In this paper, conjugate heat transfer (CHT) simulation is performed for a low-pressure stage of MGT-70, a heavy-duty gas turbine (GT) manufactured by MAPNA Group. Although the vane and the blade are uncooled, CHT analysis is performed to assess the validity of using the fluid temperature of an adiabatic simulation as the uncooled vanes or blades temperature, and also to model the heat transfer between root or shroud and vane or blade profile. To compare the resultant temperatures of CHT and adiabatic flow analysis both simulations are done, using the same boundary conditions. The vane shroud extends over the blade tip, which is of free-standing type, and there is not a shroud segment. In fact, the vane and blade share the shroud. In order to predict the shroud temperature more accurately, the vane and the blade are simulated simultaneously as a stage using appropriate interfaces. A single vane CHT simulation is also performed to evaluate the effect of blade tip flow on the shroud temperature. Furthermore, the cavity above the shroud, containing the cooling and sealing flow, is also included in the model to better prediction of the shroud temperature. In addition, the rim cavity and the labyrinth seal under the vane platform are included in the model to better predict the vane platform temperature and to capture the effect of purge flows on vane and blade temperature. Simulation results show that, although, the average bulk temperature of the profile in both CHT and adiabatic simulations are close to each other, there are great differences in temperature distribution over the suction side and pressure side. These differences are because of heat flux through the profile in CHT simulation, which results in a more realistic metal temperature distribution. Comparing the results of the single vane simulation and stage simulation no remarkable difference is observed in the temperature distribution, except for the shroud region above blade tip. This reveals that, although, the tip leakage flow is better captured in the stage simulation, it is only useful when the shroud temperature is of interest and it does not affect the vane profile temperature distribution. Finally, the inclusion rim cavity and labyrinth seal in the simulation helps to predict the mass flow distribution of purge flows and the effect of these flows on platform temperature distribution in vane and blade.

Past experiences have shown that a local wind can considerably affect the performances of powerplant cooling towers and factory chimneys. In thermal powerplants, the performance of Rankin cycles would reduce if the temperature of its condenser increases. This issue is very important to powerplants located in countries with strong local winds. To remedy the mal-performance of a natural cooling tower in windy conditions, it is required to understand the physics of flow around cooling towers more clearly. One adverse physics is known as the wind covering problem which can drastically affect the natural draught through a cooling tower in windy conditions. In this paper, we focus on wind-covering problem and its adverse impact on a real natural draught cooling tower. Contrary to the past studies, we show that wind can generally affect either positively or negatively in cooling tower performances. Surprisingly, the positive and negative roles can simultaneously occur in most times. In this paper, we use computational fluid dynamics tool to quantify the positive and negative impacts of wind on natural draught flow through dry cooling towers.

The use of air-cooled condenser (ACC) has become very popular in erecting thermal powerplants around the world since two or three decades ago. The advantages of forced convection heat cooling system, instead of the classical natural draught convection heat transfer cooling systems, promote the thermal powerplant designers and users to benefit more from such systems in their thermodynamics cycles. However, such forced convection heat transfer mechanisms, can lose their cooling efficiency in off-design ambient conditions, i.e., in high wind velocity and high ambient temperature conditions. There have already been some efforts to analyze the reduction of ACC System performance in some critical ambient conditions. This work presents a detail investigation on the performance of an ACC in real conditions of an existing powerplant. We use the computational fluid dynamics CFD tool and quantify the detail performance of the ACC system in different wind velocities and ambient temperature conditions.

Thermal powerplants report a reduction in their dry cooling tower performances due to surrounding wind drafts. Therefore, it is very important to consider the influence of wind velocity in cooling tower design; especially in geographical points with high wind conditions. In this regard, we use the computational fluid dynamics (CFD) tool and simulate a dry cooling tower in different wind velocities of 0, 5 and 10 m/s. To extend our calculations; we also consider the temperature variation of circulating water through the tower heat exchanger or deltas one-by-one. We show that some heat exchangers around the tower cannot reduce the circulating water temperature sufficiently. This causes an increase in the mean temperature of those heat exchangers. The worst performances can be attributed to heat exchanger located on side wind places. We will discuss the detail performance of each delta and their assembly in draft wind conditions. This study suggests some effective ways to overcome thermal-performance of cooling tower in wind conditions.