Vertical Tube Bundle Research Articles

Natural circulation heat transfer model development over vertical tube bundle in the condensate heat exchanger

A 330MWt integral type nuclear power plant, SMART, was developed for electricity generation and seawater desalination. Advanced design concepts were adopted such as an integral arrangement of the major components, and a passive residual heat removal system (PRHRS) to enhance the safety capability. The TASS/SMR code was developed using various thermal-hydraulic models reflecting the design features of SMART, such as the condensate heat exchanger in the passive residual heat removal system. The development and validation of the condensate heat exchanger model were performed using POSTECH and IIT heat transfer test results. The TASS/SMR code predicted well or slightly under-predicted the heat transfer coefficient at the condensate heat exchanger shell side compared with the experimental data. The heat transfer correlation considering the tube bundle effect improved the prediction of the heat transfer for a vertical tube bundle geometry.

Heat transfer correlation between Molten Salts and helical-coil tube bundle Steam Generator

A Computational Fluid Dynamic (CFD) modelling able to describe a discharge process of a Molten Salts (MS) Thermal Energy Storage system with integrated Steam Generator (TES-SG) is presented in this paper. This simulation model has been validated with experimental results obtained at the PCS Facility located at the ENEA Casaccia Research Centre in Rome. The numerical results of this model (MS velocities, temperatures and boundary heat flux distributions within the SG) have been used to derive a dimensionless form for describing fluid flow, by Reynolds number, Re, and heat transfer between MS and helical-coil tube bundle SG, by Nusselt number, Nu. The obtained correlation is: Nu=0.3146Re0.54Pr0.36, where Re and Nu are based on the outer diameter of the helical coils. It is valid for 400 to 1200 Reynolds numbers, 4 to 11 Prandtl numbers, an average winding angle of 2° and an outer diameter of the helical coils of 0.0127m. The correlation here proposed can be very useful for sizing a vertical helical-coil tube bundle SG immersed in a Molten Salts tank of a commercial CSP plant for a specific nominal power.

Assessment of RELAP5/MOD3.3 condensation models for the tube bundle condensation in the PCCS of ESBWR

The passive containment condenser system (PCCS) in an ESBWR reactor consists of vertical tube bundle submerged in a large pool of water. The condensation model for the PCCS in a thermalhydraulics code RELAP5/MOD3.3 consists of the default Nusselt model and an alternate condensation model from UCB condensation correlation. An assessment of the PCCS condensation model in RELAP5/MOD3.3 was carried out using experiments conducted on a single tube and tube bundle PCCS tests at Purdue University. The experimental conditions were simulated with the default and the alternate condensation models in the REALP5/MOD3.3 beta version of the code. The default model and the UCB model (alternate model) give quite different results on condensation heat transfer for the PCCS. The default model predicts complete condensation well whereas the UCB model predicts the through flow condensation well. Based on this study it was found that none of the models in REALP5 can predict complete condensation as well as the through flow condensation well.

Magnetic Field Structures in a Facular Region Observed by THEMIS and Hinode

The main objective of this paper is to build and compare vector magnetic maps obtained by two spectral polarimeters, i.e. THEMIS/MTR and Hinode SOT/SP, using two inversion codes (UNNOFIT and MELANIE) based on the Milne-Eddington solar atmosphere model. To this end, we used observations of a facular region within active region NOAA 10996 on 23 May 2008, and found consistent results concerning the field strength, azimuth and inclination distributions. Because SOT/SP is free from the seeing effect and has better spatial resolution, we were able to resolve small magnetic polarities with sizes of 1" to 2", and we could detect strong horizontal magnetic fields, which converge or diverge in negative or positive facular polarities. These findings support models which suggest the existence of small vertical flux tube bundles in faculae. A new method is proposed to get the relative formation heights of the multi-lines observed by MTR assuming the validity of a flux tube model for the faculae. We found that the Fe 1 6302.5 \AA line forms at a greater atmospheric height than the Fe 1 5250.2 \AA line.

Condensation in a vertical tube bundle passive condenser – Part 1: Through flow condensation

An experimental study and a boundary layer analysis were performed for the steam condensation in a vertical tube bundle passive condenser operating in a through flow mode. Four condenser tubes were submerged in a water pool and the heat from the condenser tube was removed through boiling. Experimental data were obtained for various system pressures (100–170 kPa), inlet steam flow rates (15–47 g/s) and non-condensable gas concentration (0–15%). The experimental results showed substantial deterioration in condensation when non-condensable gas was present. With increase in steam flow rate and system pressure the condensate rate increased. The boundary layer thickness and non-condensable gas concentration increased along the condenser tube length.

Waste heat recovery in the production of furnace-grade phosphoric acid

Abstract In order to improve energy conservation and environmental protection, an improved process for the production of furnace-grade phosphoric acid and new phosphoric furnace with heat recovery is proposed. This process succeeds in recovering and utilizing thermal energy released by the combustion of elemental phosphorus. As a result, the special steam boiler and plate heat exchanger used in the conventional process are not required. The combustion chamber, consisting of a vertical tube bundle, itself provides a heat exchange surface and the cooling water is circulated in a system consisting of a drum, downtakes, lower manifold, ascending tubes, upper manifold and collecting tubes. An energy and exergy analysis of the overall process reveals the energy and exergy distribution in the preparation of furnace-grade phosphoric acid and illustrates the effect on energy conservation. Some structural shortcomings of the new phosphoric furnace to be overcome are also analyzed and corresponding recommendations a...

F121 流動層内垂直管群周りの伝熱・流動特性

F121 流動層内垂直管群周りの伝熱・流動特性

The formation and behavior of fog in a tube bundle condenser

The formation and behavior of fog during partial condensation of humid air in a vertical tube bundle condenser has been investigated. For this purpose a special glass condenser has been constructed which allows to measure the aerosol parameters everywhere along the cooling tubes using an optical aerosol measurement system. At the operation conditions adjusted in the present work fog occurs only in the presence of foreign nuclei by heterogeneous nucleation. It is shown, that the total mass of fog being formed was not influenced by the number concentration of foreign nuclei. The formation of fog occurs immediately after the first contact of the humid air with the cooling wall due to local supersaturation. After the fog has been formed in the entry of the condenser, a strong decrease of fog particles has been observed further down with the total amount of fog being constant. The effect of various process settings on the resulting aerosol parameters has been investigated. Both simple and rigorous one-dimensional calculations and complex multi-dimensional simulations using CFD were carried out for the interpretation of experimental data. Although the multi-dimensional simulations showed strong local effects the one-dimensional models were suitable to predict the conditions for fog formation.

Criteria to Prevent Heat Duty Deterioration in Vertical Shell-and-Tube Heat Exchangers

In this paper, the impact of free convection on the stability of turbulent flows in the tube of a vertical tube bundle is examined and criteria for the onset of back flow are given. This has been accomplished by a one-dimensional approach to the system based on a simple momentum balance.

Preventing Heat Duty Loss in Vertical Shell and Tube Heat Exchangers

In this paper the impact of mixed convection on the stability of turbulent flows in the tubes of a vertical tube bundle is examined. This has been accomplished by a one dimensional approach to the system based on a simple momentum balance.

96/06368 Heat transfer between a vertical tube bundle and fine particles in a CFB downcomer with and without circulation of solids

96/06368 Heat transfer between a vertical tube bundle and fine particles in a CFB downcomer with and without circulation of solids

Heat transfer between a vertical tube bundle and fine particles in a CFB downcomer with and without circulation of solids

This paper reports experimental data on the heat transfer between an electrically heated vertical finned tube bundle and cracking catalyst, fluidized with air in the downcomer of a circulating fluidized bed system. The effects of the air fluidizing velocity, bed temperature and external recirculation of solids were investigated. We were particularly interested in low gas velocities in the downcomer. Up to a 40% increase in the heat transfer coefficient at low fluidizing velocity in the downcomer was obtained with the external recirculation of solids. This may be the result of increasing particle movement and mixing in the downcomer due to the external recirculation of solids. However, at higher fluidizing velocity in the downcomer, an increase in the external recirculation of solids had a smaller effect on the heat transfer coefficient. The measurements are not as complete as would be desirable as the equipment was fabricated simply to heat the recirculating solids. Nevertheless, features of the results may be of interest to designers.

A study of a high effeciency condenser in a heat pump. The development of an EHD condenser.

In FY 1984, a national project called " The Development of a Super Heat Pump Energy Accumlation System" had been started by the MOON LIGHT PROJECT PROMOTION OFFICE of the Agency of Industrial Science and Technology. In this project, experimental study was carried out for a practical condenser by utilizing EHD phenomena. This report introduces results of the EHD effect on a vertical tube with three types of electrode at atmospheric pressure, and results of the EHD effect on a vertical tube bundle at high pressure. As a result, the condensation heat transfer coefficients of three types of electrode have been increased over about 3-4.2. Also, the condensation heat transfer of tube bundle has been achieved at the level of a single tube.

Heat and mass transfer in commercial desorbers with a heating surface in the form of a vertical tube bundle and a thermofluidized heat-carrier bed

A mathematical model is presented of heat and mass transfer in a thermofluidized bed in the thermal regeneration of synthetic zeolites. Theoretical data are compared with experimental results.

Heat transfer from a vertical tube bundle under natural circulation conditions

A rectangular loop (thermosyphon) was used to measure the average heat transfer coefficients for water at atmospheric pressure under natural circulation conditions. A twenty-one tube bundle with tubes 1.65 m long and 9.55 mm in diameter, and a pitch-to-diameter ratio of 1.33, was used as a test heat exchanger in one of the vertical legs of the loop. A natural circulation flow in the loop developed due to buoyancy differences of the fluid in its two vertical legs. Flow visualization experiments were performed to determine the flow regimes associated with natural circulation flow longitudinal to a tube bundle. Empirical correlations for the average Nusselt number have been developed and are reported. Grid spacers arranged on tube bundles were shown to enhance heat transfer, especially for laminar flow, without any noticeable increase in pressure drop.

High pressure heat transfer investigations for fluidized beds of large particles and immersed vertical tube bundles

The overall heat transfer coefficient, h w, is measured for vertical tube bundles in fluidized beds of glass beads ( ƌ p = 1.25 and 3.10 mm) and sands ( ƌ p = 0.794 and 1.225 mm) at pressures of 1.1, 2.6,4.1 and 8.1 MPa and ambient temperature. Tube bundles of three different pitches (19.5, 29.3 and 39.0 mm) are employed and h w is reported as a function of velocity, G. It is found that h w increases with pressure, to a lesser extent with tube pitch, and with an increase in particle diameter. The experimental data are compared with the predictions of four theories for h w and two theories of h w,max. It appears that the theory of Ganzha et al. is most successful in reproducing the experimental data and it is recognized that the knowledge of reliable bed voidage at the heat transfer surface and in the bulk is crucial for its applicability.

Pilot and full-scale research on the vapour compression desalination process

Pilot scale tests were carried out in order to learn more about the vapour compression process at moderately high temperature (around 100°C). On the basis of the results obtained, a demonstration plant (about 240 m 3/d) was built in order to test the actual validity of the process developed. Using a new type compressor the energy consumption was satisfactorily low. By the use of a vertical tube bundle with falling brine film established by screw distributors, it was also possible to obtain high overall heat transfer coefficients.

Fluidized bed and freeboard heat transfer studies with vertical tube bundles

Heat transfer coefficients between fluidized sand beds ( d p = 222, 488 and 778 μ m ) and a bundle of six vertical stainless steel tubes ( D T = 25.4 mm ) are measured as a function of air fluidizing velocity in the maximum temperature range of 311–475K. The results are interpreted to infer the dependence of heat transfer coefficient on gas velocity, bed temperature and particle diameter. Freeboard heat transfer is also investigated by employing a bundle of six nested vertical hair-pin tubes ( D T = 12.7 mm ). Heat transfer coefficient is found to decrease to a minimum value as the gas velocity is increased but thereafter increases slowly with increase in gas velocity. The dependence of heat transfer coefficient on temperature in the range investigated here is found to be weak.

Fluidization studies in large gas—solid systems Part V. Long and short term pressure instabilities

Long and short term variations in overall bed pressure drop and also pressure non-uniformities at the base of a 1.2 × 1.2 m square cross-section fluidized bed have been investigated for a range of fluidizing conditions. The results obtained are explained in terms of the probable solid flow patterns within the bed. The marked effect of a vertical tube bundle on long term pressure non-uniformity was observed; in contrast, no effect was noted when distributor pressure drop was increased approximately fivefold.

The condensation of nitrogen vapor on the surfaces of vertical tube bundles

The condensation of nitrogen vapor on the surfaces of vertical tube bundles