the turbine engine. A key characteristic of turbine engines is that they involve fundamentally unsteady flows which must be properly treated. Space propulsion is characterized by very demanding performance requirements which frequently push systems to their limits and demand tailored designs. The hypersonic flight propulsion systems are subject to severe heat loads and the engine and airframe are truly one entity. The impact of the special demands of each of these aerospace propulsion systems on heat transfer is explored.
RECITAL SCRUTINY ON TUBE-INTUBE COMPACT HEAT EXCHANGERS
V.NATARAJAN,; Dr. P. Senthil Kumar
2011-01-01
This paper focused on the investigational cram of the recital characteristics of tube-in-tube compact heat exchangers. Experiments are conducted in the compact heat exchangers with R-134a and liquefiedpetroleum gas. The effectiveness of the heat exchangers was calculated using the experiment data and it was found that the effectiveness of heat exchanger-1 is above 75 and heat exchanger-2 is above 84% for R-134a.The effectiveness of heat exchanger-1 is about 60% and heat exchanger-2 is about 8...
The Hardy inequality and the heat equation in twisted tubes
Krejčiřík, David; Zuazua, Enrique
2010-01-01
We show that a twist of a three-dimensional tube of uniform cross-section yields an improved decay rate for the heat semigroup associated with the Dirichlet Laplacian in the tube. The proof employs Hardy inequalities for the Dirichlet Laplacian in twisted tubes and the method of self-similar variables and weighted Sobolev spaces for the heat equation. © 2010 Elsevier Masson SAS.
HEAT EXCHANGE AND AERODYNAMICS OF THE COMBINED TUBING BUNDLES WITH CROSS INCLINED FINS
Directory of Open Access Journals (Sweden)
Knyazyuk V. I
2013-04-01
Full Text Available The paper presents results of experimental research and analyses air-side thermal performance of combined tube bundles with cross inclined fins. The empirical correlations for heat transfer and flow friction of tubes with inclined fins at different orientation finned tubes relatively of air flow are presented. The errors of thermal and aerodynamic tests are 3-5% and 9.2%, respectively. The proposed correlations describe an experimental data with a coefficient of determination about 0.979-0.998. The impact of tubes arrangement in a bundle on energy performance of heat exchanger were analyzed using complete and local heat modeling methods at a stationary heat flux. Experimental research indicates that efficiency of inclined fins can be calculated by using the equation for cross rectangular fins with average deviation of ±5 %.
A REVIEW ON HEAT TRANSFER THROUGH HELICAL COIL HEAT EXCHANGERS
Surendra Vishvakarma*, Sanjay Kumbhare, K. K. Thakur
2016-01-01
This study presents a brief review of heat transfer through helical coil heat exchangers. Helical coils of circular cross section have been used in wide variety of applications due to simplicity in manufacturing. Enhancement in heat transfer due to helical coils has been reported by many researchers. While the heat transfer characteristics of double pipe helical heat exchangers are available in the literature, there exists no published experimental or theoretical analysis of a helically coile...
Two phase flow and heat transfer characteristics of a separate-type heat pipe
Tang, Zhiwei; Liu, Aijie; Jiang, Zhangyan
2011-07-01
Two phase flow and heat transfer characteristics of a separate-type heat pipe have been studied experimentally and theoretically. The experimental apparatus have the same geometry for the evaporator and the condenser which consist of 5-tube-banks, with working temperature ranges of 80-125°C. The experimental working fluid is dual-distilled water with corrosion-resistant agents. Heat transfer coefficients for boiling and condensation along with heat flux and working temperature are measured at different filling ratio. According to the results of the experiments, the optimized filling ratio ranges from 16 to 36%. Fitted correlations of average heat transfer coefficients of the evaporator and Nusselt numbers of the condenser at the proposed filling ratio are obtained. Two phase flow characteristics of the evaporator and the condenser as well as their influence on heat transfer are described on the basis of simplified analysis. Reasons for the pulse-boiling process remain to be studied.
Heat transfer coefficient for boiling carbon dioxide
DEFF Research Database (Denmark)
Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik
1998-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The calculated heat transfer coeeficient has been compared with the Chart correlation of Shah. The Chart Correlation predits too low heat transfer coefficient but the ratio...
Thermodynamics and heat transfer in fire fighting
Romanenko, P. N.; Koshmarov, Y. A.; Bashkirtsev, M. P.
1985-05-01
The book presents the fundamental principles of thermodynamics and heat transfer with particular reference to their application in problems related to fire prevention. Special attention is given to the study of unsteady heat transfer, radiant heat transfer (including radiation from flames to the surrounding), thermodynamic analysis of the growth of fires and theoretical modeling of fires in building.
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P
2013-12-10
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Shell-and-double concentric-tube heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Bougriou, Cherif; Baadache, Khireddine [University of Batna, Department of Mechanics, Batna (Algeria)
2010-03-15
This study concerns a new type of heat exchangers, which is that of shell-and-double concentric-tube heat exchangers. These heat exchangers can be used in many specific applications such as air conditioning, waste heat recovery, chemical processing, pharmaceutical industries, power production, transport, distillation, food processing, cryogenics, etc. The case studies include both design calculations and performance calculations. It is demonstrated that the relative diameter sizes of the two tubes with respect to each other are the most important parameters that influence the heat exchanger size. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Di Luozzo, N. [Laboratorio de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires - CONICET, Paseo Colon 850, C1063ACV Buenos Aires (Argentina); Fontana, M., E-mail: mfontan2006@gmail.com [Laboratorio de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires - CONICET, Paseo Colon 850, C1063ACV Buenos Aires (Argentina); Arcondo, B. [Laboratorio de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires - CONICET, Paseo Colon 850, C1063ACV Buenos Aires (Argentina)
2012-09-25
Highlights: Black-Right-Pointing-Pointer Numerical simulations of the heating by induction in steel tubes were performed. Black-Right-Pointing-Pointer Finite element method was employed in this electromagnetic-heat transfer coupled problem. Black-Right-Pointing-Pointer The outside temperature evolution of the steel tubes was determined experimentally and numerically. Black-Right-Pointing-Pointer Temperatures in the inner and outer tube surface and the heat affected zone were determined. - Abstract: The transient liquid phase bonding process is been performed to join carbon steel tubes. Fe{sub 96.2}B{sub 3.8} wt% amorphous ribbons of thickness a Almost-Equal-To 20 {mu}m have been employed as filler material. The tubes are aligned with their butted surfaces in contact with the amorphous layer. The joint is heated into a high frequency induction coil under Argon atmosphere. The temperature is raised at the highest possible rate to the process temperature (at about Almost-Equal-To 1250 Degree-Sign C) and then held for a predetermined time. In this paper, the numerical simulations of the heating stage of the bonding process have been made using the finite element method. This method had shown of being able to deal with these kind of coupled problems: electromagnetic field generated by alternating currents, eddy currents generated on the steel tube, heating of the steel tube due to joule effect and heat transfer by conduction, convection and radiation. The experimental heating stage, for its further simulation, was done with carbon steel tubes. In particular, we are interested in the temperature evolution of the tube upon heating: time to reach the process temperature at the joint, temperature differences between the inner and outer surface of the tube and the extension of the heat affected zone, taking into account the ferromagnetic-paramagnetic transition. The numerical simulations are validated by comparison with infrared radiation thermometer measurements of the
Heat Transfer in a Thermoacoustic Process
Beke, Tamas
2012-01-01
Thermoacoustic instability is defined as the excitation of acoustic modes in chambers with heat sources due to the coupling between acoustic perturbations and unsteady heat addition. The major objective of this paper is to achieve accurate theoretical results in a thermoacoustic heat transfer process. We carry out a detailed heat transfer analysis…
Çakmak, Gülşah; Yücel, H. Lütfi; Argunhan, Zeki; Yıldız, Cengiz
2012-06-01
In this article, the heat transfer, friction factor, and thermal performance factor characteristics of a concentric-tube heat exchanger are examined experimentally. A wavy inner pipe is mounted in the tube with the purpose of generating swirl flow that would help to increase the heat transfer rate of the tube. The examination is performed for a Reynolds number ranging from 2700 to 8800. An empirical correlation is also formulated to match with experimental data of the Nusselt number using the Wilson plot method. In addition, to obtain the real benefits in using the swirl generator at a constant pumping power, the thermal enhancement factor is also determined. Over the range considered, the increases in the Nusselt number, friction factor, and thermal performance factor are found to be, respectively, about 113 %, 81 %, and 196 % higher than those obtained from a smooth-surface inner pipe.
Boiling Heat Transfer of a Refrigerant Flowing Vertically Downward in a Mini-channel
Miyata, Kazushi; Mori, Hideo; Ohishi, Katsumi; Hamamoto, Yoshinori
Experiments were performed on boiling heat transfer of a refrigerant R-410A flowing vertically downward in a copper rectangular tube and a triangular tube of 1.04 mm and 0.88 mm inside hydraulic diameter, respectively,for the development of a high-performance heat exchanger using small tubes or multi-port extruded tubes for air conditioning systems. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200kg/(m2s), heat fluxes from 1 to 20 kW/m2 and quality from 0.05 to 1 at the evaporation temperature of 10 °C.Characteristics of the heat transfer coefficient and dryout quality were clarified by comparing the measurements with the data for the circular tube of 1.0 mm inside diameter previously obtained.
Directory of Open Access Journals (Sweden)
Du Xueping
2014-01-01
Full Text Available A tremendous quantity of water can be saved if the air cooling system is used, comparing with the ordinary water-cooling technology. In this study, two kinds of finned tube heat exchangers in an indirect air-cooling tower are experimentally studied, which are a plain finned oval-tube heat exchanger and a wavy-finned flat-tube heat exchanger in a cross flow of air. Four different air inlet angles (90°, 60 °, 45°, and 30° are tested separately to obtain the heat transfer and resistance performance. Then the air-side experimental correlations of the Nusselt number and friction factor are acquired. The comprehensive heat transfer performances for two finned tube heat exchangers under four air inlet angles are compared. For the plain finned oval-tube heat exchanger, the vertical angle (90° has the worst performance while 45° and 30° has the best performance at small ReDc and at large ReDc, respectively. For the wavy-finned flat-tube heat exchanger, the worst performance occurred at 60°, while the best performance occurred at 45° and 90° at small ReDc and at large ReDc, respectively. From the comparative results, it can be found that the air inlet angle has completely different effects on the comprehensive heat transfer performance for the heat exchangers with different structures.
Energy Technology Data Exchange (ETDEWEB)
Park, Chun Dong; Lee, Dong Hyun; Park, Byung-Sik; Choi, Jaejoon [Korea Institute of Energy Research (KIER), Daejeon (Korea, Republic of)
2017-02-15
In this study, the flow and heat transfer characteristics of the finned annular passage were investigated numerically. The annular passage simulates co-axial geothermal heat exchanger, and fins are installed on its inner wall to reduce heat loss from the production passage (annulus) to injection passage (inner pipe). A commercial CFD program, Ansys Fluent, was used with SST k-ω turbulence model. The effects of the geometric parameters of the fin on the inner tube were analyzed under the periodic boundary condition. The result indicated that most parameters had a tendency to increase with an increase in the height and angle of the fin. However, it was confirmed that the Nusselt number of the inner tube on the coaxial 15, 5, 0.3 was lower than that of the smooth tube. Additionally, the Nusselt number of the inner tube exhibited a tendency of decreasing with a decrease in the spacing in Coaxial 15, S{sub f}, 0.3.
Convective heat transfer enhancement with nanofluids
Rahman, Md. Habibur; Abedin, Z.
2017-12-01
Nanofluids are considered to offer important advantages over conventional heat transfer fluids. Over a decade ago, researchers focused on measuring and modeling the effective thermal conductivity and viscosity of nanofluids. Recently important theoretical and experimental research works on convective heat transfer appeared in the open literatures on the enhancement of heat transfer using suspensions of nanometer-sized solid particle materials, metallic or nonmetallic in base heat transfer fluids. The purpose of this article is to summarize recent research on fluid flow and heat transfer enhancement characteristics of nanofluids and thereby identify opportunities for future research.
Directory of Open Access Journals (Sweden)
Aboaltabooq Mahdi Hatf Kadhum
2016-01-01
Full Text Available This paper analyzes the heat transfer characteristics of an ORC evaporator applied on a diesel engine using measured data from experimental work such as flue gas mass flow rate and flue gas temperature. A mathematical model was developed with regard to the preheater, boiler and the superheater zones of a counter flow evaporator. Each of these zones has been subdivided into a number of cells. The hot source of the ORC cycle was modeled. The study involves the variable heat input's dependence on the ORC system's heat transfer characteristics, with especial emphasis on the evaporator. The results show that the refrigerant's heat transfer coefficient has a higher value for a 100% load from the diesel engine, and decreases with the load decrease. Also, on the exhaust gas side, the heat transfer coefficient decreases with the decrease of the load. The refrigerant's heat transfer coefficient increased normally with the evaporator's tube length in the preheater zone, and then increases rapidly in the boiler zone, followed by a decrease in the superheater zone. The exhaust gases’ heat transfer coefficient increased with the evaporator’ tube length in all zones. The results were compared with result by other authors and were found to be in agreement.
Study on the Influential Factors of Heat Transfer of Ground Heat Exchanger with Orthogonal Test
Su, Shunyu; Yang, Rui; Liu, Lamei; Zhou, Chuanhui; Shi, Lei
2017-08-01
Orthogonal test method could decrease experimental times and obtain better test effect. The Taguchi method, as well as mean value response and analysis of variance, were applied in this paper to study the influence of water flow velocity in pipe, diameter and water temperature of pipe inlet on heat transfer of ground heat exchanger. The optimum design parameters and the estimated values of heat flux per meter of well depth for single U-tubes are obtained. The analysis revealed that diameter is the most influential parameter for heat flux per meter of well depth in single U-tubes while water flow velocity within 0.3m/s to 0.5m/s. And water flow velocity and diameter are important influential parameters for heat flux per meter of well depth in single U-tubes while water flow velocity within 0.5m/s to 0.8m/s. Tubes with big diameters are superior to tubes with small diameters in the design of ground source heat exchanger with single U-tubes.
Comparison of heat transfer in straight and corrugated minichannels with two-phase flow
Directory of Open Access Journals (Sweden)
Peukert P.
2014-03-01
Full Text Available Measurements of heat transfer rates performed with an experimental condensation heat exchanger are reported for a corrugated minichannel tube and for a straight minichannel tube. The two cases were compared at same flow regimes. The corrugation appears advantageous for relatively low steam pressures and flow rates where much higher heat transfer rates were observed close to the steam entrance, thus allowing shortening the heat exchanger with the associated advantages of costs lowering and smaller built-up space. At high steam pressures and high flow rates both tubes performed similarly.
Heat transfer coeffcient for boiling carbon dioxide
DEFF Research Database (Denmark)
Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik
1997-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The pipe is heated by condensing R22 outside the pipe. The heat input is supplied by an electrical heater wich evaporates the R22. With the heat flux assumed constant over...... the whole surface and with measured temperature difference between the inner surface and the evaporation temperature a mean heat transfer coefficient is calculated. The calculated heat transfer coefficient has been compared with the Chart Correlation of Shah. The Chart Correlation predicts too low heat...
Coking of JP-4 fuels in electrically heated metal tubes
Smith, Arthur L; Cook, William P; Hlavin, Vincent F
1956-01-01
A limited exploratory investigation of the rate of coking of four JP-4 fuels in electrically heated metal tubes was conducted in order to provide design information for fuel prevaporizers for turbojet-engine combustors. The fuels tested included two production and two minimum-quality JP-4 type fuels. The heating tube was operated at fuel pressures of approximately 500, 400, and 50 pounds per square inch. The operating fuel temperature was varied between approximately 600 degrees and 1200 degrees F.
Dalkilic, A. S.; Acikgoz, O.; Tapan, S.; Wongwises, S.
2016-12-01
A shell and tube heat exchanger is used as a condenser and an evaporator in this theoretical study. Parametric performance analyses for various actual refrigerants were performed using well-known correlations in open sources. Condensation and evaporation were occurred in the shell side while the water was flowing in the tube side of heat exchanger. Heat transfer rate from tube side was kept constant for condenser and evaporator design. Condensing temperatures were varied from 35 to 60 °C whereas evaporating temperatures were ranging from -15 to 10 °C for the refrigerants of R12, R22, R134a, R32, R507A, R404A, R502, R407C, R152A, R410A and R1234ZE. Variation of convective heat transfer coefficients of refrigerants, total heat transfer coefficients with Reynolds numbers and saturation temperatures were given as validation process considering not only fouling resistance and omission of it but also staggered (triangular) and line (square) arrangements. The minimum tube lengths and necessary pumping powers were calculated and given as case studies for the investigated refrigerants considering validation criteria. It was understood that refrigerant type, fouling resistance and arrangement type are one of the crucial issues regarding the determination of heat exchanger's size and energy consumption. Consequently, R32 and R152a were found to require the shortest tube length and lowest pumping power in the condenser, whereas R507 and R407C have the same advantages in the evaporator. Their heat transfer coefficients were also determined larger than others as expectedly.
107-120, 2015 107 Thermal analysis of shell and tube heat
African Journals Online (AJOL)
8(2) 107-120, 2015. 117. Figure 5c. Overall heat transfer coefficient comparison between ANN prediction and Kern's method value. Figure 5d. Shell side pressure drop comparison between ANN prediction and Kern's method value. Figure 5e. Tube side pressure drop comparison between ANN prediction and Kern's method ...
Transient critical heat flux and blowdown heat-transfer studies
Energy Technology Data Exchange (ETDEWEB)
Leung, J.C.
1980-05-01
Objective of this study is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. To accomplish this task, a predictional method has been developed. Basically it involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous ''local-conditions'' hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis.
HEAT-MASS TRANSFER IN MOVING MELT
Directory of Open Access Journals (Sweden)
R. I. Yesman
2005-01-01
Full Text Available The paper gives mathematical formation and solution of the heat-mass transfer problem when liquid metals are flowing in the channels of complicated geometry. The problem is solved with the help of numerical methods. A method of control volume is used for finite-difference approximation of transfer equations. The research results can be applied for execution of a numerical experiment while investigating heat-mass transfer in liquid-metal heat-transfer and reological media.
Flow distribution and tube vibration in heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Anderson, H.L.
1985-07-01
A project was initiated to study flow distribution and tube vibration in heat exchangers. An experimental program was carried out on a full-size heat exchanger in four test phases of parametric study. The flow induced vibration data were used to quantify and develop non-intrusive vibration monitoring techniques for online problem evaluation and to study the influence of design features and conditions on the vibration. The in-tube vibration data obtained have shown that the vibroacoustic and microphone monitoring techniques to be reliable and accurate methods for the detection of tube impacting in an operating heat exchanger. Development of work on the use of a two-accelerator vibroacoustic technique for the location of impacting zones in a bundle showed promise and is currently being employed in the field. The in-tube vibration data have demonstrated the effects that changes in the design of a bundle can have on tube vibration in that bundle. These results indicate that an important factor in bundle design is the local flow distribution in areas of high vibration susceptibility. The in-tube data have demonstrated that tubes in zones other than the inlet region can be susceptible to a form of periodic resonant excitation. This observation has implications for cases where flow reduction is implemented to avoid an instability problem. Such a reduction could bring the tube bundle into a flow regime where it is susceptible to the resonant excitation. 10 refs., 55 figs., 4 tabs.
Comparative study of convective heat transfer characteristics of nanofluids
Muryam, Hina; Ramzan, Naveed; Umer, Asim; Awan, Gul Hameed; Hassan, Ali
2017-07-01
The present research is about to draw a comparison between heat transfer characteristics of gold/deionized water (DIW) and silver/DIW based nanofluid under same heat flux for laminar flow. Experiments are performed on both nanofluid by using different concentrations (0.015, 0.045, 0.0667%) of nano-particles (NPs) in DIW as a base fluid. The experimental study concludes that an appreciable intensification in heat transfer coefficient (HTC) of both nanofluid has been attained as compare to base fluid. However, gold/DIW based nanofluid exhibit better convective heat transfer intensification compared with silver/DIW based nanofluid but Shah correlation cannot predict as much augmentation as in experimental work for both nanofluid. It is also noticed that the anomalous enhancement in Nusselt number and HTC is not only due to the accession in thermal properties but also by the formation of thinner thermal boundary layer at the entrance of the tube due to NPs.
Heat Transfer and Cooling in Gas Turbines
1985-09-01
the detailed component internal heat transfer for a variety of families of cooling schemes, and (c) to choose from among and withir those families to...1965. 32. Metzger, D.E., and Grochowsky, 1.D., "Heat Transfer Between an Impinging Jet and a Rotating Dink ," J. Heat Tranafer, Trans. ASME, 99, pp. 663
REVIEW OF PCMs AND HEAT TRANSFER ENHANCEMENT ...
African Journals Online (AJOL)
HOD
for power applications. The various methods of heat transfer enhancement in latent heat storage systems were also reviewed systematically. The review showed that three commercially-available PCMs are suitable in the operating temperature range of parabolic trough plants. Many heat transfer enhancement methods ...
Engineering calculations in radiative heat transfer
Gray, W A; Hopkins, D W
1974-01-01
Engineering Calculations in Radiative Heat Transfer is a six-chapter book that first explains the basic principles of thermal radiation and direct radiative transfer. Total exchange of radiation within an enclosure containing an absorbing or non-absorbing medium is then described. Subsequent chapters detail the radiative heat transfer applications and measurement of radiation and temperature.
Heat Transfer Studies in Gun Tubes
1979-03-01
parameter studies are to be made that involve a redefinition of the geometry and node structure . Experience has shown that such problems are most easily...addition TRUMP was modified to include a subroutine, DINAM , that keeps track of the dynamic connections. The results of a few calculations with this model...beyond the scope of the present study. The present results were calculated with the geometry and node structure shown in Figure 22. The length of the
A computer program for designing fin-and-tube heat exchanger for EGR cooler application
Syaiful, Marwan, M. A.; Tandian, N. P.; Bae, M.
2016-03-01
EGR (exhaust gas recirculation) cooler is a kind of heat exchanger that is used to cool exhaust gas recirculation prior to be mixed with fresh air in an intake manifold of vehicle in order to obtain good reduction of NOxemissions. A fin-and-tube heat exchanger is more preferred as an EGR cooler than a shell-and-tube heat exchanger in this study due to its compactness. Manually designing many configurations of fin-and-tube heat exchanger for EGR cooler application consumes a lot of time and is high cost. Therefore, a computer aided design process of EGR cooler is required to overcome this problem. The EGR cooler design process was started by arranging the sequences of calculation algorithm in a computer program. A cooling media for this EGR cooler is air. The design is based on the effectiveness-number transfer unit (NTU) method. The EGR cooler design gives the geometry, heat transfer surface area, heat transfer coefficient and pressure drop of the EGR cooler. Comparison of the EGR cooler Nusselt number obtained in this study and that reported in literature shows less than 6.2% discrepancy.
CFD analysis of fin tube heat exchanger with a pair of delta winglet vortex generators
Energy Technology Data Exchange (ETDEWEB)
Hwang, Seong Won; Kim, Dong Hwan; Min, June Kee; Jeong, Ji Hwan [Pusan National Univ., Busan (Korea, Republic of)
2012-09-15
Among tubular heat exchangers, fin tube types are the most widely used in refrigeration and air-conditioning equipment. Efforts to enhance the performance of these heat exchangers included variations in the fin shape from a plain fin to a slit and louver type. In the context of heat transfer augmentation, the performance of vortex generators has also been investigated. Delta winglet vortex generators have recently attracted research interest, partly due to experimental data showing that their addition to fin-tube heat exchangers considerably reduces pressure loss at heat transfer capacity of nearly the same level. The efficiency of the delta winglet vortex generators widely varies depending on their size and shape, as well as the locations where they are implemented. In this paper, the flow field around delta winglet vortex generators in a common flow up arrangement was analyzed in terms of flow characteristics and heat transfer using computational fluid dynamics methods. Flow mixing due to vortices and delayed separation due to acceleration influence the overall fin performance. The fin with delta winglet vortex generators exhibited a pressure loss lower than that of a plain fin, and the heat transfer performance was enhanced at high air velocity or Reynolds number.
Concentric tube heat exchanger installed by twisted tapes using various wings with alternate axes
Yaningsih, Indri; Wijayanta, Agung Tri
2017-01-01
The effects of twisted tapes using various wings with alternate axes on heat transfer, flow friction and thermal performance characteristics in a concentric tube heat exchanger are experimentally investigated. The influence of wing shape including triangle, rectangle and trapezoid are also studied. The experiments are performed using twisted tape with the constant wing-chord ratio (d/W) of 0.31, constant wing-span ratio (b/W) of 0.23 and constant twist ratio (y/W) of 3.8, over a Reynolds number range of 5800-18,500. The alternate axes are made by arranging each plane of twisted tape to 60-degree difference about the adjacent plane. The tests using the plain tube and tube with typical twisted tape were also conducted for a comparison. The results show that both heat transfer rate and friction factor associated with all twisted tape are consistently higher than those without twisted tape. Under the similar operating conditions, Nusselt number, friction factor as well as thermal performance factor given by the tape with alternate-axes and trapezoidal wings are higher than those given by the others. The maximum thermal performance factor of 1.44 is found with the use of twisted tape with alternate-axes and trapezoidal wings, where the heat transfer rate and friction factor increase to 1.91 and 5.2 times of those in the plain tube, respectively.
Heat and mass transfer in particulate suspensions
Michaelides, Efstathios E (Stathis)
2013-01-01
Heat and Mass Transfer in Particulate Suspensions is a critical review of the subject of heat and mass transfer related to particulate Suspensions, which include both fluid-particles and fluid-droplet Suspensions. Fundamentals, recent advances and industrial applications are examined. The subject of particulate heat and mass transfer is currently driven by two significant applications: energy transformations –primarily combustion – and heat transfer equipment. The first includes particle and droplet combustion processes in engineering Suspensions as diverse as the Fluidized Bed Reactors (FBR’s) and Internal Combustion Engines (ICE’s). On the heat transfer side, cooling with nanofluids, which include nanoparticles, has attracted a great deal of attention in the last decade both from the fundamental and the applied side and has produced several scientific publications. A monograph that combines the fundamentals of heat transfer with particulates as well as the modern applications of the subject would be...
Literature survey of heat transfer enhancement techniques in refrigeration applications
Energy Technology Data Exchange (ETDEWEB)
Jensen, M.K.; Shome, B. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Mechanical Engineering, Aeronautical Engineering and Mechanics
1994-05-01
A survey has been performed of the technical and patent literature on enhanced heat transfer of refrigerants in pool boiling, forced convection evaporation, and condensation. Extensive bibliographies of the technical literature and patents are given. Many passive and active techniques were examined for pure refrigerants, refrigerant-oil mixtures, and refrigerant mixtures. The citations were categorized according to enhancement technique, heat transfer mode, and tube or shell side focus. The effects of the enhancement techniques relative to smooth and/or pure refrigerants were illustrated through the discussion of selected papers. Patented enhancement techniques also are discussed. Enhanced heat transfer has demonstrated significant improvements in performance in many refrigerant applications. However, refrigerant mixtures and refrigerant-oil mixtures have not been studied extensively; no research has been performed with enhanced refrigerant mixtures with oil. Most studies have been of the parametric type; there has been inadequate examination of the fundamental processes governing enhanced refrigerant heat transfer, but some modeling is being done and correlations developed. It is clear that an enhancement technique must be optimized for the refrigerant and operating condition. Fundamental processes governing the heat transfer must be examined if models for enhancement techniques are to be developed; these models could provide the method to optimize a surface. Refrigerant mixtures, with and without oil present, must be studied with enhancement devices; there is too little known to be able to estimate the effects of mixtures (particularly NARMs) with enhanced heat transfer. Other conclusions and recommendations are offered.
Activated-Carbon Sorbent With Integral Heat-Transfer Device
Jones, Jack A.; Yavrouian, Andre
1996-01-01
Prototype adsorption device used, for example, in adsorption heat pump, to store natural gas to power automobile, or to separate components of fluid mixtures. Device includes activated carbon held together by binder and molded into finned heat-transfer device providing rapid heating or cooling to enable rapid adsorption or desorption of fluids. Concepts of design and fabrication of device equally valid for such other highly thermally conductive devices as copper-finned tubes, and for such other high-surface-area sorbents as zeolites or silicates.
Finite element simulation of heat transfer
Bergheau, Jean-Michel
2010-01-01
This book introduces the finite element method applied to the resolution of industrial heat transfer problems. Starting from steady conduction, the method is gradually extended to transient regimes, to traditional non-linearities, and to convective phenomena. Coupled problems involving heat transfer are then presented. Three types of couplings are discussed: coupling through boundary conditions (such as radiative heat transfer in cavities), addition of state variables (such as metallurgical phase change), and coupling through partial differential equations (such as electrical phenomena).? A re
Numerical investigation on the convective heat transfer in a spiral coil with radiant heating
Directory of Open Access Journals (Sweden)
Đorđević Milan Lj.
2016-01-01
Full Text Available The objective of this study was to numerically investigate the heat transfer in spiral coil tube in the laminar, transitional, and turbulent flow regimes. The Archimedean spiral coil was exposed to radiant heating and should represent heat absorber of parabolic dish solar concentrator. Specific boundary conditions represent the uniqueness of this study, since the heat flux upon the tube external surfaces varies not only in the circumferential direction, but also in the axial direction. The curvature ratio of spiral coil varies from 0.029 at the flow inlet to 0.234 at the flow outlet, while the heat transfer fluid is water. The 3-D steady-state transport equations were solved using the Reynolds stress turbulence model. Results showed that secondary flows strongly affect the flow and that the heat transfer is strongly asymmetric, with higher values near the outer wall of spiral. Although overall turbulence levels were lower than in a straight pipe, heat transfer rates were larger due to the curvature-induced modifications of the mean flow and temperature fields. [Projekat Ministarstva nauke Republike Srbije, br. 42006
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
2017-01-01
Design management of a thermal energy system is a critical part of identifying basic designs that meet large scale user demand under certain operating characteristics. Fin and tube heat exchangers are among the most commonly used thermal energy systems which are generating considerable interest...... and tube heat exchanger. Computational fluid dynamic models of fin and tube heat exchanger with different fin patterns are developed to investigate the fin pattern behavior on heat transfer and pressure loss performance data. In addition, the numerical results are utilized to analyze the engineering design...... scale-up heat exchanger configurations with each fin pattern focusing on the application of chosen fin and tube heat exchanger in marine exhaust gas boiler. The analysis highlights the impact of material efficient fin patterns investigated and predicts that the polynomial and sinusoidal fin patterns...
A literature survey on numerical heat transfer
Shih, T. M.
1982-12-01
Technical papers in the area of numerical heat transfer published from 1977 through 1981 are reviewed. The journals surveyed include: (1) ASME Journal of Heat Transfer, (2) International Journal of Heat and Mass Transfer, (3) AIAA Journal, (4) Numerical Heat Transfer, (5) Computers and Fluids, (6) International Journal for Numerical Methods in Engineering, (7) SIAM Journal of Numerical Analysis, and (8) Journal of Computational Physics. This survey excludes experimental work in heat transfer and numerical schemes that are not applied to equations governing heat transfer phenomena. The research work is categorized into the following areas: (A) conduction, (B) boundary-layer flows, (C) momentum and heat transfer in cavities, (D) turbulent flows, (E) convection around cylinders and spheres or within annuli, (F) numerical convective instability, (G) radiation, (H) combustion, (I) plumes, jets, and wakes, (J) heat transfer in porous media, (K) boiling, condensation, and two-phase flows, (L) developing and fully developed channel flows, (M) combined heat and mass transfer, (N) applications, (O) comparison and properties of numerical schemes, and (P) body-fitted coordinates and nonuniform grids.
Modelling Heat Transfer of Carbon Nanotubes
Yang, Xin-She
2010-01-01
Modelling heat transfer of carbon nanotubes is important for the thermal management of nanotube-based composites and nanoelectronic device. By using a finite element method for three-dimensional anisotropic heat transfer, we have simulated the heat conduction and temperature variations of a single nanotube, a nanotube array and a part of nanotube-based composite surface with heat generation. The thermal conductivity used is obtained from the upscaled value from the molecular simulations or ex...
DEVELOPMENT OF ODS HEAT EXCHANGER TUBING
Energy Technology Data Exchange (ETDEWEB)
Mark A. Harper, Ph.D.
2002-04-01
Work continued on three major tasks of this project--increasing the circumferential strength of MA956 tubing, joining of the MA956 alloy, and determination of the high temperature corrosion limits of the MA956 alloy. With respect to increasing the circumferential strength of a MA956 tube, all of the cold working operations (0, 10, 20, 30, 40%) and annealing treatments (1000, 1150, 1300 C) have been completed. The sample microstructures produced by this processing continue to be analyzed with TEM results providing valuable information on the strengthening mechanism of this alloy. Creep testing to determine the ''stress threshold'' curves for this alloy continues. Regarding joining of the MA956 alloy, additional welds were produced with the friction welding and transient liquid phase bonding techniques. And finally, laboratory high temperature corrosion testing of the material continues in both fluid-side and fire-side simulated environments.
Directory of Open Access Journals (Sweden)
Lionel Druette
2013-01-01
Full Text Available This paper presents a new air-heating system concept for energy-efficient dwellings. It is a system designed to heat a low-energy building by coupling a heat-recovery ventilation system with a three-fluid heat exchanger located on the chimney of a wood-pellet stove. The proposed work focuses on the heat transfer that occurs between flue gases, the ventilation air and the combustion air within a triple concentric tube heat exchanger with no insulation at its outer surface. The main objective is to predict outlet temperature for the specific geometry of the heat exchanger studied here. Thus, the governing differential equations are derived for a counter-co-current flow arrangement of the three fluids. Then analytical solutions for the steady-state temperature distribution are obtained as well as the amount of heat transferred to the outside. An expression for the effectiveness of the heat exchanger is also proposed. Based on these results, calculations are performed on a case study to predict the fluid temperature distribution along the heat exchanger. Finally, a parametric study is carried out on this case study to assess the influence of the relevant parameters on the effectiveness of the heat exchanger. In addition, computation of heat losses to the outside justifies whether insulation is needed.
Conjugate heat and mass transfer in heat mass exchanger ducts
Zhang, Li-Zhi
2013-01-01
Conjugate Heat and Mass Transfer in Heat Mass Exchanger Ducts bridges the gap between fundamentals and recent discoveries, making it a valuable tool for anyone looking to expand their knowledge of heat exchangers. The first book on the market to cover conjugate heat and mass transfer in heat exchangers, author Li-Zhi Zhang goes beyond the basics to cover recent advancements in equipment for energy use and environmental control (such as heat and moisture recovery ventilators, hollow fiber membrane modules for humidification/dehumidification, membrane modules for air purification, desi
Experimental study on heat transfer characteristics of ice slurry
Energy Technology Data Exchange (ETDEWEB)
Kumano, Hiroyuki; Hirata, Tetsuo [Department of Mechanical Systems Engineering, Shinshu University, 4-17-1, Wakasato, Nagano-shi, Nagano 380-8553 (Japan); Shouji, Ryouta [Chubu Plant Service Co., Ltd., 11-22, Gohommatsu-cho, Atsuta-ku, Nagoya, Aichi 456-8516 (Japan); Shirakawa, Michito [Toyota Motor Corp., 1 Toyota-cho, Toyota, Aichi 471-8571 (Japan)
2010-12-15
Heat transfer characteristics of ice slurry were investigated experimentally. The Reynolds number, diameter of the tubes and ice packing factor (IPF) were varied as experimental parameters. For laminar flow, it was found that the ratio of the Nusselt numbers increased with the IPF, and an approximation equation of the Nusselt number could be derived using the apparent Reynolds number, IPF and the ratio of the average diameter of the ice particles to the diameter of the test tube. For turbulent flow, the ratio of the Nusselt numbers was 1 for each condition in the case of a low IPF. However, the ratio of the Nusselt numbers increased with the IPF in the high-IPF region. Moreover, the apparent Reynolds number, which can be derived by treating the ice slurry as a pseudoplastic fluid, can be used to determine the condition under which variation in the heat transfer characteristics of ice slurry in turbulent flow occurs. (author)
Numerical investigations of cooling heat transfer of supercritical water
Energy Technology Data Exchange (ETDEWEB)
Herbell, H. [EnBW Kernkraft GmbH, Kernkraftwerk Philippsburg (Germany); Starflinger, J. [IKE, Univ. of Stuttgart (Germany); Schulenberg, T. [Karlsruhe Inst. of Tech., Karlsruhe (Germany)
2011-07-01
The re-heater and the start-up system are the only basically new components in the balance of plant of the High Performance Light Water Reactor (HPLWR). Inside the tubes of the re-heater, supercritical fluid undergoes pseudo-condensing. CFD simulations have been performed in order to determine the heat transfer coefficient on the tube side more accurately. Numerical results are compared with Bruch's CO{sub 2}-experiment [12] for validation. The results illustrate the influence of buoyancy forces on the laminar turbulent transition for vertical downward flows. A simple heat transfer correlation [17] has been proposed for re-heater design, which is compared here with numerical simulations. Fluctuating density stratification is obtained for a horizontal layout which is similar to a Kelvin-Helmholtz instability. (author)
Development of a discharge-heated plasma tube
Energy Technology Data Exchange (ETDEWEB)
Cha, Byung Heon; Jin, J. T.; Nam, S. M.; Lee, S. M.; Choi, H. L.; Ko, D. K.; Kim, S. H.; Lee, Y. B.; Choi, Y. S.; Lee, J. M.; Lee, C. K.; Lee, H. G.; Lee, H. C.; Jung, S. M.; Kim, Y. J.; Choi, G. S.; Son, N. G
1999-12-01
A discharge-heated type plasma tube was designed and constructed. The structure of the laser plasma tube was designed to be easy in maintenance. The inside plasma tube was made of a high purity alumina and the thermal insulator tube was made of a porous alumina. The electrode made of tungsten was chosen for the endurance of high discharge voltage. AR coated windows were used as laser windows. A proto-type laser plasma tube was tested with a pulse modulator. An average laser output power was 32 W at the discharge voltage of 28 kV, the electric input power of 4.6 kW, and the pulse repetition rates of 10 kHz. (author)
Study and modelling of a reactional tube bundle heated by a fluidized bed
Energy Technology Data Exchange (ETDEWEB)
Collantes Hernandez, M.A.
1993-07-01
Fluidized beds exhibit two important characteristics for the heating of a reactional tube bundle: homogeneous temperature within all the fluidized bed and high heat transfer coefficient with the immersed surfaces. One of the key points for their modeling is the knowledge of the vertical and horizontal thermal conductivities and the heat transfer coefficient at the wall or with the tubes of the reactor. As thermal diffusivity data about large fluidized beds are not available in the literature, we have built a large size pilot unit (0.6 m x 1.1 m x 2.8 m) to determine these values under the conditions of a catalytic treatment of petroleum products. The measure of local temperatures and the use of a two-dimensional diffusion model have permitted us to determine thermal conductivities as a function of several parameters: fluidization velocity, height of the bed, nature and granulometry of solids and geometry of the tube bundle. On the basis of the collected experimental data, the case of a petrochemical unit has been studied. A mathematical code was developed, which permitted us to acquire the data concerning the progress of the reaction in the tubes and it also allowed us to analyse the influence of size and density of the tube bundles on the conversion. (author). 72 refs., 90 figs., 15 tabs.
Potential polymer concrete heat exchanger tubes for corrosive environments
Energy Technology Data Exchange (ETDEWEB)
Fontana, J.J.; Reams, W.; Cheng, H.C.
1986-11-01
It has long been known that carbon steel exposed to some geothermal brines is aggressively attacked, and large corrosion allowances must be made in the design of piping used in such environments. In addition, scaling of the pipes reduces the flow through within a short period of time. Several high temperature polymer concretes have been developed which can be used as non-corrosive liner materials. In addition, polymer concretes with high thermal conductivities have been developed which may be used as heat exchanger tubes for geothermal brines. Studies have indicated that polymer concretes will not scale as rapidly as carbon steel does, thus making them attractive alternatives for heat exchanger tubes. Thin walled, thermally conductive polymer concrete tubes have been made that can withstand pressures >4.1 MPa at 150/sup 0/C without leaking. Continuing studies are being made to characterize these materials and evaluate them for heat exchanger applications.
Energy Technology Data Exchange (ETDEWEB)
Boyer, B.D.; Parlatan, Y.; Slovik, G.C.; Rohatgi, U.S.
1995-09-01
RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations al these conditions were compared with the GIRAFFE data. The effects of PCCS cell nodings on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {+-}5% of the data with a three-node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer in the presence of noncondensable gases with only a coarse mesh. The cell length term in the condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.
Takahashi, Kouhei; Kanno, Tsutomu; Sakai, Akihiro; Tamaki, Hiromasa; Kusada, Hideo; Yamada, Yuka
2013-01-01
Enormously large amount of heat produced by human activities is now mostly wasted into the environment without use. To realize a sustainable society, it is important to develop practical solutions for waste heat recovery. Here, we demonstrate that a tubular thermoelectric device made of tilted multilayer of Bi(0.5)Sb(1.5)Te3/Ni provides a promising solution. The Bi(0.5)Sb(1.5)Te3/Ni tube allows tightly sealed fluid flow inside itself, and operates in analogy with the standard shell and tube heat exchanger. We show that it achieves perfect balance between efficient heat exchange and high-power generation with a heat transfer coefficient of 4.0 kW/m(2)K and a volume power density of 10 kW/m(3) using low-grade heat sources below 100°C. The Bi(0.5)Sb(1.5)Te3/Ni tube thus serves as a power generator and a heat exchanger within a single unit, which is advantageous for developing new cogeneration systems in factories, vessels, and automobiles where cooling of excess heat is routinely carried out.
Improving the thermal efficiency of a jaggery production module using a fire-tube heat exchanger.
La Madrid, Raul; Orbegoso, Elder Mendoza; Saavedra, Rafael; Marcelo, Daniel
2017-12-15
Jaggery is a product obtained after heating and evaporation processes have been applied to sugar cane juice via the addition of thermal energy, followed by the crystallisation process through mechanical agitation. At present, jaggery production uses furnaces and pans that are designed empirically based on trial and error procedures, which results in low ranges of thermal efficiency operation. To rectify these deficiencies, this study proposes the use of fire-tube pans to increase heat transfer from the flue gases to the sugar cane juice. With the aim of increasing the thermal efficiency of a jaggery installation, a computational fluid dynamic (CFD)-based model was used as a numerical tool to design a fire-tube pan that would replace the existing finned flat pan. For this purpose, the original configuration of the jaggery furnace was simulated via a pre-validated CFD model in order to calculate its current thermal performance. Then, the newly-designed fire-tube pan was virtually replaced in the jaggery furnace with the aim of numerically estimating the thermal performance at the same operating conditions. A comparison of both simulations highlighted the growth of the heat transfer rate at around 105% in the heating/evaporation processes when the fire-tube pan replaced the original finned flat pan. This enhancement impacted the jaggery production installation, whereby the thermal efficiency of the installation increased from 31.4% to 42.8%. Copyright © 2017 Elsevier Ltd. All rights reserved.
Multiphysics Numerical Modeling of a Fin and Tube Heat Exchanger
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
2015-01-01
In the present research work, a modeling effort to predict the performance of a liquid-gas type fin and tube heat exchanger design is made. Three dimensional (3D) steady state numerical model is developed using commercial software COMSOL Multiphysics based on finite element method (FEM). For the ......In the present research work, a modeling effort to predict the performance of a liquid-gas type fin and tube heat exchanger design is made. Three dimensional (3D) steady state numerical model is developed using commercial software COMSOL Multiphysics based on finite element method (FEM...
Heat transfer from humans wearing clothing
Lotens, W.A.
1993-01-01
In this monograph the effects of clothing on human heat transfer are described. The description is based on the physics of heat and mass transfer, depending on the design of the clothing, the climate, and the activity of the wearer. The resulting model has been stepwise implemented in computer
Dynamic Heat Transfer Model of Refrigerated Foodstuff
DEFF Research Database (Denmark)
Cai, Junping; Risum, Jørgen; Thybo, Claus
2006-01-01
their temperature relation. This paper discusses the dynamic heat transfer model of foodstuff inside the display cabinet, one-dimensional dynamic model is developed, and the Explicit Finite Difference Method is applied, to handle the unsteady heat transfer problem with phase change, as well as time varying boundary...
Introduction to heat transfer test setup for the SCRAP receiver
Lubkoll, Matti; Harms, Thomas M.; von Backström, Theodor W.
2017-06-01
The Spiky Central Receiver Air Pre-heater (SCRAP) receiver is a novel external tubular metallic central receiver concept. The SCRAP receiver is designed to increase an air-receivers solar-thermal performance. This is aimed to be achieved by enhancing heat transfer to the pressurized air-stream within the absorber assemblies (spikes) by utilizing an internally finned tube geometry. The fin shape is defined to create rectangular ducts as passages for the air flow, therewith a high heat transfer coefficient. The spikes are arranged in such a way that they trap incoming concentrated radiation (reduce reflection losses) and minimize thermal radiation losses from the receiver to ambient. In previous work, the modeling of a SCRAP receiver was discussed on. This included the modeling of the internal air flow and heat transfer within a spike, analysis of the optical characteristics of a SCRAP receiver and the impingement heat transfer capabilities in the spike tip (exposed to the highest flux). Further, analysis of the thermal interaction of spikes with one another and with ambient (convective and radiative heat loss) permitted drawing of first conclusions of the receiver performance potential. To validate the models predicting the pressurized air flow and heat transfer within a spike, an experimental test setup was designed, constructed and built at the heat transfer laboratories at Stellenbosch University. This work introduces the design of the test setup and will discuss preliminary results obtained during its commissioning. From first analysis the predictions made for the pressure drop within the internally finned section appear adequate. The heat transfer behavior will require further detailed analysis to develop sufficient confidence to allow for conclusions. Initial results, however, show good general agreement between measured and simulated data.
"Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"
Energy Technology Data Exchange (ETDEWEB)
Dr. Ganesh Skandan; Dr. Amit Singhal; Mr. Kenneth Eberts; Mr. Damian Sobrevilla; Prof. Jerry Shan; Stephen Tse; Toby Rossmann
2008-06-12
ABSTRACT Nanotechnology Enabled Advanced industrial Heat Transfer Fluids” Improving the efficiency of Industrial Heat Exchangers offers a great opportunity to improve overall process efficiencies in diverse industries such as pharmaceutical, materials manufacturing and food processing. The higher efficiencies can come in part from improved heat transfer during both cooling and heating of the material being processed. Additionally, there is great interest in enhancing the performance and reducing the weight of heat exchangers used in automotives in order to increase fuel efficiency. The goal of the Phase I program was to develop nanoparticle containing heat transfer fluids (e.g., antifreeze, water, silicone and hydrocarbon-based oils) that are used in transportation and in the chemical industry for heating, cooling and recovering waste heat. Much work has been done to date at investigating the potential use of nanoparticle-enhanced thermal fluids to improve heat transfer in heat exchangers. In most cases the effect in a commercial heat transfer fluid has been marginal at best. In the Phase I work, we demonstrated that the thermal conductivity, and hence heat transfer, of a fluid containing nanoparticles can be dramatically increased when subjected to an external influence. The increase in thermal conductivity was significantly larger than what is predicted by commonly used thermal models for two-phase materials. Additionally, the surface of the nanoparticles was engineered so as to have a minimal influence on the viscosity of the fluid. As a result, a nanoparticle-laden fluid was successfully developed that can lead to enhanced heat transfer in both industrial and automotive heat exchangers
Boiling heat transfer modern developments and advances
Lahey, Jr, RT
2013-01-01
This volume covers the modern developments in boiling heat transfer and two-phase flow, and is intended to provide industrial, government and academic researchers with state-of-the-art research findings in the area of multiphase flow and heat transfer technology. Special attention is given to technology transfer, indicating how recent significant results may be used for practical applications. The chapters give detailed technical material that will be useful to engineers and scientists who work in the field of multiphase flow and heat transfer. The authors of all chapters are members of the
Heat transfer coefficient of cryotop during freezing.
Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J
2013-01-01
Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).
Heat transfer correlations in mantle tanks
DEFF Research Database (Denmark)
Furbo, Simon; Knudsen, Søren
2005-01-01
Small solar domestic hot water systems are best designed as low flow systems based on vertical mantle tanks. Theoretical investigations of the heat transfer in differently designed vertical mantle tanks during different operation conditions have been carried out. The investigations are based...... on calculations with a CFD-model, which has earlier been validated by means of experiments. The CFD-model is used to determine the heat transfer between the solar collector fluid in the mantle and the walls surrounding the mantle in all levels of the mantle as well as the heat transfer between the wall...... of the inner hot water tank and the domestic water in all levels of the tank. The heat transfer analysis showed that the heat transfer near the mantle inlet port between the solar collector fluid in the mantle and the walls surrounding the mantle is in the mixed convection regime, and as the distance from...
Forced convective heat transfer in curved diffusers
Rojas, J.; Whitelaw, J. H.; Yianneskis, M.
1987-01-01
Measurements of the velocity characteristics of the flows in two curved diffusers of rectangular cross section with C and S-shaped centerlines are presented and related to measurements of wall heat transfer coefficients along the heated flat walls of the ducts. The velocity results were obtained by laser-Doppler anemometry in a water tunnel and the heat transfer results by liquid crystal thermography in a wind tunnel. The thermographic technique allowed the rapid and inexpensive measurement of wall heat transfer coefficients along flat walls of arbitrary boundary shapes with an accuracy of about 5 percent. The results show that an increase in secondary flow velocities near the heated wall causes an increase in the local wall heat transfer coefficient, and quantify the variation for maximum secondary-flow velocities in a range from 1.5 to 17 percent of the bulk flow velocity.
Heat transfer research on enhanced heating surfaces in pool boiling
Kalawa, Wojciech; Wójcik, Tadeusz M.; Piasecka, Magdalena
The paper focuses on the analysis of the enhanced surfaces in such applications as boiling heat transfer. The testing measurement module with enhanced heating surfaces was used for pool boiling research. Pool boiling experiments were conducted with distilled water at atmospheric pressure in the vessel using an enhanced sample as the bottom heating surface. The samples are soldered to a copper heating block of the round cross-section .They were placed: in the fluid (saturation temperature measurement), under the sample for temperature determination. A vessel made of four flat glass panes was used for visualization. The heated surfaces in contact with the fluid differed in roughness were smooth or enhanced. This paper analyzes the effects of the microstructured heated surface on the heat transfer coefficient. The results are presented as relationships between the heat transfer coefficient and the heat flux and as boiling curves. The experimental data obtained for the two types of enhanced heated surfaces was compared with the results recorded for the smooth heated surface. The highest local values of the heat transfer coefficient were reported for the enhanced surfaces.
DEVELOPMENT OF ODS HEAT EXCHANGER TUBING
Energy Technology Data Exchange (ETDEWEB)
Mark A. Harper, Ph.D.
2001-04-30
Work has begun under three major tasks of this project. With respect to increasing the circumferential strength of a MA956 tube, approximately 60 MA956 rods have been extruded using a 20:1 extrusion ratio and extrusion temperatures of 1000, 1075, 1150, and 1200 C. Also, creep testing is underway for the purpose of determining the ''stress threshold'' curves for this alloy. Regarding joining of the alloy MA956, work has begun on the friction welding, magnetic impulse welding, explosive welding, and transient liquid phase bonding aspects of this project. And finally, material is being prepared for the laboratory fire-side high temperature corrosion tests, with potential gas and deposits for a typical Vision 21 plant being reviewed for final determination of these variables in the test program.
Experimental study of undeveloped nucleate boiling on the horizontal tube heated by condensing steam
Energy Technology Data Exchange (ETDEWEB)
Morozov, A.V.; Remizov, O.V.; Tzyganok, A.A.; Kalyakin, D.S. [State Scientific Center of the Russian Federation, Inst. for Physics and Power Engineering named after A.I. Leypunsky, Obninsk (Russian Federation)
2011-07-01
The experimental study of undeveloped nucleate boiling on the horizontal tube heated by condensing steam has been carried out in the Institute for Physics and Power Engineering. The feature of the processes investigated was a presence of natural circulation in primary circuit of the facility. The experiments were carried out at heating steam pressure P{sub s1} = 0.35 MPa. On the base of the results of these experiments the empirical correlations for prediction of heat transfer coefficient was obtained. This correlation can be used for the substantiation of work of VVER steam generator in the condensation mode. (author)
Iwasaki, Masamichi; Saito, Hiroshi; Mochizuki, Sadanari; Murata, Akira
The effect of delta-wing-vortex generators (combination of a delta wing and a delta winglet pair) on the heat transfer performance of fin-and-tube heat exchangers for vending machines has been investegated. Flow visualizations, numerical simulations and heat transfer experiments were conducted to find an optimum geometrical shape and arrangement of the vortex generators. Maximum heat transfer enhancement was achieved by the combination of (a) the delta wing with the apex angle of 86 degrees and (b) the delta winglet pair with the inline angle of 45 degrees. In relatively low Reynolds number range, about 40 % increase in heat transfer coefficient was attained with the above mentioned combination of the vortex generators compared to the ordinary heat exchangers with plain fins. It was revealed that the heat transfer enhancement was attributed to (1) the longitudinal vortexes generated by the delta wing and (2) the reduction of wake area behind the tube. It was also found that an increase in the apex angle of the delta wing brought about heat transfer enhancement, and the scale as well as the streggth of the induced longitudinal vortices played an important role in the heat transfer performance.
Critical heat flux variations on CANDU calandria tube surface
Energy Technology Data Exchange (ETDEWEB)
Behdadi, A.; Luxat, J.C., E-mail: behdada@mcmaster.ca, E-mail: luxatj@mcmaster.ca [McMaster Univ., Engineering Physics Dept., Hamilton, Ontario (Canada)
2012-07-01
Heavy water moderator surrounding each fuel channel is one of the important safety features in CANDU reactors since it provides an in-situ passive heat sink for the fuel in situations where other engineered means of heat removal from fuel channels have failed. In a critical break LOCA scenario, fuel cooling becomes severely degraded due to rapid flow reduction in the affected flow pass of the heat transport system. This can result in pressure tubes experiencing significant heat-up during early stages of the accident when coolant pressure is still high, thereby causing uniform thermal creep strain (ballooning) of the pressure tube (PT) into contact with its calandria tube (CT). The contact of the hot PT with the CT causes rapid redistribution of stored heat from the PT to CT and a large heat flux spike from the CT to the moderator fluid. For conditions where subcooling of the moderator fluid is low, this heat flux spike can cause dryout of the CT. This can detrimentally affect channel integrity if the CT post-dryout temperature becomes sufficiently high to result in continued thermal creep strain deformation of both the PT and the CT. The focus of this work is to develop a mechanistic model to predict Critical Heat Flux (CHF) on the CT surface following a contact with its pressure tube. A mechanistic CHF model is applied based on a concept of wall dry patch formation, prevention of rewetting and subsequent dry patch spreading. Results have been compared to an empirical correlation and a good agreement has been obtained. The model has been used to predict the spatial variation of CHF over a cylinder with dimensions of CANDU CT. (author)
Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger.
Aghayari, Reza; Maddah, Heydar; Zarei, Malihe; Dehghani, Mehdi; Kaskari Mahalle, Sahar Ghanbari
2014-01-01
This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%-0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%-24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles.
DOE/ANL/HTRI heat exchanger tube vibration data bank
Energy Technology Data Exchange (ETDEWEB)
Halle, H.; Chenoweth, J.M.; Wambsganss, M.W.
1981-01-01
This addendum to the DOE/ANL/HTRI Heat Exchanger Tube Vibration Data Bank includes 16 new case histories of field experiences. The cases include several exchangers that did not experience vibration problems and several for which acoustic vibration was reported.
Fouling characteristics of compact heat exchangers and enhanced tubes.
Energy Technology Data Exchange (ETDEWEB)
Panchal, C. B.; Rabas, T. J.
1999-07-15
Fouling is a complex phenomenon that (1) encompasses formation and transportation of precursors, and (2) attachment and possible removal of foulants. A basic understanding of fouling mechanisms should guide the development of effective mitigation techniques. The literature on fouling in complex flow passages of compact heat exchangers is limited; however, significant progress has been made with enhanced tubes.
Heat transfer performance test of PDHRS heat exchangers of PGSFR using STELLA-1 facility
Energy Technology Data Exchange (ETDEWEB)
Hong, Jonggan, E-mail: hong@kaeri.re.kr; Yeom, Sujin; Eoh, Jae-Hyuk; Lee, Tae-Ho; Jeong, Ji-Young
2017-03-15
Highlights: • Heat transfer performance test of heat exchangers of PGSFR PDHRS is conducted using STELLA-1 facility. • Steady-state test results of DHX and AHX show good agreement with theoretical results of design codes. • Design codes for DHX and AHX are validated by STELLA-1 experimental results. • Heat transport capability of DHX and AHX is turned out to be satisfactory for reliable plant operation. - Abstract: The STELLA-1 facility was designed and constructed to carry out separate effect tests of the decay heat exchanger (DHX) and natural draft sodium-to-air heat exchanger (AHX), which are key components of the safety-grade decay heat removal system in PGSFR. The DHX is a sodium-to-sodium heat exchanger with a straight tube arrangement, and the AHX is a sodium-to-air heat exchanger with a helically coiled tube arrangement. The model heat exchangers in STELLA-1 have been designed to meet their own similitude conditions from the prototype ones, of which scale ratios were set to be unity in height (or length) and 1/2.5 in heat transfer rate. Consequently, the overall heat transfer coefficients and log-mean temperature differences of the prototypes have been preserved as well. The steady-state test results for each model heat exchanger obtained from STELLA-1 showed good agreement with the theoretical results of the computer design codes for thermal-sizing and a performance analysis of the DHX and AHX. In the DHX result comparison, the discrepancies in the heat transfer rate ranged from −4.4% to 2.0%, and in the AHX result comparison, they ranged from −11.1% to 12.6%. Therefore, the first step in thermal design codes validation for sodium heat exchangers, e.g., DHX and AHX, has been successfully completed with the experimental database obtained from STELLA-1. In addition, the heat transfer performance of the DHX and AHX was found to be satisfactory enough to secure a reliable decay heat removal performance.
Conjugate heat transfer characterization in cooling channels
Cukurel, Beni; Arts, Tony; Selcan, Claudio
2012-06-01
Cooling technology of gas turbine blades, primarily ensured via internal forced convection, is aimed towards withdrawing thermal energy from the airfoil. To promote heat exchange, the walls of internal cooling passages are lined with repeated geometrical flow disturbance elements and surface non-uniformities. Raising the heat transfer at the expense of increased pressure loss; the goal is to obtain the highest possible cooling effectiveness at the lowest possible pressure drop penalty. The cooling channel heat transfer problem involves convection in the fluid domain and conduction in the solid. This coupled behavior is known as conjugate heat transfer. This experimental study models the effects of conduction coupling on convective heat transfer by applying iso-heat-flux boundary condition at the external side of a scaled serpentine passage. Investigations involve local temperature measurements performed by Infrared Thermography over flat and ribbed slab configurations. Nusselt number distributions along the wetted surface are obtained by means of heat flux distributions, computed from an energy balance within the metal domain. For the flat plate experiments, the effect of conjugate boundary condition on heat transfer is estimated to be in the order of 3%. In the ribbed channel case, the normalized Nusselt number distributions are compared with the basic flow features. Contrasting the findings with other conjugate and convective iso-heat-flux literature, a high degree of overall correlation is evident.
Hydrodynamics and Heat Transfer of Discrete Droplets in Microfluidic Devices
Weber, Robert; Shajiee, Shervin; Mohseni, Kamran
2009-11-01
Electrostatic manipulation of surfaces tension forces is now a standard fluid handling technique in microfluidic devices. In this investigation electrowetting on dielectric (EWOD) is employed in order to use discrete droplets for thermal management of compact micro systems. Both hydro- and thermodynamics of digitized droplets are investigated by experimental, theoretical and computational means. EWOD devices have been built on silicon substrates with highly doped layers replacing metal electrodes, and higher quality thermal oxides replacing the more expensive PECVD oxides. In parallel, an experimental test rig has been built to measure the heat transfer rate of the slug flow at a macro scale. Droplets at several length and speed are created systematically. Average heat transfer rates and Nusselt numbers in constant heat flux in a tube has been experimentally measured for continuous and discrete water flow cases and the results have been compared with numerical results.
An analytical dynamic model of heat transfer from the heating body to the heated room
Directory of Open Access Journals (Sweden)
Mižáková Jana
2017-01-01
Full Text Available On the base of mathematical description of thermal balance the dynamic model of the hot-water heating body (radiator was designed. The radiator is mathematically described as a heat transfer system between heating water and warmed-up air layer. Similarly, the dynamic model of heat transfer through the wall from the heated space to the outdoor environment was design. Both models were interconnected into dynamic model of heat transfer from the heating body to the heated room and they will be implemented into simulation model of the heating system in Matlab/Simulink environment.
Heat transfer enhancement using 2MHz ultrasound.
Bulliard-Sauret, Odin; Ferrouillat, Sebastien; Vignal, Laure; Memponteil, Alain; Gondrexon, Nicolas
2017-11-01
The present work focuses on possible heat transfer enhancement from a heating plate towards tap water in forced convection by means of 2MHz ultrasound. The thermal approach allows to observe the increase of local convective heat transfer coefficients in the presence of ultrasound and to deduce a correlation between ultrasound power and Nusselt number. Heat transfer coefficient under ultrasound remains constant while heat transfer coefficient under silent conditions increases with Reynolds number from 900 up to 5000. Therefore, heat transfer enhancement factor ranges from 25% up to 90% for the same energy conditions (supplied ultrasonic power=110W and supplied thermal power=450W). In the same time cavitational activity due to 2MHz ultrasound emission was characterized from mechanical and chemical viewpoints without significant results. At least, Particle Image Velocimetry (PIV) measurements have been performed in order to investigate hydrodynamic modifications due to the presence of 2MHz ultrasound. It was therefore possible to propose a better understanding of heat transfer enhancement mechanism with high frequency ultrasound. Copyright © 2017 Elsevier B.V. All rights reserved.
Manufacturing of tailored tubes with a process integrated heat treatment
Hordych, Illia; Boiarkin, Viacheslav; Rodman, Dmytro; Nürnberger, Florian
2017-10-01
The usage of work-pieces with tailored properties allows for reducing costs and materials. One example are tailored tubes that can be used as end parts e.g. in the automotive industry or in domestic applications as well as semi-finished products for subsequent controlled deformation processes. An innovative technology to manufacture tubes is roll forming with a subsequent inductive heating and adapted quenching to obtain tailored properties in the longitudinal direction. This processing offers a great potential for the production of tubes with a wide range of properties, although this novel approach still requires a suited process design. Based on experimental data, a process simulation is being developed. The simulation shall be suitable for a virtual design of the tubes and allows for gaining a deeper understanding of the required processing. The model proposed shall predict microstructural and mechanical tube properties by considering process parameters, different geometries, batch-related influences etc. A validation is carried out using experimental data of tubes manufactured from various steel grades.
Continuation of Studies on Development of ODS Heat Exchanger Tubing
Energy Technology Data Exchange (ETDEWEB)
Lawrence Brown; David Workman; Bimal Kad; Gaylord Smith; Archie Robertson; Ian Wright
2008-04-15
The Department of Energy (DOE), National Energy Technology Center (NETL), has initiated a strategic plan for the development of advanced technologies needed to design and build fossil fuel plants with very high efficiency and environmental performance. These plants, referred to as 'Vision 21' and FutureGen programs by DOE, will produce electricity, chemicals, fuels, or a combination of these products, and possibly secondary products such as steam/heat for industrial use. MA956 is a prime candidate material being considered for a high temperature heat exchanger in the 'Vision 21' and FutureGen programs. This material is an oxide dispersion strengthened (ODS) alloy; however, there are some gaps in the data required to commit to the use of these alloys in a full-size plant. To fill the technology gaps for commercial production and use of the material for 'Advanced Power Generation Systems' this project has performed development activity to significant increase in circumferential strength of MA956 as compared to currently available material, investigated bonding technologies for bonding tube-to-tube joints through joining development, and performed tensile, creep and fire-side corrosion tests to validate the use and fabrication processes of MA956 to heat exchanger tubing applications. Development activities within this projected has demonstrated increased circumferential strength of MA956 tubes through flow form processing. Of the six fabrication technologies for bonding tube-to-tube joints, inertia friction welding (IFW) and flash butt welding (FBW) were identified as processes for joining MA956 tubes. Tensile, creep, and fire-side corrosion test data were generated for both base metal and weld joints. The data can be used for design of future systems employing MA956. Based upon the positive development activities, two test probes were designed and fabricated for field exposure testing at 1204 C ({approx}2200 F) flue gas. The probes
Heat Transfer Phenomena of Supercritical Fluids
Energy Technology Data Exchange (ETDEWEB)
Krau, Carmen Isabella; Kuhn, Dietmar; Schulenberg, Thomas [Forschungszentrum Karlsruhe, Institute for Nuclear and Energy Technologies, 76021 Karlsruhe (Germany)
2008-07-01
In concepts for supercritical water cooled reactors, the reactor core is cooled and moderated by water at supercritical pressures. The significant temperature dependence of the fluid properties of water requires an exact knowledge of the heat transfer mechanism to avoid fuel pin damages. Near the pseudo-critical point a deterioration of heat transfer might happen. Processes, that take place in this case, are not fully understood and are due to be examined systematically. In this paper a general overview on the properties of supercritical water is given, experimental observations of different authors will be reviewed in order to identify heat transfer phenomena and onset of occurrence. The conceptional design of a test rig to investigate heat transfer in the boundary layer will be discussed. Both, water and carbon dioxide, may serve as operating fluids. The loop, including instrumentation and safety devices, is shown and suitable measuring methods are described. (authors)
Various methods to improve heat transfer in exchangers
Pavel, Zitek; Vaclav, Valenta
2015-05-01
The University of West Bohemia in Pilsen (Department of Power System Engineering) is working on the selection of effective heat exchangers. Conventional shell and tube heat exchangers use simple segmental baffles. It can be replaced by helical baffles, which increase the heat transfer efficiency and reduce pressure losses. Their usage is demonstrated in the primary circuit of IV. generation MSR (Molten Salt Reactors). For high-temperature reactors we consider the use of compact desk heat exchangers, which are small, which allows the integral configuration of reactor. We design them from graphite composites, which allow up to 1000°C and are usable as exchangers: salt-salt or salt-acid (e.g. for the hydrogen production). In the paper there are shown thermo-physical properties of salts, material properties and principles of calculations.
Hydraulic Validation of the LHC Cold Mass Heat Exchanger Tube
Provenaz, P
1998-01-01
The knowledge of the helium mass flow vs. the fraction of the tube wetted by the liquid helium II in the heat exchanger is a crucial input parameter for the heat exchange since the heat flux is direct ly proportional to the wetted surface. In the range of liquid and gas velocities inside the heat exchanger, the liquid flow behaves like in an open channel. Looking at the flow equations for such a s ituation, the velocity depends on the fluid properties only by the friction factor which is a function of the Reynolds number. Thus it was decided to build an experiment with water in order to check t he open channel equations in the heat exchanger geometry. This paper shows the results for water and gives the extrapolation for helium.
Nanoparticle enhanced ionic liquid heat transfer fluids
Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.
2014-08-12
A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.
Radiative Heat Transfer in Fractal Structures
Nikbakht, Moladad
2017-01-01
The radiative properties of most structures are intimately connected to the way in which their constituents are ordered on the nano-scale. We have proposed a new representation for radiative heat transfer formalism in many-body systems. In this representation, we explain why collective effects depend on the morphology of structures, and how the arrangement of nanoparticles and their material affects the thermal properties in many-body systems. We investigated the radiative heat transfer probl...
Heat transfer in an airfoil shaped strut
Crawford, James Douglas
The heat transfer from a hot primary flow stream passing over the outside of an airfoil shaped strut to a cool secondary flow stream passing through the inside of that strut was studied experimentally and numerically. The results showed that the heat transfer on the inside of the strut could be reliably modeled as a developing flow and described using a power law model. The heat transfer on the outside of the strut was complicated by flow separation and stall on the suction side of the strut at high angles of attack. This separation was quite sensitive to the condition of the turbulence in the flow passing over the strut, with the size of the separated wake changing significantly as the mean magnitude and levels of anisotropy were varied. The point of first stall moved by as much as 15% of the chord, while average heat transfer levels changed by 2-5% as the inlet condition was varied. This dependence on inlet conditions meant that comparisons between experiment and steady RANS based CFD were quite poor. Differences between the CFD and experiment were attributed to anisotropic and unsteady effects. The coupling between the two flows was shown to be quite low - that is to say, heat transfer coefficients on both the inner and outer surfaces of the strut were relatively unaffected by the temperature of the strut, and it was possible to predict the temperature on the strut surface quite reliably using heat transfer data from decoupled tests, especially for CFD simulations.
Energy Technology Data Exchange (ETDEWEB)
Bergles, A.E.; Junkhan, G.H.; Webb, R.L.
1979-06-01
This report for the first quarter of 1979 summarizes visits and contacts relative to the theory and practice of heat transfer enhancement. The Technical Literature File and Manufacturers' File were expanded, and the initial Patent Technology Information File was completed. Application studies on enhancement of waste heat recuperators and laminar internal flow heat transfer are described. A comprehensive bibliography on laminar flow enhancement is included. The Technology study on performance of internally finned tubes is complete. New data for the heat transfer and friction characteristics of internally finned tubes will be analyzed to develop rationally based correlations. An assessment of natural convection from rough surfaces was performed. Major effort was directed toward planning of the Research Workshop on Energy Conservation Through Enhanced Heat Transfer. The Workshop, scheduled for May 24 and May 25, 1979 in Chicago, will be co-sponsored by NSF.
Electrohydrodynamic (EHD) enhancement of boiling heat transfer of R113+WT4% ethanol
Energy Technology Data Exchange (ETDEWEB)
Oh, Si Doek [Hyosung Corporation, Seoul (Korea, Republic of); Kwak, Ho Young [Chungang University, Seoul (Korea, Republic of)
2006-05-15
Nucleate boiling heat transfer for refrigerants, R113, and R113+wt14% ethanol mixture, an azeotropic mixture under electric field was investigated experimentally in a single-tube shell/tube heat exchanger. A special electrode configuration which provides a more uniform electric field that produces more higher voltage limit against the dielectric breakdown was used in this study. Experimental study has revealed that the electrical charge relaxation time is an important parameter for the boiling heat transfer enhancement under electric field. Up to 1210% enhancement of boiling heat transfer was obtained for R113+wt4% ethanol mixture which has the electrical charge relaxation time of 0.0053 sec whereas only 280% enhancement obtained for R113 which has relaxation time of 0.97 sec. With artificially machined boiling surface, more enhancement in the heat transfer coefficient in the azeotropic mixture was obtained.
Heat and mass transfer in materials processing
Tanasawa, Ichiro; Lior, Noam
Various papers on heat and mass transfer in materials processing are presented. The topics addressed include: heat transfer in plasma spraying, structure of ultrashort pulse plasma for CVD processing, heat flow and thermal contraction during plasma spray deposition, metal melting process by laser heating, improved electron beam weld design and control with beam current profile measurements, transport phenomena in laser materials processing, perspectives on integrated modeling of transport processes in semiconductor crystal growth, numerical simulation of natural convection in crystal growth in space and on the earth, conjugate heat transfer in crystal growth, effects of convection on the solidification of binary mixtures. Also discussed are: heat transfer in in-rotating-liquid-spinning process, thermal oscillations in materials processing, modeling and simulation of manufacturing processes of advanced composite materials, reaction engineering principles of combustion synthesis of advanced materials, numerical evaluation of the physical properties of magnetic fluids suitable for heat transfer control, and measurement techniques of thermophysical properties of high temperature melts. (For individual items see A93-10827 to A93-10843)
Theory of Periodic Conjugate Heat Transfer
Zudin, Yuri B
2012-01-01
This book presents the theory of periodic conjugate heat transfer in a detailed way. The effects of thermophysical properties and geometry of a solid body on the commonly used and experimentally determined heat transfer coefficient are analytically presented from a general point of view. The main objective of the book is a simplified description of the interaction between a solid body and a fluid as a boundary value problem of the heat conduction equation for the solid body. At the body surface, the true heat transfer coefficient is composed of two parts: the true mean value resulting from the solution of the steady state heat transfer problem and a periodically variable part, the periodic time and length to describe the oscillatory hydrodynamic effects. The second edition is extended by (i) the analysis of stability boundaries in helium flow at supercritical conditions in a heated channel with respect to the interaction between a solid body and a fluid; (ii) a periodic model and a method of heat transfer sim...
Electronic Equipment Cooling by Simultaneous Heat and Mass Transfer,
ELECTRONIC EQUIPMENT, COOLING, HEAT TRANSFER, SUPERSONIC AIRCRAFT, HIGH ALTITUDE, DENSITY, THERMAL STRESSES, AIR, COOLING AND VENTILATING EQUIPMENT, FLUIDS, COOLANTS, HEAT EXCHANGERS, WATER, MASS TRANSFER .
Directory of Open Access Journals (Sweden)
Ashish Agarwal
2016-03-01
Full Text Available In the presented study the shell and tube type latent heat storage (LHS has been designed for solar dryer and paraffin wax is used as heat storage material. In the first part of the study, the thermal and heat transfer characteristics of the latent heat storage system have been evaluated during charging and discharging process using air as heat transfer fluid (HTF. In the last section of the study the effectiveness of the use of an LHS for drying of food product and also on the drying kinetics of a food product has been determined. A series of experiments were conducted to study the effects of flow rate and temperature of HTF on the charging and discharging process of LHS. The temperature distribution along the radial and longitudinal directions was obtained at different time during charging process to analyze the heat transfer phenomenon in the LHS. Thermal performance of the system is evaluated in terms of cumulative energy charged and discharged, during the charging and discharging process of LHS, respectively. Experimental results show that the LHS is suitable to supply the hot air for drying of food product during non-sunshine hours or when the intensity of solar energy is very low. Temperature gain of air in the range of 17 °C to 5 °C for approximately 10 hrs duration was achieved during discharging of LHS.
Enhanced heat transfer in confined pool boiling
Rops, C.M.; Lindken, R.; Velthuis, J.F.M.; Westerweel, J.
2009-01-01
We report the results of an experimental investigation of the heat transfer during nucleate boiling on a spatially confined boiling surface. The heat flux as a function of the boiling surface temperature was measured in pool boiling pots with diameters ranging from 15 mm down to 4.5 mm. It was found
Interactive Heat Transfer Simulations for Everyone
Xie, Charles
2012-01-01
Heat transfer is widely taught in secondary Earth science and physics. Researchers have identified many misconceptions related to heat and temperature. These misconceptions primarily stem from hunches developed in everyday life (though the confusions in terminology often worsen them). Interactive computer simulations that visualize thermal energy,…
Theory of periodic conjugate heat transfer
Zudin, Yuri B
2016-01-01
This book presents the theory of periodic conjugate heat transfer in detail. It offers a simplified description of the interaction between a solid body and a fluid as a boundary value problem of the heat conduction equation for the solid body.
Influence of the degree of thermal contact in fin and tube heat exchanger
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
2016-01-01
is simulated in the present study. The performance of the heat exchanger is characterized in terms of overall heat transfer coefficient, Colburn j-factor, flow resistance factor, and efficiency index. Results obtained from numerical modeling are useful to examine the impact of the degree of thermal contact...... efficiency index of 9.131 and lower flow resistance factor of 0.123 among the cases investigated and highlights the need for perfect thermal contact between fin and tubes to meet the application based requirements....
Energy Technology Data Exchange (ETDEWEB)
Eoh, Jae Hyuk; Choi, Sun Rock; Lee, Hyeong Yeon; Han, Ji Woong; Lee, Tae Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2012-05-15
The conceptual design of a 600MWe demonstration sodium-cooled fast reactor (hereafter called DSFR-600) has been performed by the Korea Atomic Energy Research Institute (KAERI). In order to enhance plant safety, reliable decay heat removal (DHR) systems with natural circulation flow have been considered, and different kinds of sodium-to-air heat exchangers were employed as an ultimate heat sink for this type of DHR system. The DHR system comprises two diverse heat removal loops, and the heat load imposed on the primary sodium pool is safely rejected into the environment through different shapes of final aircoolers. Serpentine- and helical-coil type sodium-to-air heat exchangers have been considered for the purpose. The former is called FDHX (Forced-draft sodium-to-air heat exchanger) and the latter is simply called AHX. For a general sodium-to-air heat exchanger design, convection resistance at shell-side air flow path becomes a dominant factor affecting the mechanism of conjugate heat transfer from the sodium flow inside the tube to the air path across the sodium tube wall. To this end, performance evaluation of a sodium-to-air heat exchanger is one of the most important tasks to secure the overall performance of a DHR system. This study introduces one-dimensional design approach of a finned-tube sodium-to-air heat exchanger using reasonable heat transfer and pressure drop models, and provides detailed design parameters with heat transfer tube arrangement including the factors of fin-effect. The operational strategy regarding sodium freezing protection of the FDHX unit was briefly discussed as well
Heat transfer and temperature distribution in a catalyst oven of 250mm diameter
Energy Technology Data Exchange (ETDEWEB)
Kling, G.
1942-01-29
The catalyst oven tested was a tube, which was surrounded by a steam-heated jacket, had air passing upward through it, and was filled with cylindrical pills of catalysts. Measurement of heat flow, temperature, and pressure drop was taken at various places in the tube and at various flow rates of air. Higher flow rates of air produced a quicker reaching of a steady-state temperature distribution in the catalyst tube, but even then there was strong temperature gradient from the heated walls of the tube down to the middle of the tube. The report gave formulas for calculating the heat-conductivity coefficient for the catalyst from temperatures at various positions, specific heat of the air, amount of air, and dimensions of catalyst space. Also it gave a formula for calculating the Reynolds number from the specific gravity of the air, velocity of the air in an empty tube, viscosity of the air, and the dimensions of the catalyst pills. Among other graphs with the report was a graph plotting the heat-conductivity coefficient against the Reynolds number. The report also contained some discussion about how the functions would change if different gases were used, if temperature conditions were changed, or if the gas were heated before entry into the tube. The report also gave formulas for calculating pressure drops, heat transfer coefficients, Nusselt numbers, and Peclet numbers. 1 figure, 1 table, 8 graphs.
Osman, Arafa Mohamed
1987-05-01
The inverse heat transfer problem is one of considerable practical interest in the analysis and design of experimental heat transfer investigations. The analytical and experimental investigation of the inverse heat transfer coefficients in multi-dimensional convective heat transfer applications is examined. An application considered is the sudden quenching of a hot solid in a cold liquid. Other applications include thermal analysis of forced convection over impulsively started solid bodies and investigation of short duration wind tunnel experiments. The primary aim is to describe methods and algorithms for the solution of the ill-posed inverse heat transfer coefficient problem. The solution method used is an extension of the sequential future-information method of Beck. Numerical experiments are conducted for a systematic investigation of the developed algorithms on selected heat transfer coefficient test cases. The overall objective of the experimental work is to investigate the early transients in the heat transfer coefficients from spheres in one- and two-dimensional quenching experiments. Several experiments were performed by plunging hollow spheres in either ethylene glycol or water. The developed methods are used for the analysis of the quenching experiments for the estimation of the transient heat transfer coefficients. Analysis of the results indicate that the transient inverse technique has the capability of estimating early transients and subsequent quasi-steady state values of the heat transfer coefficients in a single transient experiment.
Heat transfer with freezing and thawing
Lunardini, VJ
1991-01-01
This volume provides a comprehensive overview on the vast amount of literature on solidification heat transfer. Chapter one develops important basic equations and discusses the validity of considering only conductive heat transfer, while ignoring convection, in the large class of materials which make up the porous media. Chapters 2 to 4 deal with problems that can be expressed in plane (Cartesian) coordinates. These problems are further divided into boundary conditions of temperature, prescribed heat flux, and surface convection. Chapter 5 examines some plane geometries involving three-dime
Heat transfer at a stagnation point of impinging round air jet at low Reynolds numbers
Directory of Open Access Journals (Sweden)
Lemanov Vadim
2017-01-01
Full Text Available This work presents experimental investigation of average and pulsation thermal characteristics at the stagnation point of a round impinging air jet at low Reynolds numbers. In the experiments, the average and pulsation values of heat flux, heat transfer coefficient and Nusselt number were measured. At low Reynolds numbers (Re<4000, in contrast to the known monotonous increase in heat transfer, a non-monotonic change in heat transfer is shown. With an outflow from the tube, a significant increase in Nusselt number is observed in comparison with the case, when the jet flows from a nozzle, and this increase can be 300-500%.
Application of the Critical Heat Flux Look-Up Table to Large Diameter Tubes
Directory of Open Access Journals (Sweden)
M. El Nakla
2013-01-01
Full Text Available The critical heat flux look-up table was applied to a large diameter tube, namely 67 mm inside diameter tube, to predict the occurrence of the phenomenon for both vertical and horizontal uniformly heated tubes. Water was considered as coolant. For the vertical tube, a diameter correction factor was directly applied to the 1995 critical heat flux look-up table. To predict the occurrence of critical heat flux in horizontal tube, an extra correction factor to account for flow stratification was applied. Both derived tables were used to predict the effect of high heat flux and tube blockage on critical heat flux occurrence in boiler tubes. Moreover, the horizontal tube look-up table was used to predict the safety limits of the operation of boiler for 50% allowable heat flux.
Kuroda, Kiyonori; Otsuki, Masafumi; Yazaki, Kohei; Sei, Yoshihisa; Akita, Munetaka; Yoshizawa, Michito
2018-01-11
A polyaromatic tube with a subnanometer-sized cavity was efficiently prepared on a gram-scale through the stereo-controlled cyclotrimerization of a diphenylanthracene derivative as a key step. The facile exterior alkylation of the polyaromatic framework leads to a moderately fluorescent tube (R = -OC10H21; ΦF = 20%) in the solid state. The emission intensity of the solid-state alkyl-substituted tube is remarkably enhanced upon heating (up to 1.6 times, ΦF = 31%) as well as doping with fluorescent dyes (up to 4.2 times, ΦF = 83%) through efficient energy transfer. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Modeling microscale heat transfer using Calore.
Energy Technology Data Exchange (ETDEWEB)
Gallis, Michail A.; Rader, Daniel John; Wong, Chung-Nin Channy; Bainbridge, Bruce L.; Torczynski, John Robert; Piekos, Edward Stanley
2005-09-01
Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.
Microscale and nanoscale heat transfer fundamentals and engineering applications
Sobhan, CB
2008-01-01
Preface Introduction to Microscale Heat Transfer Microscale Heat Transfer: A Recent Avenue in Energy Transport State of the Art: Some Introductory Remarks Overview of Microscale Transport Phenomena Discussions on Size-Effect Behavior Fundamental Approach for Microscale Heat Transfer Introduction to Engineering Applications of Microscale Heat Transfer Microscale Heat Conduction Review of Conduction Heat Transfer Conduction at the Microscale Space and Timescales Fundamental Approach Thermal Conductivity Boltzmann Equation and Phonon Transport Conduction in Thin Films
Heat Transfer Characteristics in Crank-Shape Thermosyphons
Imura, Hedeaki; Koito, Yasushi
A two-phase closed thermosyphon is applied to gas-to-gas heat exchangers, the cooling of heat generation devices, the melting of snow, the prevention from icing of water on roads and so on. Generally, straight tubes are used as the thermosyphon. However, because of the limited space for the straight thermosyphon to be installed, it is considered that a bent thermosyphon is enforced to employ. In response to this, fundamental experiments are conducted on the heat transfer characteristics in a two-phase crank shape closed thermosyphon, in which an evaporator and a condenser are vertically positioned, and a connecting adiabatic section is horizontal. Ethylene glycol aqueous solutions which have lower freezing points and hydrofluoroether 7100 and 7200 which do not contain chloride are used as the working fluids Heat transfer coefficients and critical heat fluxes in the thermosyphon are measured by changing the amount of charged working fluid (0.30,0.40,0.50 and 0.60 of the evaporator volume),the temperature of the adiabatic section (40,50,60,70 and 80°C) and heat flux (from 4.0 kW /m2 to critical). The experimental results are shown and compared with those taken using water as the working fluid.
Effect of Twisted-Tape Turbulators and Nanofluid on Heat Transfer in a Double Pipe Heat Exchanger
Directory of Open Access Journals (Sweden)
Heydar Maddah
2014-01-01
Full Text Available Heat transfer and overall heat transfer in a double pipe heat exchanger fitted with twisted-tape elements and titanium dioxide nanofluid were studied experimentally. The inner and outer diameters of the inner tube were 8 and 16 mm, respectively, and cold and hot water were used as working fluids in shell side and tube side. The twisted tapes were made from aluminum sheet with tape thickness (d of 1 mm, width (W of 5 mm, and length of 120 cm. Titanium dioxide nanoparticles with a diameter of 30 nm and a volume concentration of 0.01% (v/v were prepared. The effects of temperature, mass flow rate, and concentration of nanoparticles on the overall heat transfer coefficient, heat transfer changes in the turbulent flow regime Re≥2300, and counter current flow were investigated. When using twisted tape and nanofluid, heat transfer coefficient was about 10 to 25 percent higher than when they were not used. It was also observed that the heat transfer coefficient increases with operating temperature and mass flow rate. The experimental results also showed that 0.01% TiO2/water nanofluid with twisted tape has slightly higher friction factor and pressure drop when compared to 0.01% TiO2/water nanofluid without twisted tape. The empirical correlations proposed for friction factor are in good agreement with the experimental data.
Heat Transfer and Latent Heat Storage in Inorganic Molten Salts for Concentrating Solar Power Plants
Energy Technology Data Exchange (ETDEWEB)
Mathur, Anoop [Terrafore Inc.
2013-08-14
A key technological issue facing the success of future Concentrating Solar Thermal Power (CSP) plants is creating an economical Thermal Energy Storage (TES) system. Current TES systems use either sensible heat in fluids such as oil, or molten salts, or use thermal stratification in a dual-media consisting of a solid and a heat-transfer fluid. However, utilizing the heat of fusion in inorganic molten salt mixtures in addition to sensible heat , as in a Phase change material (PCM)-based TES, can significantly increase the energy density of storage requiring less salt and smaller containers. A major issue that is preventing the commercial use of PCM-based TES is that it is difficult to discharge the latent heat stored in the PCM melt. This is because when heat is extracted, the melt solidifies onto the heat exchanger surface decreasing the heat transfer. Even a few millimeters of thickness of solid material on heat transfer surface results in a large drop in heat transfer due to the low thermal conductivity of solid PCM. Thus, to maintain the desired heat rate, the heat exchange area must be large which increases cost. This project demonstrated that the heat transfer coefficient can be increase ten-fold by using forced convection by pumping a hyper-eutectic salt mixture over specially coated heat exchanger tubes. However,only 15% of the latent heat is used against a goal of 40% resulting in a projected cost savings of only 17% against a goal of 30%. Based on the failure mode effect analysis and experience with pumping salt at near freezing point significant care must be used during operation which can increase the operating costs. Therefore, we conclude the savings are marginal to justify using this concept for PCM-TES over a two-tank TES. The report documents the specialty coatings, the composition and morphology of hypereutectic salt mixtures and the results from the experiment conducted with the active heat exchanger along with the lessons learnt during
3D NUMERICAL SIMULATIONS OF THE THERMAL PROCESSES IN THE SHELL AND TUBE HEAT EXCHANGER
Directory of Open Access Journals (Sweden)
Mića V. Vukić
2014-01-01
Full Text Available A shell and tube heat exchanger (STHE is one of the most often used apparatuses in chemical industry. One of the main goals of the STHE manufacturers is to improve their exploitation reliability and efficiency. Two approaches to the STHE design improvement are possible: experimental investigation, which is very expensive and time-consuming because of the shell side complex geometry, and numerical investigations. Numerical simulations can be used to check the old and to develop new and more efficient STHE designs. In this paper, the results of the numerical investigations of fluid flow and heat transfer in the laboratory experimental STHE are presented. Numerical simulation has been performed by using the PHOENICS code. The tube bundle has been modeled by using the concept of porous media. Standard k-e turbulence model is used.
Two-phase flow heat transfer of propane vaporization in horizontal minichannels
Energy Technology Data Exchange (ETDEWEB)
Pamitran, Agus Sunjarianto; Choi, Kwang Il; Oh, Jong Taek; Park, Ki Won [Chonnam National University, Yeosu (Korea, Republic of)
2009-03-15
Experiments were performed on the convective boiling heat transfer in horizontal minichannels using propane. The test section was made of stainless steel tubes with inner diameters of 1.5 mm and 3.0 mm and lengths of 1000 mm and 2000 mm, respectively, and it was uniformly heated by applying an electric current directly to the tubes. Local heat transfer coefficients were obtained for a heat flux range of 5-20 kW m{sup -2}, a mass flux range of 50-400 kg m{sup -2} s{sup -1}, saturation temperatures of 10, 5, and 0 .deg. C and quality ranges of up to 1.0. The nucleate boiling heat transfer contribution was predominant, particularly at the low quality region. Decreases in the heat transfer coefficient occurred at a lower vapor quality with a rise of heat flux and mass flux, and with a lower saturation temperature and inner tube diameter. Laminar flow appeared in the minichannel flows. A new boiling heat transfer coefficient correlation that is based on the superposition model for propane was developed with 8.27% mean deviation
Evaluation of heat transfer enhancement in air-heating collectors
Energy Technology Data Exchange (ETDEWEB)
Mattox, D. L.
1979-06-01
The present research effort was initiated for the purpose of increasing the thermal efficiency of air heating solar collectors through identification and development of optimum design and operation criteria for solar absorber-to-air heat exchangers. Initially this effort took the form of a solar collector systems analysis to evaluate the impact of various techniques for enhancing the heat transfer between the absorber and air stream on overall thermal performance of the entire solar collector. This systems analysis resulted in the selection of solar collector designs providing ducted cooling air on the absorber shaded side as a base line. A transient heat transfer analysis of a complete solar air heating collector was used to demonstrate that an optimum absorber-to-air heat exchanger design could be provided with several interrupted fin configurations. Additional analyses were performed to establish that the maximum solar collector thermal performance to required pumping power was realized for a Reynolds number range of 1000 to 2000. This Reynolds number range was used to establish a theoretical design limit curve for maximum thermal performance versus required pumping power for all interrupted fin designs as published in the open literature. Heat and momentum transfer empirical relationships were defined for scaling the state-of-the-art high conductance fin designs identified from a compact configuration to the less compact designs needed for solar collectors.
Axial flow heat exchanger devices and methods for heat transfer using axial flow devices
Koplow, Jeffrey P.
2016-02-16
Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.
Energy Technology Data Exchange (ETDEWEB)
Dyrboel, Susanne
1998-05-01
Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For lager thickness dimensions the resulting heat transfer through the
Single phase channel flow forced convection heat transfer
Energy Technology Data Exchange (ETDEWEB)
Hartnett, J.P.
1999-04-01
A review of the current knowledge of single phase forced convection channel flow of liquids (Pr > 5) is presented. Two basic channel geometries are considered, the circular tube and the rectangular duct. Both laminar flow and turbulent flow are covered. The review begins with a brief overview of the heat transfer behavior of Newtonian fluids followed by a more detailed presentation of the behavior of purely viscous and viscoelastic Non-Newtonian fluids. Recent developments dealing with aqueous solutions of high molecular weight polymers and aqueous solutions of surfactants are discussed. The review concludes by citing a number of challenging research opportunities.
Fin-and-tube heat exchanger enhancement with a combined herringbone and vortex generator design
DEFF Research Database (Denmark)
Välikangas, Turo; Singh, Shobhana; Sørensen, Kim
2018-01-01
Vortex generators (VGs) are the most commonly investigated enhancement methods in the field of improved heat exchangers. The aim of present work is to study the effect of VGs in a fin-and-tube heat exchanger (FTHE) with herringbone fin shape. The delta winglet VG design with length (s) and height...... (H) is selected based on previous studies. The investigated VG design is simple and considered realistic from the manufacturing point of view. The combined enhancement with herringbone fin and the VG is evaluated by simulating the conjugate heat transfer and the air flow. The structured mesh...... is created for both solid and fluid domains to solve the model numerically using a coupled open source solver in OpenFOAM. The influence of flow condition on the performance enhancement is studied by changing the Reynolds number in a range Re=1354–6157. The study showed that VGs not only increase the heat...
Analysis Of The Extrusion Process Of A Square Tube Multi-Channel Heat Pipe
Directory of Open Access Journals (Sweden)
Kim K.S.
2015-06-01
Full Text Available Heat pipes have been recently in use for cooling purposes in various fields, including electronic circuit boards and vehicle parts that generate large amounts of heat. In order to minimize the loss of heat transferred, there is a need to maximize the contact area of the working fluid. This study produced a square tube multi-channel heat pipe to replace the existing circular pipe type to maximize the internal surface area thereof. This expands the surface, allowing the working fluid to come into contact with a wider area and enhancing thermal radiation performance. A mold for the production for such a product was designed, and finite element simulation was performed to determine whether production is possible.
A numerical study of momentum and forced convection heat transfer ...
African Journals Online (AJOL)
ASME J. Heat Transfer, Vol. 99, 180-186. [2] Webb B.W., Ramadhyani S., 1985. Conjugate heat transfer in a channel with staggered ribs, Int. J. Heat Mass. Transfer, Vol. 28, 1679-1687. [3] Kelkar K.M.&Patankar S.V., 1987. Numerical prediction of flow and heat transfer in a parallel plate channel with staggered fins, ASME J.
Convective heat transfer in non-uniformly heated corrugated slots
Abtahi, Arman; Floryan, J. M.
2017-10-01
An analysis of heat transfer in non-uniformly heated corrugated slots has been carried out. A sinusoidal corrugation is placed at the lower plate that is exposed to heating consisting of uniform and sinusoidal components, while the upper smooth plate is kept isothermal. The phase difference ΩTL describes the shift between the heating and geometric non-uniformities. The analysis is limited to heating conditions that do not give rise to secondary motions. Depending on ΩTL, the conductive heat flow is directed either upwards, or downwards, or is eliminated. Its magnitude is smallest for the long-wavelength systems and largest for the short-wavelength systems, and it increases proportionally to the corrugation amplitude and heating intensity. The same heating creates horizontal temperature gradients that give rise to convection whose form depends on ΩTL. Convection consists of counter-rotating rolls with the size dictated by the system wavelength when the hot spots (points of maximum temperature) overlap either with the corrugation tips or with the corrugation bottoms. Thermal drift forms for all other values of ΩTL. The convective heat flow is always directed upwards, and it is the largest in systems with wavelengths comparable to the slot height. The magnitude of the overall heat flow increases proportionally to the heating intensity when conductive effects dominate and proportionally to the second power of the heating intensity when convection dominates. It also increases proportionally to the corrugation amplitude. The system characteristics are dictated by convection when the relative position of the heating and corrugation patterns eliminates conduction. Addition of the uniform heating component amplifies the above processes, while uniform cooling reduces them. The processes described above are qualitatively similar for all Prandtl numbers of practical interest with the magnitude of the convective heat flow increasing with Pr.
Babu, C. Rajesh; Kumar, P.; Rajamohan, G.
2017-07-01
Computation of fluid flow and heat transfer in an economizer is simulated by a porous medium approach, with plain tubes having a horizontal in-line arrangement and cross flow arrangement in a coal-fired thermal power plant. The economizer is a thermal mechanical device that captures waste heat from the thermal exhaust flue gasses through heat transfer surfaces to preheat boiler feed water. In order to evaluate the fluid flow and heat transfer on tubes, a numerical analysis on heat transfer performance is carried out on an 110 t/h MCR (Maximum continuous rating) boiler unit. In this study, thermal performance is investigated using the computational fluid dynamics (CFD) simulation using ANSYS FLUENT. The fouling factor ε and the overall heat transfer coefficient ψ are employed to evaluate the fluid flow and heat transfer. The model demands significant computational details for geometric modeling, grid generation, and numerical calculations to evaluate the thermal performance of an economizer. The simulation results show that the overall heat transfer coefficient 37.76 W/(m2K) and economizer coil side pressure drop of 0.2 (kg/cm2) are found to be conformity within the tolerable limits when compared with existing industrial economizer data.
Transportation and adhesion of asphaltenes in a heat exchanger tube through CFD simulations
Emani, Sampath; Ramasamy, M.; Shaari, Ku Zilati Ku
2017-07-01
Asphaltenes are identified as the main cause of crude oil fouling in preheat trains. The understanding of individual trajectory of asphaltenes particles, transportation behavior of the fouling precursors in the domain and the effect of various attractive and/or repulsive forces acting on the asphaltenes particles, which lead to an increase/decrease in the deposition, have been impeded by a shortage of information. In the present work, an attempt has been made to understand the transportation and adhesion behavior of asphaltenes in a heat exchanger tube through Computational Fluid Dynamics approach. A Lagrangian based discrete-phase model has been implemented to understand the hydrodynamics of asphaltenes particles and the effect of various forces on the asphaltenes particles deposition on the heat transfer surfaces. The effect of wall shear stress, surface roughness, and temperature difference on asphaltenes deposition is also reported. From the CFD analysis, the net mass deposition of the asphaltenes particles is minimized with an increase in wall shear stress and surface roughness. The asphaltenes particles in the region where the temperature difference between the bulk and wall is lower at a constant wall temperature are carried forward with the flow and particles with higher temperature difference between the bulk and wall at constant wall temperature are attracted towards the heat transfer surface and deposited on the wall of the heat exchanger tube.
Metallized Gelled Propellant Heat Transfer Tests Analyzed
Palaszewski, Bryan A.
1997-01-01
A series of rocket engine heat transfer experiments using metallized gelled liquid propellants was conducted at the NASA Lewis Research Center. These experiments used a small 20- to 40-lbf thrust engine composed of a modular injector, an igniter, a chamber, and a nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-wt % loadings of aluminum particles. Gaseous oxygen was used as the oxidizer. Heat transfer measurements were made with a rocket engine calorimeter chamber and nozzle with a total of 31 cooling channels. Each channel used water flow to carry heat away from the chamber and the attached thermocouples; flow meters allowed heat flux estimates at each of the 31 stations.
Heat transfer applications for the practicing engineer
Theodore, Louis
2011-01-01
This book serves as a training tool for individuals in industry and academia involved with heat transfer applications. Although the literature is inundated with texts emphasizing theory and theoretical derivations, the goal of this book is to present the subject of heat transfer from a strictly pragmatic point of view. The book is divided into four Parts: Introduction, Principles, Equipment Design Procedures and Applications, and ABET-related Topics. The first Part provides a series of chapters concerned with introductory topics that are required when solving most engineering problems, inclu
Microscale surface modifications for heat transfer enhancement.
Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C
2013-10-09
In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 μm for the reference smooth surface to 19.5 μm for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process.
Dynamic friction modelling in heat exchanger tube simulations
Energy Technology Data Exchange (ETDEWEB)
Tan, X.; Rogers, R.J. [Univ. of New Brunswick, Fredericton, New Brunswick (Canada). Dept. of Mechanical Engineering
1996-12-01
A force-balance friction model has been developed to describe dynamic friction phenomena in multi-degree of freedom vibration systems and validated for a two degree-of-freedom (2dof) lumped mass vibration system. It has been implemented into VIBIC, a finite element code for the vibration of beams with intermittent contact, to improve the prediction of tube wear rate in the simulation of shell-and-tube heat exchangers. The friction model has been tailored for VIBIC for various kinds of supports: circular, semi-circular scallop-bar, and arbitrary flat-bar supports. Simulations for single fuel pin vibration have been compared with experimental data on wear work rate for different test conditions, gaps and preloads.
Heat transfer in thin, compact heat exchangers with circular, rectangular, or pin-fin flow passages
Olson, D. A.
1992-01-01
Heat transfer and pressure drop have been measured of three thin, compact heat exchangers in helium gas at 3.5 MPa and higher, with Reynolds numbers of 450 to 36,000. The flow geometries for the three heat exchanger specimens were: circular tube, rectangular channel, and staggered pin fin with tapered pins. The specimens were heated radiatively at heat fluxes up to 77 W/sq cm. Correlations were developed for the isothermal friction factor as a function of Reynolds number, and for the Nusselt number as a function of Reynolds number and the ratio of wall temperature to fluid temperature. The specimen with the pin fin internal geometry had significantly better heat transfer than the other specimens, but it also had higher pressure drop. For certain conditions of helium flow and heating, the temperature more than doubled from the inlet to the outlet of the specimens, producing large changes in gas velocity, density, viscosity, and thermal conductivity. These changes in properties did not affect the correlations for friction factor and Nusselt number in turbulent flow.
Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer
Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso
2014-01-01
This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described. PMID:25386758
Heat flux sensors for infrared thermography in convective heat transfer.
Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso
2014-11-07
This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described.
Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer
Directory of Open Access Journals (Sweden)
Giovanni Maria Carlomagno
2014-11-01
Full Text Available This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors’ research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described.
Heat Transfer in Directional Water Transport Fabrics
Directory of Open Access Journals (Sweden)
Chao Zeng
2016-10-01
Full Text Available Directional water transport fabrics can proactively transfer moisture from the body. They show great potential in making sportswear and summer clothing. While moisture transfer has been previously reported, heat transfer in directional water transport fabrics has been little reported in research literature. In this study, a directional water transport fabric was prepared using an electrospraying technique and its heat transfer properties under dry and wet states were evaluated, and compared with untreated control fabric and the one pre-treated with NaOH. All the fabric samples showed similar heat transfer features in the dry state, and the equilibrium temperature in the dry state was higher than for the wet state. Wetting considerably enhanced the thermal conductivity of the fabrics. Our studies indicate that directional water transport treatment assists in moving water toward one side of the fabric, but has little effect on thermal transfer performance. This study may be useful for development of “smart” textiles for various applications.
Fouling of HVAC fin and tube heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Siegel, Jeffrey; Carey, Van P.
2001-07-01
Fin and tube heat exchangers are used widely in residential, commercial and industrial HVAC applications. Invariably, indoor and outdoor air contaminants foul these heat exchangers. This fouling can cause decreased capacity and efficiency of the HVAC equipment as well as indoor air quality problems related to microbiological growth. This paper describes laboratory studies to investigate the mechanisms that cause fouling. The laboratory experiments involve subjecting a 4.7 fins/cm (12 fins/inch) fin and tube heat exchanger to an air stream that contains monodisperse particles. Air velocities ranging from 1.5-5.2 m/s (295 ft/min-1024 ft/min) and particle sizes from 1--8.6 {micro}m are used. The measured fraction of particles that deposit as well as information about the location of the deposited material indicate that particles greater than about 1 {micro}m contribute to fouling. These experimental results are used to validate a scaling analysis that describes the relative importance of several deposition mechanisms including impaction, Brownian diffusion, turbophoresis, thermophoresis, diffusiophoresis, and gravitational settling. The analysis is extended to apply to different fin spacings and particle sizes typical of those found in indoor air.
Laminar convective heat transfer of non-Newtonian nanofluids with constant wall temperature
Hojjat, M.; Etemad, S. Gh.; Bagheri, R.; Thibault, J.
2011-02-01
Nanofluids are obtained by dispersing homogeneously nanoparticles into a base fluid. Nanofluids often exhibit higher heat transfer rate in comparison with the base fluid. In the present study, forced convection heat transfer under laminar flow conditions was investigated experimentally for three types of non-Newtonian nanofluids in a circular tube with constant wall temperature. CMC solution was used as the base fluid and γ-Al2O3, TiO2 and CuO nanoparticles were homogeneously dispersed to create nanodispersions of different concentrations. Nanofluids as well as the base fluid show shear thinning (pseudoplastic) rheological behavior. Results show that the presence of nanoparticles increases the convective heat transfer of the nanodispersions in comparison with the base fluid. The convective heat transfer enhancement is more significant when both the Peclet number and the nanoparticle concentration are increased. The increase in convective heat transfer is higher than the increase caused by the augmentation of the effective thermal conductivity.
Topology optimization for transient heat transfer problems
DEFF Research Database (Denmark)
Zeidan, Said; Sigmund, Ole; Lazarov, Boyan Stefanov
, TopOpt has later been extended to transient problems in mechanics and photonics (e.g. [5], [6] and [7]). In the presented approach, the optimization is gradient-based, where in each iteration the non-steady heat conduction equation is solved,using the finite element method and an appropriate time......The focus of this work is on passive control of transient heat transfer problems using the topology optimization (TopOpt) method [1]. The goal is to find distributions of a limited amount of phase change material (PCM), within a given design domain, which optimizes the heat energy storage [2]. Our...
Cooperative heat transfer and ground coupled storage system
Metz, P.D.
A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.
Heat Transfer Coefficient Measurement for Downward Facing Flow Boiling Heat Transfer
Energy Technology Data Exchange (ETDEWEB)
Jung, Jun Yeong; Jeong, Yong Hoon [KAIST, Daejeon (Korea, Republic of)
2016-05-15
To evaluate heat transfer capability of the ERVC, estimating heat transfer coefficient (HTC) is important. In this study, the HTCs were experimentally measured, and large break loss of coolant accident (LLOCA) was used as basic accident. At the lower head outer wall, heat transfer phenomenon was downward facing flow boiling heat transfer. Because, natural circulation occurred. Hence, to simulate the flow boiling, water loop was designed. The reactor vessel lower head was simulated as 2-D slice main heater. To simulate the heat transfer characteristics of material and geometry, the main heater was made of SA508 consisting the reactor vessel, and its radius curvature was 2.5 m. The main heater outer surface (facing to air) temperature was measured by infrared (IR) camera, and the inner surface (facing to working fluid) temperature was calculated by solving conduction equation of main heater. The main heater heat flux was under CHF value of previous research. The results of 60 .deg. and 90 .deg. were used as representative angular location data. LLOCA was used as basic accident. Through this experiment, the HTC data was produced for SA508 heat transfer surface material and 2.5 m of radius curvature. The HTCs result shown different trend at each angular location. The HTCs commonly increased with heat flux increment, but the trends were different for angular location.
Energy Technology Data Exchange (ETDEWEB)
Triplett, C.E.
1996-12-01
This thesis presents the results of an experimental investigation of natural convection heat transfer in a staggered array of heated cylinders, oriented horizontally within a rectangular enclosure. The main purpose of this research was to extend the knowledge of heat transfer within enclosed bundles of spent nuclear fuel rods sealed within a shipping or storage container. This research extends Canaan`s investigation of an aligned array of heated cylinders that thermally simulated a boiling water reactor (BWR) spent fuel assembly sealed within a shipping or storage cask. The results are presented in terms of piecewise Nusselt-Rayleigh number correlations of the form Nu = C(Ra){sup n}, where C and n are constants. Correlations are presented both for individual rods within the array and for the array as a whole. The correlations are based only on the convective component of the heat transfer. The radiative component was calculated with a finite-element code that used measured surface temperatures, rod array geometry, and measured surface emissivities as inputs. The correlation results are compared to Canaan`s aligned array results and to other studies of natural convection in horizontal tube arrays.
Supercritical heat transfer in an annular channel with bilateral heating
Energy Technology Data Exchange (ETDEWEB)
Sergeev, V.V.; Gal' chenko, E.F.; Remizov, O.V.
1986-09-01
This paper presents the experimental investigation of the degradation of heat transfer accompanying an ascending flow of a steam-water mixture and the development of an engineering method for calculating supercritical heat transfer in a vertical annular channel with bilateral heating. The experimental setup is described. The temperature of the exothermic surfaces from the indications of the thermocouples are determined taking into account their individual calibration, the temperature drops in the wall, and thermal losses. The temperature distribution along the length and periphery of the exothermic surfaces of the annular channel is shown and the dependence of the critical steam content on the power fed to the outer wall of the channel with different mass velocities is presented.
Evaporative Heat Transfer Mechanisms within a Heat Melt Compactor
Golliher, Eric L.; Gotti, Daniel J.; Rymut, Joseph Edward; Nguyen, Brian K; Owens, Jay C.; Pace, Gregory S.; Fisher, John W.; Hong, Andrew E.
2013-01-01
This paper will discuss the status of microgravity analysis and testing for the development of a Heat Melt Compactor (HMC). Since fluids behave completely differently in microgravity, the evaporation process for the HMC is expected to be different than in 1-g. A thermal model is developed to support the design and operation of the HMC. Also, low-gravity aircraft flight data is described to assess the point at which water may be squeezed out of the HMC during microgravity operation. For optimum heat transfer operation of the HMC, the compaction process should stop prior to any water exiting the HMC, but nevertheless seek to compact as much as possible to cause high heat transfer and therefore shorter evaporation times.
Ribeiro, Carla
2017-01-01
The double-wall paper cup is an everyday object that can be used in the laboratory to study heat transfer. The experiment described here has been done by physics students aged 12-13 years; it can also be used in a different context to prompt debate about environmental issues.
Free convection film flows and heat transfer
Shang, Deyi
2010-01-01
Presents development of systematic studies for hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, and accelerating film flow of non-Newtonian power-law fluids. This book provides a system of analysis models with a developed velocity component method.
A Paradox in Radiation Heat Transfer
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 12; Issue 4. A Paradox in Radiation Heat Transfer. J Srinivasan. Classroom Volume 12 Issue 4 April 2007 pp 85-91. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/012/04/0085-0091. Keywords. Radiation ...
Endwall convective heat transfer for bluff bodies
DEFF Research Database (Denmark)
Wang, Lei; Salewski, Mirko; Sundén, Bengt
2012-01-01
The endwall heat transfer characteristics of forced flow past bluff bodies have been investigated using liquid crystal thermography (LCT). The bluff body is placed in a rectangular channel with both its ends attached to the endwalls. The Reynolds number varies from 50,000 to 100,000. In this stud...
Conjugate problems in convective heat transfer
Dorfman, Abram S
2009-01-01
The conjugate heat transfer (CHT) problem takes into account the thermal interaction between a body and fluid flowing over or through it, a key consideration in both mechanical and aerospace engineering. Presenting more than 100 solutions of non-isothermal and CHT problems, this title considers the approximate solutions of CHT problems.
Determination of the convective heat transfer coefficient
Spierings, D.; Bosman, F.; Peters, T.; Plasschaert, F.
The value of the convective heat transfer coefficient (htc) is determined under different loading conditions by using a computer aided method. The thermal load has been applied mathematically as well as experimentally to the coronal surface of an axisymmetric tooth model. To verify the assumptions
Forced Convection Heat Transfer in Circular Pipes
Tosun, Ismail
2007-01-01
One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…
Numerical Modeling of Ablation Heat Transfer
Ewing, Mark E.; Laker, Travis S.; Walker, David T.
2013-01-01
A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.
Numerical Modeling of Fin and Tube Heat Exchanger for Waste Heat Recovery
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
In the present work, multiphysics numerical modeling is carried out to predict the performance of a liquid-gas fin and tube heat exchanger design. Three-dimensional (3D) steady-state numerical model using commercial software COMSOL based on finite element method (FEM) is developed. The study...
Energy Technology Data Exchange (ETDEWEB)
Minocha, Nitin [Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094 (India); Joshi, Jyeshtharaj B., E-mail: jbjoshi@gmail.com [Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094 (India); Department of Chemical Engineering, Institute of Chemical Technology, Matunga, Mumbai 400 019 (India); Nayak, Arun K. [Reactor Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India); Vijayan, Pallippattu K., E-mail: vijayanp@barc.gov.in [Reactor Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India)
2016-08-15
Highlights: • Investigation of three-dimensional natural convection and thermal stratification inside large water pool. • Effect of inclination (α) of condenser tube on fluid flow and heat transfer. • The heat transfer was found to be maximum for α = 90° and minimum for α = 15°. • Laminar-turbulent natural convection and heat transfer in the presence of longitudinal vortices. - Abstract: Many advanced nuclear reactors adopt methodologies of passive safety systems based on natural forces such as gravity. In one of such system, the decay heat generated from a reactor is removed by isolation condenser (ICs) submerged in a large water pool called the Gravity Driven Water Pool (GDWP). The objective of the present study was to design an IC for the passive decay heat removal system (PDHRS) for advanced nuclear reactor. First, the effect of inclination of IC tube on three dimensional temperature and flow fields was investigated inside a pilot scale (10 L) GDWP. Further, the knowledge of these fields has been used for the quantification of heat transfer and thermal stratification phenomenon. In a next step, the knowledge gained from the pilot scale GDWP has been extended to design an IC for real size GDWP (∼10,000 m{sup 3}). Single phase CFD simulation using open source CFD code [OpenFOAM-2.2] was performed for different tube inclination angles (α) (w.r.t. to vertical direction) in the range 0° ⩽ α ⩽ 90°. The results indicate that the heat transfer coefficient increases with increase in tube inclination angle. The heat transfer was found to be maximum for α = 90° and minimum for α = 15°. This behavior is due to the interaction between the primary flow (due to pressure gradient) and secondary flow (due to buoyancy force). The primary flow enhanced the fluid sliding motion at the tube top whereas the secondary flow resulted in enhancement in fluid motion along the circumference of tube. As the angle of inclination (α) of the tube was increased, the
Improved Corrosion Resistance of a Heat Exchanger Using a Copper Tube Coated with Tin
National Research Council Canada - National Science Library
FUKUSHIMA, Makoto; YONESAKI, Takahiro; TAKIZAWA, Kikuo; SUSAI, Takashi
2000-01-01
The outer face of copper tubes used in a heat exchanger were coated with tin. The tubes were brazed with various types of solder in order to evaluate their corrosion resistance in a H2S gas environment...
Parabolic solar cooker: Cooking with heat pipe vs direct spiral copper tubes
Craig, Omotoyosi O.; Dobson, Robert T.
2016-05-01
Cooking with solar energy has been seen by many researchers as a solution to the challenges of poverty and hunger in the world. This is no exception in Africa, as solar coking is viewed as an avenue to eliminate the problem of food insecurity, insufficient energy supply for household and industrial cooking. There are several types of solar cookers that have been manufactured and highlighted in literature. The parabolic types of solar cookers are known to reach higher temperatures and therefore cook faster. These cookers are currently being developed for indoor cooking. This technology has however suffered low cooking efficiency and thus leads to underutilization of the high heat energy captured from the sun in the cooking. This has made parabolic solar cookers unable to compete with other conventional types of cookers. Several methods to maximize heat from the sun for indirect cooking has been developed, and the need to improve on them of utmost urgency. This paper investigates how to optimize the heat collected from the concentrating types of cookers by proposing and comparing two types of cooking sections: the spiral hot plate copper tube and the heat pipe plate. The system uses the concentrating solar parabolic dish technology to focus the sun on a conical cavity of copper tubes and the heat is stored inside an insulated tank which acts both as storage and cooking plate. The use of heat pipes to transfer heat between the oil storage and the cooking pot was compared to the use of a direct natural syphon principle which is achieved using copper tubes in spiral form like electric stove. An accurate theoretical analysis for the heat pipe cooker was achieved by solving the boiling and vaporization in the evaporator side and then balancing it with the condensation and liquid-vapour interaction in the condenser part while correct heat transfer, pressure and height balancing was calculated in the second experiment. The results show and compare the cooking time, boiling
Energy Technology Data Exchange (ETDEWEB)
Ma, Zhiwen [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Martinek, Janna G [National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2017-06-03
Concentrating solar power (CSP) technology is moving toward high-temperature and high-performance design. One technology approach is to explore high-temperature heat-transfer fluids and storage, integrated with a high-efficiency power cycle such as the supercritical carbon dioxide (s-CO2) Brayton power cycle. The s-CO2 Brayton power system has great potential to enable the future CSP system to achieve high solar-to-electricity conversion efficiency and to reduce the cost of power generation. Solid particles have been proposed as a possible high-temperature heat-transfer medium that is inexpensive and stable at high temperatures above 1,000 degrees C. The particle/heat exchanger provides a connection between the particles and s-CO2 fluid in the emerging s-CO2 power cycles in order to meet CSP power-cycle performance targets of 50% thermal-to-electric efficiency, and dry cooling at an ambient temperature of 40 degrees C. The development goals for a particle/s-CO2 heat exchanger are to heat s-CO2 to =720 degrees C and to use direct thermal storage with low-cost, stable solid particles. This paper presents heat-transfer modeling to inform the particle/s-CO2 heat-exchanger design and assess design tradeoffs. The heat-transfer process was modeled based on a particle/s-CO2 counterflow configuration. Empirical heat-transfer correlations for the fluidized bed and s-CO2 were used in calculating the heat-transfer area and optimizing the tube layout. A 2-D computational fluid-dynamics simulation was applied for particle distribution and fluidization characterization. The operating conditions were studied from the heat-transfer analysis, and cost was estimated from the sizing of the heat exchanger. The paper shows the path in achieving the cost and performance objectives for a heat-exchanger design.
Fluid flow and heat transfer in an air-to-water double-pipe heat exchanger
Sheikholeslami, M.; Gorji-Bandpy, M.; Ganji, D. D.
2015-11-01
This paper reports experimental and numerical investigations on flow and heat transfer in an air-to-water double-pipe heat exchanger. The working fluids are air and water. To achieve fully developed conditions, the heat exchanger was built with additional lengths before and after the test section. The inner and outer tube was made from copper and Plexiglas, respectively. The experiments are conducted in the range of air flow Reynolds number for various cases with different water flow rate and water inlet temperature. Correlations for the Nusselt number and friction factor are presented according to experimental data. Also the commercial code ANSYS 15 is used for numerical simulation. Results show that the Nusselt number is an increasing function of Reynolds number and Prandtl number which are calculated at bulk temperature.
Directory of Open Access Journals (Sweden)
N. A. Nesenchuk
2013-01-01
Full Text Available Directions pertaining to intensification of convective heat transfer in a soft heating device have been experimentally investigated in the paper and the most efficient one has been selected that is creation of artificial roughness on the device surface. The considered heating device for a heat supply system of a mobile object has been made of soft polymer material (polyvinyl chloride. Following evaluation results of heat exchange intensification a criteria equation has been obtained for calculation of external heat transfer with due account of heat transfer intensification.
Heat Transfer in Health and Healing.
Diller, Kenneth R
2015-10-01
Our bodies depend on an exquisitely sensitive and refined temperature control system to maintain a state of health and homeostasis. The exceptionally broad range of physical activities that humans engage in and the diverse array of environmental conditions we face require remarkable strategies and mechanisms for regulating internal and external heat transfer processes. On the occasions for which the body suffers trauma, therapeutic temperature modulation is often the approach of choice for reversing injury and inflammation and launching a cascade of healing. The focus of human thermoregulation is maintenance of the body core temperature within a tight range of values, even as internal rates of energy generation may vary over an order of magnitude, environmental convection, and radiation heat loads may undergo large changes in the absence of any significant personal control, surface insulation may be added or removed, all occurring while the body's internal thermostat follows a diurnal circadian cycle that may be altered by illness and anesthetic agents. An advanced level of understanding of the complex physiological function and control of the human body may be combined with skill in heat transfer analysis and design to develop life-saving and injury-healing medical devices. This paper will describe some of the challenges and conquests the author has experienced related to the practice of heat transfer for maintenance of health and enhancement of healing processes.
Radiative heat transfer in fractal structures
Nikbakht, M.
2017-09-01
The radiative properties of most structures are intimately connected to the way in which their constituents are ordered on the nanoscale. We have proposed a new representation for radiative heat transfer formalism in many-body systems. In this representation, we explain why collective effects depend on the morphology of structures, and how the arrangement of nanoparticles and their material affects the thermal properties in many-body systems. We investigated the radiative heat transfer problem in fractal (i.e., scale invariant) structures. In order to show the effect of the structure morphology on the collective properties, the radiative heat transfer and radiative cooling are studied and the results are compared for fractal and nonfractal structures. It is shown that fractal arranged nanoparticles display complex radiative behavior related to their scaling properties. We showed that, in contrast to nonfractal structures, heat flux in fractals is not of large-range character. By using the fractal dimension as a means to describe the structure morphology, we present a universal scaling behavior that quantitatively links the structure radiative cooling to the structure gyration radius.
CFD modelling of shell-side asphaltenes deposition in a shell and tube heat exchanger
Emani, Sampath; Ramasamy, M.; Shaari, Ku Zilati Ku
2017-07-01
Asphaltenes are identified as the main cause of crude oil fouling in the shell and tube exchangers. There are occasions where the crude oil flows through the shell side of the heat exchangers and some fouling is reported in the shell side of those heat exchangers. Understanding the fouling phenomena in the shell sides requires the knowledge on the irregular fluid flow paths and most susceptible locations of particles deposition. In the present work, an attempt has been made to investigate the effect of shear stress and surface roughness on shell-side asphaltenes deposition in a shell and tube heat exchanger through Computational Fluid Dynamics approach. The hydrodynamics of asphaltenes particles and the effect of various forces on the asphaltenes deposition on the heat transfer surfaces has been investigated through a Lagrangian based discrete-phase model. From the CFD analysis, the net mass deposition of the asphaltenes particles reduces with an increase in surface roughness from 0 to 0.04 mm and wall shear stress from 0 to 0.04 Pa for flow velocity 1 m/s, respectively. The asphaltenes mass deposition becomes constant with further increase in wall shear stress and surface roughness.
Effects of fouling in heat transfer equipment
Energy Technology Data Exchange (ETDEWEB)
Ganapathy, V. (ABCO Industries, Abilene, TX (United States))
1993-03-04
Fouling between the hot and cold streams in heat transfer equipment is a major reason boilers, heaters, and heat exchangers do not perform according to original specifications. Commonly used fluids such as water and air have well-established fouling factors. However, the factors for some industrial effluents, particularly for flue gas streams resulting from the combustion or incineration of solid or liquid fuels, can be determined only through operating experience. The paper discusses the signs of fouling, and how expensive fouling can be illustrating the second with three example problems.
Laboratory simulation of heat exchange for liquids with Pr > 1: Heat transfer
Belyaev, I. A.; Zakharova, O. D.; Krasnoshchekova, T. E.; Sviridov, V. G.; Sukomel, L. A.
2016-02-01
Liquid metals are promising heat transfer agents in new-generation nuclear power plants, such as fast-neutron reactors and hybrid tokamaks—fusion neutron sources (FNSs). We have been investigating hydrodynamics and heat exchange of liquid metals for many years, trying to reproduce the conditions close to those in fast reactors and fusion neutron sources. In the latter case, the liquid metal flow takes place in a strong magnetic field and strong thermal loads resulting in development of thermogravitational convection in the flow. In this case, quite dangerous regimes of magnetohydrodynamic (MHD) heat exchange not known earlier may occur that, in combination with other long-known regimes, for example, the growth of hydraulic drag in a strong magnetic field, make the possibility of creating a reliable FNS cooling system with a liquid metal heat carrier problematic. There exists a reasonable alternative to liquid metals in FNS, molten salts, namely, the melt of lithium and beryllium fluorides (Flibe) and the melt of fluorides of alkali metals (Flinak). Molten salts, however, are poorly studied media, and their application requires detailed scientific substantiation. We analyze the modern state of the art of studies in this field. Our contribution is to answer the following question: whether above-mentioned extremely dangerous regimes of MHD heat exchange detected in liquid metals can exist in molten salts. Experiments and numerical simulation were performed in order to answer this question. The experimental test facility represents a water circuit, since water (or water with additions for increasing its electrical conduction) is a convenient medium for laboratory simulation of salt heat exchange in FNS conditions. Local heat transfer coefficients along the heated tube, three-dimensional (along the length and in the cross section, including the viscous sublayer) fields of averaged temperature and temperature pulsations are studied. The probe method for measurements in
Ameri, Ali; Shyam, Vikram; Rigby, David; Poinsatte, Phillip; Thurman, Douglas; Steinthorsson, Erlendur
2014-01-01
Computational fluid dynamics (CFD) analysis using Reynolds-averaged Navier-Stokes (RANS) formulation for turbomachinery-related flows has enabled improved engine component designs. RANS methodology has limitations that are related to its inability to accurately describe the spectrum of flow phenomena encountered in engines. Examples of flows that are difficult to compute accurately with RANS include phenomena such as laminar/turbulent transition, turbulent mixing due to mixing of streams, and separated flows. Large eddy simulation (LES) can improve accuracy but at a considerably higher cost. In recent years, hybrid schemes that take advantage of both unsteady RANS and LES have been proposed. This study investigated an alternative scheme, the time-filtered Navier-Stokes (TFNS) method applied to compressible flows. The method developed by Shih and Liu was implemented in the Glenn-Heat-Transfer (Glenn-HT) code and applied to film-cooling flows. In this report the method and its implementation is briefly described. The film effectiveness results obtained for film cooling from a row of 30deg holes with a pitch of 3.0 diameters emitting air at a nominal density ratio of unity and two blowing ratios of 0.5 and 1.0 are shown. Flow features under those conditions are also described.
Ameri, Ali A.; Shyam, Vikram; Rigby, David; Poinsatte, Phillip; Thurman, Douglas; Steinthorsson, Erlendur
2014-01-01
Computational fluid dynamics (CFD) analysis using Reynolds-averaged Navier-Stokes (RANS) formulation for turbomachinery-related flows has enabled improved engine component designs. RANS methodology has limitations that are related to its inability to accurately describe the spectrum of flow phenomena encountered in engines. Examples of flows that are difficult to compute accurately with RANS include phenomena such as laminar/turbulent transition, turbulent mixing due to mixing of streams, and separated flows. Large eddy simulation (LES) can improve accuracy but at a considerably higher cost. In recent years, hybrid schemes that take advantage of both unsteady RANS and LES have been proposed. This study investigated an alternative scheme, the time-filtered Navier-Stokes (TFNS) method applied to compressible flows. The method developed by Shih and Liu was implemented in the Glenn-Heat-Transfer (Glenn-HT) code and applied to film-cooling flows. In this report the method and its implementation is briefly described. The film effectiveness results obtained for film cooling from a row of 30deg holes with a pitch of 3.0 diameters emitting air at a nominal density ratio of unity and two blowing ratios of 0.5 and 1.0 are shown. Flow features under those conditions are also described.
Heat Transfer and Pressure Drop in Concentric Annular Flows of Binary Inert Gas Mixtures
Reid, R. S.; Martin, J. J.; Yocum, D. J.; Stewart, E. T.
2007-01-01
Studies of heat transfer and pressure drop of binary inert gas mixtures flowing through smooth concentric circular annuli, tubes with fully developed velocity profiles, and constant heating rate are described. There is a general lack of agreement among the constant property heat transfer correlations for such mixtures. No inert gas mixture data exist for annular channels. The intent of this study was to develop highly accurate and benchmarked pressure drop and heat transfer correlations that can be used to size heat exchangers and cores for direct gas Brayton nuclear power plants. The inside surface of the annular channel is heated while the outer surface of the channel is insulated. Annulus ratios range 0.5 spacer ribs, or other surfaces.
Prediction of the heat transfer coefficient for ice slurry flows in a horizontal pipe
Energy Technology Data Exchange (ETDEWEB)
Kousksou, T.; Jamil, A.; Zeraouli, Y. [Laboratoire de Thermique Energetique et Procedes, Avenue de l' Universite, BP 1155, 64013 Pau Cedex (France); El Rhafiki, T. [Laboratoire de Thermique Energetique et Procedes, Avenue de l' Universite, BP 1155, 64013 Pau Cedex (France); Laboratoire d' Energetique, Mecanique des Fluides et Sciences des Materiaux, Universite AbdelMalek Essaidi, 90000 Tetouan (Morocco)
2010-06-15
In this study, heat transfer for ice slurry flows was investigated. For the experiments, ice slurry was made from 9% ethanol-water solution flow in a 20 mm internal diameter, 1000 mm long horizontal copper tube. The ice slurry was heated by a cylindrical electrical resistance. Experiments of the melting process were conducted with changing the ice slurry mass flux rate and the heat flux. The enthalpy-porosity formulation was used to predict the ice slurry temperature and the local values of heat transfer coefficient in the exchanger. Measurements and data acquisition of ice slurry temperature and mass flow rate at the inlet and outlet are performed. It was found that the heat transfer rates increase with the mass flow rate, the ice fraction and the heat flux density. However, the effect of ice fraction appears not to be significant at high mass flow rates. In addition, the correlation proposed by Christensen and Kauffeld gives good agreement with numerical results. (author)
Energy Technology Data Exchange (ETDEWEB)
Bednarski, A.; Ligeza, S.; Montewski, W.; Ozga, A.; Steinmec, E.
1979-10-01
An oil heat-transfer agent, suitable for operation in the temperature range of 30-360 degrees, containing hydrocarbon oil with a boiling point of 5% above 360 degrees and 2% alkylphenolate or alkaline or alkaline-earth metal with a reserve alkalinity to 300 mg KOH/g, and to 5% alkenylksuccinic anhydride with a molar weight of 1000-1600 and content of nitrogen to 2.5%, or alkylthiophosphonate with a molecular weight to 1500 and phosphorus content to 2%. The oil used in the heat-transfer agent contains over 25% aromatic hydrocarbons containing 4-40% aromatic C atoms, 3-40% naphthene carbon atoms and 25-75% paraffin carbon atoms, and to 3% tar. Data are given describing the high oxidation stability and low tendency to deposit formation of oil compositions obtained according to the patent.
Heat transfer modeling an inductive approach
Sidebotham, George
2015-01-01
This innovative text emphasizes a "less-is-more" approach to modeling complicated systems such as heat transfer by treating them first as "1-node lumped models" that yield simple closed-form solutions. The author develops numerical techniques for students to obtain more detail, but also trains them to use the techniques only when simpler approaches fail. Covering all essential methods offered in traditional texts, but with a different order, Professor Sidebotham stresses inductive thinking and problem solving as well as a constructive understanding of modern, computer-based practice. Readers learn to develop their own code in the context of the material, rather than just how to use packaged software, offering a deeper, intrinsic grasp behind models of heat transfer. Developed from over twenty-five years of lecture notes to teach students of mechanical and chemical engineering at The Cooper Union for the Advancement of Science and Art, the book is ideal for students and practitioners across engineering discipl...
Principles of heat and mass transfer
Incropera, Frank P; Bergman, Theodore L; Lavine, Adrienne S
2013-01-01
Completely updated, the seventh edition provides engineers with an in-depth look at the key concepts in the field. It incorporates new discussions on emerging areas of heat transfer, discussing technologies that are related to nanotechnology, biomedical engineering and alternative energy. The example problems are also updated to better show how to apply the material. And as engineers follow the rigorous and systematic problem-solving methodology, they'll gain an appreciation for the richness and beauty of the discipline.
Heat transfer in multi-phase materials
Öchsner, Andreas
2011-01-01
This book provides a profound understanding, which physical processes and mechanisms cause the heat transfer in composite and cellular materials. It shows models for all important classes of composite materials and introduces into the latest advances. In three parts, the book covers Composite Materials (Part A), Porous and Cellular Materials (Part B) and the appearance of a conjoint solid phase and fluid aggregate (Part C).
Heat transfer studies on spiral plate heat exchanger
Directory of Open Access Journals (Sweden)
Rajavel Rangasamy
2008-01-01
Full Text Available In this paper, the heat transfer coefficients in a spiral plate heat exchanger are investigated. The test section consists of a plate of width 0.3150 m, thickness 0.001 m and mean hydraulic diameter of 0.01 m. The mass flow rate of hot water (hot fluid is varying from 0.5 to 0.8 kg/s and the mass flow rate of cold water (cold fluid varies from 0.4 to 0.7 kg/s. Experiments have been conducted by varying the mass flow rate, temperature, and pressure of cold fluid, keeping the mass flow rate of hot fluid constant. The effects of relevant parameters on spiral plate heat exchanger are investigated. The data obtained from the experimental study are compared with the theoretical data. Besides, a new correlation for the Nusselt number which can be used for practical applications is proposed.
Heat transfer with freezing in a scraped surface heat exchanger
Energy Technology Data Exchange (ETDEWEB)
Lakhdar, M.B. [LGL France Refrigerating Division, Genas (France); Cerecero, R.; Alvarez, G.; Guilpart, J. [Cemagref, Antony cedex (France). Food Process Engineering; Flick, D. [Institut National Agronomique, Paris (France); Lallemand, A. [Institut National des Sciences Appliquees de Lyon (France). Centre de Thermique
2005-01-01
An experimental study was carried out on a scraped surface heat exchanger used for freezing of water-ethanol mixture and aqueous sucrose solution. The influence of various parameters on heat transfer intensity was established: product type and composition, flow rate, blade rotation speed, distance between blades and wall. During starting (transient period) the solution is first supercooled, then ice crystals appear on the scraped surface (heterogeneous nucleation) and no more supercooling is observed. It seems that, when blades are 3 mm far from the surface, a constant ice layer is formed having this thickness and acting as a thermal resistance. But when the blades rotate at 1 mm from the surface, periodically all the ice layer is removed despite the surface is not really scraped. This could simplify ice generator technology. An internal heat transfer coefficient was defined; it depends mainly on rotation speed. Correlations were proposed for its prediction, which could be applied, at least as a first approach, for the most common freezing applications of scraped surface heat exchanger i.e. ice creams (which are derived from sucrose solutions) and two-phase secondary refrigerants (which are principally ethanol solutions). (author)
Refrigeration. Heat Transfer. Part I: Evaporators and Condensers
DEFF Research Database (Denmark)
Knudsen, Hans-Jørgen Høgaard
2002-01-01
The note gives an introduction to heat transfer with phase shift. Pool Boiling, Flow Boiling, Condensation.......The note gives an introduction to heat transfer with phase shift. Pool Boiling, Flow Boiling, Condensation....
Conjugate Problems in Convective Heat Transfer: Review
Directory of Open Access Journals (Sweden)
Abram Dorfman
2009-01-01
Full Text Available A review of conjugate convective heat transfer problems solved during the early and current time of development of this modern approach is presented. The discussion is based on analytical solutions of selected typical relatively simple conjugate problems including steady-state and transient processes, thermal material treatment, and heat and mass transfer in drying. This brief survey is accompanied by the list of almost two hundred publications considering application of different more and less complex analytical and numerical conjugate models for simulating technology processes and industrial devices from aerospace systems to food production. The references are combined in the groups of works studying similar problems so that each of the groups corresponds to one of selected analytical solutions considered in detail. Such structure of review gives the reader the understanding of early and current situation in conjugate convective heat transfer modeling and makes possible to use the information presented as an introduction to this area on the one hand, and to find more complicated publications of interest on the other hand.
Characteristics of microencapsulated PCM slurry as a heat-transfer fluid
Energy Technology Data Exchange (ETDEWEB)
Yamagishi, Yasushi [Daido Hoxan Inc., Osaka (Japan); Takeuchi, Hiromi; Pyatenko, A.T. [Hokkaido National Industrial Research Inst., Sapporo (Japan); Kayukawa, Naoyuki [Hokkaido Univ., Sapporo (Japan). Center for Advanced Research of Energy Technology
1999-04-01
The hydrodynamic and heat-transfer characteristics of slurry containing microencapsulated phase-change materials (MCPCMs) were investigated experimentally for use as a heat-transfer fluid. Pressure drop and local convective heat-transfer coefficients of the slurry flows in a circular tube with uniform heat flux were measured. Slurries consisting of octadecane (C{sub 18}H{sub 38}) contained in 2--10-{micro}m-dia. microcapsules and pure water were used. The particle volume fractions in the slurry were varied up to 0.3. Results showed that increases in particle volume fractions caused the slurry flow structure to change from turbulent to laminar, and the pressure-drop reduction of the slurry flow relative to a single-phase water flow was under the same flow-rate conditions. The heat-transfer performance of the slurry also depended on the change in flow structure. When the MCPCMs melted, the local heat-transfer coefficients for turbulent slurry flows increased relative to those for nonmelting slurry. This phenomenon was influenced by the MCPCM fraction, the degree of turbulence, and the heating rate at the tube wall. The experimental data will be useful in the design of thermal-energy transportation systems using MCPCM slurry.
Experimental investigation of post-dryout heat transfer in an annulus with spacers
Persson, Per; Hedberg, Stellan; Anglart, Henryk
2004-01-01
Experimental investigation of the post-dryout heat transfer in annulus test section has been performed in the high-pressure two-phase loop at the Royal Institute of Technology (KTH), Nuclear Reactor Technology division. The test section has an annular geometry with 10 mm rod outer diameter and 22.1 mm tube inner diameter. Seven spacers are located along the test section to keep the rod and the tube equidistant along the test section. Both the tube and the rod are manufactured of Inconel 600 t...
Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles
Clark, William M.; Shevlin, Ryan C.; Soffen, Tanya S.
2010-01-01
This paper addresses a controversy regarding the effect of bottle material on the thermal performance of beverage bottles. Experiments and calculations that verify or refute advertising claims and represent an interesting way to teach heat transfer fundamentals are described. Heat transfer coefficients and the resistance to heat transfer offered…
Free convection effects and radiative heat transfer in MHD Stokes ...
Indian Academy of Sciences (India)
which controls the gasification rate of the energetic material for estimating heat transfer. Radiation effect on flow and heat transfer is important in the context of space technology and processes involving high temperature. In recent years, the problems of free convective and heat transfer flows through a porous medium under ...
Enhancement of heat transfer using varying width twisted tape inserts
African Journals Online (AJOL)
user
width twisted tape inserts, ASME Transactions, Vol. 122, pp. 143-149. Naphon P., 2006. Heat transfer and pressure drop in the horizontal double pipes with and without twisted tape insert, International communications in Heat and Mass Transfer, Vol. 33, pp. 166-175. Promvonge P. and Eiamsa-ard S., 2007. Heat transfer ...
Low-Flow Film Boiling Heat Transfer on Vertical Surfaces
DEFF Research Database (Denmark)
Munthe Andersen, J. G.; Dix, G. E.; Leonard, J. E.
1976-01-01
The phenomenon of film boiling heat transfer for high wall temperatures has been investigated. Based on the assumption of laminar flow for the film, the continuity, momentum, and energy equations for the vapor film are solved and a Bromley-type analytical expression for the heat transfer...... length, an average film boiling heat transfer coefficient is obtained....
Forced convective boiling heat transfer of R-410A in horizontal minichannels
Energy Technology Data Exchange (ETDEWEB)
Pamitran, A.S.; Choi, Kwang-Il [Graduate School, Chonnam National University, San 96-1, Dunduk-Dong, Yeosu, Chonnam 550 749 (Korea, Republic of); Oh, Jong-Taek [Department of Refrigeration Engineering, Chonnam National University, San 96-1, Dunduk-Dong, Yeosu, Chonnam 550 749 (Korea, Republic of); Oh, Hoo-Kyu [Department of Refrigeration and A/C Engineering, Pukyong National University, 100, Yongdang-Dong, Nam-Ku, Busan 608 739 (Korea, Republic of)
2007-01-15
Convective boiling heat transfer experiments were performed in horizontal minichannels with binary mixture refrigerant, R-410A. The test section is made of stainless steel tubes with inner diameters of 1.5mm and 3.0mm and with lengths of 1500mm and 3000mm, respectively, and is uniformly heated by applying electric current directly to the tubes. Local heat transfer coefficients were obtained for a heat flux range of 10-30kWm{sup -2}, a mass flux range of 300-600kgm{sup -2}s{sup -1}, and quality ranges of up to 1.0. The experimental results were mapped on Wang et al.'s (C.C. Wang, C.S. Chiang, D.C. Lu, Visual observation of two-phase flow pattern of R-22, R-134a, and R-407C in a 6.5-mm smooth tube, Experimental, Thermal and Fluid Science 15 (1997) 395-405) and Wojtan et al.'s (L. Wojtan, T. Ursenbacher, J.R. Thome, Investigation of flow boiling in horizontal tubes: part I - a new diabatic two-phase flow pattern map, International Journal of Heat and Mass Transfer 48 (2005) 2955-2969) flow pattern maps to observe the flow regimes. Laminar flow appears in flow with minichannels. A new boiling heat transfer coefficient correlation based on the superposition model for R-410A was developed with 11.20% mean deviation; it showed a good agreement between the measured data and the calculated heat transfer coefficients. (author)
Low heat transfer oxidizer heat exchanger design and analysis
Kanic, P. G.; Kmiec, T. D.; Peckham, R. J.
1987-01-01
The RL10-IIB engine, a derivative of the RLIO, is capable of multi-mode thrust operation. This engine operates at two low thrust levels: tank head idle (THI), which is approximately 1 to 2 percent of full thrust, and pumped idle (PI), which is 10 percent of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient engine thermal conditioning; PI operation provides vehicle tank pre-pressurization and maneuver thrust for log-g deployment. Stable combustion of the RL10-IIB engine at THI and PI thrust levels can be accomplished by providing gaseous oxygen at the propellant injector. Using gaseous hydrogen from the thrust chamber jacket as an energy source, a heat exchanger can be used to vaporize liquid oxygen without creating flow instability. This report summarizes the design and analysis of a United Aircraft Products (UAP) low-rate heat transfer heat exchanger concept for the RL10-IIB rocket engine. The design represents a second iteration of the RL10-IIB heat exchanger investigation program. The design and analysis of the first heat exchanger effort is presented in more detail in NASA CR-174857. Testing of the previous design is detailed in NASA CR-179487.
Directory of Open Access Journals (Sweden)
Pooranachandran Karthik
2015-01-01
Full Text Available In the present work, an experimental investigation is carried out to analyze the heat transfer characteristics of a louvered fin and elliptical tube compact heat exchanger used as a radiator in an internal combustion engine. Experiments are conducted by positioning the radiator in an open-loop wind tunnel. A total of 24 sets of air, water flow rate combinations are tested, and the temperature drops of air and water were acquired. A numerical analysis has been carried out using Fluent software (a general purpose computational fluid dynamics simulation tool for three chosen data from the experiments. The numerical air-side temperature drop is compared with those of the experimental values. A good agreement between the experimental and numerical results validates the present computational methodology.
Directory of Open Access Journals (Sweden)
Mohseni-Languri Ehsan
2008-01-01
Full Text Available The two-dimensional fluid flow and heat transfer in a circular tube heat exchanger with two elliptic obstacles at the back is studied numerically. The computational domain consists of a circular tube and two elliptic obstacles that are situated after the tube, such that the angle between their centerlines and the direction of free coming flow is 45 degrees. The numerical solution is achieved by numerical integration of full Navier-Stokes and energy equations over the computational domain, using finite volume method. The fluid flow is assumed to be laminar, incompressible and steady-state with constant thermo-physical characteristics. In this study major thermo-fluid parameters such as temperature, pressure and velocity fields as well as Nusselt number and friction factor variations are computed and some results are presented in the graphs. It is shown that using of elliptic obstacles leads to an increase in the average Nusselt number and also pressure. .
Infrared thermography for convective heat transfer measurements
Energy Technology Data Exchange (ETDEWEB)
Carlomagno, Giovanni Maria; Cardone, Gennaro [University of Naples Federico II, Department of Aerospace Engineering, Naples (Italy)
2010-12-15
This paper deals with the evolution of infrared (IR) thermography into a powerful optical tool that can be used in complex fluid flows to either evaluate wall convective heat fluxes or investigate the surface flow field behavior. Measurement of convective heat fluxes must be performed by means of a thermal sensor, where temperatures have to be measured with proper transducers. By correctly choosing the thermal sensor, IR thermography can be successfully exploited to resolve convective heat flux distributions with both steady and transient techniques. When comparing it to standard transducers, the IR camera appears very valuable because it is non-intrusive, it has a high sensitivity (down to 20 mK), it has a low response time (down to 20 {mu}s), it is fully two dimensional (from 80 k up to 1 M pixels, at 50 Hz) and, therefore, it allows for better evaluation of errors due to tangential conduction within the sensor. This paper analyses the capability of IR thermography to perform convective heat transfer measurements and surface visualizations in complex fluid flows. In particular, it includes the following: the necessary radiation theory background, a review of the main IR camera features, a description of the pertinent heat flux sensors, an analysis of the IR image processing methods and a report on some applications to complex fluid flows, ranging from natural convection to hypersonic regime. (orig.)
46 CFR 153.430 - Heat transfer systems; general.
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...
Matsunaga, Takeshi; Yoshida, Suguru
A method which is generally applicable to predict the axially local (circumferentially averaged) heat transfer coefficient for refrigerant with oil contained flowing in horizontal evaporator tubes was developed by modifying a prediction method for pure refrigerants. The dimensionless correlation for an annular flow regime takes account of the influence of oil on an improvement or a reduction in the heat transfer, in addition to the change of the properties due to the addition of oil. For a separated flow regime, the correlations of the average heat transfer coefficients in the top part and the bottom part and their boundary angle were developed by modifying each correlation for pure refrigerants. The circumferentially averaged heat transfer coefficient for the separated flow regime can be obtained by using the solution of the steady heat conduction equation in the tube wall, to which the values calculated from the above correlations are applied as the boundary conditions at the inside surface of the tube. Which flow regime, annular or separated, prevails can be determined by the correlation of the boundary angle. The present prediction method was confirmed to be applicable to various kinds of refrigerant-oil mixture.
Heat transfer, condensation and fog formation in crossflow plastic heat exchangers
Brouwers, Jos; van der Geld, C.W.M.
1996-01-01
In this paper heat transfer of air-water-vapour mixtures in plastic crossflow heat exchangers is studied theoretically and experimentally. First, a model for heat transfer without condensation is derived, resulting in a set of classical differential equations. Subsequently, heat transfer with wall
Analytical model of heat transfer in porous insulation around cold pipes
DEFF Research Database (Denmark)
Guldbrandsen, Tom; Karlsson, Per W.; Korsgaard, Vagn
2011-01-01
A thermal insulation system is analysed that consists of a cold tube insulated with a porous material faced with a vapour retarding foil.Water vapour will diffuse through the vapour retarding foil and condense on the cold tube. To avoid build-up of water in the insulation a hydrophilic wicking...... cloth is wrapped around the cold tube and extended through a slit in the tubular insulation and a slot in the facing to the ambient so that condensed water can evaporate into the air. Some of the moisture in that part of the wicking cloth situated in the slit in the tubular insulation will diffuse...... backwards to the cold pipe and contribute to the heat uptake of the cold tube. This part is calculated for the stationary case and compared with the sensible heat transfer through the tubular shaped insulation material, using measured dry λ values and measured fictitious moist λ values....
Heat and Mass Transfer in a Falling Film Evaporator with Aqueous Lithium Bromide Solution
Olbricht, M.; Addy, J.; Luke, A.
2016-09-01
Horizontal tube bundles are often used as falling film evaporators in absorption chillers, especially for systems working at low pressure as H2O/LiBr. Experimental investigations are carried out in a falling film evaporator consisting of a horizontal tube bundle with eighty horizontal tubes installed in an absorption chiller because of a lack of consistent data for heat and mass transfer in the literature. The heat and mass transfer mechanisms and the flow pattern in the falling film are analysed and compared with correlations from literature. The deviations of the experimental data from those of the correlations are within a tolerance of 30%. These deviations may be explained by a change of the flow pattern at a lower Reynolds number than compared to the literature.
Counterflow Regolith Heat Exchanger Project
National Aeronautics and Space Administration — The counterflow regolith heat exchanger (CoRHE) is a device that transfers heat from hot regolith to cold regolith. The CoRHE is essentially a tube-in-tube heat...
Heat transfer model for quenching by submerging
Energy Technology Data Exchange (ETDEWEB)
Passarella, D N; Varas, F [Departamento de Matematica Aplicada II, E.T.S. de Ing. de Telecomunicacion, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain); MartIn, E B, E-mail: diego@dma.uvigo.es, E-mail: fvaras@uvigo.es, E-mail: emortega@uvigo.es [Area de Mecanica de Fluidos, E.T.S. de Ing. Industriales, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain)
2011-05-01
In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.
Heat transfer unit and method for prefabricated vessel
Energy Technology Data Exchange (ETDEWEB)
Tamburello, David A.; Kesterson, Matthew R; Hardy, Bruce J.
2017-11-07
Vessel assemblies, heat transfer units for prefabricated vessels, and methods for heat transfer prefabricated vessel are provided. A heat transfer unit includes a central rod, and a plurality of peripheral rods surrounding the central rod and connected to the central rod. The plurality of peripheral rods are movable between a first collapsed position and a second bowed position, wherein in the second bowed position a midpoint of each of the plurality of peripheral rods is spaced from the central rod relative to in the first position. The heat transfer unit further includes a heat transfer element connected to one of the plurality of peripheral rods.
Energy Technology Data Exchange (ETDEWEB)
Hsieh, S.; Bonilla, C.F.
1975-01-01
Mercury vapor up to 500 psia was condensed outside a cylindrical tube in both horizontal and vertical positions. Results show consistently low heat transfer coefficients compared to Nusselt's theory. Two auxiliary mercury vapor condensers downstream of the boiler vent were used to control and safeguard the system. Constantan wires were spot welded on the surface inside the test condenser tube. The heat flux ranged from 20,000 to 45,000 Btu/h-ft/sup 2/ and the temperature differences between vapor and condensing wall from 6 to 50/sup 0/F. The condensation heat transfer coefficients, ranging from 850 to 3,500 Btu/h-/sup 0/F-ft/sup 2/, are only about 3 to 9 percent of those predicted by Nusselt's theory. Due to the positive pressure in the system for most test runs, the chance of any in-leakage of noncondensable gases into the boiler is extremely small. Since no substantial change of heat transfer rate resulted from wide variations in the heat load on the reflux condenser at some specific heat flux on the test condenser tube, the low heat transfer rate of mercury vapor condensation was not due to the presence of any non-condensable gas. The test data for high vapor pressure up to 500 psia reveal that the heat transfer coefficient is independent of the vapor pressure level. The condensation coefficients calculated based on kinetic theory are much smaller than unity and decreasewith vapor pressure. It is hypothesized that dimer content in the metal vapor phase might behave as non-condensable or semi-condensable gas and create a diffusional barrier at the vapor-liquid interface near the condensate film. This dimer vapor could be the main cause of interfacial resistance during metal vapor condensation process. 41 figures, 7 tables, 58 references. (DLC)
Heat Transfer Model for Hot Air Balloons
Llado-Gambin, Adriana
A heat transfer model and analysis for hot air balloons is presented in this work, backed with a flow simulation using SolidWorks. The objective is to understand the major heat losses in the balloon and to identify the parameters that affect most its flight performance. Results show that more than 70% of the heat losses are due to the emitted radiation from the balloon envelope and that convection losses represent around 20% of the total. A simulated heating source is also included in the modeling based on typical thermal input from a balloon propane burner. The burner duty cycle to keep a constant altitude can vary from 10% to 28% depending on the atmospheric conditions, and the ambient temperature is the parameter that most affects the total thermal input needed. The simulation and analysis also predict that the gas temperature inside the balloon decreases at a rate of -0.25 K/s when there is no burner activity, and it increases at a rate of +1 K/s when the balloon pilot operates the burner. The results were compared to actual flight data and they show very good agreement indicating that the major physical processes responsible for balloon performance aloft are accurately captured in the simulation.
Heat transfer in rotor/stator cavity
Tuliszka-Sznitko, Ewa; Majchrowski, Wojciech; Kiełczewski, Kamil
2011-12-01
In the paper we analyze the results of DNS/LES of the flow with heat transfer in the rotor/stator cavity. The rotor and the outer cylinder are heated. Computations have been performed for wide range of Reynolds numbers and aspect ratios. Computations are based on the efficient pseudo-spectral Chebyshev-Fourier method. In LES we used a Lagrangian dynamic subgrid-scale model of turbulence. Analysis allowed to check the influence of the aspect ratio and Reynolds number on the statistics and the structure of the flow. We analyzed all six Reynolds stress tensor components, turbulent fluctuations, three turbulent heat fluxes and different structural parameters which can be useful for modeling purposes. The distributions of Nusselt numbers obtained for different Re and aspect rations along disks are given. We also investigated influence of thermal Rosssby number as well as distributions of temperature along heated disk on statistics. Computations have shown that turbulence is mostly concentrated in the stator boundary layer with a maximum at the junction between the stator and the outer cylinder. The results are compared to the experimental and numerical data taken from literature.
Porous media heat transfer for injection molding
Beer, Neil Reginald
2016-05-31
The cooling of injection molded plastic is targeted. Coolant flows into a porous medium disposed within an injection molding component via a porous medium inlet. The porous medium is thermally coupled to a mold cavity configured to receive injected liquid plastic. The porous medium beneficially allows for an increased rate of heat transfer from the injected liquid plastic to the coolant and provides additional structural support over a hollow cooling well. When the temperature of the injected liquid plastic falls below a solidifying temperature threshold, the molded component is ejected and collected.
Computational fluid mechanics and heat transfer
Pletcher, Richard H; Anderson, Dale
2012-01-01
""I have always considered this book the best gift from one generation to the next in computational fluid dynamics. I earnestly recommend this book to graduate students and practicing engineers for the pleasure of learning and a handy reference. The description of the basic concepts and fundamentals is thorough and is crystal clear for understanding. And since 1984, two newer editions have kept abreast to the new, relevant, and fully verified advancements in CFD.""-Joseph J.S. Shang, Wright State University""Computational Fluid Mechanics and Heat Transfer is very well written to be used as a t
The impact of heat transfer on Murphree tray efficiency
Energy Technology Data Exchange (ETDEWEB)
Kaeser, M.; Pritchard, C.L. [University of Edinburgh (United Kingdom). Institute for Energy Systems
2006-12-15
This work features the experimental determination of heat transfer coefficients and Murphree tray efficiencies on a diabatic (heat-transferring) distillation tray. The present investigation, focussing on the impact of heat transfer on sieve tray performance, is part of a long-term project on heat integrated distillation columns (HIDiC). Heat transfer coefficients and tray efficiencies have been determined experimentally for the methanol/water system in a 150mm diameter distillation column. The heat-transferring tray was operated in both heating and cooling modes, with heat fluxes up to 50 and 100kWm{sup -2}, respectively. The experimental data from these diabatic experiments were compared with data obtained from the same column in adiabatic mode and were correlated with the vapour velocity and the heat flux to/from the tray. (author)
Burgher, J. K.; Finkel, D.; Adesope, O. O.; Van Wie, B. J.
2015-01-01
This study used a within-subjects experimental design to compare the effects of learning with lecture and hands-on desktop learning modules (DLMs) in a fluid mechanics and heat transfer class. The hands-on DLM implementation included the use of worksheets and one of two heat exchangers: an evaporative cooling device and a shell and tube heat…
Energy Technology Data Exchange (ETDEWEB)
Fetkovich, J.G.
1976-12-01
A complete system designed to measure, with high precision, changes in heat transfer rates due to fouling and corrosion of simulated heat exchanger tubes, at sea and under OTEC conditions is described. All aspects of the system are described in detail, including theory, mechanical design, electronics design, assembly procedures, test and calibration, operating procedures, laboratory results, field results, and data analysis programs.
A SINDA '85 nodal heat transfer rate calculation user subroutine
Cheston, Derrick J.
1992-01-01
This paper describes a subroutine, GETQ, which was developed to compute the heat transfer rates through all conductors attached to a node within a SINDA '85 thermal submodel. The subroutine was written for version 2.3 of SINDA '85. Upon calling GETQ, the user supplies the submodel name and node number which the heat transfer rate computation is desired. The returned heat transfer rate values are broken down into linear, nonlinear, source and combined heat loads.
Heat and mass transfer in building services design
Moss, Keith
1998-01-01
Building design is increasingly geared towards low energy consumption. Understanding the fundamentals of heat transfer and the behaviour of air and water movements is more important than ever before. Heat and Mass Transfer in Building Services Design provides an essential underpinning knowledge for the technology subjects of space heating, water services, ventilation and air conditioning. This new text: *provides core understanding of heat transfer and fluid flow from a building services perspective *complements a range of courses in building services engineering *
Method of calculating heat transfer in furnaces of small power
Directory of Open Access Journals (Sweden)
Khavanov Pavel
2016-01-01
Full Text Available This publication presents the experiences and results of generalization criterion equation of importance in the analysis of the processes of heat transfer and thermal calculations of low-power heat generators cooled combustion chambers. With generalizing depending estimated contribution of radiation and convective heat transfer component in the complex for the combustion chambers of small capacity boilers. Determined qualitative and quantitative dependence of the integrated radiative-convective heat transfer from the main factors working combustion chambers of small volume.
Heat Transfer Phenomena in Supercritical Water Nuclear Reactors
Energy Technology Data Exchange (ETDEWEB)
Mark H. Anderson; MichaelL. Corradini; Riccardo Bonazza; Jeremy R. Licht
2007-10-03
A supercritical water heat transfer facility has been built at the University of Wisconsin to study heat transfer in ancircular and square annular flow channel. A series of integral heat transfer measurements has been carried out over a wide range of heat flux, mas velocity and bulk water temperatures at a pressure of 25 MPa. The circular annular test section geometry is a 1.07 cm diameter heater rod within a 4.29 diameter flow channel.
Active chimney effect using heated porous layers: optimum heat transfer
Mehiris, Abdelhak; Ameziani, Djamel-Edine; Rahli, Omar; Bouhadef, Khadija; Bennacer, Rachid
2017-05-01
The purpose of the present work is to treat numerically the problem of the steady mixed convection that occurs in a vertical cylinder, opened at both ends and filled with a succession of three fluid saturated porous elements, namely a partially porous duct. The flow conditions fit with the classical Darcy-Brinkman model allowing analysing the flow structure on the overall domain. The induced heat transfer, in terms of local and average Nusselt numbers, is discussed for various controlling parameters as the porous medium permeability, Rayleigh and Reynolds numbers. The efficiency of the considered system is improved by the injection/suction on the porous matrices frontier. The undertaken numerical exploration particularly highlighted two possible types of flows, with and without fluid recirculation, which principally depend on the mixed convection regime. Thus, it is especially shown that recirculation zones appear in some domain areas under specific conditions, obvious by a negative central velocity and a prevalence of the natural convection effects, i.e., turnoff flow swirls. These latter are more accentuated in the areas close to the porous obstacles and for weak permeability. Furthermore, when fluid injection or suction is considered, the heat transfer increases under suction and reduces under injection. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage II (ICOME 2016)", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui
Heat and mass transfer during baking: product quality aspects
Asselman, A.; Straten, van G.; Hadiyanto, H.; Boom, R.M.; Esveld, D.C.; Boxtel, van A.J.B.
2005-01-01
Abstract Most food product qualities are developed during heating processes. Therefore the internal heating and mass transfer of water are important aspects in food processing. Heating of food products is mostly induced by convection heating. However, the number applications of convective heating in
Steady-state and transient heat transfer through fins of complex geometry
Directory of Open Access Journals (Sweden)
Taler Dawid
2014-06-01
Full Text Available Various methods for steady-state and transient analysis of temperature distribution and efficiency of continuous-plate fins are presented. For a constant heat transfer coefficient over the fin surface, the plate fin can be divided into imaginary rectangular or hexangular fins. At first approximate methods for determining the steady-state fin efficiency like the method of equivalent circular fin and the sector method are discussed. When the fin geometry is complex, thus transient temperature distribution and fin efficiency can be determined using numerical methods. A numerical method for transient analysis of fins with complex geometry is developed. Transient temperature distributions in continuous fins attached to oval tubes is computed using the finite volume - finite element methods. The developed method can be used in the transient analysis of compact heat exchangers to calculate correctly the heat flow rate transferred from the finned tubes to the fluid.
Energy Technology Data Exchange (ETDEWEB)
Haberski, R.J.; Bentz, J.C.
1979-04-01
This study was performed to establish a conceptual design and cost evaluation of an advanced technology mechanical draft wet/dry and natural draft dry cooling systems for large electric power plants using a high performance integral fin-tube heat transfer surface. This study was part of an overall DOE program to develop and demonstrate advanced concept cooling systems for large electric power plants. The results obtained show significant economic advantages compared to results previously published for conventional cooling systems. These advantages are due to the higher heat transfer and lower pressure loss which occur with the use of the selected multi-port integral fin-tubes.
Energy Technology Data Exchange (ETDEWEB)
Shamsudin, Shaiful Rizam; Salleh, M.A.A. Mohd; Rahmat, Azmi; Anuar, Mohd Arif [Universiti Malaysia Perlis (UniMAP) (Malaysia). Center of Excellence Geopolymer and Green Technology (CEGeoGTech); Harun, Mohd; Zayid, Hafizal [Malaysian Nuclear Agency, Selangor (Malaysia). Industry Technology Div.; Noor, Mazlee Mohd [Universiti Malaysia Perlis (UniMAP) (Malaysia). School of Materials Engineering
2015-05-01
AISI type 316L stainless steel was used as a heat exchanger tube material in an inter-cooler column. After less than a year of operation, severe corrosion failures occurred and a transverse opening leakage was observed on one of the heat exchanger tubes. The failed tube was carefully analyzed using various metallurgical laboratory equipments. The root cause of the tube leakage was believed due to the presence of horizontal micro and macro pores as a hydrogen gas entrapment during casting of the parent ingot. The overlapped and gaping pores formed notch on the shell side of the tube surface, and it increasingly evident when the use of a high-energy water-jet and metal brush as cleaning procedure results in an establishment of pitting type local-action corrosion cells penetrated the tube wall. As a result, corrosive fluid in the tube side dissolved into the cooling water, accelerating the corrosion process.
Hu, Wanling; Wang, Liangbi; Guan, Yong; Hu, Wenju
2017-09-01
In real application, the shape of the vortex generator has great influence on the heat transfer and flow resistance characteristics of tube bank fin heat exchanger. Therefore, the effect of the shape of the vortex generator on heat transfer performance of such heat exchanger should be considered. In this paper, the effect of three different shaped vortex generators (i.e. delta winglet, rectangular winglet and trapezoid winglet) on heat transfer intensity and secondary flow intensity of a circular tube bank fin heat exchanger was numerically studied. The results show that with increasing Re, overall average Nu and the non-dimensional secondary flow intensity Se m increase however friction factor f decreases. A corresponding relationship can be found between Nu and Se m, which indicates that the secondary flow intensity determines the heat transfer intensity in the fin-side channel of circular tube bank fin heat exchanger with different shaped vortex generators on the fin surfaces. Under the identical pumping power constrain, the optimal shape of the vortex generators is the delta winglet vortex generators for the studied cases.
Heat transfer in a confined impinging jet with swirling velocity component
Petera, Karel; Dostál, Martin
Heat transfer measurements based on an infrared experimental method (TOIRT) are compared with CFD simulations of a confined impinging jet with tangential velocity component. The tangential velocity component added to a pure impinging jet introduces into the flow field and heat transfer some similarities with real industrial processes like agitated vessels with axial-flow impellers. The tangential velocity component significantly influences the velocity field and heat transfer intensity in the stagnant region when compared to the classic impinging jet characteristics. Several turbulence models were used in numerical simulations of an agitated vessel with axial-flow impeller in a draft tube. Heat transfer coefficients at the vessel bottom were evaluated using the TOIRT method and compared with numerical results. The lateral heat conduction in the impinged wall was analysed with the conclusion that it has relatively small impact on the measured heat transfer coefficients. Quite good agreement of experimental data and simulation results was achieved concerning the size and position of the heat transfer maximum at the vessel bottom.
Heat transfer in a confined impinging jet with swirling velocity component
Directory of Open Access Journals (Sweden)
Petera Karel
2017-01-01
Full Text Available Heat transfer measurements based on an infrared experimental method (TOIRT are compared with CFD simulations of a confined impinging jet with tangential velocity component. The tangential velocity component added to a pure impinging jet introduces into the flow field and heat transfer some similarities with real industrial processes like agitated vessels with axial-flow impellers. The tangential velocity component significantly influences the velocity field and heat transfer intensity in the stagnant region when compared to the classic impinging jet characteristics. Several turbulence models were used in numerical simulations of an agitated vessel with axial-flow impeller in a draft tube. Heat transfer coefficients at the vessel bottom were evaluated using the TOIRT method and compared with numerical results. The lateral heat conduction in the impinged wall was analysed with the conclusion that it has relatively small impact on the measured heat transfer coefficients. Quite good agreement of experimental data and simulation results was achieved concerning the size and position of the heat transfer maximum at the vessel bottom.
A heat exchanger model for air-to-refrigerant fin-and-tube heat exchanger with arbitrary fin sheet
Energy Technology Data Exchange (ETDEWEB)
Singh, Varun; Aute, Vikrant; Radermacher, Reinhard [Department of Mechanical Engineering, University of Maryland, 4164 Glenn L Martin Hall, College Park, MD 20742 (United States)
2009-11-15
A new model for simulating air-to-refrigerant fin-and-tube heat exchangers, with arbitrary fin sheet which encompasses variable tube diameters, variable tube locations, variable tube pitches, internal as well as external jagged edges, variable number of tubes per bank and variable location of fin cuts, is introduced. This model is based on a segment-by-segment approach and is developed to be a general purpose and flexible simulation tool. To account for fin conduction and air propagation through the heat exchanger, it is spatially modeled on a Cartesian grid. A new methodology for air side propagation, required for arbitrary fin sheets, is introduced. The model prediction is validated against experimental data for a condenser using R410A as the working fluid. The predicted results agree within {+-}5% of overall heat load, and {+-}25% for total refrigerant pressure drop. (author)
Mahood, Hameed B.; Campbell, A. N.; Baqir, Ali Sh.; Sharif, A. O.; Thorpe, R. B.
2017-12-01
Energy usage is increasing around the world due to the continued development of technology, and population growth. Solar energy is a promising low-grade energy resource that can be harvested and utilised in different applications, such solar heater systems, which are used in both domestic and industrial settings. However, the implementation of an efficient energy conversion system or heat exchanger would enhance such low-grade energy processes. The direct contact heat exchanger could be the right choice due to its ability to efficiently transfer significant amounts of heat, simple design, and low cost. In this work, the heat transfer associated with the direct contact condensation of pentane vapour bubbles in a three-phase direct contact condenser is investigated experimentally. Such a condenser could be used in a cycle with a solar water heater and heat recovery systems. The experiments on the steady state operation of the three-phase direct contact condenser were carried out using a short Perspex tube of 70 cm in total height and an internal diameter of 4 cm. Only a height of 48 cm was active as the direct contact condenser. Pentane vapour, (the dispersed phase) with three different initial temperatures (40° C, 43.5° C and 47.5° C) was directly contacted with water (the continuous phase) at 19° C. The experimental results showed that the total heat transfer rate per unit volume along the direct contact condenser gradually decreased upon moving higher up the condenser. Additionally, the heat transfer rate increases with increasing mass flow rate ratio, but no significant effect on the heat transfer rate of varying the initial temperature of the dispersed phase was seen. Furthermore, both the outlet temperature of the continuous phase and the void fraction were positively correlated with the total heat transfer rate per unit volume, with no considerable effect of the initial temperature difference between the dispersed and continuous phases.
Boiling local heat transfer enhancement in minichannels using nanofluids
Chehade, Ali Ahmad; Gualous, Hasna Louahlia; Le Masson, Stephane; Fardoun, Farouk; Besq, Anthony
2013-03-01
This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance.
Boiling local heat transfer enhancement in minichannels using nanofluids
2013-01-01
This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance. PMID:23506445
Heat transfer assembly for a fluorescent lamp and fixture
Siminovitch, Michael J.; Rubenstein, Francis M.; Whitman, Richard E.
1992-01-01
In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure.
Heat transfer assembly for a fluorescent lamp and fixture
Siminovitch, M.J.; Rubenstein, F.M.; Whitman, R.E.
1992-12-29
In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure. 11 figs.
Convective heat transfer in porous media
Cheng, P.
Recent emerging technologies on the extraction of geothermal energy, the design of insulation systems for energy conservation, the use of aquifers for hot-water storage, the disposal of nuclear wastes in sub-seabeds, the enhanced recovery of oils by thermal methods, and the design of catalyst-bed reactors have demanded an improved understanding of heat transfer mechanisms in fluid-filled porous media. Experiments have been conducted to investigate the onset of free convection in rectangular and cylindrical enclosures filled with porous media and heated from below. The Nusselt numbers determined from these experiments during steady conditions are correlated in terms of the Rayleigh number. The data for free convection in rectangular geometries show considerable scattering among investigators using different porous media and fluids. Recently, some data has been obtained for free convect on in water-filled glass beads adjacent to a heated vertical flat plate, a horizontal cylinder and between vertical concentric cylinders. The data obtained at low Rayleigh numbers is found to be in good agreement with theoretical predictions based on Darcy's law.
Hassan, Ali; Ramzan, Naveed; Umer, Asim; Ahmad, Ayyaz; Muryam, Hina
2017-08-01
The enhancement in the convective heat transfer coefficient of the ethylene glycol (EG) base cuprous oxide (Cu2O) nanofluids were investigated. The nanofluids of different volume concentrations i-e 1%, 2.5% and 4.5% were prepared by the two step method. Cuprous oxide (Cu2O) nanoparticles were ultrasonically stirred for four hours in the ethylene glycol (EG). The experimental study has been performed through circular tube geometry in laminar flow regime at average Reynolds numbers 36, 71 and 116. The constant heat flux Q = 4000 (W/m2) was maintained during this work. Substantial enhancement was observed in the convective heat transfer coefficient of ethylene glycol (EG) base cuprous oxide (Cu2O) nanofluids than the base fluid. The maximum 74% enhancement was observed in convective heat transfer coefficient at 4.5 vol% concentration and Re = 116.
DEFF Research Database (Denmark)
Zhang, Ji; Diao, Yanhua; Zhao, Yaohua
2017-01-01
This work experimentally studied the single-phase heat transfer and pressure drop characteristics by using two heat transfer enhancement techniques (micro fin structure and nanofluids) in multiport minichannel flat tube (MMFT). MMFT consisted of numerous parallel rectangular minichannels...... and is widely used in industry as the heat transfer unit of a heat exchanger. Firstly, the enhanced heat transfer performances by individually using one enhancement technique were investigated by testing Nusselt number, friction factor and performance evaluation criterion (PEC). In this section, five MMFTs...... enhancement techniques, Nusselt number increases by up to 158% at about Re = 3600 and the maximum PEC value can reach 2.0 at Re = 5150. Finally, an optimal heat transfer scheme was proposed based on test data....
Directory of Open Access Journals (Sweden)
Kalaiselvam Sivakumar
2016-01-01
Full Text Available Free cooling is the process of storing the cool energy available in the night ambient air and using it during the day. The heat exchanger used in this work is a modular type which is similar to the shell and tube heat exchanger. The shell side is filled with Phase Change Materials (PCM and air flow is through the tubes in the module. The modules of the heat exchanger are arranged one over other with air spacers in between each module. The air space provided in between the module in-creases the retention time of the air for better heat transfer. Transient Computational Fluid Dynamics modeling is carried out for single air passage in a modular heat exchanger. It shows that the PCM phase transition time in the module in which different shape of fins is adopted. The module with rectangular fins has 17.2 % reduction in solidification compared with the plain module. Then steady state numerical analysis is accomplished to the whole module having the fin of high heat transfer, so that pressure drop, flow and thermal characteristics across the module and the air spacers are deter-mined for various air inlet velocities of 0.4 to 1.6 m/s. To validate the computational results, experiments are carried out and the agreement was found to be good.
Measurement of heat transfer coefficient using termoanemometry methods
Directory of Open Access Journals (Sweden)
Dančová P.
2014-03-01
Full Text Available This work deals with a measurement of heat transfer from a heated flat plate on which a synthetic jet impacts perpendicularly. Measurement of a heat transfer coefficient (HTC is carried out using the hot wire anemometry method with glue film probe Dantec 55M47. The paper brings also results of velocity profiles measurements and turbulence intensity calculations.
Boiling Heat-Transfer Processes and Their Application in the Cooling of High Heat Flux Devices
1993-06-01
presented previously in Eq. (8). Bjorge , et al. (Ref. 170) and Stephan and Auracher (Ref. 171) later presented variations of the superposition approach...ofHeat Transfer, Vol. 90, May 1968, pp. 239-247. 170. Bjorge , R. W., Hall, G. R., and Rohsenow, W. M. "Correlation of Forced Convection Boiling Heat... Communications on Heat Mass Transfer, Vol. 18, No.5, September-October 1991, pp. 659-667. 383. Boyd, R. D., Sr. "Critical Heat Flux and Heat Transfer
Influence of structural design condensing part of NH3 heat pipe to heat transfer
Directory of Open Access Journals (Sweden)
Vantúch Martin
2014-03-01
Full Text Available The article describes influence design heat exchangers to efficiency condensation liquid ammonia in the gravitational heat pipe. Analyse adverse factors in the operation and flow of ammonia in heat pipe. Also describes heat transfer characteristics of heat pipe in low-potential geothermal heat transport simulations.
Loop heat pipes - highly efficient heat-transfer devices for systems of sun heat supply
Energy Technology Data Exchange (ETDEWEB)
Maydanik, Yu. [Ural Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of Thermophysics
2004-07-01
Loop heat pipes (LHPs) are hermetic heat-transfer devices operating on a closed evaporation-condensation cycle with the use of capillary pressure for pumping the working fluid [1]. In accordance with this, they possess all the main advantages of conventional heat pipes, but, as distinct from the latter, have a considerably higher heat-transfer capacity, especially when operating in the ''antigravity'' regime, when heat is transferred from above downwards. Besides, LHPs possess a higher functional versatility, are adaptable to different operating conditions and provide great scope for various design embodiments. This is achieved at the expense of both the original design of the device and the properties of the wick - a special capillary structure used for the creation of capillary pressure. The LHP schematic diagram is given in Fig. 1. The device contains an evaporator and a condenser - heat exchanger connected by means of smooth-walled pipe-lines with a relatively small diameter intended for separate motion of vapor and liquid. At present loop heat pipes are most extensively employed in thermoregulation systems of spacecrafts. Miniature LHPs are used for cooling electronics and computers. At the same time there exists a considerable potential of using these devices for the recovery of low-grade (waste) heat from different sources, and also in systems of sun heat supply. In the latter case LHPs may serve as an efficient heat-transfer link between a sun collector and a heat accumulator, which has a low thermal resistance and does not consume any additional energy for pumping the working fluid between them. (orig.)
Numerical study of heat and mass transfer of ammonia-water in falling film evaporator
Bu, Xianbiao; Ma, Weibin; Huang, Yuanfeng
2012-05-01
To investigate the performance of the heat and mass transfer of ammonia water during the process of falling film evaporation in vertical tube evaporator, a mathematical model of evaporation process was developed and solved based on stream function. Then an experimental study of falling film evaporation was carried out in order to validate the mathematical model. A series of parameters, such as velocity, film thickness and concentration, etc., were obtained from the mathematical model. The calculated results show that the average velocity and the film thickness change sharp at the entrance region when x 100 mm. The film thickness depends largely on the flow rate of solution. It is observed that the heating power and mass flow of solution significantly affect the concentration difference between the inlet and outlet of evaporation tube. The calculated results reveal that the tube length has a significant impact on the amounts of ammonia vapor evaporated. It is suggested that the roll-worked enhanced tube should be used in order to decrease the concentration gradient in the film thickness direction and enhance the heat and mass transfer rate. Furthermore, the experimental and calculated results indicate that the inlet solution concentration has a great influence on the heat exchange capacity, the amounts of ammonia vapor evaporated and the evaporation pressure.
Design of shell-and-tube heat exchangers when the fouling depends on local temperature and velocity
Energy Technology Data Exchange (ETDEWEB)
Butterworth, D. [HTFS, Hyprotech, Didcot (United Kingdom)
2002-07-01
Shell-and-tube heat exchangers are normally designed on the basis of a uniform and constant fouling resistance that is specified in advance by the exchanger user. The design process is then one of determining the best exchanger that will achieve the thermal duty within the specified pressure drop constraints. It has been shown in previous papers [Designing shell-and-tube heat exchangers with velocity-dependant fouling, 34th US national Heat Transfer Conference, 20-22 August 2000, Pittsburg, PA; Designing shell-and-tube heat exchangers with velocity-dependant fouling, 2nd Int. Conf. on Petroleum and Gas Phase Behavior and Fouling, 27-31 August 2000, Copenhagen] that this approach can be extended to the design of exchangers where the design fouling resistance depends on velocity. The current paper briefly reviews the main findings of the previous papers and goes on to treat the case where the fouling depends also on the local temperatures. The Ebert-Panchal [Analysis of Exxon crude-oil, slip-stream coking data, Engineering Foundation Conference on Fouling Mitigation of Heat Exchangers, 18-23 June 1995, California] form of fouling rate equation is used to evaluate this fouling dependence. When allowing for temperature effects, it becomes difficult to divorce the design from the way the exchanger will be operated up to the point when the design fouling is achieved. However, rational ways of separating the design from the operation are proposed. (author)
Parametric study of fluid flow and heat transfer over louvered fins of air heat pump evaporator
National Research Council Canada - National Science Library
Tomasz Muszyński; Sławomir Marcin Kozieł
2016-01-01
Two-dimensional numerical investigations of the fluid flow and heat transfer have been carried out for the laminar flow of the louvered fin-plate heat exchanger, designed to work as an air-source heat pump evaporator...
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers
de Jong, Anne; Wijnant, Ysbrand H.; de Boer, Andries
2014-01-01
A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic
Heat transfer burnout of Mark VIII fuel
Energy Technology Data Exchange (ETDEWEB)
Bernath, L.
1956-08-01
The operating conditions to which the special Mark VIII quatrefoils will be exposed during the proposed piloting program have been compared with the conditions required to cause burnout, using an established method of calculating these conditions. The results of this comparison permit the following conclusions to be drawn: (1) With normal flow of coolant through the special elements the heat flux to be encountered in the R-8 cycle (1400 MW) will be 70% or that required to cause burnout (30% margin from burnout). (2) With a reduction of coolant flow to 82% of normal through one tube of a special element, burnout of that fuel column is possible in the R-8 cycle. (3) In the R-6 cycle (1280 MW), the margin from burnout in the special Mark VIII quatrefoils is 42% with full flow and 20% with the above reduced coolant flow. A similar comparison of operating conditions predicted for the L-3 cycle (full Mark VIII charge) shows that, even at the highest power level (1250 MW), the margin from burnout is greater than 55% with normal flow and 40% with reduced flow.
Nonequilibrium Fluctuational Quantum Electrodynamics: Heat Radiation, Heat Transfer, and Force
Bimonte, Giuseppe; Emig, Thorsten; Kardar, Mehran; Krüger, Matthias
2017-03-01
Quantum-thermal fluctuations of electromagnetic waves are the cornerstone of quantum statistics and inherent to phenomena such as thermal radiation and van der Waals forces. Although the principles are found in elementary texts, recent experimental and technological advances make it necessary to come to terms with counterintuitive consequences at short scales—the so-called near-field regime. We focus on three manifestations: (a) The Stefan-Boltzmann law describes radiation from macroscopic bodies but fails for small objects. (b) The heat transfer between two bodies at close proximity is dominated by evanescent waves and can be orders of magnitude larger than the classical (propagating) contribution. (c) Casimir forces, dominant at submicron separation, are not sufficiently explored for objects at different temperatures (at least experimentally). We explore these phenomena using fluctuational quantum electrodynamics (QED), introduced by Rytov in the 1950s, combined with scattering formalisms. This enables investigation of different material properties, shapes, separations, and arrangements.
Kissing heat transfer between the wraps of a scroll pump
Energy Technology Data Exchange (ETDEWEB)
Sunder, S.; Smith, J.L. Jr. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Mechanical Engineering
1996-12-31
Conductances associated with the various modes of internal heat transfer in a scroll pump are estimated. Heat transfer through transient contact between scroll wraps (kissing heat transfer) is found to be a dominant mode of heat transfer between discharge and suction sides of the pump. Such heat transfer is characterized by significant steady-state heat fluxes across the wraps of a scroll pump. Experiments on a specially instrumented scroll compressor provide evidence of significant heat fluxes across the wraps of the scroll pump. Estimation of the contact angle between wraps based on Hertzian stresses, as well as an oil film demonstrate that kissing heat transfer is a plausible mechanism of heat transfer in these pumps. Contact angles inferred from experimental data are also shown to be of the same order of magnitude as those predicted by Hertzian stress calculations. It is shown that the heat fluxes observed in the kissing heat transfer experiment are too large to be explained by convection between gas and wall in the scroll pump.
Performance Assessment in a Heat Exchanger Tube with Opposite/Parallel Wing Twisted Tapes
Directory of Open Access Journals (Sweden)
S. Eiamsa-ard
2015-02-01
Full Text Available The thermohydraulic performance in a tube containing a modified twisted tape with alternate-axes and wing arrangements is reported. This work aims to investigate the effects of wing arrangements (opposite (O and parallel (P wings at different wing shapes (triangle (Tri, rectangular (Rec, and trapezoidal (Tra wings and on the thermohydraulic performance characteristics. The obtained results show that wing twisted tapes with all wing shape arrangements (O-Tri/O-Rec/O-Tra/P-Tri/P-Rec/P-Tra give superior thermohydraulic performance and heat transfer rate to the typical twisted tape. In addition, the tapes with opposite wing arrangement of O-Tra, O-Rec, and O-Tri give superior thermohydraulic performances to those with parallel wing arrangement of P-Tra, P-Rec, and P-Tri around 2.7%, 3.5%, and 3.2%, respectively.
Heat transfer in heated industrial premises with using radiant heating system
Directory of Open Access Journals (Sweden)
Nagornova Tatiana A.
2017-01-01
Full Text Available The results of mathematical modeling of heat transfer processes in a closed air volume surrounded by enclosing constructions, heated by supplying energy to the upper contour of gas infrared radiators are represented. Regimes of turbulent natural conjugate convection in the region bounded by solid walls are investigated. Two-dimensional nonstationary problem is solved in the framework of the Navier -Stokes equations for gas and thermal conductivity for solid walls. Nonstationary processes of heat propagation in course of time and essential heterogeneity of temperature fields and heat fluxes are established.
Energy Technology Data Exchange (ETDEWEB)
Kim, Hwan Yeol; Kim, Hyung Rae; Kang, Deog Ji; Song, Jin Ho; Bae, Yoon Yeong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2008-03-15
Heat transfer experiments in an annulus passage were performed using SPHINX (Supercritical Pressure Heat transfer Investigation for NeXt generation), which was constructed at KAERI (Korea Atomic Energy Research Institute), to investigate the heat transfer behaviors of supercritical CO{sub 2}. CO{sub 2} was selected as the working fluid to utilize its low critical pressure and temperature when compared with water. The mass flux was in the range of 400 to 1200 kg/m{sup 2} s and the heat flux was chosen at rates up to 150 kW/m{sup 2}. The selected pressures were 7.75 and 8.12 MPa. At lower mass fluxes, heat transfer deterioration occurs if the heat flux increases beyond a certain value. Comparison with the tube test results showed that the degree of heat transfer deterioration in the heat flux was smaller than that in the tube. In addition, the Nusselt number correlation for a normal heat transfer mode is presented.