Fengzhong Sun

THREE-DIMENSIONAL REGULARITIES OF DISTRIBUTION OF AIR- INLET CHARACTERISTIC VELOCITY IN NATURAL-DRAFT WET COOLING TOWER

A model for heat and mass transfer in a natural-draft wet cooling tower was established. Numerical simulation with the k-ε turbulent model was conducted. Distribution rules of air inlet aerodynamic field were studied. Field experiments were done in a cooling tower in power plant, and the test data was compared with the related results. The definition of characteristic air velocity was proposed and its influencing factors, such as the cross-wind velocity and circumferential angle, were quantitatively studied. It can be used to evaluate the performance of cooling tower and to calculate the ventilation quantity and resistance of air inlet. It is also a theoretical basis for cooling tower design and performance optimization.

The Coupling Effect Research of Ash Deposition and Condensation in Low Temperature Flue Gas

Ash deposition is a key factor that deteriorates the heat transfer performance and leads to higher energy consumption of low pressure economizer working in low temperature flue gas. In order to study the ash deposition of heat exchange tubes in low temperature flue gas, two experiments are carried out with different types of heat exchange tubes in different flue gas environments. In this paper, Nusselt Number Nu and fouling factor are calculated to describe the heat transfer characteristics so as to study the ash deposition condition. The scanning electron microscope (SEM) is used for the analysis of ash samples obtained from the outer wall of heat exchange tubes. The dynamic process of ash deposition is studied under different temperatures of outer wall. The results showed that ash deposition of heat exchanger will achieve a stable state in constant flue gas environment. According to the condition of condensation of acid vapor and water vapor, the process of ash deposition can be distinguished as mere ash deposition, acid-ash coupling deposition, and acid-water-ash coupling deposition.

Experimental study of condensation heat transfer characteristics of horizontal tube bundles in vacuum states

To develop an excellent heat transfer element under the vacuum condition, experiments about the heat transfer performance of horizontal tube bundles of different materials under various vacuum conditions were carried out, including the stainless steel tube, the brass tube, the Ni-based implanted steel tube and the ion implanted brass tube. The relative trends show that the condensation heat transfer coefficient and the overall heat transfer coefficient of bundles of four materials all increase with the vacuum degree, especially, those of the Ni-based implanted steel tube and the ion implanted brass tube. Under a high vacuum condition (0.07 MPa), the condensation heat transfer coefficient of the Ni-based implanted steel tube bundle is about 1.4 times of that of the stainless steel tube bundle, the condensation heat transfer coefficient of the ion implanted brass tube bundle is found to be about 1.3 times of that of the common brass tube bundle. Therefore, according to the condensation heat transfer characteristics studied under high vacuum conditions, it is believed that a dropwise condensation is partly achieved on the surface of these two implanted tube bundles, and the ion implantation is shown to be an effective method to achieve the dropwise condensation. Based on this study, it is believed that the Ni-based steel tube may replace the brass tube, which is more expensive as a heat transfer component.

Research on the Effect of Cross-wind to Temperature Difference and Efficiency of Natural Draft Counter flow Wet Cooling Tower

The experiment in terms of heat transfer performance of natural draft counter-flow wet cooling Tower (NDCWCT) is done for cases with cross-wind conditions. The variation of circulating-water temperature difference (Δt) and cooling coefficient of efficiency (η) with cross-wind velocity, circulating water inlet temperature and flow rate, are shown under cross-wind conditions, compared with cases without wind. According to experimental results, it is found that Δtand η are influenced by the cross-wind, Δt and η can decrease mostly by 9.2% and 9.6%, respectively. When the critical Fr l number is less than 0.153, Δtand η decrease with increasing cross-wind velocity, however, when it is greater than 0.153, Δt and η increase with increasing cross-wind velocity.

Three-dimensional numerical analysis of wet cooling tower

A mathematical model for water evaporation and water droplet movement is established to describe the air-water interaction in natural draft wet cooling tower (NDWCT).The standard k e − model is used to close the Reynolds average Navier-Stokes equations. The three-dimensional heat and mass transfer process in NDWCT is simulated to analyze the crosswind effect on wet cooling tower performance. It is found that the heat and mass transfer in fill zone is seriously affected by crosswind, while the wet cooling tower performance is improved when crosswind velocity is higher than 5 . Conditions and locations for good cooling performance are pointed out. -1 ms ⋅

Performance Deterioration Mechanism Analysis of Natural Draft Cooling Towers Under Crosswind Conditions

Based on the developed three-dimensional computation model of natural draft wet cooling towers, the effect of crosswind on circumferential distribution of air radial pressure gradient and velocity at tower air inlet was studied, and the effect of crosswind on total air inflow rate, transverse mass flow rate, vertical mass flow rate and water temperature drops of the three zones (i.e. spray zone, filling zone and rain zone) were also analyzed. Analysis of crosswind effect on air flow field in heat and mass transfer zone indicates that the induced longitudinal eddy causes reduction of effective ventilation area in filling zone. Results showed that crosswind destroys the uniform air inflow, reducing the total air inflow mass rate and the effective ventilation area of filling zone, resulting in cooling performance deterioration of natural draft wet cooling towers.Copyright

Dropwise Condensation on Nickel-based Coating Tube

Dropwise condensation on Nickel-based alloy coating (NBAC) tube has been experimentally investigated. In addition, the mechanism of dropwise condensation facilitated by the nickel-based alloy coating tube has been analyzed. All the work done provides scientific basis for the further research and application of the new surface modification technology.

The Flow Characteristics of Flue Gas Between the Fins of a Single Spiral Finned Tube

The spiral finned tubes are used as the substitute of bare tubes in heat exchangers, which is an effective method to reduce abrasion and fouling in boilers. The cold state test with PDA system has been made to study the distribution of granule concentration between fins. This experimental research has laid the foundation of analysis for further study why the spiral finned tube can reduce abrasion and fouling.Copyright