Condenser Tubes Research Articles

Replacement of Present Conventional Condenser of Household Refrigerator by Louver Fin Micro-Channel Condenser

In this paper, numerical simulation of wire on tube condenser and louver fin micro-channel heat exchanger is discussed. Simulation data of both heat exchangers were compared with the experimental data, and they show good agreement. In case of louver fin micro-channel heat exchanger, prediction error of heat capacity was within ± 5%. In addition, from the result of simulation, it was found that, for same thermal performance, micro-channel heat exchanger occupies less space as well as requires less refrigerant charge than wire on tube condenser. Therefore, in this paper, two louver fin micro-channel condensers are proposed to replace wire on tube condenser of household refrigerator. Response surface methodology was used to find out the optimal condition of the louver fin micro-channel condenser.

Experimental Investigation of Condensation Heat Transfer Characteristics of R-134a Vapor in Horizontal Heat Exchanger

An experimental investigation of refrigerant R-134a two-phase flow condensation heat transfer coefficient and pressure drop in condenser tube section of refrigeration system under different operating conditions is presented. The experimental and theoretical investigations are based on test conditions in range of 10 -17 kW/m2 for heat flux, 42-63 kg/m2s for mass flux, vapor quality 1-0.03 and saturation temperature 44 to 49˚C. The experimental tests are conducted on test rig supplied with a test section to simulate the water cooled double pipe heat exchanger, which is designed and constructed in the present work. “The experimental results have revealed that, the heat flux and mass flux have significant impacts on the heat transfer coefficient. “The heat transfer coefficient was increased with increase in heat flux and mass flux at prescribed test conditions, where the enhancement in heat transfer coefficient was about 47% and 14% for relatively higher heat flux and mass flux, respectively. “The enhancement in the heat transfer coefficient was about 51% for relatively lower saturation temperature 45.97˚C and 43% for higher vapor quality 0.88 compared to other values at constant test conditions. “The pressure drop was higher in the range of 12% and 49% for relatively higher mass flux and heat flux respectively. “The present work results have validated by comparison with predictive models and with similar research work results and the comparison has revealed an acceptable agreement.

Thermal design, rating and second law analysis of shell and tube condensers based on Taguchi optimization for waste heat recovery based thermal desalination plants

The present work discusses the design and selection of a shell and tube condenser used in Low Temperature Thermal Desalination (LTTD). To optimize the key geometrical and process parameters of the condenser with multiple parameters and levels, a design of an experiment approach using Taguchi method was chosen. An orthogonal array (OA) of 25 designs was selected for this study. The condenser was designed, analysed using HTRI software and the heat transfer area with respective tube side pressure drop were computed using the same, as these two objective functions determine the capital and running cost of the condenser. There was a complex trade off between the heat transfer area and pressure drop in the analysis, however second law analysis was worked out for determining the optimal heat transfer area vs pressure drop for condensing the required heat load.

Condensation Heat Transfer and Pressure Drop of R-404A in 7.0 mm O.D. Smooth and Microfin Tube at Low Mass Fluxes

R-404A condensation heat transfer and pressure drop data are provided for 7.0[Formula: see text]mm O.D. smooth and microfin tubes. Tests were conducted for a range of mass fluxes (from 80 to 200[Formula: see text]kg/m2s) and quality (from 0.2 to 0.8). The heat flux was 6[Formula: see text]kW/m2 and saturation temperature was 45[Formula: see text]C. It was found that both the heat transfer enhancement factor and the pressure drop penalty factor increase as mass flux increases. The range of pressure drop penalty factor (0.99–1.27) was smaller than that of heat transfer enhancement factor (1.21–1.96). Smooth tube heat transfer coefficients and pressure drops are reasonably predicted by Shah [An improved and extended general correlation for heat transfer during condensation in plain tubes, Int. J. HVAC&R Res. 15 (2009) 889–913] and Jung and Radermacher [Prediction of pressure drop during horizontal annular flow boiling of pure and mixed refrigerants, Int. J. Heat Mass Transfer 32 (1989) 2435–2446] correlation, respectively. For the microfin tube, however, all the existing correlations do not adequately predict the present data. Poor predictions may be attributed to the lack of R-404A and low mass flux data in their database.

Method for evaluating the effect of inclination on the performance of large flattened-tube steam condensers with visualization of flow regimes

An experimental study of convective steam condensation inside a large, inclined, flattened-tube air-cooled condenser for power plants is presented. This is the second of a four-part group of papers. The first part presents pressure drop and visualization results, while this study presents the experimental method along with heat transfer results. Follow-up papers present further heat transfer results and the effect of inclination.The condenser in this study is steel with brazed aluminum fins. The condenser measures 10.72 m in length, with a cross section of 214 mm × 16 mm. The condenser tube was cut in half lengthwise and covered with a polycarbonate viewing window in order to provide visualization access simultaneously with the heat transfer measurements. Inlet steam mass flux ranged from 6.2 to 9.5 kg m−2 s−1, and condenser capacity varied from 25 to 31 kW. The angle of inclination was varied from horizontal to 75° downward. The experiments were performed with a uniform fin-face velocity of crossflowing air at 2.2 m/s.Condenser capacity was found to increase linearly with increasing downward inclination angle of the condenser, at a rate of 0.041% per degree of inclination below horizontal. This improvement was found to be the result of improved drainage and increased void fraction near the condenser outlet.

Numerical Simulation and Optimization of the Screwed Tube Slot Pitch in New Condenser Tube Slot

In order to improve the heat transfer efficiency of the condenser, a new type of heat exchange tube has been adopted. The heat transfer effect of the new heat exchange tube was further improved because of the screwed pipe. However, due to the complex flow in the condenser, research on this new type of heat exchange tube is mostly in the theoretical stage. In this paper, we present a numerical simulation approach to optimize the slot pitch and verify the results by experiment.

Study on Temperature and Stress of Hydration Heat of Mass Concrete in Arch Bridge Bearing Platform

Through the simulation of finite element construction, the temperature and stress of hydration heat in mass concrete construction of arch bridge bearing platform were analyzed, and the necessity of setting condenser tube for temperature control was put forward. Based on the monitoring of the site construction of the mass concrete, the temperature and stress of the concrete under the corresponding temperature were obtained when concrete pouring into the mold, and were compared with the theoretical calculation data. Results showed the expected effect was achieved. Practice shows that the temperature control measures for the bridge are effective, and no concrete cracks were found in the mass concrete of the bearing platform. This has a certain reference and guidance for the construction of mass concrete of platform for the similar bridges.

Effect of inclination angle on the condensation of R134a inside an inclined smooth tube

Almost all work on condensation in tubes were conducted for smooth tubes in a horizontal or vertical orientation, and little has been done at other inclination angles. Recent experimental works with condensation at different inclination angles showed that the pressure drops were a function of inclination angle. It was therefore the purpose of this paper to numerically investigate the pressure drop of condensation inside a smooth tube at different inclination angles, and to give additional perspectives and insight to previous experimental works. The case study investigated was a smooth tube with an inner diameter of 8.38mm and a length of 1488mm. The condensing fluid was R134a and the saturation temperature was 40°C. Simulations were conducted at a heat flux of approximately 5kW/m2, at mass fluxes of 100–600kg/m2s, and the inclination angles were varied from vertical downward to vertical upward. The Volume of Fluid (VOF) multiphase flow formulation was used and ANSYS FLUENT was used as solver of the governing equations. The predicted results showed a good agreement with experimental data. It was found that the effect of inclination angle on pressure drop and void fraction became negligible at high mass fluxes and vapour qualities. The pressure drop increased as the void fraction increased. The pressure drops also increased when the mass fluxes increased. These increases were more significant at high vapour qualities.

Numerical study of the thermo-flow performances of novel finned tubes for air-cooled condensers in power plant

Air-cooled condenser is the main equipment of the direct dry cooling system in a power plant, which rejects heat of the exhaust steam with the finned tube bundles. Therefore, the thermo-flow performances of the finned tubes have an important effect on the optimal operation of the direct dry cooling system. In this paper, the flow and heat transfer characteristics of the single row finned tubes with the conventional flat fins and novel jagged fins are investigated by numerical method. The flow and temperature fields of cooling air for the finned tubes are obtained. Moreover, the variations of the flow resistance and average convection heat transfer coefficient under different frontal velocity of air and jag number are presented. Finally, the correlating equations of the friction factor and Nusselt number versus the Reynolds number are fitted. The results show that with increasing the frontal velocity of air, the heat transfer performances of the finned tubes are enhanced but the pressure drop will increase accordingly, resulting in the average convection heat transfer coefficient and friction factor increasing. Meanwhile, with increasing the number of fin jag, the heat transfer performance is intensified. The present studies provide a reference in optimal designing for the air-cooled condenser of direct air cooling system.

Experience in Operating the Condenser Ball-Cleaning System of the T-250/300-240 Power Generating Unit at the Minsk CHP-4

During its operation, the Minsk CHP-4 branch of Minskenergo RUE implemented many different measures to improve the technical and economic performance indicators and to increase the efficiency of both the installed turbine and boiler equipment and the plant as a whole. The device being used for cleaning condenser tubes by porous rubber balls is a preventive ecologically friendly means for maintaining a clean cooling surface of the condenser tube systems.

Thermal management of machine compartment in a built-in refrigerator

In general a multi-door refrigerator machine compartment comprises of fan, condenser, compressor, control box, drain tray, and drain tubes. The performance of machine compartment depends upon the efficiency of heat extraction or heat exchange from heat generating components such as condenser and compressor. The efficiency of heat exchange can be improved by addressing two major factors, namely (1) Air bypass and (2) Hot air recirculation. The hot air recirculation in the machine compartment for builtin multi-door refrigerator configuration is the focus of this study. The results from Computational Fluid Dynamics (CFD) simulations show that efficiency of heat exchange for built-in application is lower than that for free-standing configuration. Recirculation of hot air and reduction in airflow are the two major factors which contribute towards the variation in machine compartment performance. The CFD simulations were coupled with Partial Factorial Design of Experiment (DoE) approach to systematically investigate the effect of variables such as (a) side gap and top gap between kitchen cabinetry and the refrigerator, (b) the baffle/flap (i.e. back and bottom of machine compartment) on the performance effectiveness of machine compartment. The results of the simulation provided critical design improvement directions resulting in performance improvement. Furthermore, the CFD simulation results were also compared to test data and the results compared favourably.

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.

Dynamic modeling and operation optimization for the cold end system of thermal power plants during transient processes

This paper focuses on the dynamic modeling of the cold end system of a thermal power plant and its operation optimization during cycling load processes. A revised logarithm mean temperature difference is recommended to calculate the heat transfer quantity between exhaust steam and condenser tubes. With this method, a condenser model is developed with a maximum relative error limited within 3%. Coupled with a turbo-generator, a condenser, water pumps, and a cooling tower, a closed cooling system model is established. The total power supply (TPS) during cycling load is calculated and analyzed to optimize the operation during transient processes. A method for obtaining the maximum value of TPS is provided and used to calculate the optimal operating load rate points for switching pumps (OPSP). OPSP increases with the cycling load rate (Ve) during loading up processes decreases with Ve during loading down processes. When Ve is identical, OPSP declines with the ambient temperature for the loading up and down processes. TPS during transient processes is relevant with the switching pump load rate. The maximum value of difference in TPS with different switching pump periods is 691.4 (kW h) for switching pump numbers from 3 to 2 during loading down processes.

Control strategy and experimental analysis of a direct-expansion solar-assisted heat pump water heater with R134a

A direct-expansion solar-assisted heat pump (DX-SAHP) system was designed and built in Qingdao China, which was used to supply domestic hot water. The system mainly consisted of a bare solar collector/evaporator with area of 1.56 m2, a rotary-type hermetic compressor with rated power of 400 W, an electronic expansion valve (EEV) and a micro-channel aluminum flat tube condenser with single surface area of 0.435 m2 surrounding a 0.195 m3 water tank. The system was charged with 800 g of R134a. Based on the degree of superheat at the outlet of the solar collector/evaporator, a control strategy for the system was developed and tested over a wide range of operating conditions, which proved that it could regulate the degree of superheat in range of 5–10 °C effectively. Then the thermal performance of the system was experimentally studied under various operating conditions. Experimental results showed that for most of the time in 2016, when the 0.195 m3 water was heated to the temperature between 55 °C and 60 °C, the coefficient of performance (COP) of the prototype device was higher than 3.0. As the solar radiation intensity or ambient temperature increased, the COP of the system increased, and the heating time decreased.

Enhancing the detection efficiency of condensation particle counters for sub-2 nm particles

The detection efficiency of Condensation Particle Counters (CPCs) reduces drastically as particle size becomes smaller than 2nm. Increasing the supersaturation in order to enhance the detection efficiency, has limited applicability because the onset supersaturation value of droplet formation by homogeneous nucleation is very close to the heterogeneous onset supersaturation for sub-2nm particles. In this work we introduce a new method for increasing the detection efficiency of CPCs for sub-2nm particles, which relies mainly on controlling the spatial distribution of the supersaturation profile by simply modifying the operating temperatures of the CPC. We evaluated the new method by generating monodisperse particles in the size range of 0.98–4.50nm and used them to characterize a TSI 3025 CPC. We achieved significant increase of the detection efficiency for sub-2nm particles. Furthermore, we calculated the supersaturation field developed in the condenser tube with a finite element model and used it to determine the detection efficiency according to heterogeneous nucleation theory. These calculations reveal that the observed increase of the detection efficiency can be explained by the manipulation of the spatial distribution of the supersaturation field. The method introduced here can greatly improve the detection efficiency of CPCs and in the meantime further extend their use for particle sizing purposes in the sub-2-nm range.

Second-Law Analysis: A Powerful Tool for Analyzing Computational Fluid Dynamics (CFD) Results

Second-law analysis (SLA) is an important concept in thermodynamics, which basically assesses energy by its value in terms of its convertibility from one form to another.[...]

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.

Design and control methods of a condenser cleaning robot

As the condenser has complicated indoor environment and it’s difficult for the cleaning robot to complete cleaning, this paper deeply researches tele-operation system of intelligent cleaning robot, designs hardware architecture and software system at tele-operation control platform, including design of human-machine interface on the tele-operation control platform and software and hardware design of joystick force feedback controller. It designs the ontology mechanical structure, electromechanical control system, communication control program and picture processing program of intelligent cleaning robot. Industrial personal computer is used for data processing and motion control in the electromechanical control system. Test results show that the operation system herein can be used to effectively solve the problems in design and control of tele- operation system of intelligent cleaning robot and implement online high-pressure water-jetting cleaning of a condenser tube, so as to ensure efficient and safe operation of condensers in the large power plant.

High-efficiency condenser of steam from a steam–gas mixture

The design of a module for a high-efficiency condenser of steam with a high content (up to 15%) of noncondensable gases (NCGs) with a nearly constant steam–gas mixture (SGM) velocity during the condensation of steam has been developed. This module provides the possibility to estimate the operational efficiency of six condenser zones during the motion of steam from the inlet to the SGM suction point. Some results of the experimental tests of the pilot high-efficiency condenser module are presented. The dependence of the average heat transfer coefficient k on the volumetric NCG concentration v has been derived. It is shown that the high-efficiency condenser module can provide a moderate decrease in k from 4400–4600 to 2600–2800 W/(m2 K) at v ≈ 0.5–9.0%. The heat transfer coefficient distribution over different module zones at a heat duty close to its nominal value has been obtained. From this distribution, it can be seen that the average heat transfer coefficient decreases to 2600 W/(m2 K) at an NCG concentration v = 7.5%, but the first condenser sections (1–3) retain high values of k at a level of no lower than 3200 W/(m2 K), and the last sections operate less well, having k at a level of 1700 W/(m2 K). The dependence of the average heat transfer coefficient on the water velocity in condenser tubes has been obtained at a nearly nominal duty such that the extrapolation of this dependence to the water velocity of 2 m/s may be expected to give k = 5000 W/(m2 K) for relatively pure steam, but an increase in k at v = 8% will be smaller. The effect of the gas removal device characteristic on the operation of the high-efficiency condenser module is described. The design developed for the steam condenser of a gas-turbine plant with a power of 25 MW, a steam flow rate of 40.2 t/h, and a CO2 concentration of up to 12% with consideration for the results of performed studies is presented.

The design of countercurrent evaporative condensers with the hybrid method

The heat and mass transfer in evaporative condensers are complex to model analytically and numerical simulations, when applied to multi-phase fluid dynamics in complex paths, often involve too high computational costs. Experimental campaigns at full scale of different heat transfer geometries and tube arrangements involve long lead times and high costs as well. The aim of the present work is to overcome the present limitations and to apply a new method to evaluate the overall performance of the countercurrent evaporative condensers, starting from the experimental, numerical or analytical data with a small scale approach. A test bench has been purposely designed and built up in order to reach and keep constant all the parameters determining the evaporative condenser heat transfer performance. In previous experimental contributions available in the literature, the air conditions were not controlled: here, an air handling unit placed before the evaporative condenser inlet allows to set up temperature and relative humidity of air in large ranges. An extended experimental campaign has been carried out to get affordable data to be used to find a relationship correlating the dry bulb temperature and relative humidity of air after its interaction with water and the condenser tubes surfaces, while all the parameters were set up and controlled. The regression function fits well the experimental data as the predicted values of temperature and relative humidity are characterized by a maximum percent deviation lower than 2.5% and 4% respectively. An iterative procedure was then implemented to determine the conditions of air going through the evaporative condenser in order to extend small scale results to full scale performance according to real geometries. The effect of the water flow rate on the cooling capacity was investigated and the results show that an increase of 50% of the sprayed water leads to an increase of 14% of the performance.