24,177 research outputs found
An investigation of air and water dual adjustment decoupling control of surface heat exchanger
The terminal equipment of central cooling system accounts for a significant proportion of the total system's energy consumption. Therefore, it is important to reduce the terminal equipment energy consumption in central air conditioning system. In this study, the difference of the effect of the chilled water flow rate and air supply rate on the surface cooler during the heat transfer process is taken into full account. Matlab/Simulink simulation software is used to model and simulate the heat transfer of surface cooler of the main terminal equipment of air conditioning system. Simulation tests and experimental validations are conducted by using variable chilled water flow rate and variable air supply rate control mode separately. The experiment results show that the simulation model can effectively predict the heat transfer performance of heat exchanger. Further, the study introduced a dual feedback control mode, which synchronously regulates the chilled water flow rate and air supply rate. Also, under certain conditions, the complex heat transfer process of the surface cooler can be decoupled, and single variable control pattern is used to separately regulate the chilled water flow rate and air supply rate. This can effectively shorten the system regulation time, reduce overshoot and improve control performance
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Processing of immiscible alloys by a twin-screw rheomixing process
Immiscible alloys with a microstructure in which a soft phase dispersed homogeneously in a hard matrix have great potential applications in advanced bearing systems, especially for automotive industry. Though the melt of an immiscible alloy is miscible at the temperature above the miscibility gap, it decomposes into two liquids when it passes through the liquid miscibility gap. Despite great efforts made worldwide, including extensive space experiments, no casting techniques so far can produce the desirable microstructure. Based on the extensive experience in mixing the immiscible organic liquids offered by the polymer processing community, a rheomixing process for immiscible alloys has been successfully developed at Brunel University using a twin-crew extruder. This paper presents the twin-screw rheomixing process and the experimental results on rheomixing of the immiscible Zn-Pb alloys
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Twin-screw rheomoulding of AZ91D Mg-alloys
Twin-screw rheomoulding is a new semisolid process for the near net shape production
of metal’s components. It includes the advantage combination in both die-casting and
injection moulding. In this unique process, a liquid alloy is fed into a twin-screw
extruder, where the alloy is intensively sheared and cooled into the interval of liquidus
and solidus to produce semisolid slurry with fine primary particles of pre-determined
volume fraction. The well-sheared semisolid slurry is then discharged into a shot
cylinder and subsequently injected into a mould cavity for component shaping. This
paper introduces the development of the prototype machine and the experimental work
carried out with industrial AZ91D magnesium alloy. The operating characteristics of the
newly developed machine, microstructures and mechanical properties of rheomoulded
AZ91D magnesium alloy will be reported
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