Exploration of regional surface average heat flow from meteorological and geothermal series

We attempt to compute the Surface Average Heat Flow （SAHF） from long-term temperature observations of one hundred seventy-seven observational points at the depths of 0.8, 1.6, and 3.2 m, which were relatively evenly distributed in China's Mainland. We first employ Fourier transformation to remove the influence of atmospheric temperature variations from the observation series, which are classified into the type of the steady-state temperature monotonously increasing with depth （type I） and other three types. Then we compare our results obtained from the data of type I, of which the values are thought to equal to those of the mean borehole heat flow, with those obtained from traditional heat flow observations mainly distributed in North China Craton. In computations of the SAHF at the observation stations, we deduce the thermal diffusivity and volumetric specific heat of the soil by employing harmonic solutions of the heat conduction equation for the same moisture group as the first step, and then we determine the SAHF using Fourier＇s law. Our results indicate that the SAHF derived from shallow earth geothermal data can reflect the heat flow field to a large extent.

Theoretical Study of Combustion Processes in Aero Gas Turbines for Air Craft Engines

Combustion process involves various physical and chemical processes which govern and control flames initiation in aero gas turbine engines. During certain flying conditions, at full load, unexpected critical situation may take place in such engines called blow off conditions, which leads to flames diminishing in the combustion chamber of such engines. Gas motion, flow velocity and turbulence kinetic energy are the most important parameters in ensuring flame stabilities. These parameters play a tremendous role and effects on this phenomenon. In gas turbines, the flame exists within a high velocity, non-uniform and intensely turbulent flow field, therefore careful temperature control is vital. Another important factor which must be considered to avoid blow off conditions, is mixture strength. Nearly, all modern gas turbines, due to emissions restrictions, operate on lean mixture conditions which are hard to ignite and lower flame temperatures and thus more risk to reach blow off conditions which leads to a complete flame extinction. These conditions may exist in an air craft engines due to sharp changes in loading parameters, (θL): pressure (Pu), temperature (Tu), mass flow rate (), and cross sectional area (Au). At present there is no detailed theory of gas turbine combustion. Therefore, we must resort to simple models and experimental correlations. This paper investigates the blow-off phenomena in aero gas turbine engines, its causes and estimation of required energy to ensure recovery (re-ignition) again inside the combustion chamber. Identifying the conditions at which blow-off takes place and associated loading parameters (θL) which are a function of (A, T, P, and ). The paper also, quantify the recovery conditions (required energy to re-ignition, change in loading parameter (Δq) Power, Required VHRR: (Volumetric Heat Release Rate) and changes in other loading variables (ρ: density, T: Temperature, P: Pressure, and : mass flow rate) tarts with discussing causes of blow off along with effecting operating conditions.

Analysis of ice slurry production by direct contact heat transfer of air and water solution

In this paper, a novel system using direct contact heat transfer between air and water solution was proposed to generate ice slurry. The heat transfer process and the system performance were studied; energy efficiency coefficients of 0.038, 0.053, and 0.064 were obtained using different solutions. An empirical relationship between the volumetric heat transfer coefficient U v and the main parameters was obtained by fitting the experimental data. The U v calculated from the empirical formula agreed with the experimental U v quite well with a relative error of less than 15%. Based on the empirical formula, a laboratory-scale direct contact ice slurry generator was then constructed, with practical application in mind. If the air flow rate is fixed at 200 m 3 /h, the ice production rate will be 0.091 kg/min. The experimental results also showed that the cold energy consumption of the air compressor accounted for more than half of the total amount. To improve the system energy efficiency coefficient, it is necessary to increase the air pipes insulation and the solution's thermal capacity, and also it is appropriate to utilize the free cold energy of liquefied natural gas (LNG).