This article proposes a dual heat source heat pump bathroom unit with preheater which is feasible for a single family. The system effectively integrates the air source heat pump (ASHP) and wastewater source heat pump (WSHP) technologies, and incorporates a preheater to recover shower wastewater heat and thus improve the total coefficient of performance (COP) of the system, and it has no electric auxiliary heating device, which is favorable to improve the security of the system operation. The process simulation software ASPEN PLUS, widely used in the design and optimization of thermodynamic systems, was used to simulate various cases of system use and to analyze the impact of the preheater on the system. The average COP value of a system with preheater is 6.588 and without preheater it is 4.677. Based on the optimization and analysis, under the standard conditions of air at 25 °C, relative humidity of 70%, wastewater at 35 °C, wastewater flow rate of 0.07 kg/s, tap water at 15 °C, and condenser outlet water temperature at 50 °C, the theoretical COP of the system can reach 9.784 at an evaporating temperature of 14.96 °C, condensing temperature of 48.74 °C, and preheated water temperature of 27.19 °C.

Currently, many efforts have been made to improve the approach to build kinetic models. Based on mathematical algorithms, a novel method (named DIM method) of kinetic analysis was introduced in detail. A formula combining differential and integral was deduced and applied to the determination of the mechanism function f(α). Subsequently, multivariable linear regression was conducted to simultaneously obtain the apparent activation energy E, pre-exponential factor A, and oxygen concentration exponent n. In the application of pulverized coal combustion under different oxygen concentrations (3%, 5%, 10%, 15%, and 21%), E, A, and n were calculated as 258,164 J/mol, 6.660 × 10¹⁷ s⁻¹, and 3.326, respectively, and the mechanism function f(α) was determined as the Avrami-Erofeev equation. A validation was performed under a 7% oxygen concentration, which shows that the DIM method has a higher accuracy. This work can provide a reference for the study of kinetic analysis.

The fire triggered by the leak of combustible gas is a serious threat to the safety of the public and firefighters. Backdraft is a special fire phenomenon in a limited-ventilation apartment. It can develop from fires of combustibles that become oxygen-starved and continue to generate a fuel-rich environment. If abundant fresh air is abruptly supplied by opening a door or a window, the hot gas in this vitiated apartment will rapidly combust and a fire ball and a blast wave will take place. This paper presents laws of gas fire backdraft phenomenon based on series of experimental tests in a reduced-scale compartment (length×width×height with 1.08m×0.36m×0.72m), fitted with an opening which could be changed in six cases quickly. The effects of varying ventilation conditions, ignition locations, and mass fluxes of gas leakage are discussed. In addition, the effect of the gas fire backdraft phenomenon on the temperature of the compartment is analyzed. The experimental results and the analysis show that the smaller the opening is, the further the ignition osition is away from the center of the compartment and the larger the mass flux of gas leakage is, the more easily the gas fire backdraft is produced. Furthermore, it is found that the ventilation condition is the key parameter determining the occurrence of gas fire backdraft, followed by the ignition position, and the mass flux of gas leakage through the analysis of orthogonal experiments.

Selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) has been widely investigated to reduce NO_x emissions from combustion processes, which cause environmental challenges. However, most of the current work on NO_x reduction has focused on using feed gas without CO₂ or containing small amounts of CO₂. In the future, oxy-fuel combustion will play an important role for power generation, and this process generates high concentrations of CO₂ in flue gas. Therefore, studies on the SCR process under concentrated CO₂ atmosphere conditions are important for future SCR deployment in oxy-fuel combustion processes. In this work, Mn- and Ce-based catalysts using activated carbon as support were used to investigate the effect of CO₂ on NO conversion. A N₂ atmosphere was used for comparison. Different process conditions such as temperature, SO₂ concentration, H₂O content in the feed gas and space velocity were studied. Under Mn-Ce/AC conditions, the results suggested that Mn metal could reduce the inhibition effect of CO₂ on the NO conversion, while Ce metal increased the inhibition effect of CO₂. High space velocity also resulted in a reduction of CO₂ inhibition on the NO conversion, although the overall performance of SCR was greatly reduced at high space velocity. Future investigations to design novel Mn-based catalysts are suggested to enhance the SCR performance under concentrated CO₂ atmosphere conditions.