Temperature Field Of System Research Articles

Relationship between infrared spectral emissivity and temperature distribution of thermophotovoltaic systems

Matching the thermal radiation power spectrum to the band gap of photovoltaic cells is an important factor governing the efficiency of thermophotovoltaic systems. The ability of the emitter to achieve low radiation outside the operating spectrum of the photovoltaic cells effectively minimizes energy waste. In this study, we designed and developed a thermophotovoltaic system with a hexahedral structure and measured the effect of surface emissivity on the temperature distribution of the system. Comparing different thermal emitters at a fixed heat-source power of 200 W, the system core temperature reached 839 K and 900 K under standard atmospheric and vacuum conditions, respectively. The trend of the simulation was consistent with that of the experiment. Thus, we established a pattern of emissivity on the system temperature field and created a basis for a more efficient design of thermophotovoltaic systems.

Stationary Temperature Field of a Separation System with Active Thermal Protection Possessing Feedback and Anisotropic Coating

The problem of the determination of the stationary temperature field of a system simulated by a wall separating two different media is formulated. On the one hand, the wall is equipped with an anisotropic thermal-protective coating, which is exposed to local thermal effects in conditions of heat transfer with the external environment, as well as a thermoactive gasket that operates according to the feedback principle. The solution was obtained with the methods of integral transformations in an analytically closed form.

Analysis of the Effects of Thermal Environment on Optical Systems for Navigation Guidance and Control in Supersonic Aircraft Based on Empirical Equations.

The thermal environment is an important factor in the design of optical systems. This study investigated the thermal analysis technology of optical systems for navigation guidance and control in supersonic aircraft by developing empirical equations for the front temperature gradient and rear thermal diffusion distance, and for basic factors such as flying parameters and the structure of the optical system. Finite element analysis (FEA) was used to study the relationship between flying and front dome parameters and the system temperature field. Systematic deduction was then conducted based on the effects of the temperature field on the physical geometry and ray tracing performance of the front dome and rear optical lenses, by deriving the relational expressions between the system temperature field and the spot size and positioning precision of the rear optical lens. The optical systems used for navigation guidance and control in supersonic aircraft when the flight speed is in the range of 1–5 Ma were analysed using the derived equations. Using this new method it was possible to control the precision within 10% when considering the light spot received by the four-quadrant detector, and computation time was reduced compared with the traditional method of separately analysing the temperature field of the front dome and rear optical lens using FEA. Thus, the method can effectively increase the efficiency of parameter analysis and computation in an airborne optical system, facilitating the systematic, effective and integrated thermal analysis of airborne optical systems for navigation guidance and control.

Uniformity factor of temperature difference in heat exchanger networks

A uniformity factor of temperature difference (UFTD) is proposed and set up to guide the optimization of Heat exchanger network (HEN). At first, the factor is presented to evaluate the whole enhancement of HEN by handling the logical mean temperature difference as two-dimensional discrete temperature field in system. Then, the factor is applied to different HENs, of which the comparison indicates that a more uniform discrete temperature field leads to a lower UFTD which correlated with a better whole enhancement to improve the optimization level of HEN. A novel stage-wise superstructure model where inner utility can be generated is presented for further analysis of correlation between UFTD and the efficiency of HEN, and more optimal HEN structures can be obtained as inner utility added. Inner utility appears to violate the thermodynamic law, but it makes the discrete temperature field more uniform and improves the heat transfer efficiency of the whole HEN, which brings much more profit than the side effect of inner utility. In sum, the UFTD can not only evaluate the optimization level of the HEN, but also be an optimization object to design new HEN with higher efficiency of energy utilization and lower total annual cost.

Influence of Structural Parameters of Electromagnetic Harmonic Movable Teeth Transmission on System Loss

In view of the characteristics of electromagnetic harmonic movable teeth transmission system, the heat loss has been analyzed in this paper based on basic assumptions. At the same time, the calculation methods of electromagnetic loss and mechanical loss in system have been also discussed. Moreover, the influence of changes of system parameters on electromagnetic loss and mechanical loss has been analyzed through employing the field-circuit coupling finite element method. According to the analysis results, the numerical calculation model of the three-dimensional temperature field of system can be established. And the theoretical basis can be provided for the optimization design of electromagnetic harmonic movable teeth transmission system and the improvement of transmission efficiency of transmission system.

Dynamics of three-dimensional temperature field in electrical system of floor heating

In the paper dynamics of a three-dimensional temperature field in the system of direct floor heater was investigated. A step response (heating on curve) and local and global time constants of the device were determined. Then, a spatial–temporal distribution of the field in the system controlled by the on–off regulator was found. The mathematical model of heat propagation was a non-homogeneous and homogeneous equation of a three-dimensional diffusion with an adequate set of boundary conditions. Four methods were applied for the solution of the above: superposition of states (coupled with separation of variables), finite elements, criterion of an averaged time constant and superposition of step characteristics. It was found that time profiles of the temperature depend very strongly on the position of an observing point. All relations were processed numerically. The obtained results are presented in a graphic form. A physical interpretation of the achieved solutions is included.

Theory of thermal ignition

1. The dependence of the upper limit of the system of spontaneous combustion upon the degree of autocatalytic character of the process was established by an analysis of the nonstationary temperature field in systems with an autocatalytic mechanism of decomposition. 2. The possibility of separating the time lag of combustion into the warmup time and induction period was demonstrated within the entire region of spontaneous combustion in the case of weakly accelerating processes, and close to the lower limit of spontaneous combustion in the case of strongly accelerating processes.