Metal fiber surface combustion technology has become one of the most promising low nitrogen combustion technologies for gas boilers because of its advantages of stable combustion process and uniform temperature distribution. Based on the low-nitrogen combustion experimental data of metal fiber surface in limited space, this study established a three-dimensional physical model of metal fiber surface combustion and carried out the full-premixed combustion numerical solution based on the porous medium resistance model, metal fiber turbulence model and EDC combustion model. It obtained the flame combustion conditions and the velocity characteristics of hot smoke flow field of metal fiber surface combustion in limited space, as well as the temperature field distribution and fuel distribution in furnace. Considering the influence of different excess air coefficient, it studied the emission characte-ristics and average generation rate distribution of prompt NO_x and thermal NO_x on metal fiber surface. The results show that under different excess air coefficients, the generation rate of prompt NO_x is faster than that of thermal NO_x. However, limited by the effective reaction space and reaction duration, the volume occupied by prompt NO_x in the furnace is much smaller than that of thermal NO_x. With the increase of excess air coefficient, the generation rate and emission of thermal NO_x gradually decrease. When α=1.6, the emission of NO_x from flue gas outlet is 22.55 mg/m³, which meets the standard of low nitrogen combustion. Therefore, in addition to changing the flame temperature, oxygen concentration and combustion mode, the generation of thermal NO_x can be suppressed by controlling the excessive air coefficient, and ultralow nitrogen combustion of industrial gas boilers can also be effectively achieved.

For the thermal management of high power consumption modules in 5G communication base stations, this study proposed a phase change heat transfer module with roll bond aluminum vapor chamber, in which the evaporation chamber of the module is interconnected with the flow channels of all vapor chambers. By constructing a performance testing platform, experimental studies were conducted to investigate the heat transfer performance of the module under different filling ratios. The impacts of the boiling state and the flow distribution of the working fluid on both temperature uniformity and heat dissipation efficiency of the module were analyzed. Additionally, the variation in surface temperature distribution of the heat source under different lateral inclination angles was also explored. The research results indicate that under the condition of an input power not exceeding 400 W, as the filling ratio increases, the total thermal resistance of the phase change heat transfer module initially decreases and then increases, reaching its minimum at a filling ratio of 15.0% with the lowest total thermal resistance being 0.2116 ℃/W. Appropriately reducing the filling ratio induces boiling of the liquid working fluid at the bottom of the vapor chambers, thereby promoting the balanced distribution of gaseous working fluid among different vapor chambers and enhancing both the heat dissipation efficiency and temperature uniformity of the phase change heat transfer module. At input powers of 350 W and 400 W respectively, reducing the filling ratio from 30.0% to 15.0% leads to a decrease in the standard deviation of temperatures among the vapor chambers by 40.92% and 34.04%, resulting in a significant improvement in temperature uniformity. When the tilt angle of the phase change heat transfer module changes, the liquid level in the evaporation chamber shifts, leading to uneven temperature distribution on the heat source surface. This adverse effect becomes more pronounced with increasing inclination. At a tilt angle of 10.0° (under the same power conditions), the maximum temperature difference on the heat source surface increases to more than 11.7 times that under horizontal placement.

In order to improve the performance of the integrated micro-channel heat exchanger, this study established the steady-state heat transfer model of an integrated micro-channel heat exchanger, and studied the influence law of the structural parameters and operation parameters on it. The integrated micro-channel heat exchanger used R245fa as working medium. It studied the effects of heat exchanger and heat exchanger heat pipe spacing on the total thermal resistance and air-side pressure drop of the system by using the model, which was verified by experiments previously. The results show that when the evaporation section air volume of the integrated micro-channel heat exchanger is 0.41 m³/s, condensing section air volume is 0.21 m³/s and the total thermal resistance of the heat exchanger system is 0.0380 m²·K/W. With the increase of circulating air volume in the condensing section and the evaporation section, the air-side pressure drop of the micro-channel heat exchanger increases, and the total thermal resistance decreases. The downtrend of the total thermal resistance of the micro-channel heat exchanger decreases gradually with the increase of air volume. In scope of this research, it is concluded that the appropriate air volume in the evaporation section is 0.45 m³/s, and that in the condensation section is 0.69 m³/s. With the increase of the integrated micro-channel heat exchanger heat pipe spacing, the total thermal resistance of the micro-channel heat exchanger increases, and the air-side pressure drop of the micro-channel heat exchanger decreases in the evaporation section. When the heat exchanger heat pipe spacing is 6 mm, the comprehensive performance of the integrated micro-channel heat exchanger is the best. The research results provide a reference for the design of cooling equipment for communication base stations and the optimization of the structure and control parameters of the micro-channel heat exchanger.

Communication base stations are facing the problems of uneven heat dissipation and high energy consumption of the heat dissipation systems. The separated heat pipe heat exchanger can replace air-conditioning in communication base stations and effectively reduce the energy consumption of base station heat dissipation systems. The heat transfer performance of separated heat pipe heat exchanger is affected by factors such as filling ratio, working fluid type and air volume. In order to study the influence of different factors on heat transfer performance, the difference between theoretical filling ratio and the actual filling ratio was analyzed through theoretical calculation. The experimental platform was built to study the heat transfer performance of heat exchanger under different filling ratios, the difference of heat exchanger performance under different high and medium temperature working fluids, and the influence of indoor and outdoor fan power change on heat exchanger performance. The study finds that when the working fluid R134a is used, the error between the theoretical value and the actual value of the minimum filling ratio is 4.74%, the optimal filling ratio range of the heat exchanger is 27.1%~47.9%, the optimal filling ratio is 31.6%, and the equivalent heat transfer coefficient of the heat exchanger under the optimal filling ratio is 909 W/℃. With the increase of filling ratio, the phase change area inside the heat exchanger increases first and then decreases, and the heat transfer form changes from sensible heat transfer of vapor working fluid to latent heat transfer of the phase change of the working fluid, and then to sensible heat transfer of the liquid working fluid. The high temperature working fluid is not suitable for the separated heat pipe heat exchanger. When using the high temperature working fluid, there is no obvious phase change area inside the heat exchanger. The lower the boiling point of the working fluid is used, the larger the phase change area, the better the performance of heat exchanger, and the larger the range of its optimal filling ratio. With the increase of power of indoor and outdoor fans, the performance of the heat exchanger increases rapidly and then slows down. However, due to the poor heat dissipation conditions on evaporator side, the improvement of the heat transfer performance of the system by increasing the power of internal fan is more significant than that of the external fan.

Studying the effect of Ozone (O₃) on polycyclic aromatic hydrocarbon (PAH) during the combustion process of biodiesel can provide new insights for reducing soot emissions. A skeletal reaction mechanism of biodiesel surrogates coupled with an O₃ reaction mechanism and a PAH reaction mechanism was constructed for modeling the effect and mechanism of O₃ on PAH formation in a counterflow flame of biodiesel surrogates. The final mechanism consists of 138 species and 608 reactions. Analysis show that the addition of O₃ creates a localized rapid temperature rise zone on the fuel side. As the initial O₃ mole fraction increases, the temperature rise rate in this zone intensifies and its position shifts closer to the fuel outlet, resulting from the preliminary oxidation of the fuel releasing heat. Furthermore, the maximum mole fraction of PAH initially increases and subsequently decreases with increasing initial O₃ mole fraction. When initial O₃ mole fraction increases to 0.04, the maximum mole fraction of major PAH such as benzene (A₁), naphthalene (A₂), anthracene (A₃), and pyrene (A₄) are 4.57, 6.76, 16.16, 12.38 times that at initial O₃ mole fraction of 0.00, respectively. The addition of O₃ has a significant impact on the concentration of PAH, and has the greatest impact on A₃. At the same time, the pathway of benzene (A₁) generation shifts from C₂H₂-dominated to C₂H₃-dominated mechanisms. And when initial O₃ mole fraction increases to 0.12, the maximum mole fractions of A₁, A₂, A₃, and A₄ are 0.880, 0.357, 0.375, and 0.143 times that at initial O₃ mole fraction of 0.00. It is because that the C₂H₃ radicals are oxidized, thereby inhibiting the production of A₁.