Effect Of Tube Bundle Research Articles

Heat transfer enhancement of helical tubes during pool boiling

This research utilizes experimental measures to investigate the heat transfer mechanism of helical tubes during saturated pool boiling. Experiments were carried out using R-134a and R-513A as working fluids, with saturation temperatures of 4.4 °C and 15 °C and heat fluxes ranging from 5 to 50 kW/m2. The helical tube surface was heated by hot water with ascending heat flux. The helical test tubes used in this study are annealed smooth copper tubes with an outer diameter of 6.35 mm, tube thickness of 0.7 mm, coil diameter of 58.85 mm, number of turns of 3.5, and tube pitches ranging from 7 to 21 mm. Experimental results show that the tube bundle effect also exists in helical tubes as the boiling heat transfer coefficient obtained from helical tubes is significantly higher than that of single straight tubes predicted by the Cooper correlation. Furthermore, the boiling heat transfer coefficients obtained are greatly influenced by the tube pitch and show a tendency to increase with the decrease in tube pitch. In addition, larger and faster-moving bubbles are observed near the upper part of the helical tube due to agitations generated from the bottom part.

Heat transfer evaluation of natural convection outside the condenser in Passive Residual Heat Removal System of Molten Salt Reactor

A full scale water-cooled Passive Residual Heat Removal System was designed and built for a 2 MW Molten Salt Reactor. In the process of heating the water tank, the heat transfer characteristics of the condenser in the system had an important impact on the temperature distribution and the development of thermal stratification in the water tank. Therefore, the heat transfer characteristics of the condenser at single-phase natural convection stage need to be experimentally researched and theoretically analyzed. Aiming at the condenser in the system, a series of experiments were carried out. Considering the influence of tube bundle effect on natural convection heat transfer, a set of theories using hydraulic diameter as characteristic length were put forward and applied to analyze the experimental results, which indicated the good agreement with the previous correlations consequently. This study can provide theoretical feasibility and experimental reference for the design of commercial molten salt reactor system in the future.

Research on film condensation heat transfer of the shell side of the spiral coil heat exchanger

The theoretical basis for the calculation of shell side condensation of the spiral coil heat exchanger is weak. In order to solve the problem of pure steam film condensation heat transfer of the shell side of the spiral coil heat exchanger, the theoretical model of the homogeneous flow was established. Considering the centrifugal force, two different mathematical models were established and the heat transfer characteristics were studied. The solution formula of the heat transfer coefficient and thickness of first layer liquid film, meanwhile, was obtained. The theoretical formula of the membrane-like condensation heat transfer of the heat exchanger was worked out, based on the calculation model of the heat transfer coefficient of one-component working fluid outside the tube bundle, considering the effect of tube bundle. The two calculated results in this paper and the theoretical result of Bays and McAdams were compared with experimental values respectively. The results show that the relative error between the calculated values obtained by the two theoretical models and experimental values is 7.48% (ignoring centrifugal force), 3.05% (considering centrifugal force), while the relative error between Bays and McAdams’s result and the experimental value is 61.3%. The correctness of the theoretical models proposed in this paper are verified. The theoretical models can be used to calculate the film condensation heat transfer of the spiral coil heat exchanger.

Effectively designed shell‐tube heat exchangers considering cost minimization and energy management

AbstractCost optimization, which is expressed as a set of analytical variables, is a key objective in economic design approaches of shell‐and‐tube heat exchangers. This study has provided new design techniques based on tube bundle effect on the economic optimization design of shell‐and‐tube heat exchangers. Also the objective of this paper is to develop the cost estimating for the new modified shell‐and‐tube heat exchangers by introducing new objective functions. According to the results the best configuration choice will obviously be the one with the least irreversibility, that is, with the lowest exergy destruction rate and lower annual capital cost. Also, the combined reduction of annual capital investment and operating cost by the new design technique led to a decrease in the overall costs of about 10% to 24% in comparison with original design. So the proposed design technique shows potential for improvement and economic optimization of shell‐and‐tube heat exchangers.

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.

水平円柱下流の気液界面積濃度分布の遷移

Measurements of the interfacial area concentration and the void fraction in a vertical upward air-water two-phase flow downward of single horizontal tube and horizontal tube bundle were carried out by a double sensor electrical conductivity probe. The test section comprised a 50mm × 50mm square channel partially obstructed by the single horizontal tube and the horizontal tube bundle inside. Five types of the test sections which the horizontal tube arrangement is different were used to provide various distributions of air-water two-phase flow downstream of the test section. The superficial gas velocity and superficial liquid velocity ranged from 0.02 to 0.20 m/s and from 0.13 to 0.53 m/s, respectively. Local flow measurements were performed at the three axial locations of z (z') = 110 (70), 340 (300), and 640 (600) mm and the transverse locations from r = 3 to 25 mm. The single horizontal tube and the horizontal tube bundle effect the distributions of the interfacial area concentration and the void fraction at z (z') = 110 (70). This effect was decreased along the flow direction due to the diffusion of bubble toward horizontal direction. At high gas flow rate conditions, void fraction increase, while interfacial area concentration decrease with increasing gas flow rate because of the bubble coalescence.

Condensation in a vertical tube bundle passive condenser – Part 2: Complete condensation

An experimental study of the tube bundle effect on heat removal capabilities in complete condensation mode of a passive condenser was performed. A full scale test section, with four condenser tubes, was designed and constructed to simulate operating conditions of a passive containment cooling system. For complete condensation analysis, pure steam was supplied to the test section and heat transfer properties were measured for pressure from 100 to 280 kPa. The condensation heat transfer results were similar to the findings from single tubes, except for a slightly higher condensate mass flux. This was determined to be a result of turbulent mixing in the secondary boiling water caused by the tube bundle.

Bundle effect of ammonia/lubricant mixture boiling on a horizontal bundle with enhanced tubing and inlet quality

Shell-side heat transfer coefficients of individual tubes for ammonia/lubricant mixture boiling on a 3 × 5 enhanced tube bundle were measured, enabling a detailed study of tube bundle effect under the influences of inlet quality, concentration of miscible lubricant (co-polymer of polyalkylene glycol, PAG), saturation temperature, and heat flux. Tests were conducted in the range of heat flux from 3.2 to 32.0 kW/m 2, simulated inlet quality from 0.0 to 0.4, saturation temperature from −13.2 to +7.2 °C, and lubricant concentration from 0 to 10%. The data show that bundle effect is more significant at a higher saturation temperature. Most of the data in the bottom row are lower than the single-tube heat transfer coefficient data at a low saturation temperature. Lubricant renders the heat transfer coefficient lower in lower rows and higher in higher rows, therefore a larger range of data variation.

Experimental investigation on ammonia spray evaporator with triangular-pitch plain-tube bundle, Part I: tube bundle effect

The experiment of spray evaporation of ammonia was conducted using spray nozzles distributing liquid ammonia downward onto a horizontal, 3–2–3 triangular-pitch plain-tube bundle. Heat transfer performance of individual tubes in the tube bundle was studied by changing saturation temperature, heat flux, spray flow rate, nozzle height, and nozzle type. The present data suggest that the tube bundle effect is less significant at a lower saturation temperature, a lower spray flow rate, a smaller nozzle height, and with standard-angle compared with wide-angle nozzles. Mechanism causing variation of individual tubes' heat transfer performance was studied. Results were compared with ammonia spray evaporation in a square-pitch plain-tube bundle.

Heat transfer in nucleate boiling outside horizontal tube bundles. 2nd report Prediction for tube bundle effect.

Heat transfer in nucleate boiling from a tube in a horizontal bundle deviates from that on a single tube in a pool. This difference refers to the tube bundle effect for brevity, which implies enhancement or deterioration in heat transfer. This paper presents a predictive method for enhanced heat transfer by adopting a model similar to that proposed by Mikic and Rohsenow for pool boiling, in which heat is transferred by two convective components, one due to generating bubbles and another due to flowing bubbles, and the latter contribution accounts for the enhancement of heat transfer in a tube bundle. The prediction for various bundles of different numbers of tubes in a vertical row and for different distributions of heat flux reproduces well the experimental data in the whole range of heat flux supplied to the tube concerned under various pressures.

The Influence of Bypass Channels on the Laminar Flow Heat-Transfer and Fluid Friction Characteristics of Shell and Tube Heat Exchangers

This paper discusses the effect of tube bundle to shell clearance, mean oil temperature, mean water temperature, and oil flow rate on the shell-side heat-transfer film coefficients and pressure losses for laminar flow in unbaffled and cross-baffled heat exchangers. The results for cross-baffled heat exchangers can be correlated by considering the flow to be a combination of flows parallel to the tubes and across the tubes.