scholarly journals Investigation of Heat Transfer in a Large-Scale External Heat Exchanger with Horizontal Smooth Tube Bundle

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5553
Author(s):  
Artur Blaszczuk ◽  
Szymon Jagodzik
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Fluidized Bed ◽  
Tube Bundle ◽  
External Heat ◽  
Average Heat Transfer Coefficient ◽  
Average Heat ◽  
External Heat Exchanger

In the research work, energy transport between a dense fluidized bed and submerged horizontal tube bundle is analyzed in the commercial external heat exchanger (EHE). In order to investigate the heat transfer behavior, the authors carried out eight performance tests in a fluidized bed heat exchange chamber with a cross-section of 2.7 × 2.3 m in depth and width and a height of 1.3 m. The authors have been developing a mechanistic model for the prediction of the average heat transfer coefficient, which includes the effect of the geometric structure of the tube bundle and the location of the heat transfer surface on the heat transfer rate. The computational results depict that the average heat transfer coefficient is essentially affected by superficial gas velocity and suspension density rather than bed particle size. The empirical correlations have been proposed for predicting heat transfer data since the existing literature data is not sufficient for industrial fluidized bed heat exchangers. On the basis of the evaluated operating conditions of an external heat exchanger, the optimal conditions where heat transfer occurs could be deduced. The developed mechanistic heat transfer model is validated by experimental data under the examined conditions.

Study on Free Convection Heat Transfer in a Finned Tube Array

2015 ◽  
Vol 23 (01) ◽  
pp. 1550007 ◽  
Author(s):  
Ryoji Katsuki ◽  
Tsutomu Shioyama ◽  
Chikako Iwaki ◽  
Tadamichi Yanazawa
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Finned Tube ◽  
Average Heat Transfer Coefficient ◽  
Average Heat ◽  
Finned Tubes ◽  
Air Cooled Heat Exchanger ◽  
The Heat Transfer Coefficient

We have been developing a free convection air cooled heat exchanger without power supply to improve economic efficiency and mechanical reliability. However, this heat exchanger requires a larger installation area than the forced draft type air cooled heat exchanger since a large heating surface is needed to compensate for the small heat transfer by natural convection. Therefore, we have been investigating a heat exchanger consisting of an array of finned tubes and chimney to increase the heat transfer coefficient. Since the heat transfer characteristics of finned tube arrays have not been clarified, we conducted experiments with a finned tube array to determine the relation between the configuration of finned tubes and the heat transfer coefficient of a tube array. The results showed that the average heat transfer coefficient increased with pitch in the vertical direction, and became constant when the pitch was over five times the fin diameter. The average heat transfer coefficient was about 1.4 times higher than that of a single finned tube in free space. The ratio of the average heat transfer coefficient of the finned tube array with chimney to that of a single finned tube was found to be independent of the difference in temperature between the tube surface and air.

Heat Transfer between Fluidized Bed and Horizontal Bundle of Tubes in a Vertical Channel

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Mohamed A Moawed ◽  
Nabil S. Berbish ◽  
Ahmed A. Allam ◽  
Ahmed R. El-Shamy ◽  
Karam M. El-Shazly
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Fluidized Bed ◽  
Test Section ◽  
Particle Diameter ◽  
Average Heat Transfer Coefficient ◽  
Average Heat ◽  
Tube Arrangement ◽  
Transition Channel

The present work aims to study the fluidization and heat transfer characteristics around a single horizontal heated tube, in-line tubes arrangement and staggered tubes arrangement immersed in a gas fluidized bed. The experiments were carried out on a square test section column (16 cm x 16 cm x 95 cm) from a steel sheet of 3 mm thickness. Each arrangement of the tubes is installed in a separate test section. The plane tube bank for both in-line and staggered tubes arrangement consists of 5 rows and four tubes per row in equal vertical and horizontal pitch arrangement. The experimental setup has a transition channel with the same square section and 30 cm height. The other side of the transition channel has one hole of 5 mm inside diameter and 30 mm long to measure the pressure before the distributor plate. The bed material used is sand particles of different sizes (1400 µm, 1600 µm, and 1850 µm). For the tested arrangements, the results show that the average heat transfer coefficient increases with the increase of the fluidizing velocity and with the decrease in particle diameter. Also, the comparison between the in-line and staggered tube arrangement showed that, the average heat transfer coefficient in case of staggered is higher than that of the in-line tube arrangement. Moreover, empirical correlations for the average Nusselt number of the tested arrangements using the experimental data are presented.

Nucleate Boiling Characteristics of R-113 in a Small Tube Bundle

1992 ◽  
Vol 114 (2) ◽  
pp. 425-433 ◽  
Author(s):  
P. J. Marto ◽  
C. L. Anderson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Tube Bundle ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Average Heat Transfer Coefficient ◽  
Average Heat

Heat transfer measurements were made during nucleate boiling of R-113 from a bundle of 15 electrically heated, smooth copper tubes arranged in an equilateral triangular pitch. The bundle was designed to simulate a portion of a refrigeration system flooded-tube evaporator. The outside diameter of the tubes was 15.9 mm, and the tube pitch was 19.1 mm. Five of the tubes that were oriented in a vertical array on the centerline of the bundle were each instrumented with six wall thermocouples to obtain an average wall temperature and a resultant average heat transfer coefficient. All tests were performed at atmospheric pressure. The majority of the data were obtained with increasing heat flux to study the onset of nucleate boiling and the influence of surface “history” upon boiling heat transfer. Data taken during increasing heat flux showed that incipient boiling was dependent upon the number of tubes in operation. The operation of lower tubes in the bundle decreased the incipient boiling heat flux and wall superheat of the upper tubes, and generally increased the boiling heat transfer coefficients of the upper tubes at low heat fluxes where natural convection effects are important. The boiling data confirmed that the average heat transfer coefficient for a smooth-tube bundle is larger than obtained for a single tube.

Design of Miniature Liquid Cooler for LED

2011 ◽  
Author(s):  
Henrik So̸rensen ◽  
So̸ren N. Bertel
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Swirling Flow ◽  
Scale Model ◽  
Tube Length ◽  
Average Heat Transfer Coefficient ◽  
Light Emitting ◽  
Average Heat

An investigation of the average heat transfer coefficient in a heat exchanger for cooling of light-emitting diodes has been carried out by using CFD. The numerical calculations show good agreements with experimentally obtained data on a full scale model. Both CFD and experiments are carried out for Reynolds numbers in the range of 1000 to 10000, where the resulting average heat transfer coefficient is up to 5 times higher than expected values based on classical analytical expressions for the heat transfer coefficient. The explanation for the significant increase in the average heat transfer coefficient shall be found in a relative short tube length combined with a strong swirling flow inside the heat exchanger.

ANALYSIS OF METHODS FOR CALCULATING HEAT TRANSFER IN THERMOELECTRIC COOLING SYSTEMS FOR HEAT-STRESSED ELEMENTS

2021 ◽  
pp. 21-31
Author(s):  
С.В. Бородкин ◽  
А.В. Иванов ◽  
И.Л. Батаронов ◽  
А.В. Кретинин
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cooling System ◽  
Average Heat Transfer Coefficient ◽  
The Finite Element Method ◽  
Differential Heat ◽  
Average Heat ◽  
Principal Possibility

На основе уравнений теплопереноса в движущейся среде и соотношений теплопередачи в термоэлектрическом охладителе приведен сравнительный анализ методик расчета поля температуры в теплонапряженном элементе. Рассмотрены методики на основе: 1) теплового баланса, 2) среднего коэффициента теплоотдачи, 3) дифференциального коэффициента теплоотдачи, 4) прямого расчета в рамках метода конечных элементов. Установлено, что первые две методики не дают адекватного распределения поля температур, но могут быть полезны для определения принципиальной возможности заданного охлаждения с использованием термоэлектрических элементов. Последние две методики позволяют корректно рассчитать температурное поле, но для использования третьей методики необходим дифференциальный коэффициент теплоотдачи, который может быть найден из расчета по четвертой методике. Сделан вывод о необходимости комбинированного использования методик в общем случае. Методы теплового баланса и среднего коэффициента теплоотдачи позволяют определить принципиальную возможность использования термоэлектрического охлаждения конкретного теплонапряженного элемента (ТЭ). Реальные параметры системы охлаждения должны определяться в рамках комбинации методов дифференциального коэффициента теплоотдачи и конечных элементов (МКЭ). Первый из них позволяет определить теплонапряженные области и рассчитать параметры системы охлаждения, которые обеспечивают тепловую разгрузку этих областей. Второй метод используется для проведения численных экспериментов по определению коэффициента теплоотдачи реальной конструкции The article presents on the basis of the equations of heat transfer in a moving medium and the relations of heat transfer in a thermoelectric cooler, a comparative analysis of methods for calculating the temperature field in a heat-stressed element. We considered methods based on: 1) heat balance, 2) average heat transfer coefficient, 3) differential heat transfer coefficient, 4) direct calculation using the finite element method. We established that the first two methods do not provide an adequate distribution of the temperature field but can be useful for determining the principal possibility of a given cooling using thermoelectric elements. The last two methods allow us to correctly calculate the temperature field; but to use the third method, we need a differential heat transfer coefficient, which can be found from the calculation using the fourth method. We made a conclusion about the need for combined use of methods in a general case. The methods of thermal balance and average heat transfer coefficient allow us to determine the principal possibility of using thermoelectric cooling of a specific heat-stressed element. The actual parameters of the cooling system should be determined using a combination of the differential heat transfer coefficient and the finite element method. The first of them allows us to determine the heat-stressed areas and calculate the parameters of the cooling system that provide thermal discharge of these areas. The second method is used to perform numerical experiments to determine the heat transfer coefficient of a real structure

Experimental Study on Compact External Heat Exchanger for a 4 MWth Circulating Fluidized Bed Combustor

2013 ◽  
Vol 448-453 ◽  
pp. 3259-3269
Author(s):  
Zhi Wei Li ◽  
Hong Zhou He ◽  
Huang Huang Zhuang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Fluidized Bed ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cooling Water ◽  
External Heat ◽  
Circulating Ash ◽  
Fluidized Bed Combustor ◽  
External Heat Exchanger

The characteristics of the external heat exchanger (EHE) for a 4 MWth circulation fluidized bed combustor were studied in the present paper. The length, width and height of EHE were 1.5 m, 0.8 m and 9 m, respectively. The circulating ash flow passing the heating surface bed could be controlled by adjusting the fluidizing air flow and the heating transferred from the circulating ash to the cooling water. The ash flow rate passing through the heat transfer bed was from 0.4 to 2.2 kg/s. The ash average temperature was from 500 to 750 °C. And the heat transfer rate between the ash and the cooling water was between 150 and 300 W/(m2·°C). The relationships among the circulating ash temperature, the heat transfer, heat transfer rate, the heat transfer coefficient and the circulating ash flow passing through the heating exchange cell were also presented and could be used for further commercial EHE design.

scholarly journals Evaluation of Alternative Designs for a High Temperature Particle-to-sCO2 Heat Exchanger

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Clifford K. Ho ◽  
Matthew Carlson ◽  
Kevin J. Albrecht ◽  
Zhiwen Ma ◽  
Sheldon Jeter ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
High Temperature ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Fluidized Bed ◽  
Structural Reliability ◽  
Packed Bed ◽  
Heat Losses ◽  
Transient Operation

This paper presents an evaluation of alternative particle heat-exchanger designs, including moving packed-bed and fluidized-bed designs, for high-temperature heating of a solar-driven supercritical CO2 (sCO2) Brayton power cycle. The design requirements for high pressure (≥20 MPa) and high temperature (≥700 °C) operation associated with sCO2 posed several challenges requiring high-strength materials for piping and/or diffusion bonding for plates. Designs from several vendors for a 100 kW-thermal particle-to-sCO2 heat exchanger were evaluated as part of this project. Cost, heat-transfer coefficient, structural reliability, manufacturability, parasitics and heat losses, scalability, compatibility, erosion and corrosion, transient operation, and inspection ease were considered in the evaluation. An analytic hierarchy process was used to weight and compare the criteria for the different design options. The fluidized-bed design fared the best on heat transfer coefficient, structural reliability, scalability, and inspection ease, while the moving packed-bed designs fared the best on cost, parasitics and heat losses, manufacturability, compatibility, erosion and corrosion, and transient operation. A 100 kWt shell-and-plate design was ultimately selected for construction and integration with Sandia's falling particle receiver system.

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