VAV

Variable Air Volume (VAV) system has been widely used in order to reduce energy consumption. However, operation performance and energy consumption may not be as good as expectation in practical projects due to some failures. Hunting of control parameters is one of the typical failures, which may result in dissatisfying the owner’s requirements, abrading the actuators and reducing the service life of the equipment. In this paper, hunting problem is divided into three categories and several solutions are suggested.

Space conditions are directly controlled by terminal boxes in variable air volume (VAV) air handling unit (AHU) systems. The terminal box either modulates airflow or adjusts discharge air temperature. Conditioned space will have thermal discomfort by less air circulation if the airflow and discharge air temperature are not suitable. The objective of this study is to estimate an optimal value of the airflow and discharge air temperature, which maintains room thermal comfort.

The objective of this paper is to apply a novel decoupling control method, direct feedback linear (DFL),to VAV air-conditioning system, which is differences from local linear decoupling control method. Amodel of VAV air-condition room is developed by a typical air conditioning system. Using DFL control,decoupling control is realized among multi-control loops in VAV air conditioning system and a linearmulti-inputmulti-output model is obtained. According to the VAV air conditioning model the real-timeDFL control system is designed and simulated based on MATLAB/SIMLINK.

In recent years, in the quest focused about energy conservative building design, as a high efficiencyair conditioning scheme, the variable air volume (VAV) systems owe their growing popularity in heating,ventilation and air conditioning (HVAC) applications. This paper reports the simulation study toinvestigate the inherent operational characteristics of direct expansion (DX) VAV air conditioning (A/C)unit when the supply air fan and compressor speeds are varied based on the thermal load persisting inthe conditioned space.

The characteristics of a hybrid air-conditioning system, utilizing natural and mechanical ventilation, is investigated in an office setting. The characteristics of the indoor environment are examined with CFD(Computational fluid Dynamics) simulation under various conditions of incoming outdoor air. The control of the room air conditioning system (VAY system) is included in the calculation through changing the supply air volume to keep the task zone's temperature at a target temperature.

Samples of 31 different air filters, representative of the designs and efficiency range of those used in general ventilation, were tested at constant airflow. The complete array of ASHRAE Standard 52.1 tests was run on these filters, plus particle-size efficiency tests and tests measuring the reentrainment of dust from the filters when subjected to ultra-clean air flow. Additional samples of the same filters were then subjected to the same test array, except that VAV flow was simulated.