An experimental study is conducted using the single-factor experimental method on a closed-loop heat pump drying system incorporating air bypass and series-connected external auxiliary condenser. The research focused on analyzing the influence principles of material loading, circulating air velocity, expansion valve opening and air bypass rate on the specific moisture extraction rate (SMER). The results demonstrated that under optimal refrigerant charge (645 g) and identical drying duration, the system exhibited an optimal material loading of 1.845 kg. SMER is initially observed to increase then decrease with rising air circulation velocity. Superheat is increased and evaporation temperature is decreased by reducing the expansion valve opening, leading to enhanced dehumidification capacity and SMER. Maximum energy consumption reduction of 10.7% and SMER improvement of 20% are achieved by this configuration compared to 5 ℃ superheat conditions. An optimal air bypass ratio of 0.6 is identified for the system, resulting in a 35.7% SMER enhancement relative to non-bypass operation.

Aiming at the problem of the operating parameters on the atomization of snow by internal mixed gas-liquid two-phase flow nozzles in snow-making machines, an artificial snow-making environment simulation room is set up, and the experimental study on the snow density of a new type of internal mixed gas-liquid two-phase flow nozzles with different operating parameters is carried out. Based on the snow crystal growth theory, the effect of operating parameters on the snow density of the atomizing nozzle is revealed, which provides theoretical support for the design and optimization of the snow-making machine. The snow density change rule of the atomizing nozzle under different air-water pressure ratio and wet bulb temperature is studied, and the main conclusions show that: the air-water pressure ratio is 0.4 MPa:0.4 MPa, 0.5 MPa:0.45 MPa, 0.5 MPa:0.4 MPa, and under the same ambient temperature condition, the reduction of the air-water pressure ratio can improve the snow density; the wet bulb temperature varies in the range of -20.23- -5.36 ℃, and the snow density changes in the range of -20.23- -5.36 ℃, under the same conditions of air-water pressure ratio, increasing the wet bulb temperature can improve the snow density.

To investigate the cooling load variation induced by unorganized infiltration airflow in platform screen door metro stations, field measurements and numerical simulations are conducted at a non-transfer underground platform screen door metro station in Shanghai. A simplified simulation model for unorganized infiltration airflow is developed and validated using on-site infiltration airflow data collected at platform screen doors and station entrances/exits during train arrival and departure cycles. The dynamic variation patterns of unorganized infiltration airflow are systematically analyzed, and the validated model is employed to calculate real-time infiltration load profiles for two typical scenarios of weekdays and weekends. The results show that the infiltration air load is increased during the peak passenger flow period, and the maximum infiltration air loads on weekdays and weekends are 29.8% and 30.8%, respectively.

A fault diagnosis migration method based on CNN-FT (convolutional neural network with fine-tuning)is proposed, which leverages the informative prior knowledge from the source-domain variable refrigerant flow system to establish a diagnostic model for the target variable refrigerant flow system. Firstly, the source-domain is pre-trained, and the optimal CNN model is found by parameter optimization. Then the pre-training model is migrated to the target domain, and only a small amount of target data is used to train the top layer of CNN, with an accuracy of 86.71%. The previous network layer is thawed in turn for fine-tuning, and the accuracy rate is improved to 95.83%, which is significantly better than the target domain specific training (81.02%) and the source domain model direct migration (33.45%).

In order to improve the fire-fighting efficiency of fire-fighting aircraft, the discharge characteristics of water extinguishing agent by establishing a working medium discharge model of gravity spraying system is simulated, the influence of the type of working medium and the size of water tank on the discharge process is analyzed. The results showed that the discharge rate in 6 s is 9% slower than that of water when the polymer gel extinguishing agent is used instead of water as the working medium, which meets the emission requirements in actual application scenarios. However, the commonly used shrinkage criteria are no longer applicable to the discharge process of water tanks of different sizes, so the shrinkage criteria applicable to the gravity spraying system are established, and the shrinkage test platform is built to verify the emission model. The results show that the most suitable shrinkage criteria number for the gravity spraying system is Froude number.

To investigate the heat transfer characteristics of phase change microcapsule suspensions in a circular tube, the discrete phase model (DPM) is used to simulate the flow and heat transfer of phase change microcapsule particles in the tube, and the equivalent heat capacity method is used to study the phase change process of microcapsules during the flow, and the effects of flow rate, concentration and heating power on the heat transfer characteristics of suspensions are investigated. The results show that the average local heat transfer coefficient of microencapsulated phase change material slurry (MPCS) with flow rates of 1.0 m/s, 1.22 m/s and 1.4 m/s increases with increasing of flow rate when the phase change microcapsules (PCM) is completely melted. The local surface heat transfer coefficient of the suspension increases with increasing of concentration when the MPCS with mass fractions of 2%, 5% and 8% can be completely melted. Increasing power can accelerate the melting process of PCM and allows the local surface heat transfer coefficient in the tube to reach its peak more quickly.

A three-dimensional computational fluid dynamics (CFD) model coupled with reaction kinetics and transport processes is established to investigate the effects of cooling water velocity, tube layer spacing and inter-tube spacing on temperature distribution, pressure drop and CO2 conversion. The results show that, when the flow rate of cooling water is increased from 0.2 m/s to 1.8 m/s, the maximum temperature in the reaction zone is decreased by 4.01 ℃, but the CO2 conversion rate is decreased from 26% to 24.14% due to kinetic inhibition. CO2 conversion can be increased to 31.22% by increasing layer spacing (5-30 cm), but the hot spot temperature is increased by 39.18 ℃. The conversion rate is slightly increased (24.54%-26.57%) by the expansion of tube spacing (30-60 mm)through reducing the heat transfer efficiency. The synergistic mechanism of flow-heat-transfer reaction is revealed, and the gradient layer spacing design is proposed to balance the demand of heat transfer and the optimization of reaction kinetics.

The research object is an office building in Suzhou which is equipped with a radiation and fresh air system with separate temperature and humidity control based on the form of energy storage tanks. The models of the direct supply form of air source heat pumps and the radiation and fresh air system with separate temperature and humidity control based on the form of energy storage tanks are established by using Trnsys. These models are validated using measured data from the actual systems. A comparative analysis of simulation results between systems with and without energy storage water tank is conducted. The findings indicate that integrating 0.15 m3, 0.2 m3, 0.5 m3, and 1 m3 energy storage water tanks into direct supply systems reduces fluctuations in main unit outlet water temperature, decreasing start-stop frequencies by 57.8%, 60.9%, 71.1% and 77.2% respectively. However, energy consumption slightly increases by 2.1%, 2%, 2.4% and 3.1%, respectively. The coefficient of performance of the heat pump unit remains unchanged regardless of water tank volume or system configuration.

Aiming at the energy consumption prediction problem of an air-conditioning system in a shopping mall in Wuhan, the data mining method is used for modeling processing, in which the Savitzky-Golay smoothing algorithm is introduced to perform noise reduction processing on the original data, and the long short-term memory neural network algorithm is used to predict and analyze the instantaneous energy consumption. The results show that compared with methods such as back-propagation neural network, recurrent neural network and gated recurrent unit, the long short-term memory neural network has highest prediction accuracy, in which the determination coefficient is 0.861. The denoising of raw data using the Savitzky-Golay smoothing algorithm significantly enhances prediction accuracy by reducing the influence of noise, achieving a coefficient of determination of 0.955 with a increasing of 10.9%. The feasibility of the proposed method for energy consumption prediction in chilled water systems of commercial buildings is thereby validated.

Using the dynamic load simulation method of DeST software, the hourly heating and cooling loads under different conditions are investigated, and the load calculation method for residential buildings applying the air-source heat pump cooling and heating system in hot summer and cold winter areas is proposed. The intermittent coefficients and intra-house heat transfer qh for different types of rooms are analyzed. The results show that, in summer, the living room with an area of 29-45 m2 should have set at 1.5 and qh at 55 W/m2, the bedroom with an area of 15-20 m2 should have set at 1.4 and qh at 55 W/m2, and the bedroom with an area of 8-15 m2 should have set at 1.0 and qh at 60 W/m2. In winter, the living room with an area of 29-45 m2 should have set at 2.0 and qh at 40 W/m2, the bedroom with an area of 15-20 m2 should have set at 1.6 and qh at 40 W/m2, and the bedroom with an area of 8-15 m2 should have set at 1.5 and qh at 45 W/m2. The total system load should be set at 0.7 in summer and 1.1 in winter, with qh set at 13 W/m2 in summer and 12 W/m2 in winter. Window-wall ratio and orientation correction values are provided, where rooms with a summer window-wall ratio greater than 0.3 should be reduced by 0.1 from the original recommended values, and north-facing rooms in winter should be reduced by 0.1 from the original recommended values.

To address the issue of non-energy-efficient behavior resulting from human operations during system runtime, this study utilizes cumulative operational data from the 2022 cooling season to establish a back propagation neural network energy consumption prediction model. The model is subsequently validated, with the average error meeting precision requirements. Leveraging the energy consumption prediction model, a genetic algorithm is employed for optimization, and the results are compared with those obtained through manual experiential adjustments. The findings indicate that, energy savings are achieved through parameter adjustments using the genetic algorithm outperform those based on human experience. Notably, within the load interval accounting for the longest operational duration (from 30% to 50%), energy savings reach 7.84%.

In combination with the transportation of tropical fruit durian on the China/Kunming-Laos/Vientiane Railway, the respiratory intensity of durian at 5 ℃, 10 ℃, 15 ℃ and 25 ℃ is tested. CO2 respiratory intensity at 25 ℃ is 107.51 mg/(kg·h), which is three times of 33.11 mg/(kg·h) at 5 ℃. Based on the results of respiratory intensity testing, the heat transfer of the box under typical operating conditions such as pre cooling, empty box cooling and railway transportation when loading durian was analyzed and calculated. Under the pre-cooling condition of loading durian, the total heat transfer is the highest, about 14.6 kW. Durian respiratory heat is the main source of heat, accounting for 80.49%, and the corresponding required cooling capacity is 16.8 kW. Further calculation and analysis are conducted on the impact of key parameters such as the comprehensive heat transfer coefficient of the box, external environmental temperature, and durian respiration intensity on the cooling capacity.

In order to study the “partial space” operation mode of the variable air volume air-conditioning system for large space public buildings, numerical simulation and experimental validation methods are adopted to analyze the distribution characteristics of temperature and velocity fields under three operation modes of full-space mode, conference zone-only mode and work zone-only mode. Control strategies and key parameters are identified. The results show that in the two “partial space” operation modes, the temperature in the area where the personnel are located can be maintained near the set value, the air diffusion performance index is higher, and the annual power consumption of the air-conditioning unit is reduced by 35.4% and 52.1%, respectively.

Hazard and operability (HAZOP) analysis, layer of protection analysis (LOPA) and the safety integrity level (SIL) risk reduction value methodology are employed to assess the safety of an ammonia/carbon dioxide cascade refrigeration system. By analyzing the potential risks, hazards and possible deviations during operation are identified, the effectiveness of existing safety control measures is assessed, and the risk reduction achieved is quantified. The HAZOP method effectively identifies potential hazards in the system; the LOPA method helps quantify risks and reduce the frequency of risks associated with independent protection layers; the SIL risk reduction value methodology provides a quantitative basis for evaluating the effectiveness of risk mitigation. The analysis results indicate that the risk reduction target for the evaporator side (ammonia refrigeration side) is 71, with a safety integrity risk reduction value of -0.14, necessitating the addition of safety equipment with a safety integrity level (SIL) of 1 to ensure system safety. It is also recommended that the safety evaluation and analysis of this refrigeration system be emphasized during the development of industry standards.