Fault Diagnosis Approach of Local Ventilation System in Coal Mines Based on Multidisciplinary Technology

In order to reduce the probability of fault occurrence of local ventilation system in coal mine and prevent gas from exceeding the standard limit, an approach incorporating the reliability analysis, rough set theory, genetic algorithm (GA), and intelligent decision support system (IDSS) was used to establish and develop a fault diagnosis system of local ventilation in coal mine. Fault tree model was established and its reliability analysis was performed. The algorithms and software of key fault symptom and fault diagnosis rule acquiring were also analyzed and developed. Finally, a prototype system was developed and demonstrated by a mine instance. The research results indicate that the proposed approach in this paper can accurately and quickly find the fault reason in a local ventilation system of coal mines and can reduce difficulty of the fault diagnosis of the local ventilation system, which is significant to decrease gas exploding accidents in coal mines.

Local and Whole Ventilation of Rainwear with Different Aperture Designs

Aperture design is very important in the design process of rainwear,as garment aperture is one of the main pathways for air exchange between clothing microclimate and the environment.The purpose of this study was to investigate the effects of aperture design on whole and local ventilations of rainwear.Ventilation was measured by a tester developed based on the steady-state method.A rainwear suit with top and bottom was chosen as the basic ensemble.Apertures were added at the arm,chest,back and knee separately.Local ventilation of the arm,chest,back and whole ventilation of the top and bottom in different walking and wind conditions were measured.Local and whole ventilations at five aperture conditions for the top and four for the bottom were studied.The results indicated that local ventilation value of the chest was the biggest and the arm was the smallest.Whole ventilation of the suit was the biggest when walking at 5.6 km/h,with all the designed apertures opened.Local ventilation value was bigger when opening arm aperture than that of opening chest or back aperture.The bottom ventilation was the highest when both front and back apertures were opened.

Simulation-aided development of a compact local ventilation unit with the use of CFD analysis

Insufficient fresh air supply due to the increased air tightness of building envelopes after building renovations and window upgrades is a major concern of HVAC engineering today.The paper demonstrates the application of CFD simulations in the development of a compact decentralised ventilation unit with integrated heat recovery system for local ventilation of rooms,targeting this common issue.The device houses an innovative cyclically rotating recuperative heat exchanger,allowing effective condensate removal and de-icing in winter for its independent operation throughout the year.The paper introduces the ventilation unit,describes preparation of its numerical models,and conducts CFD simulation using Ansys Fluent software.The initial design of the device was improved following the findings of the numerical analysis,and the proposed adjustments were tested through follow-up CFD simulations,confirming that the desired outcomes were achieved.A separate CFD analysis was performed to assess the use of different air supply elements at the air outlet to the room,recommending the use of adjustable nozzles.A prototype ventilation unit was manufactured and the volume flow rate under different operating conditions was measured to be compared with the simulation results.The outcome of the research is a new type of compact local ventilation unit.An increase in device energy efficiency was achieved,with the aid of simulations,while maintaining its compact size.In addition to presenting the potential of using variant CFD analysis in the development of new HVAC equipment,the paper also indicates the drawbacks of using the Multiple Reference Frame(MRF)method to approximate the rotation of radial fan impellers in CFD simulations.