Research on optimization and design methods for air distribution system based on target values

To achieve sufficient air conditioning of large buildings,reasonable air distribution in indoor spaces is an effective method for creating stratified air conditioning.Therefore,optimizing the air distribution in large buildings is extremely significant.In this paper,we expound on a new method for air distribution design and optimization based on target value evaluation and summarize the relevant design processes based on an orthogonal test and by decoupling the effects of the size of the tuyere,airflow temperature,air-supply angle and velocity on air distribution.Then,we present a design case.To optimize the distribution of a lateral air supply in winter,the deflection angle,velocity and temperature of the air supply can be determined in turn.For the large and tall building types addressed in this paper,the optimal air-supply angle is 2°,the optimal air-supply velocity is 8 m/s,and the optimal air-supply temperature is 19℃.

Body-centered-cubic structure and weak anharmonic phonon scattering in tungsten

It was recently found that the anharmonic phonon–phonon scattering in tungsten is extremely weak at high frequencies,leading to a predominance of electron-phonon scattering and consequently anomalous phonon transport behaviors.In this work,we calculate the phonon linewidths of W along high-symmetry directions from first principles.We find that the weak phonon–phonon scattering can be traced back to two factors.The first is the triple degeneracy of the phonon branches at the P and H points,a universal property of elemental body-centered-cubic(bcc)structures.The second is a relatively isotropic character of the phonon dispersions.When both are met,phonon–phonon scattering rates must vanish at the P and H points.The weak phonon–phonon scattering feature is also applicable to Mo and Cr.However,in other elemental bcc substances like Na,the isotropy condition is violated due to the unusually soft character of the lower transverse acoustic phonon branch along the Γ-N direction,opening emission channels and leading to much stronger phonon–phonon scattering.We also look into the distributions of electron meanfree paths(MFPs)at room temperature in tungsten,which can help engineer the resistivity of nanostructured W for applications such as interconnects.