Optimisation design and verification of the acoustic environment for multimedia classrooms in universities based on simulation

The acoustic environment of the classroom is one of the most important factors influencing the teaching and learning effects of the teacher and students.It is critical to ensure good speech intelligibility in classrooms.However,due to some factors,it may not be easy to achieve an ideal classroom acoustic environment,especially in large-scale multimedia classrooms.In a real renovation project of 39 multimedia classrooms in a university,seven typical rooms were selected,and the acoustic environment optimisation design and verification for these multimedia classrooms were performed based on simulation.First,the acoustic and sound reinforcement design schemes were determined based on the room acoustics software ODEON.Next,the effects of the optimisation design were analysed,and the simulated and measured results were compared;the accuracy of using the reduced sound absorption coefficients,which were determined empirically,was also examined.Finally,the recommended reverberation times(RTs)in multimedia classrooms corresponding to speech intelligibility were discussed,the effectiveness of the speech transmission index(STI)as a primary parameter for classroom acoustic environment control was considered,and the acoustic environment under the unoccupied and occupied statuses was compared.The results revealed that although there are many factors influencing the effect of classroom acoustic environment control,an adequate result can be expected on applying the appropriate method.Considering both the acoustic design and visual requirements also makes the classroom likely to have a good visual effect in addition to having a good listening environment.

Reliability Based Multi-Objective Thermodynamic Cycle Optimisation of Turbofan Engines Using Luus-Jaakola Algorithm

Aircraft engine design is a complicated process,as it involves huge number of components.The design process begins with parametric cycle analysis.It is crucial to determine the optimum values of the cycle parameters that would give a robust design in the early phase of engine development,to shorten the design cycle for cost saving and man-hour reduction.To obtain a robust solution,optimisation program is often being executed more than once,especially in Reliability Based Design Optimisations(RBDO)with Monte-Carlo Simulation(MCS)scheme for complex systems which require thousands to millions of optimisation loops to be executed.This paper presents a fast heuristic technique to optimise the thermodynamic cycle of two-spool separated flow turbofan engines based on energy and probability of failure criteria based on Luus-Jaakola algorithm(LJ).A computer program called Turbo Jet Engine Optimiser v2.0(TJEO-2.0)has been developed to perform the optimisation calculation.The program is made up of inner and outer loops,where LJ is used in the outer loop to determine the design variables while parametric cycle analysis of the engine is done in the inner loop to determine the engine performance.Latin-Hypercube-Sampling(LHS)technique is used to sample the design and model variations for uncertainty analysis.The results show that optimisation without reliability criteria may lead to high probability of failure of more than 11%on average.The thrust obtained with uncertainty quantification was about 25%higher than the one without uncertainty quantification,at the expense of less than 3%of fuel consumption.The proposed algorithm can solve the turbofan RBDO problem within 3 min.

Excel as an Educational Platform for Design Analyses of Fluid-Thermal Systems

Equipped with its Solver and-in and VBA, Microsoft Excel makes an ideal educational platform for design analyses of fluid-thermal systems. This paper illustrates this capability by considering a common type of these systems;which is the double-pipe heat exchanger. While Solver is used for the optimisation analysis, VBA is used for the development of a user-defined function (UDF) that determines the optimum standard-pipe size for the system.

Optimisation of the double skin facade in hot and humid climates through altering the design parameter combinations

Architects welcome double skin facade(DSF)due to its aesthetic quality.The first DSF structure was intended to prevent cold weather and strong winds.Nowadays,the application of DSF under different climates has been investigated in many previous studies.Fiowever,little work had been done on the behaviour of DSF in hot and humid climates.Therefore,this paper aimed to extend the application into this specific climate and Guangzhou was selected as the sample city.Both the climate and the design influence the performance of DSF.In this paper,rather than explore how each design parameter influences the performance,the design was evaluated from an overall aspect.The Designbuilder software was used to build the single skin facade(SSF)and double skin facade base model.Annual HVAC energy consumption for both the two models was calculated and compared.An optimisation process was conducted to figure out what kinds of parameter combination could make the design more energy-saving and thermally comfortable.The results indicated that it was possible to design an energy-saving DSF system applied in hot and humid climates compared with the SSF model.The efficiency of the DSF could be further enhanced with a better parameter combination.The optimised options had some features in common,which could provide some inspirations for the application of DSF in hot and humid climates.

Design optimisation of mean room surface exitance and total corneal illuminance using Monte Carlo simulation

In lighting design,mean room surface exitance(MRSE)has been known as an indicator of the adequacy of illumination in an indoor space.Recent studies have suggested an exponential model relating MRSE and the observer’s retinal response.This is particularly applicable in a room with homogenous room surface reflectance and a constant total corneal illuminance,which is the total illuminance received at the eye.However,accuracy of the exponential model is yet to be assessed in detail.Furthermore,the implication on interior lighting design is also yet to be quantified.This study thus aims to assess the accuracy of the exponential model and to optimise the output variables.Random computations using Monte Carlo simulation are performed for various input variables,followed with sensitivity and uncertainty analyses and optimisation.Prediction errors of the exponential model are found between-10%and 6%.The MRSE is highly influenced by surface reflectance,whereas the total corneal illuminance is influenced by the source luminous flux.Optimum design parameters are obtained by minimising the ratio between total corneal illuminance and MRSE.Overall,this study provides guidelines in lighting design practice for enhancing room spatial brightness while minimising energy use.