Vertical Tube Condenser Research Articles

Comparison of theoretical methods for describing the heat transfer in vertical tube condensers under conditions corresponding to the condensation of flue gas from a biomass boiler

Abstract A theoretical and experimental study was conducted on water vapor condensation in a vertical tube condenser under conditions corresponding to the condensation of flue gas from biomass boiler where flue gas is considered as a mixture of water vapor and a high content of noncondensable gas (NCG). Four fundamental theoretical methods were identified to determine the heat transfer coefficient and condenser heat output - Empirical correlations, Heat and mass transfer analogy, Diffusion layer theory, Boundary layer theory. These methods were compared with respect to usability in the design of flue gas condensers in energy systems and experimentally verified. Experiments were carried out in a 1.5 m long vertical double-pipe condenser with a condensing gas flowing downward in an inner tube with a diameter of 25 mm. The mass concentration of NCG in a mixture with water vapor ranged from 11 to 86 vol.% and the inlet Reynolds number of the condensing gas ranged from 1936 to 14408, which corresponds with the conditions of condensing flue gas from biomass boilers. The boundary layer theory is very complex and impractical for the calculation of heat exchangers. Empirical correlations have a wide dispersion of the result, because they take into account only the basic parameters of the process. However, Heat and mass transfer analogy and Diffusion layer theory seem to be the most suitable for flue gas condensers since they capture the physical essence of the phenomena.

Effect of flow velocity on the process of air-steam condensation in a vertical tube condenser

This article describes the influence of flow velocity on the condensation process in a vertical tube. For the case of condensation in a vertical tube condenser, both the pure steam condensation process and the air-steam mixture condensation process were theoretically and experimentally analyzed. The influence of steam flow velocity on the value of the heat transfer coefficient during the condensation process was evaluated. For the condensation of pure steam, the influence of flow velocity on the value of the heat transfer coefficient begins to be seen at higher speeds, conversely, this effect is negligible at low values of steam velocity. On the other hand, for the air-steam mixture condensation, the influence of flow velocity must always be taken into account. The flow velocity affects the water vapor diffusion process through non-condensing air. The presence of air significantly reduces the value of the heat transfer coefficient. This drop in the heat transfer coefficient is significant at low velocities; on the contrary, the decrease is relatively small at high values of the velocity.

Research of Interficial Shear effects on Heat Transfer Characteristics of Complete Condensation in Vertical Tube

The effects of interficial shear between liquid film and flowing-steam cannot be neglected during the steam condensation process in vertical tubes, and the Nusselt condensation model should be modified. In this paper, the heat transfer characteristics of steam condensation in vertical tube were investigated by experiments. Both the Nusselt theoretical model and the modified model considering interficial shear effects were adopted and compared with the experimental measurements. The results show that interfacial shear stress have significant influence on the liquid film flow state and thin liquid film thickness, which further results in higher condensation heat transfer coefficient. As the modified model considers interficial shear correctly, and its calculation results agree well with the experimental results.

Condensation of the air-steam mixture in a vertical tube condenser

This paper deals with the condensation of water vapour in the presence of non-condensable air. Experimental and theoretical solutions of this problem are presented here. A heat exchanger for the condensation of industrial waste steam containing infiltrated air was designed. The condenser consists of a bundle of vertical tubes in which the steam condenses as it flows downwards with cooling water flowing outside the tubes in the opposite direction. Experiments with pure steam and with mixtures of steam with added air were carried out to find the dependence of the condensation heat transfer coefficient (HTC) on the air concentration in the steam mixture. The experimental results were compared with the theoretical formulas describing the cases. The theoretical determination of the HTC is based on the Nusselt model of steam condensation on a vertical wall, where the analogy of heat and mass transfer is used to take into account the behaviour of air in a steam mixture during the condensation process. The resulting dependencies obtained from the experiments and obtained from the theoretical model have similar results. The significant decrease in the condensation HTC, which begins at very low air concentrations in a steam mixture, was confirmed.

Experimental analysis of steam condensation in vertical tube with small diameter

Thermal design of tubular heat exchanger based on condensation heat of water steam requires knowledge of condensation heat transfer in the each tube. This paper is just aimed on experimental analysis of steam condensation in vertical copper tube in length of 1285mm with 2.0mm inner diameter and 0.5mm wall thickness. Experimental measurement is performed in 12 steps with variable inlet temperature and mass flow rate of water steam. The heat transfer coefficient on the inner surface of tube in condensation zone is calculated by Thermal resistance method and Wilson plot method. The correlation quality of results obtained from both methods is 98.8%. The results are compared with other experimental studies and also correlated with five chosen equations for prediction of condensation heat transfer coefficient. The correlation quality of results obtained from this experimental analysis and four tested equations is over 96.6%, only theoretically determined Nusselt equation undervalues condensation heat transfer coefficient as is known. The Nusselt equation does not take to account waves on condensate surface. These waves on condensate surface are caused by flow of water steam in tube and the wave’s effect is approximately 20.5% in this presented case.

RETRACTED: Visualization experiments on the condensation process in the vertical tube condenser of a loop thermosyphon

RETRACTED: Visualization experiments on the condensation process in the vertical tube condenser of a loop thermosyphon

Modeling of condensation heat transfer for a PRHRS heat exchanger in a SMART-P plant

A theoretical model using a heat and mass transfer analogy and a simple model using Lee and Kim's [Lee, K.-Y., Kim, M.H., 2008a. Experimental and empirical study of steam condensation heat transfer with a noncondensable gas in a small-diameter vertical tube. Nucl. Eng. Des. 238, 207–216] correlation were developed to investigate steam condensation in the presence of a noncondensable gas inside a vertical tube submerged in pool water. Rohsenow's correlation was used to consider the secondary pool-boiling heat transfer. Both models were assessed with the experimental data of Oh and Revankar [Oh, S., Revankar, S.T., 2005a. Investigation of the noncondensable effect and the operational modes of the passive condenser system. Nucl. Technol. 152, 71–86; Oh, S., Revankar, S.T., 2005b. Effect of noncondensable gas in a vertical tube condenser. Nucl. Eng. Des. 235, 1699–1712; Oh, S., Revankar, S.T., 2005c. Complete condensation in a vertical tube passive condenser. Int. Commun. Heat Mass Trans. 32, 593–602; Oh, S., Revankar, S.T., 2005d. Analysis of the complete condensation in a vertical tube passive condenser. Int. Commun. Heat Mass Trans. 32, 716–727; Oh, S., Revankar, S.T., 2006. Experimental and theoretical investigation of film condensation with noncondensable gas. Int. J. Heat Mass Trans. 49, 2523–2534; Oh, S., Gao, H., Revankar, S.T., 2007. Investigation of a passive condenser system of an advanced boiling water reactor. Nucl. Technol. 158, 208–218] for low pressure and Kim [Kim, S.J., 2000. Turbulent film condensation of high pressure steam in a vertical tube of passive secondary condensation system. Ph.D. dissertation, Korea Advanced Institute of Science and Technology] for high pressure, which were obtained from in-tube steam condensation with air in the pool water. These models predicted the data of Oh and Revankar well, but they slightly underestimated the data of Kim. The design of the Passive Residual Heat Removal System (PRHRS) condensation heat exchanger was evaluated with the theoretical model at real operating conditions (e.g., secondary pool-boiling, high system pressure). The PRHRS condensation heat exchanger designed was estimated to remove sufficiently the remaining heat in a reactor during a major accident.

06/00706 Effect of non-condensable gas in a vertical tube condenser: Oh, S. and Revankar, S. T. Nuclear Engineering and Design, 2005, 235, (16), 1699–1712.

06/00706 Effect of non-condensable gas in a vertical tube condenser: Oh, S. and Revankar, S. T. Nuclear Engineering and Design, 2005, 235, (16), 1699–1712.

A model for the performance of a vertical tube condenser in the presence of noncondensable gases

Some proposed vertical tube condensers are designed to operate at high noncondensable fractions, which warrants a simple model to predict their performance. Models developed thus far are usually not self-contained as they require the specification of the wall temperature to predict the local condensation rate. The present model attempts to fill this gap by addressing the secondary side heat transfer as well. Starting with a momentum balance which includes the effect of interfacial shear stress, a Nusselt-type algebraic equation is derived for the film thickness as a function of flow and geometry parameters. The heat and mass transfer analogy relations are then invoked to deduce the condensation rate of steam onto the tube wall. Lastly, the heat transfer to the secondary side is modelled to include cooling by forced, free or mixed convection flows. The model is used for parametric simulations to determine the impact on the condenser performance of important factors such as the inlet gas fraction, the mixture inlet flowrate, the total pressure, and the molecular weight of the noncondensable gas. The model performed simulations of some experiments with pure steam and air-steam mixtures flowing down a vertical tube. The model predicts the data quite well. The model described also provides a basis under which the presence of aerosol particles in the gas stream could be analyzed.

Hybrid Evaporative – Condenser Cooling Tower

Abstract The need to save energy in power producing and power consuming systems and the fact that evaporative cooling is the most efficient method for heat rejection led to the design and testing of a model of a special cooling tower, fn this hybrid system an evaporative condenser is being built into the cooling tower and the advantages of evaporative cooling are combined with those of a wet cooling tower, causing a lower condensing temperature or saving heat transfer area or both. The present work not only deals with the development of a practical model of a cooling tower module but also further develops, modifies and consolidates a computer program originally designed for horizontal finned or bare tube condensers. These modifications are associated with the vertical tube condenser in the hybrid tower considered in this work. It is shown that the performance of the model tower can be predicted by use of this computer program, as previously shown by Leidenfrost and Korenic for a different geometry. It is ...