Yuetao Shi

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.

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.

Experimental Measurement of Flue Gas Temperature Versus Ash Accumulation

It is known that particle accumulation is beneficial for dust removal in industry. In order to understand better particle accumulation mechanism, experiments were carried out to analyze the influence of flue gas temperature and humidity on ash accumulation. It is found that the Engineering Acid Dew Temperature (EADT) of flue gas is an important parameter that determines the efficiency of particle accumulation. When the gas temperature is lower than the EADT, the sulfuric acid in the flue gas and ash humidity rise dramatically, which leads to particle accumulation. In order to improve the collection efficiency, the flue gas temperature can be controlled to trigger particle accumulation.

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